p chassis alignmentprocess

8/13/2019 P Chassis AlignmentProcess

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P Chassis

for Motorhomes

General Information

for Alignment

http://users.sisna.com/cebula/P-Chassis-AlignmentProcess.pdf Version 1.4 December ! ""#


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$ntroductionThe intent of this document is to provide both reference information and guidance to getthe Chevrolet P Chassis to perform as it was designed to perform and maybe even make afew improvements. I've tried to highlight these in bold.

A majority of the information is taken from the !!" and !!# $Chevrolet Motor Home ChassisService Guide% for the P Chassis. &owever the information has been presented in what is feltto be a logical se(uence to accomplish that most elusive item for this chassis ) goodhandling.

Age is the common enemy of the chassis. It has been around a long time and many of theolder motorhomes on this chassis are showing signs of age. The idea here is to simply getappropriate repairs done to bring the chassis back to good condition and then figure out thecorrect specifications for alignment.

Along the way you have probably encountered your share of not*so*competent mechanicsand+or alignment shops. ,atter of fact many alignment shops simply don't know how todeal with this motorhome version of the P Chassis and wind up treating it like a truck.

-e will show you that simply telling the alignment shop that it's a $P/ Chassis% will almostguarantee you an incorrect alignment. 0our Class A motorhome is 12T built on a $P/Chassis%. The correct general term is a $,otorhome P Chassis%. The P Chassis was alsoused for what is referred to as a Commercial 34orward Control5 truck. The same chassisseries has been used for 6/ 67/ 6/ P7/ P/ and ,otorhomes under a '7 * "7'designation. -hat's more the alignment specs are different for the motorhome chassisbecause they were made slightly different.

If you decide to do some of the repair work yourself such as replacing bushings remember

that you can generally 'rent' specialty front end tools from your local parts store at a cost of8/.// when you buy the parts from them. A deposit is all that is generally re(uired. 0ou canprobably get some good instructions on safely using the tools too.

Chevrolet had # model numbers for the ,otor &ome P Chassis only the ones with '*"7'were destined for Class A motorhomes. Class C motorhomes were also built on some ofthe Commercial truck chassis. Those Class C models would rightfully be referred to as usingthe 'P*/' Chassis and would use the alignment specs for the truck version.

P/97 7"% wheelbaseP7 * "7 #% wheelbase

P:7 * "7 "!% wheelbaseP97 * "7 #9% wheelbaseP!7 * "7 !/% wheelbase 3;tart*up production in !!5 3!."% wheels5P7/7 * "7 7/9% wheelbase 3;tart*up production in !995 3!."% wheels5P77 * "7 779% wheelbase

The ,otorhome Chassis also has different frame rails.


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Table of Contents

%he Process.................................................................................................................. 1&orn Parts................................................................................................................... 1Air 'ags....................................................................................................................... #&eight..........................................................................................................................(%ires............................................................................................................................. )*ide +eight................................................................................................................ 1",rame Angle...............................................................................................................1Alignment.................................................................................................................. 1(Appendi A ,ront oad +eight Cur0e................................................................... 1Appendi ' *ear oad +eight Cur0e....................................................................."Appendi C V$2..................................................................................................... 1Appendi D An Alignment Primer......................................................................... 4Appendi 3 %ire $nflation as of 15...................................................................Appendi , %o6ing................................................................................................ (+o6 do $ determine m7 rear ale ratio8.....................................................................(

Appendi 9 Chart for properl7 matching tires to rims/6heels...............................&eights &orsheet....................................................................................................;"


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The Process

The first step to maintaining proper vehicle handling is through the regular inspection andreplacement of suspension bushings ball joints tie rod ends and just about everything elsethat makes up the front and rear end suspensions of the motorhome.

The second step is to perform a suspension alignment. ;ounds straightforward enough butthe P Chassis has been given a reputation for not handling very well even after an alignmenthas been done. The catch seems to be that many of the motorhomes e=periencing drivabilityproblems have old worn saggy parts. ;ound familiar? 1ot only that but there doesn't seemto be a lot of e=pertise out there in alignment shops for this chassis. In other words youhave to take the ball in your own hands and verify everything is checked and in good shape


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a=le housing and suspension parts too.

