driveline slack?

[lb7lbz]

alright guys i know there have been a bunch of posts about this,but i havnt seen an answer yet. both my truck 01 ext. cab and my friends truck 02 ext. cab do the exact same thing. when you stop you get a clunk and again on takeoff clunk. i know by experience that you can somewhat control this by how you stop and go.niether of these trucks did this when new, so there has to be a solution. i'm tired of hearing "they all do it live with it", if it didnt do it for the first 100000 miles there has got to be something wrong now. could anyone point me in the right direction? this is very irratating hauling a trailer through stop and go all day. thanx in advance

[Hook_'em_Horns!]

alright guys i know there have been a bunch of posts about this,but i havnt seen an answer yet. both my truck 01 ext. cab and my friends truck 02 ext. cab do the exact same thing. when you stop you get a clunk and again on takeoff clunk. i know by experience that you can somewhat control this by how you stop and go.niether of these trucks did this when new, so there has to be a solution. i'm tired of hearing "they all do it live with it", if it didnt do it for the first 100000 miles there has got to be something wrong now. could anyone point me in the right direction? this is very irratating hauling a trailer through stop and go all day. thanx in advance
My '02 started doing the same thing around 87k, traded at 97k. I suspected wear in the ring and pinion, although that usually has some whine frequency to go along with it that I didn't have.

Start with a drive-line shop to pull the drive-shaft assembly and check the u-joints, carrier bearing and balance while your there. Then pull the cover and inspect the rear. Next is the Allison.

I didn't want to deal with it, the 100k warranty was coming up, I needed a complete brake redo, the tires were worn and the harness for the Cruise control had an intermittent short. They were giving 'em away with employee pricing, so I traded away the problems for the same model with more options and a lower payment.

[mr. monte]

if these are 4 wheel drive, in might be the transfer case chain has stretched

[DmaxMaverick]

It's not that complicated. The vast majority of "clunk after a stop" complaints are caused by the driveshaft spline. Numerous threads and TSB's on it. Lube it, and it'll disappear for a while (until the lithium grease dissipates).

A distant second cause is driving habit. If you are a "two foot driver", the tranny won't shift to 1st gear until there is 0% throttle input at 0 MPH. If you have the slightest throttle input, and creep through a stop, the abrupt downshift to 1st happens as soon as you pour on the coals. Later TCM programming reduced this condition considerably.

The 2001 models were the worst for these issues. Later models are progressively better, but can still present under the right (wrong) conditions in any model year. There could be a mechanical slack issue happening, but it is very rare and unlikely. Don't go looking inside gearboxes until you've eliminated the most common, easy fixes........Unless you have a particular taste for untamed waterfowl.

[dually2002]

Had similar problem on 02. When stopping from a speed that the tranny was in 5th gear upon almost reaching a dead stop I would get a shudder in the drivetrain like the tranny was shifiting into 1st gear but was already in 1st. Upon releasing brake after dead stop it would do it again and the whole cycle would repeat itself after another shift cycle. Bought truck with 25k and did this continuously until 65k when I installed Kennedy custom tune PCM. The problem has vanished. This problem was driving me nuts and is the main reason I joined the fourm to try and get a handle on it. Since the problem disappeared when the programming on the power control module was changed leads me to think it is a blurp in the factory programming. Shudder is not a good definition. It was like a normal downshift but down shifiting to an non existing gear.

[Hook_'em_Horns!]

On my ’02 I had experienced the occasional near stop shifting issue, almost to a stop and change to go but I attributed that to my confusing the Allison in to thinking I was truly stopping. It learned from the mistake and later never occurred. And occasionally after stopped the 'Clang' would make you think, "what the?"

The ‘Slack’ I was describing (and, I believe lb7lbz also) is from leaving a stop a noticeable ‘Clunk’ as in loose slack in the drive-line. When going from Forward to Reverse, the same slack is apparent also.

When you’re backing a trailer and during pull-ups is when it is the worse while shifting back and forth under load, at times ‘Clanging’.

[DmaxMaverick]

On my ’02 I had experienced the occasional near stop shifting issue, almost to a stop and change to go but I attributed that to my confusing the Allison in to thinking I was truly stopping. It learned from the mistake and later never occurred. And occasionally after stopped the 'Clang' would make you think, "what the?"

The ‘Slack’ I was describing (and, I believe lb7lbz also) is from leaving a stop a noticeable ‘Clunk’ as in loose slack in the drive-line. When going from Forward to Reverse, the same slack is apparent also.

When you’re backing a trailer and during pull-ups is when it is the worse while shifting back and forth under load, at times ‘Clanging’.

Sounds like driveshaft spline/yoke. Try greasing it (inside the yoke).

Starting, stopping, forward to reverse, reverse to forward, backing, pulling, pushing, etc., is causing spring wrap and driveshaft angle changes. Very likely your issue. Grease is cheap, but go ahead and start replacing hard parts if that's your fancy. You may have something worn beyond spec or broken, but it isn't the case, more often than not. If you are already scratching your head, doing so after the simple checks doesn't cost you any more.

