Allison/Single Driveshaft clunk at stop & start

[Billy14]

Had the single driveshaft replacement installed about a month ago. Dealer did a wonderful job removing the carrier brg.

Just before a complete stop & when the brake pedal is released to start, the truck now has a noticeable double clunk. Narrowed it down to the drive train was not unwinding.

Pulled the shaft out & the spline was almost dry with a considerable amount of grey metallic residue. I cleaned out the female spline & smeared a VERY thin film of high-temp grease in the spline teeth & grooves.

Unbelievable difference. Truck runs so smooth & even rides softer on rough surfaces probably because the drive train can flex as it is supposed to. smile.gif Problem is, the clunk is beginning to come back. Dealer says the driveshaft is supposed to be installed DRY. :confused: Go figure!

Anyone think the Transynd would help with it's superior lubricating properties over the Dextron III?

Billy

[BradL]

Billy14,

Mine does the same thing - dealer first installed the one piece dry, I took it back, dealer lubed the shaft, and now it needs to be lubed again.

At the time service writer mentioned may need to go to a nickle plated shaft?

[2DAMAX]

I would think the updated 1 piece shaft should have the nickle plated shaft????

[Billy14]

Are you guys telling me there IS a Nickle plated shaft available from GM or are you suggesting an aftermarket product?

Billy

[Jimamatic]

Billy14.
Sorry to here about your problem. Hope you get it
figured out. Mine does the same thing on the stop
and start, and I have the two piece. after hearing
about your problem with the one piece, I'm not
sure I want to get mine done. I've heard
about the drive train winding and unwinding
before on previous posts. Foregive my lack of
understanding but, what does that mean exactly?
Does the system bind up somehow?

---------------------
01 2500hd cc sb 4x4 D/A

[Billy14]

Jimamatic,

Remember the famous Physics quote? For every action there is a reaction.

Due to the flex of the suspension & chassis along with rubber motor & tranny mounts, the yoke on the differential is constantly pitching up & down. In conjunction with this, if you can visualize the truck starting off (rear end sucks down) & stopping (rear end pitches up). There is about a 3 - 5 degree angle the drive shaft follows from the tranny to the differential. If this angle is increased (by stopping) the measured distance between the tranny & rear end will increase. Something has to give, the purpose of a splined coupling. If the male & female members cannot slide smoothly under a light load they will reach a point of stress, or pressure, where they finally break free under a heavier load. This is the clunk we are feeling. Lubeing the spline on my truck & others is proof this is the problem area because the clunk was completely eliminated, but only for about 2,000 miles.

The scary part is since the spline is not sealed, the grease must be working it's way out probably mixing with the transmission fluid.

This is why I posed the question regarding the Transynd. If it's lubricating properties are better then the Dextron III, maybe it would reduce the friction enough to let the spline slip freely as it should.

Could this be why some are having pinion seal & bearing failure? If the drive shaft cannot slide smoothly, considerable thrust loads will be applied to both the transmission output shaft & the pinion brgs. in the differential.

Billy

[ 04-18-2002: Message edited by: Billy14 ]</p>

[AlaskaDmax]

http://www.nhtsa.dot.gov/cars/problems/

They have TSBs listed for this.

[Jimamatic]

Thanks Billy14. That explains why it could happen
on either the one or two piece shaft. As you
stated, could be causing pinion seal and bearing
failure. I have some dampness showing around my
pinion already with only 4000 miles. Thanks again,
that was a great explanation.

[Billy14]

Hey guys,

Clunk was getting worse so stopped by the dealer yesterday. Service mgr. got on the computer & found no TSB's for my truck for nickel plated spline. He will call GM Monday to see if anything is in the works or comments.

In the mean time, he said a lot of Tahoe's & light trucks had the same problem & they were sent some special grease from GM to lube the spline. Filled a coffee cup full & gave it to me. Said it wouldn't cause any problems if it weeped into the tranny fluid. Came home, pulled the shaft, cleaned out the female end with spray brake cleaner & smeared it heavy into the spline channels as per his & a mechanics instructions. WOW, what a difference. So Smooooooth. smile.gif smile.gif

Couldn't get a make or number on the grease but it should be easily identified. Dark cherry red, really sticky like honey but of course thicker. They claim it clings better & won't wash out like regular bearing grease. Solved the problem on the Tahoes & others for over a year without re-lubeing. I'll wait & see. Post again if he finds anything from GM on Monday.

Billy

[YZF1R]

Remember the old days? They used to have a little gizzy on there called a grease zerk like class 8 trucks. I guess it wouldn't work though if open to the trans.

[acidburn]

Mines doing the same thing at stop and starts, will keep ya posted.
1050 miles on the truck.
I thought it was the trans , what you guys say makes more sense.
We need to figure this out.
I'll share as i collect info etc.
Thx guys,
Gary

[AKDmax]

Mine does something similar. I get a little bump after backing up about 5 feet. That's the only time it does it. 700 miles. Any clues?

[Billy14]

If the clunk bothers you, it's a pretty simple task to find out if this is the problem. (Single drive shaft only).

All you need is an 11mm boxed in wrench & 20 - 30 minutes. I still mark the U joint caps so the shaft can be installed back in the diff. yoke in the same position. Like I was taught in the old days. Slide the shaft out of the tranny (I had to jerk on mine it was so tight).
Clean out the female spline on the drive shaft(spray brake cleaner worked great) & smear a little grease as far in as you can with a wooden tongue depresser. Stick it back in the tranny & work the shaft back & forth a few times. Tighten the caps, hop in, fire her up, & maybe you'll be as amazed as I was. Like a different truck.

WARNING! When asked IF I were to have tranny problems & warranty down the road, my dealer told me not to worry about grease weeping out and mixing with the tranny fluid. Wouldn't hurt. I probably have a satellite watching every move I make now.

Billy

[Derek M]

I had mine in today to the dealer so they could address the bump/slack issue. The updated the PCM so says the work order. PCM not TCM??? After driving it home, condition still exists. Looks as if they'll be getting it back tomorrow.