Proper lube of ball joints means lifting the motorhome by a frame member so thesuspension hangs free and then lube the Eerks. Don't forget to wipe the Eerks clean beforeyou lube. 2therwise you will be pushing gritty dirt into the joint. If the motorhome is liftedfor lubrication by driving up on wheel ramps the ball joints are under enough tension toinhibit full flow around the entire ball socket. -hen lifted it is a good time to check balljoint wear.

To do this you will need a caliper that will measure the lower ball joint distance between thetip of the ball stud and tip of the grease fitting below the ball joint while the suspensionhangs free. Then change the point you are lifting the front end so that you are supportingthe weight of the control arms at each wheel or each lower control arm. Again measurebetween the same points on each lower ball joint. The difference between the twomeasurements for each should not e=ceed +7 of an inch. emember even new ball jointshave play in them. If they didn't they wouldn't move. If you replace replace in pairs.

ook at all the rubber washers and bushings for cracks bulges and wear. The upper and

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lower control arm bushings get pretty bad after /*7/ years. These are cheap to buy andlabor is the real cost. If you can replace them yourself do it. Also using a spray*on rubberlube on suspension points on a regular basis is cheap insurance ) once you know they are ingood shape.An improvement you can make is to use the newer poly bushings.

The steering linkage is located forward of the front cross member. The P Chassis linkage isillustrated below. ;teering effort is transmitted to left* and right*hand adjustable tie rodsthrough a relay rod. The relay rod is connected to an idler arm on the right and to thepitman arm on the left. The fit of the shafts in the linkage support assemblies should be tightwith end play not e=ceeding .//. If it e=ceeds .// inches in either assembly adjust towithin / to .// inches. ;et large lock nut tor(ue cap to 7" ft. lbs. and then loosen +F turnand tighten lock nut. If there is side play replace the bushings. ube the linkage under'normal' conditions every #"// miles or every /// miles if used in 'dusty' conditions. The$support assembly% in the illustration below is also known as a $bellcrank%. These twobellcranks are obvious points for improvement. More modern versions are much moreheavy duty, the SuperSteer version is one to consider. Expensive, but one of the bestimprovements to make for handling.

,any motorhomes sit in storage for a long time between use. That steering damper 3it's

really a shock absorber5 can accumulate rust on its horiEontal e=posed rod. If it does getheavily rusted and you just jump in after a long storage period and drive off that rusty rodmay rip up the seal as soon as it moves inward when you turn the steering wheel. 6ood ideato check it and possibly clean it off. Turn the steering wheel so as to e=tend the rod fullywhile you check it. If it's badly rusted it's probably a good idea to replace the damper. ;amething applies to the shocks. Think about some preventive measures added to your pre*

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frame mounts. ,ake sure those mounts are tight and all the bushings are in good shape.Animprovement to this stabili"er bar is to replace it with a much stronger version suchas the I#$ % &'() version and use polyurethane bushings. *he % &'() bars availableare %+ to % times stronger than the stock % %'-) sway bar.

The front wheel bearings re(uire lube every 7/// miles with high*temperature grease )really. Check the bearings by raising the motorhome and supporting it at the front lowercontrol arm on each side. 1ow you can spin the wheel and check for noise or roughness. Tocheck for tight or loose bearings grip the tire at the top and bottom and move the wheelassembly in and out on the spindle. If hub assembly movement is less than .// inch 3tootight5 or more than .//" inch 3too loose5 adjustment is needed.

The adjustments steps areG

. emove the hub cap or wheel disc from the wheel.7. emove the dust cap from the hub.. emove the cotter pin from the spindle and spindle nut.:. Tighten the spindle nut to 7 ft. lbs. while turning the wheel assembly forward by hand to

fully seat the bearings. This will remove any grease which could cause e=cessive wheelbearing play later.