[Dinkie Diesel]

When you stop you get a clunk and again on takeoff clunk. I know by experience that you can somewhat control this by how you stop and go.niether of these trucks did this when new, so there has to be a solution. i'm tired of hearing "they all do it live with it", if it didnt do it for the first 100000 miles there has got to be something wrong now. could anyone point me in the right direction? this is very irratating hauling a trailer through stop and go all day. thanx in advance

I have the same thing going on. Not so much when I'm stopping but when I take off. A faint clunk is heard everytime. I crawled under it this week and checked U-Joints, shocks, springs shackles, etc. I don't see anything that is out of order. I looked at that bellows covering the drive spline. I looked for a zerk but don't find one. How are you supposed to grease this spline? I have a 2001 Crew K2500 with 63,000 on it.

I did find that the drivers side overload spring in the rear has lost both the front and rear snubber so it metal to metal contact when the overload kicks in but that's not the noise/clunk I am hearing.

The spline sounds plausible. Can I take the drive shaft loose and put Moly Paste on the spline?

[DmaxMaverick]

The yoke spline is lube by removal and packing. No grease zerk.

The spring insulators missing is not new. I had mine replaced just about monthly while under warranty. Haven't replaced them since the warranty ran out. They are too expensive, and the noise isn't that bad. At least not bad enough at $15+ ea, dealer list.

[Dinkie Diesel]

It's not that complicated. The vast majority of "clunk after a stop" complaints are caused by the driveshaft spline. Numerous threads and TSB's on it. Lube it, and it'll disappear for a while (until the lithium grease dissipates).

A distant second cause is driving habit. If you are a "two foot driver", the tranny won't shift to 1st gear until there is 0% throttle input at 0 MPH. If you have the slightest throttle input, and creep through a stop, the abrupt downshift to 1st happens as soon as you pour on the coals. Later TCM programming reduced this condition considerably.

The 2001 models were the worst for these issues. Later models are progressively better, but can still present under the right (wrong) conditions in any model year. There could be a mechanical slack issue happening, but it is very rare and unlikely. Don't go looking inside gearboxes until you've eliminated the most common, easy fixes........Unless you have a particular taste for untamed waterfowl.

I am giving thought to using a product made for Honda motorcycles. They specify a Moly paste 60% for their rear shaft driven splines. Think this will work on the driveshaft spline of my truck? I am so sick and tired of feeling/hearing that clunk!!!

[DmaxMaverick]

Molybdenum disulfide grease (Moly) is good stuff for high pressure/load applications (was specified for most aircraft landing gear, until recently). Lithium is better. You'll have to check on your brand of Moly compatibility with ATF, which is in the TC (or tranny if 2wd). One may break down or diminish the other, as the spline isn't isolated from the gearbox lube.

[dually2002]

I had the same symptoms on my dually and I changed the centering bearing or carrier bearing and for the time being the problem is gone. The rubber surrounding the old bearing on the bottom was collapsed. I'm figuring that it threw the geometry on the drive shafts off enough that the rear shaft was buckling instead of sliding evenly for and aft like it should. The shaft that has the male splines the one that hooks to the differential has a light blue coating or plating on it. The female end of the other shaft had a light coat of grease that was still good. I assume that using this plating,grease and the weather boot is why its a non serviceable component. I replaced it with a new GM bearing and the rubber is beefier than on the old bearing. This is a pressed on bearing so if you change one make allowances for it. I took mine to a machine shop to get replaced. I would use a GM bearing because the machine shop I went to replaced a NAPA brand bearing with about two weeks service on it with a GM bearing a few days before he did mine.

[Dinkie Diesel]

Molybdenum disulfide grease (Moly) is good stuff for high pressure/load applications (was specified for most aircraft landing gear, until recently). Lithium is better. You'll have to check on your brand of Moly compatibility with ATF, which is in the TC (or tranny if 2wd). One may break down or diminish the other, as the spline isn't isolated from the gearbox lube.

I don't think my slip joint is in the transmission tailhousing. I believe mine is a two-piece driveshaft and the spline is outboard of the tranny. 2001 2500 Crew Cab 4x4 8ft bed. If I remember this is not the one that had the recall for that big tube aluminum replacement prop shaft. Thanks for your help and input.


Jeff

[DmaxMaverick]

I don't think my slip joint is in the transmission tailhousing. I believe mine is a two-piece driveshaft and the spline is outboard of the tranny. 2001 2500 Ext Cab 4x4 8ft bed. If I remember this is not the one that had the recall for that big tube aluminum replacement prop shaft. Thanks for your help and input.


Jeff

Ex-cab/LB, and CC-SB (both 4x4) were the models most effected by the "launch shudder", and the campaign replacement of the 2 piece prop shaft with the telephone pole aluminum single. Shorter and longer wheelbase trucks didn't have the issue (or there were too few complaints to address it). Launch shudder and spring wrap are two entirely different issues, with unique remedies. "Frame beaming" is/was another issue associated with very long wheelbases, but again, a different issue/remedy.

