Alignment Specifications

[The_Handier_Man1]

From: txmoparmuscle  (Original Message)
Sent: 3/7/2006 3:50 PM

Does anyone have a manual that lists the alignment specs for an 81 M600?

Thanks
Richard



From: DaveVa78Chieftain
Sent: 3/7/2006 4:47 PM

I was under the impression that Class A Dodge motorhome production was shut down during the 1979-1980 Chrysler bailout.  I have never seen any data past 1979 for Dodge Class A chassis'.   There may have been Class C van chassis development though.  Have you ever decoded the Dodge chassis VIN number?  With a M600, you may actually have a left over 79 chassis.  Those were the big long chassis.  I don't recall any Winnebago that had it.  Some of the other mfg's built 30-32ft chasis'.  Any way, I think the larger chassis settings are the same as the others:
Camber: +2
Toe-in: 0.06" - 0.18"

Camber/Caster requires bending of the axles to perform.   These chassis are sensitive to Toe-in.

Dave



From: txmoparmuscle
Sent: 3/7/2006 5:37 PM

Thanks Dave,

You're probably right. The Foretravel tag says manufactured October 1981 and it's titled as an 82 but the Dodge Vin has a 9 in the 6th digit which I think denotes the year the chassis was built which would be 79.

I have a shimmy that I'm trying to fix. It drives great no wander or pulling. Until it gets to 60 or so you can drive it with one hand even when a big truck passes, but when I get it above about 60 a shimmy will sometimes begin and get worse as it goes faster. Sometimes it will be driving perfectly at 65 and then hit a bump or rut in the road and it will start to shimmy. If I'm coming to a curve and wait to start turning into it till I have to turn it a little hard the shimmy will go away.

I have new tires at the proper inflation pressure for the load. When they were installed I had the two that took the least amount of weights put on the front. I also have since put Dyna Beads in the front tires. I'm pretty sure it's not the tires or wheels. I have checked all the tie rod ends and they are tight with no play. I've also checked the king pins and they are tight. The wheel bearings are tight. The steering box has no play in it. What's unusual is the shimmy doesn't shake the steering wheel at all but it shakes the entire coach.

I leveled the coach and put a protractor on the spring pad and I came up with 7 degrees positive. I know this probably isn't very accurate but it seemed a little excessive. I haven't rough measured the toe in with a tape. I'll do that tomorrow.

The camber would require bending the axle to change but the castor is set with tapered shims between the axle and springs. There is a truck shop close by that can do the alignment but I wanted to have the correct specs because I didn't think that they would have them and might just check it and say it's ok.

Do you think the toe in may be the culprit? 



From: txmoparmuscle
Sent: 3/7/2006 5:48 PM

Oops, I forgot to tell you what it is. It's a 36 ft Foretravel with a tag axle.



From: 79brave
Sent: 3/7/2006 8:12 PM

My 78-79 Dodge motor home chassis says M600
camber     +1 deg.
*caster        +2 ""
pivot pin inclination 7.0 deg
toe-in [hub height]  0"-.125"
clearance to bushing .002"
turning angles [2] base tire
            left  37 deg
            right 39 deg
* caster varies with front and rear spring loads [frame slope] and therefore should be checked with the vehicle loaded. caster should be increased if vehicle wanders. caster should be decresed if steering effort is very high, especially when corning.

I hope this is what you are looking for
Hal



From: denisondc
Sent: 3/7/2006 9:52 PM

If it doesnt shake the steering wheel at all, but shakes the entire coach, I would suspect you have a driveshaft problem - bad universal joint, or bad center support bearing. The long wheelbase chassis might have two of the center support bearings.
Usually a shimmy related to an RV wheel happens at speeds like 40 to 50 mph. This is due to the natural frequency of the wheel/hub, which is determined by the mass; close to 200 pounds.
The natural frequency for driveshaft vibration is higher, since it has less mass,: Each section of the driveshaft might only weigh 20 or 30 pounds.
You might want to check the tighteness of the nut that holds the rear yoke onto the pinion shaft too. 



From: DaveVa78Chieftain
Sent: 3/8/2006 8:15 AM

Toe-in can be finicky I believe.  I seem to recall that these ran better closer to 0 rather than at the max (use Hal's data).  Acting up at speed like that is frequently a tire balancing issue.  Did you have a bubble or dynamic balance performed?  I have a simular situation (entire coach shaking but is not felt in steering wheel) but have not resolved it yet.  Engine/tranny rebuild is more pressing at the moment.  It may not be the front tires creating the problem.  Weak springs or shocks maybe the issue.  Once the vibration is setup it may be oscillating.

Dave



From: Slantsixness
Sent: 3/8/2006 9:37 AM

I'm betting on the driveshaft or center bearing being bad. An alignment problem bad enough to shake the front end would be obvious, like worn King Pins, bad tires or wheels ( i agree with Dave on the wheel balancing possibility), and would show up even at low speeds.

Another concern is the tag axle. If the spring are weak on the tag axle, it could be "bouncing" when at speed. I've seen that on busses once in awhile.....

Chrysler made motorhome chassis (by special order) up to 1992, but they are few and far betwen. There was an 88 or 89 360 powered 38 foot mobile medical center on Ebay last month, the thing was Purple and hideous,  but made by Winnebago! I also know where there's an 88 Winnebago on a dodge 360 5 lug budd M600 chassis and it's a full up all fiberglass body built by Winnebago (looks like a Le Sharo, but bigger with a caravan-like front grille and headlights... interesting....It's sitting in a junkyard from a front end collision. At one time, they were trying to sell it to me. It was fixable, but I'm not for sure if it's still all there now, it might be stripped out. Keep in mind there was no PRODUCTION of M series or P series since 1980, these are special order made chassis only. With a Tag axle, this is likely a special order chassis, too.