".


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Doesn't sound like something you can easily determine? Take it to a mechanic you trust.

Air Bags

Air bags are an interesting item to folks with this chassis. eaks can be located by removing

the bag from the vehicle inflating it and submerging it ) just like looking for a tire leak.Actually if it doesn't hold pressure you have a leak. The logical repair is a replacement. Ifyou replace replace bags as a pair.

There are basic guidelines for inflation depending on which version of the P Chassis youhave. The air pressure should never be under / P;I unless you are removing+replacing theairbag.Air 'ags ,ront:

4or a ://*lb suspension :/*"/ P;I.4or a "///*lb suspension "/ P;I.4or a "//*lb suspension #/ P;I.4or a ""//*lb suspension !/ P;I.

The 6, part number is F##F7 for the bags used in the :// and "///*lb suspensions.The 6, part number is "F99 for the bags used in the "// and ""//*lb suspensions.This is an Airlift &.D.


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matched to the actual axle weight of your coach and you can eliminate the air bagswhen done properly.

ne improvement you might want to consider for the rear is installation of a reartrack bar. *his will help with that /tail0wagging0the0dog) feeling you might beexperiencing, this is a good modification if you tow something heavy.

Weight

-ait a second.


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the suggested improvement parts.

Almost.

&ow about those tires?

Tires

1o brand or type tire recommendation is presented here. &owever the first rule is that youdo not mi= different types of tires on the vehicle such as radial bias and bias*belted tirese=cept in emergencies.


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7.50-16 Bias Ply

PSI

30

C,D,

E

35

C,D,

E

40

C,D,

E

45

C,D,

E

50

D,E

55

D,E

60

D,E

65

E

70

E

75

E

Lbs per

tire-Single

1620 1((" 1;" "#" 1" ;1" 44" #" #(" ()"

Lbs per

tire-

Duals

14;" 1# 1#" 1)1 1;" "4" 14" 4 ;4 44"

ooks like "/ P;I would be a good choice for both the front and rear tires in the chartabove. The placard for this particular motorhome said F/ P;I. This is probably because ofthe accepted rule to add " ) / P;I if you intend to hit F"mph or better and also to helpcover a bit of loss between air checks. A oad ange D or @ tire will do the trick if younever cold inflate over F/ lbs. If you think you need F" lbs. A oad ange @ tire would be

re(uired. Incidentally many of these tires have a ma=imum speed rating on them. F",phma= is not uncommon. Also


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duals are properly spaced from each other. If the duals touch sidewalls they won't last andare a haEard. 3If you do decide on bigger or wider tires work with a pro. ;ubstitutingT7"+9"F tires in place of #."/*F tires is probably not going to work in the dualsposition without changing rims too ) they would be too close together.5


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height. Another option is to take the measurements mark the position of each corner tireand turn the motorhome around 9/ degrees park in the same marks facing the oppositedirection and check the four points again. An average of each reading should bring you closeto actual. 2f course you need to start this with an almost*level location. This won't workvery well if you do it on the side of a hill.

@AG

The reason the rear ride height is important to us is because it can affect the handling.


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is full to the appropriate level and changed on a regular basis. All lubricants loseeffectiveness over time. @very four oil changes 3'normal' or 'dusty' cycle5 will do the job. Thedifferential can run a temperature appro=imately // degrees above the ambienttemperature. Air passing over the housing is the only thing that carries away this heat. ,akesure the housing is not severely covered with dirt or dried mud which will insulate and helpretain and increase the heat. 36o back to the car wash and hit the housing with the high*pressure spray.5 The e=haust pipe shouldn't be too near the housing. Don't mi= lubricantbrands ) this can cause foaming and reduce heat transfer. If you run at high speeds it cancause aeration and heat transfer capability will be diminished.