Your truck has 2 slip-yokes. One at the TC, and the other at the carrier. Still, the 2 piece shaft carrier bearing and isolator are maintenance items ("wear" items), requiring service periodically. Service intervals are dependent on service type, climate, and driving habits. I have seen a design change of the carrier isolator, but don't know if this was an "improvement", or just a tooling change. They haven't been in service long enough to say they last any longer under the same conditions.

[Dinkie Diesel]

Thanks Maverick,
I just completed the task of smearing a little grease on the spline on my two-piece prop shaft at the carrier bearing. All I can say is "Blow me down" (Popeye). I was so sure before I started this it wasn't going to help the problem and even more so I was not going to have a good time getting the cross bearing strap bolts loose or the bellows off at the joint. It all came right off, easily. I smeared a little grease on both the male and female sections of the spline and slapped it back together. Took it for a test drive and Viola!!!! It doesn't clunk anymore. After sliding the joint apart I would have bet big money that this wasn't the problem as there was still some grease visable and the spline was smooth sliding apart.
I have been going over this in my mind so many times for years now. Thought it could have been fuel splash. Broken spring. U-Joint. Brakes. Allison not downshifting to first. Body joint. I refused to believe it was the spline. Now after spending 8 minutes on this much covered problem, my truck runs like a brand new one without the clunk. Mine was so bad I was getting 1, 2 and sometimes 3 clunks as I accelerated.

ps I made a typo (now corrected) in my response above. I have a Crew Cab not Ext.


Thanks again guys

[mattb5150]

I have an 03 extra cab short bed, so a one piece driveline. Just had the transfer case repaired with the adapt-a-case from Kennedy to prevent the case wear thru and a new rear case half, around $1k with parts and labor, and now I have the clunk. Don't think I had it before and I can manipulate it if I very slowly come to a stop. I read this post and was prepared to grease the splines. However once I pulled the shaft out it had ATF on it, Mobil 1 ATF that I just had them put in so I won't have to worry about it for a while. I don't see how greasing the splines will help if they already have ATF on them? Also don't want to contaminate the ATF with the grease going into the case so I put it back together without adding grease. Any thoughts? Could it need a TCM reflash instead?

Matt

[DmaxMaverick]

The spline is bathed in ATF, absent the grease.

Grease it. Be happy. No clunk. And the grease won't "contaminate" your ATF.

[DILYSI Dave]

New guy here - be gentle.

I just picked up a 2002 2500HD with the Allison. Crew cab, Long bed, 2WD. I've got the clunk. Sounds like some greasing is in order. Anybody got any tips / how to? Does the front spline just slide out of the trans? Will I lose fluid when it does? How about the rear? Just a U-Joint with a couple of straps, or is it something fancier? I've owned the thing for ~48 hours and haven't even climbed under it yet, so if it's all very obvious stuff, I apologize for the dumb questions.

[DmaxMaverick]

New guy here - be gentle.

I just picked up a 2002 2500HD with the Allison. Crew cab, Long bed, 2WD. I've got the clunk. Sounds like some greasing is in order. Anybody got any tips / how to? Does the front spline just slide out of the trans? Will I lose fluid when it does? How about the rear? Just a U-Joint with a couple of straps, or is it something fancier? I've owned the thing for ~48 hours and haven't even climbed under it yet, so if it's all very obvious stuff, I apologize for the dumb questions.

Welcome aboard, Dave!

If ALL you are doing is greasing the spline, it is simple (actually more simple on a 2-piece shaft, like yours). Drop the center carrier, and it will allow enough to slide out the yoke from the tranny (it just slides out, nothing holding it in). Otherwise, you can remove the U-joint. There will be some ATF leakage, but how much depends on the fluid level (don't top it off until AFTER the grease job) and the attitude the truck sits. To minimize leakage, point the truck downhill a bit if you can. It helps to jack/stand the rear for a little extra working room, and helps minimize leakage. If you are on a level surface, the trucks are normally (OEM) in a nose-down attitude, so that helps a little. If you have the nose (grill) higher than the rear, it will leak more. Either way, have a pan handy to catch what runs/drips out. If your ATF level was good before you started the job, just add back about the amount lost during the grease job (fresh ATF, don't put back the stuff that leaks out). If it's a cup or less, don't worry about it at all. The tranny won't miss that little amount. The tranny has an over/underfill margin of about a quart, so if you are in the range, it'll be happy.

Also, if you are leaving the rear wheels on the ground, set the E-brake and place the tranny selector out of P, then back to P. This will unload the shaft (releases the parking pawl), so you won't have to fight it later.

And....Never any dumb questions around here. Sometimes some dumb answers, though....

[mattb5150]

Wow,

I shouldn't have doubted you Mav, this worked great on my truck now it as smooth as silk when I come to a stop.

Matt

[DmaxMaverick]

Wow,

I shouldn't have doubted you Mav, this worked great on my truck now it as smooth as silk when I come to a stop.

Matt

That's great! Glad to be of service.

[mattb5150]

Shortly after my last posting the clunk returned intermittently, even after greasing the drive shaft splines. Then I started looking at my records and found that I was overdue for a transmission fluid change. Had a local shop remove all old fluid and put in Valvoline synthetic ATF, no more clunk since then.

Matt