Tom



From: txmoparmuscle
Sent: 3/8/2006 10:19 AM

Thanks for the replies. It doesn't really feel like a tire out of balance. They were spin balanced when I put them on and I also added Dyna Beads to the front tires. I've also installed new shocks on the front. It's more of a low frequency side to side shake than an up and down vibration, if I change lanes hard or go into a corner a little hard it will go away. The tag axle has air bags and changing the air pressure doesn't make a difference. It definately seems to be coming from the front. I've had the wife sit on the bed in the back and it doesn't seem to shake nearly as bad as the front. I thought about the drive shaft but wouldn't it be more of a high frequency vibration?

DIV>



From: denisondc
Sent: 3/8/2006 12:52 PM

The driveshaft vibration would be fairly high in frequency, and proportional to speed, IF.....it was a 'Bent driveshaft'. It could come and go under loading if it were a U-joint breaking up; but when my center bearing when out - the shaking was intrusive, was not as rapid as a bent driveshaft would be, and was non-linear with changing speed. This was because the failed bearing and its torn-up rubber matrix allowed the driveshaft to wobble out of line under loading and flop around.
My RV had made the vibration and the noise briefly 2 or 3 times before, a few miles earlier, and I was still pondering what it could be and whether I should pull off the road and investigate, when it finally commenced louder/worse and didn't subside until I was almost totally stopped - like 2 mph.
A good way to test might be to jack it up so the drive wheels on one side were airborne. Chock the wheels securely on the side not jacked up of course. Underneath, try to wiggle any part of the driveshaft, including the center bearing. Do this while it is in neutral, so you can turn the driveshaft. There should be Zero movement felt at each of the joints, except for the rotational play between the pinion and bevel gears in the differential.
With some strength you should be able to rotate the driveshaft, and there should be no crunching noises! Maybe some minor brake shoe dragging noises though.
It could still be a siezed up needle bearing though. So start the engine and put it in drive, and see if you can repeat the shaking. Dont run it too fast, 35-40 on the speedo should be plenty. Remember, when only one side of the rear wheels are turning, they are spinning at twice the speedometer indicated speed.
This would be a good time to ensure all of the zerk fittings on the driveshaft have been lubed.
I had a 52 Ford F1 pickup truck, with high mileage. About once each two years I would unbolt the differential cover, and replace the (grade 9 bolts holding the bevel gear to the differential carrier. They would shear off, one by one, the broken pieces dropping harmlessly down to the bottom of the differential housing. I still dont understqand why they didnt all snap off at the same time, but they never did.

The heavier the part that is loose or out of balance, the slower the shaking will be.
You dont have any 'failed' spring shackles or bushings do you? Or a cracked motor mount or rear tranny support?



From: DaveVa78Chieftain
Sent: 3/8/2006 1:16 PM

BTW,
My guess is that Foretravel added the tag axle.  Dave Denison's comment about spring shackles/bushings is in-line with my weak spring/shock thought.  Does it only do it when you have that car trailer hooked up?  (i.e tongue weight making the front end float which could allow wheel hop).  The pic does look like the rearend is riding low

Dave



From: txmoparmuscle
Sent: 3/8/2006 3:56 PM

Yes the tag was added by Foretravel. I think that picture is some what of an optical illusion, maybe the way I was holding the camera, when I put the trailer on it doesn't sag but about a half inch if that much. It doesn't matter if the trailer is hooked up or not, water tank full or empty, waste tanks full or empty, it is about the same. If it starts shaking and I slow down to under 60 it completely goes away. At 55 it is as smooth as silk. It's baffling that the front end shakes like it does but you don't feel it in the steering wheel at all.

The spring shackles and bushings all look ok, I tried moving them back and forth with a large pry bar and they seem to be tight. I checked the driveshaft and it has 4 u-joints and 2 swing bearings and is about a mile long. One of the swing bearings seems to be tight. The other has a slight amount of slack between the rubber cushion and the bearing like the rubber has dried and shrunk a little but it's not all hammered out like it had been beating severely on it. I may try to shim it tight and see if that makes a difference. The u-joints are all tight with no play. I greased them while I was under it. If I pull the shafts to change that swing bearing I'll replace both of them and all 4 u-joints. I don't want to have to do it but once.

The motor mounts and trans mounts are ok. The brake drum on the back of the transmission has no play in it. I have driven it with the dog house off and the engine isn't bouncing around like it was transmitting the shake to the coach.

It just seems that the shaking is way too slow and violent for the drive shaft to be causing it. It just doesn't seem that the drive shaft would have enough mass to shake the whole front of the coach this much. As you move towards the back of the coach the shaking gets less and less. At 60 the drive shaft is turning about 3000 rpm. Wouldn't the shake be more like a high pitched vibration if the drive shaft was the cause?

I checked the toe in with a tape as as near as I can tell it's at zero or maybe toed out a little. I think I'm going to put a little in and drive it and see what happens. I have an appointment Friday to have the front end lined up and I hope that takes care of it. I'll post the results as soon as I get back.



From: txmoparmuscle  (Original Message)
Sent: 3/13/2006 7:05 PM

The alignment shop wasn't able to get to aligning the front end last Friday. I had measured the toe-in with a tape and as close as I could tell it was zero. I decided to put some in so I turned the tie-rod one turn. What a difference! It didn't get rid of all of it but it was nowhere near as bad. It still sometimes shakes a little when you hit a bump in the road but it is just noticeable not scary as it was before. I think I'm going to put another half a turn in and see what happens. I'm also going to have to get the cruise control fixed. On the way to the races Friday night a couple of times I looked down and was running nearly 70 before when it got to about 65 you knew how fast you were going.

Thanks for the help.