ide height for the P Chassis rear is checked on each side between the top of the a=le tubeand the bottom of the frame above the a=le tube. 0ou are looking for this $D% measurementto be e(ual side*to*side. If these are not e(ual your weight side*to*side may be une(ual orsprings may be sagging. In any case an attempt should be made to get these as e(ual aspossible. Check Appendi= < for information on the rear spring capacities for various PChassis models. 3The illustration has a single on the left and a dual on the right because itapplies to either situation including non*motorhome versions of the P Chassis.5

&ere is a case study right out of the Chevy P Chassis manualG

$6, CA;@ ;TBD0G A motor home was loaded to a ma=imum 6>- both front and rear. ;ufficient airwas applied to a typical after*market leveling device to establish a 'dead*level' frame. In this case studywheel travel was limited to O inch before the after*market device $went solid metal*to*metal% betweenthe rear a=le and the frame. This severe limitation on wheel travel promoted a $crash*through situation%on even the slightest bump. The force from this $crash*through situation% was transmitted into thevehicle frame rear a=le and the coach itself. 6, has determined that these types of after*market levelingdevices can be very damaging to the motor home and also can affect vehicle handling and are therefore

potentially very dangerous.

$If vehicle weights cannot be shifted due to vehicle build consideration should be given to adding springleaves or spacer blocks.%

The spacer blocks mentioned above refer to making the side*to*side rear ride height

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measurement e(ual. 3This supposes that the weight is not in e=cess of the a=le rating and youhave moved your movable stuff around to help balance the side*to*side weight.5 ;pacerblocks are fabricated in local machine shops.

12T@G The addition of a spacer block 3 7 H% wide F% long thickness as needed5 canactually improve overall ride (uality while the addition of a leaf tends to reduce the ride(uality of the vehicle. A new motorhome manufactured with an e=tra spring on one side is abad design. They didn't get the weight balance right and compensated with the springs. 0ouwould also have to be very careful in this situation with the tire inflation. The heavier side isthe weight to use to determine the correct pressure for all tires on that a=le. 0ou cannotsimply divide the total a=le weight in half in this situation ) that can be dangerous.

The thickness of the spacer block is determined by the difference in the side*to*sidemeasurements at the rear a=le. 2nce the thickness is determined and the block fabricated aO inch hole is drilled in the center. A slip*fit dowel as long as the thickness of the spacerblock is inserted into the hole of the block. This keeps the center of the a=le and thee=isting spring properly aligned. The B*bolts will need to be replaced with longer ones if the

spacer block is more than O% thick. Also the rear fle=ible brake hose that runs from theframe to the a=le may need to be lengthened since you are increasing the distance from itsmount on the frame to the connection on the a=le. Check by slowly lifting the rear by theframe and allow the rear a=le to hang loose.


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to some e=tent. 2nce complete with the work in the rear re*check the front. If you 'twist'the rear the front will be affected.

421TG

Coil springs sometimes break near the end and wedge in place without obvious indication ofthe failure. ook hard. If you think this might have happened the only way to prove it is toremove the spring.

In the front the measurement is checked on each side between the lower control arm rubberbumper bracket and cross member flange. This measurement must be perpendicular to thecross member flange. It is from $iron to iron%. The rubber bumper is ignored. ook at theillustration below.

Key here is that both sides of the front a=le should be the same and this measurement isused in the CA;T@ determination. The front air bags should be inflated to the

recommended pressure for your chassis. Don't attempt to raise or lower the chassismeasurements using the air bags. 3If your motorhome has air bags that have been added tothe rear to compensate for sagging springs make sure they are set to the pressure you planon maintaining in them.5

1ow take that front measurement and find it in the top row of the chart below then go



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down to the $,2T2 &2,@% row to get the degree setting. This is the initial point forthe CA;T@ setting. This chart is from the !!" $Chevrolet ,otor &ome Chassis ;ervice6uide% for the P Chassis but applies to all manufactured.

1ote the various vehicles in the first column that use the P Chassis. Also note that there is aseparate line for the ,2T2 &2,@ version. It is different from the $P*7/ /% line. Thereis a distinct possibility that an alignment shop will use the incorrect numbers if you tell themto align $my P/ chassis%.


