# Shudder under load.



## dlcs (Sep 2, 2004)

My '99 Silverado 2500 w/6.0 auto makes shudder under load. I notice when i pull a trailer or have a pallet of salt in the bed. Has been doing this for quite awhile, not anything new. U joints have been raplaced recently, new plugs. I'm not sure what causes this, does nayone else expirience this problem?


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## fatboy (Dec 6, 2006)

I had this in my 02 2wd chev and i thought the trans was on its way out, then i noticed a u joint squeak when i back up so i replaced all the u joints and its gone! sounded crazy to me too, maybe coincidence, I don't know!!!


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## sweetk30 (Sep 3, 2006)

what kind of spark plugs? the newer vehicles are vary vary fussy on the brand and model plugs put in them. i have had lots of skips under load and bad idel problems trace back to the i just did my own tune up. and thay installed wrong plugs. 

so with that did you install acdelco correct plugs in your gm?


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## dlcs (Sep 2, 2004)

sweetk30;356965 said:


> what kind of spark plugs? the newer vehicles are vary vary fussy on the brand and model plugs put in them. i have had lots of skips under load and bad idel problems trace back to the i just did my own tune up. and thay installed wrong plugs.
> 
> so with that did you install acdelco correct plugs in your gm?


Yeah, they were Acdelco. The funny thing is it only does it when taking off from a dead stop, very short shudder.


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## Bad Luck (Sep 30, 2004)

dlcs;356978 said:


> Yeah, they were Acdelco. The funny thing is it only does it when taking off from a dead stop, very short shudder.


Have you ever had your driveshaft dropped and the splines lubed?


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## dlcs (Sep 2, 2004)

Bad Luck;357074 said:


> Have you ever had your driveshaft dropped and the splines lubed?


We did that when we change the u-joints. I'm just hoping its not the transmission.


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## Sydenstricker Landscaping (Dec 17, 2006)

Could it possibly be the rubber trans/transfer case mount be loose or bad??? Or maybe a bad motor mount? Im not a mechanical genius, just shootin a few ideas for ya


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## fatboy (Dec 6, 2006)

Mine was the same, just when pulling away, very short and went away quick. Did your problem start after the u joints were changed? not trying to be a smart ass or anything but it sounds exactly like what mine did!


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## dlcs (Sep 2, 2004)

All the u-joints have been replaced and the back two have been replaced twice. The problem was there before I changed them and its still there after they were change. Funny thing is you don't feel it unless you have a load in the bed or pulling a trailer. Seems when it shudders, the the back end of the truck is sagging a little from the weight. I know my springs are a little weak, I just wonder if when the truck sags it puts the drive shaft at a weird angle, causing the u-joints to bind?


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## dlcs (Sep 2, 2004)

thermos;357128 said:


> Could it possibly be the rubber trans/transfer case mount be loose or bad??? Or maybe a bad motor mount? Im not a mechanical genius, just shootin a few ideas for ya


Might be? I'm going to try and get it in the shop tomorrow. I'll have them check the mounts too.


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## fatboy (Dec 6, 2006)

sounds like you could be on the right track with that.


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## B&B (Nov 4, 2006)

dlcs;357199 said:


> Funny thing is you don't feel it unless you have a load in the bed or pulling a trailer. Seems when it shudders, the the back end of the truck is sagging a little from the weight. I know my springs are a little weak, I just wonder if when the truck sags it puts the drive shaft at a weird angle, causing the u-joints to bind?


Your real close there. This isn't an uncommon problem on these truck's as GM put a bulletin out for this (although it wasn't just for when the truck was loaded). What happends is the splined yoke at the front of the drive shaft develop's a wear pattern in a specific spot on the spline's and when you load the truck down is pushes the yoke forward to an unworn section of the yoke and then the yoke bind's up on the mating spline's on the T-case output shaft. Replacing the yoke will fix your problem.


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## dlcs (Sep 2, 2004)

B&B;357259 said:


> Your real close there. This isn't an uncommon problem on these truck's as GM put a bulletin out for this (although it wasn't just for when the truck was loaded). What happends is the splined yoke at the front of the drive shaft develop's a wear pattern in a specific spot on the spline's and when you load the truck down is pushes the yoke forward to an unworn section of the yoke and then the yoke bind's up on the mating spline's on the T-case output shaft. Replacing the yoke will fix your problem.