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3a5 A down0in0rearframe angle must be subtracted from apositivecaster specification.3b5An up0in0rearframe angle must be added to apositivecaster specification. 3This is

the most common situation.53c5 A down0in0rearframe angle must be added to a negativecaster specification.

3d5An up0in0rearframe angle must be subtracted from a negativecaster specification.

30ou can make up the measuring tool by picking up a cheap plastic protractor file a smallnotch at the / center on the flat side. Then capture a knotted string in that notch with aweight at the end of the string hanging down to indicate the degree of angle * not rocketscience. 2f course if your eyesight is as bad as mine get a big protractor.5 Also note thatearly versions of the P Chassis ;ervice ,anual had the words 'added' and 'subtracted' in a

b above reversed and c d above reversed. Their instructions were backward and incorrect.

As an e=ample let's assume you previously measured front ride height on both sides as :+7%. The table says the CA;T@ should be set to Q degrees.


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MODEL CAMBER TOE-IN (IN.)

91"! " .> ;/1#?

9;" .> ;/1#?

CA@@ A

=%* +=3 ; 5

.> B .> "> to ."#>

Toe*in was reduced from "+F inch in !9" as part of a 6, trend reducing toe*in. Ife(uipped with radial tires some tire manufacturers would suggest toe*in specifications of+7 inch to +9 inch.


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1234A*56A*I2S70our Class A motorhome should no longer be yanking on your shoulder sockets and youcan enjoy the ne=t trip a little better. 0ou also should now have a better feel for why somemaintenance needs to be done the airbags should be consistently inflated to the same

pressures and the tire pressures maintained properly. They all affect handling and safety.

The Appendices following this are for further information.

A and < help in determining if your springs are up to snuff.

C will give you the ability to interpret your >I1 number.

D is basic information on the adjustable points of an alignment.

@ is a couple of pages from the P Chassis manual with tire inflation information. This isgeneric and you should use the manufacturer's chart for your brand and model tire.

4 is derived from the P Chassis manual to help you determine if you are e=ceeding thetowing recommendation for your configuration. 0ou might be surprised here.

6ood luck,ike Cebula

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Appendix A 8 9ront 6oad :eight 1urve

Known weights compared to actual dimensions can determine if the spring is performing

according to its rating. Actual measurements will be NH*inch on the chart and normallyconsidered within the spring makers production capability.



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Appendix 8 4ear 6oad :eight 1urve

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Appendix 1 8 ;I2

!#! * !9/


C P % 3 7 & 3 1 0 0 0 0 1

1. S'lli() *i+isi(

2. Cassis Ty'

3. E()i(' *'s/ii(

4. S'i's5. By Ty'

6. M'l %'a

7. Ass'ly Pla(

8. 'i/l' S''(/''

1.

Selling Division

C- C'+l'

T- GMC T9

2.

Chassis Tye

C- C(+'(i(al

!- 4-:''l i+'"- ;:a C(l :/(ii> +' 6000 G?R>>>C(+'(i(al 'ls(ly "1&77$, All 'ls"1&78-7&$

D - 250 Si=T - 2&2 Si=

- 305-2 8

0 - 350-2 83 - 350-4 8

4 - 400-4 8

S - 454-4 8>

- 454-4 8>>

D- 250 Si=T - 2&2 Si=

4 - 305-2 8

3 - 350-4 8R - 400-4 8

S - 454-4 8>>>

- 454-4 8>>>>

- 5.7L *i's'l>>>>>>>>>M !' Cassis'ls "1&77 (ly$>>>>>1078-7& (ly$

D - 250 Si=T- 2&2 Si=

" - 305-2 8

3 - 350-4 8 "LS&$* - 350-4 8 "LT&$

P - 350-2 8 "L;5$

R - 400-4 8 "L;4$

S - 454-4 8 "L;8$W- 454-4 8 "LE4$/- 400-4 8 "LE4$- 5.7L *i's'l

).

Body Tye Code

1- 4- Ca

2- ;:a C(l Cassis$- Cassis-Ca Ca:ay a(#- Pi9

)- C'+y a(/a(a S'a(/al' a(

+- Sa( S+a(/Rally'- M !' Cassis

-- Bla


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!9 ) !9


Co8ntry1 .S. Bil

2 Ca(aia( Bil

@ @aa( Bil

*an89act8rer

G G'('al Ms8 s

B C'+l' T9 (l''

C C'+l' T9

* GMC T9 (l''

GMC Bs>T GMC T9% s 10 ' ass'()'s

"0WR Range

B 3001 - 4000

C 4001 - 5000

* 5001 - 6000

E 6001 - 7000

; 7001 - 8000

G 8001 - &000

! &001 - 10,000

@ 10,001 - 14,000

F 14,001 - 16,000

Code Series1 - 1/2 T(

2 - 3/4 T(

3 - 1 T(8 - 1/2 T( -"ElCai(/Caall'$

Body Tye

0 S'a( Pi9

1 !i-C'/Ca:ay/iliy B=

2 ;:a C(l

3 ;-* Ca

4 T:-* Ca

5 a(

6 Sa(

7 M !' Cassis8 iliy "@iy/Bla 4 = 2

T C(+'(i(al Ca> 4 = 4? El Cai(/Caall'> S-10/15

ear

B - 1&81

C - 1&82

* - 1&83

E - 1&84

; - 1&85

G - 1&86

Chec: Digit

%ngine

>A 3.8L 6 "L*5$

A 1.&L L4 "sJ 5.7L *i's'l "L;&$> ; El Cai(/Caall' 'ls (ly

Assem5ly Plant

B - Bali', M*

; - ;li(, M

@ - @a('s+ill', ?

S - S. Lis, M

E - P(ia Eas, M

- P(ia, M

J - ; ?ay(',

1 - sa:a,

2 - Mai(', !

3 - *'i, M

4 - Sa),

7 - Ls:(, !

8 - Si'+', LA

0 - P(ia, M

Prod8ction Se;8ence


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!9: * !!"



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Appendix $ 8 An Alignment #rimer



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Appendix E 8 *ire Inflation



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Appendix 9 8 *owing

The 6C- 36ross Combination -eight ating5 includes weight of both the motorhomeand anything being towed.

2nly the >9 and diesel models are shown here. The combination of engine and rear a=leratios are the determining factor for the 6C- on the P Chassis.

GCWR 10,000 10,500 11,000 11,500 12,000 12,500 13,500 14,000 14,500 15,000 16,000 19,000

329$23@ *3A* A3 *A%$@

.( ;"5V) 9A@

;.") ;.; ;.4 ;.(; 4.1" 4.#

#. V)D$3@3

;.4 ;.(; 4.1" 4.# .1;

(.4 445V) 9A@

;.1 ;.4 ;.(; 4.1" 4.#4.))

=otorhome chassis onl7.

2%3:

9C&* for unit 6ith 4)"3 transmission is 1!"""E 6ith 9V&* of 1#!""E.,or 9V&*s less than 1#!"""E! the maimum 9C&* is 1!"""E.=a 9C&* 6ith the 4( transmission is 1!"""E for all 9V&*s 1" F before5.

CA


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2et ; digits indicates the da7 built - epressed in Mulian Date formast digit indicates the shift 1K1st shift! Knd shift. DonNt ha0e an7 idea 6hat thepurpose of this is.5

Another 6a7 is to tr7 and find the *P codes sticer some6here in the coach! 7our

Che07 dealer can interpret it for 7ou. %he *P info $ ha0e is:

*P "## is 4.1"*P "" is 4.#

DonNt ha0e info for the 4.)) or an7 others.

%hose are the eas7 6a7s.