Can you post the number of that TSB. My dealer says they can't find it. I take my truck in this afternoon, we'll see what happens. Thanks for the help.


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## B&B (Nov 4, 2006)

I'll see if I can dig up the number.


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## B&E snowplowing (Oct 4, 2006)

*Shudder Under Load*

I had the EXACT same problem, changed everything, I was about to even change the front axles, when we found out I had a cracked flywheel, changed flywheel, problem gone.

Hope that helps


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## B&B (Nov 4, 2006)

Here's the GM bulletin.....Clunk, Bump or Squawk when Vehicle Comes to Complete Stop or Accelerating from Complete Stop (Replace Rear Drive Shaft Nickel-Plated Slip Yoke) #01-04-17-004 - (Oct 5, 2001)
Clunk, Bump or Squawk when Vehicle Comes to Complete Stop or Accelerating from Complete Stop (Replace Rear Drive Shaft Nickel-Plated Slip Yoke )
1999-2002 Chevrolet and GMC Extended Cab Short Box Pickup Models (Silverado and Sierra)

with 4L60-E (RPO M30) or 4L80-E (RPO MT1) Automatic Transmission and Automatic 4WD (RPO NP8)

Condition
Some customers may comment on a clunk, bump or squawk noise when the vehicle comes to a stop or when accelerating from a complete stop.

Cause
A slip/stick condition between the transfer case output shaft and the drive shaft slip yoke may cause this condition.

Correction
Replace the rear drive shaft slip yoke with a new nickel plated slip yoke, P/N 12477702 (1500 Series) or 12477704 (2500 Series).


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## dlcs (Sep 2, 2004)

Thanks for all the help guys.


I got my truck back this afternoon. They showed me the same bullitan that was posted above and said that doesn't apply to my truck. They said my slip yoke was ok. They said that they have heard the same problem on other extended cab, long bed trucks and have under warranty replaced the driveshaft with a one piece unit and took care of the problem. But they said it wouldn't hurt a thing to leave it alone and to replace it would cost me $800. I don't want to spend $800. They told me that when the truck is squating from a heavy load or trailer it puts a bind on the two piece driveshaft and causes a short shuder when accelerating from a complete stop. One thing they suggested was to put a set of air bags on to stop the squating when hauling a load. I appreciate all the help.


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## Rcgm (Dec 17, 2000)

[email protected];357129 said:


> Mine was the same, just when pulling away, very short and went away quick. Did your problem start after the u joints were changed? not trying to be a smart ass or anything but it sounds exactly like what mine did!


LOL Mine does the same thing started after u joints were replaced.

RCGM
Brad


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## Rcgm (Dec 17, 2000)

B&B;357614 said:


> Here's the GM bulletin.....Clunk, Bump or Squawk when Vehicle Comes to Complete Stop or Accelerating from Complete Stop (Replace Rear Drive Shaft Nickel-Plated Slip Yoke) #01-04-17-004 - (Oct 5, 2001)
> Clunk, Bump or Squawk when Vehicle Comes to Complete Stop or Accelerating from Complete Stop (Replace Rear Drive Shaft Nickel-Plated Slip Yoke )
> 1999-2002 Chevrolet and GMC Extended Cab Short Box Pickup Models (Silverado and Sierra)
> 
> ...


SO is it ok to not do anything?

RCGM
Brad


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## kysnowman (Jan 6, 2007)

I've got a dodge 3500 and my truck is doing exactly the same thing. I've got over a 100K and it's been doing this since 50K. Dodge calls it shutter shift I believe were the drive shaft lines up. 
Mine does it when I take off from about 4mph to 12mph. It's gotten worse over time. Dodge has worked on it 4 times and says that's the best we can. It's gotten worse and called them again now they say U-joint.
I know you just replaced your U-joints but it still could be it, or your drift shaft not lining up. I believe it's one of those two are my problems. I would like to see what you find out.


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## kysnowman (Jan 6, 2007)

You will probably find it will get worse with time. Mine used to do it only under a load and now it does it empty. But it's awful loaded sound and feels like something is about ready to drop.


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