%he hard 6a7 is a little more difficult 6ith a motorhome than 6ith a car! but is absolutel7the most accurate especiall7 if 7ou suspect a pre0ious o6ner changed out the rear end -here goes:

*aise the rear ale off the ground! support! support! choc front 6heels and then supportsome more to mae sure it is safe. %ransmission should be in neutral and emergenc7brae off chocs - remember85. Oou are going to be


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Aendi@ " Chart 9or roerly matching tires to rims=>heels.

$nformation obtained from the 14 %ire and *im Association Oearboo.

T?R% S?% 1 APPR70%D R?* C7


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Weights Wor:sheet

4rom PlateG ActualsG6A-421T eft 4ront ight 4ront Total

RRRRRRRRRRRR RRRRRRRRRRRR RRRRRRRRRRRR RRRRRRRRRRRR

6A-@A eft ear ight ear Total

RRRRRRRRRRRR RRRRRRRRRRRR RRRRRRRRRRRR RRRRRRRRRRRR

Tag eft ear Tag ight ear Total

T2TA RRRRRRRRRRRR RRRRRRRRRRRR RRRRRRRRRRRR6A-RRRRRRRRRRRR RRRRRRRRRRRRTotal Actual -eight

I15

RRRRRRRRRRRR >I1 S RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR

6C-Capability3Appendi= 45

RRRRRRRRRRRR

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4nderstanding motorhome >eights

0ou've probably heard it said that a chain is only as strong as its weakest link. This theoryapplies to motorhome chassis as well.

The chassis manufacturer establishes weight ratings and limitations based on the majorcomponents of the system the engine transmission brakes a=les tires and frame. Thesecomponents are designed to accommodate a particular weight and if they are overloadedtheir life e=pectancy diminishes rapidly.

;o it is important for motorhome owners to understand the various weight definitions usedby motorhome and chassis manufacturers. 2f course the ne=t step is to have yourmotorhome weighed after you have loaded it for travel to make sure it falls within thevarious ratings.

-eight definitions

3;?43gross vehicle weight rating5G the ma=imum permissible weight of the fully loadedmotorhome including li(uids passengers and cargo. The 6>- is e(ual to or greater thanthe sum of the unloaded vehicle weight 3B>-5 plus the net carrying capacity 31CC5.

31?43gross combination weight rating5G the value specified by the motorhomemanufacturer as the ma=imum allowable combined weight of the motorhome and theattached towed vehicle.

3A?43gross a=le weight rating5G the ma=imum allowable weight each a=le assembly isdesigned to carry as measured at the tires including the weight of the assembly itself.6A- is established by considering the rating of each of its components 3tires wheels

springs and a=le5 and rating the a=le on its weakest link. The 6A- assumes that the load ise(ual on each side of the vehicle.

R0?A >eight la5el

In ;eptember !!F the ecreation >ehicle Industry Association 3>IA5 established are(uirement for its > manufacturer members to disclose weight carrying information thatwould assist both a buyer and an owner in understanding and complying with weightlimitations of motorhomes. The following terms and their associated weights are reflectedon a label found in a cabinet inside the coach.

5;?3unloaded vehicle weight5G the weight of the motorhme as built at the factory with fullfuel engine oil and coolants. The B>- does 12T include cargo fresh water P gasoccupants or dealer*installed accessories.

2113net carrying capacity5G the ma=imum weight of all occupants including the driverfood tools P gas fresh water personal belongings dealer*installed accessories and the

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tongue weight of the towed vehicle that can be carried by this motorhome. 31CC can bedetermined by subtracting the B>- from the 6>-.5

It's important to look at the definition of each term particularly the B>- and 1CC. 1otethat B>- is defined as leaving the factory with full fuel oil and coolants. The 1CCrepresents how much MstuffM including fresh water the motorhome can carry.

The B>- does not include the weight of any dealer*installed accessories which means thebuyer must deduct the weight of these accessories from the 1CC.

Keep in mind that 1CC is the total carrying capacity. &owever the distribution of theweight plays a role. ;o it may not be possible to load a motorhome to its 1CC withoute=ceeding an a=le or tire rating. -eighing your motorhome by individual wheel positionafter you have loaded it is the only way to be certain that you are not e=ceeding anylimitations.

In ;eptember 7/// the >IA modified the label to provide more detail for the

buyer+owner. The term 1CC is no longer used. Two new terms are found on the labelalong with their associated weightsG

S1?43sleeping capacity weight rating5G the manufacturerUs designated number of sleepingpositions multiplied by ": pounds 3#/ kilograms5.

1113cargo carrying capacity5G the 6>- minus each of the followingG B>- full fresh3potable5 water weight 3including water heater5 full P*gas weight and ;C-.

This new label permits the buyer+owner to determine the carrying capacity 3CCC5 based ona personal calculation of actual passengers carried the amount of fresh water on board and

the amount of P*gas carried.

Bse the >IA label as a guide to narrow your selection of vehicles but keep in mind itslimitations.

This information was provided by A'Weigh We Go a national weight safety program that is now a serviceof the !ecreation "ehicle Safety #ducation $oundation %!"S#$& The $oundation sponsors nine !"safety programs and conducts educational seminars

Ho> to >eigh yo8r motorhome

The first time to weigh your motorhome is even before you finaliEe the purchase. That wayyou can determine whether the vehicle will meet your needs in terms of carrying capacity.

?eigh before you pay



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-hen purchasing a motorhome you may not find a place to weigh your motorhome wheelby wheel as weighing e=perts recommend. &owever you can weigh each a=le. Then youcan evaluate the placement of storage areas li(uid tanks major appliances slideoutsgenerator P*gas tank etc. to see whether the distribution of these heavy components couldcause problems. If the capacity is not reasonably distributed you may have difficulty loadingthe coach within its limits.

-hen buying or weighing a coach you must have a good knowledge of your personalweight carrying re(uirements. To help in your calculations here are the appro=imate weights3pounds per gallon5 of the li(uids motorhomes can carryG

water ** 9.V A full F/ gallon water tank uses up nearly "// pounds of your capacitygasoline ) ".FVdiesel fuel ** F.9Vpropane ** :.7.

-hen determining your re(uirements keep in mind that everything you put in the > has

weight. -e know from our weighing program that the average couple carries appro=imately7/// pounds of MstuffM and many full*timing couples may carry as much as /// pounds.

-eighing your motorhome is critical to ensuring that no ratings limitations are e=ceeded.

?eighing by wheel positionIdeally you will weigh the motorhome by individual wheel position. Considering themultitude of floor plans slideouts generators holding tanks and the location of storagespace available >s are fre(uently severely biased to one corner or one a=le.

If you weigh your > on a truck scale by a=le and find that the vehicle is within 6>- it

could be that the vehicle e=ceeds a tire rating especially if the 6A- is e(ual to the sum ofthe tire ratings which is fre(uently the case.

5se a certified scaleTo weigh your vehicle by individual wheel position we suggest you use a certified scale.MCertifiedM means that a (ualifying agency inspects the scale periodically to verify itsaccuracy. ,ost truck stop scales are certified as are most grain elevators co*ops and otherscales used in various trades.

The key is to find a scale that permits you to place individual wheel positions on the scaleindependently while keeping the vehicle level and all wheels in the same plane. It is notcritical to have the wheel in a particular position on the scale and do not be concerned withwhat portion of the motorhome is on the scale and what portion is not. The individualwheel loads will be the same regardless of your position on the scale as long as you keep thevehicle level.

$etermining the loads-hen weighing a motorhome in this manner first determine the individual wheel loads

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then calculate the a=le loads and the actual gross vehicle weight. Add the wheel loads foreach a=le and compare the total to the 6A- for that a=le. If the total is greater than the6A- then you e=ceed this rating. If the total is at or near the 6A- a tire overload isprobably.

1ow add all of the wheel loads together and compare that total to the 6>- for yourcoach. If the total e=ceeds the 6>- then you e=ceed that rating.

*ire ratings

p chassis alignmentprocess

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