shudder in 4wd under torque load

[coker6303]

I have a shudder in the drive train that only exist when I'm in 4wd, lock the converter, and roll into the throttle. The more power I push it to the more violent the vibration becomes. No vibration in 2wd, only in 4wd.

Any suggestions on where to start looking for a problem?

Russ

 

[SIKDMAX]

Id say your front driveshaft U-joints most likely.

Also check front diff mounts, CV joints, possibly hubs.

How many miles on the truck?

Edit* Hmmm LMM.... prob low miles./

Modified anything up front? Doubtful, but perhaps check front pipe exhaust for rattles.

How do you feel it? Through the steering wheel or seat or ?

 

[coker6303]

The truck has 41K miles on it.

The shudder is through the body/seat of the truck, not so much in the steering. I have crawled under the truck but I didn't notice anything that stood out. I'll have to do further inspection of the diff mounts and u-joints. This has just developed recently, I'd like to solve it before it does further damage.:thumb:

 

[SIKDMAX]

I take it the truck is offroaded some? Id definitely check the front u joints, or look for signs of rubbing on the front driveshaft from something hitting while torquing under load.

 

[coker6303]

The truck has 245/65r16 street tires on it, so I don't play off road. 4wd is engaged when the roads are slick (during rainy weather) or if I am pulling a heavy load on dirt roads The only front end abuse it has seen is a 4wd launch that I did before learning of the "must do" upgrades on chevy front's. During that launch it hopped and screwed the alignment up some but I never found any damage, had it realigned and went about my business (not doing 4wd launches). The shudder didn't start right after the incident, but 20K miles later (now).

Would it be possible that the t-case mount could be letting it torque in 4wd causing a wobble in the front drive shaft?

 

[coker6303]

If I understand the Chevy front drive train, the front drive shaft, CV's, and ring/pinion are theoretically not supposed to be rotating unless it is engaged in 4wd - Correct?

 

[miles long]

If I understand the Chevy front drive train, the front drive shaft, CV's, and ring/pinion are theoretically not supposed to be rotating unless it is engaged in 4wd - Correct?
I believe they all rotate 100% of the time.

 

[coker6303]

Well I think I stumbled across the answer. I had someone wiggle the steering wheel slightly (again) while I looked at all of the steering components and sure enough, the shaft coming out of the gear box where the pitman arm connects has lateral movement. Looks like it walks side to side approx. 1/8" while the steering wheel is being moved back and forth. Everything else looks to be tight and secure. Anyone seen this before? No oil leaking from the gear box.

 

[krispetersen4]

I have the same shudder in my 2003 with 90000. I can feel it through the floor and not the steering.

 

[Big Block 88]

Are you referring to the intermidiate shaft?? You would fell a clunk and vibration in the floor pedals and steering wheel. It's one GMT800 issues that never got resolved i have removed my shaft twi0ce and filled it with grease and put it back in in just 40K miles

 

[coker6303]

my 4wd shudder is through the floor and not in the steering, which is odd after finding this other problem. As I said earlier, I have a bit of slack in the steering (probably not noticeable unless you are picky) and I found that the splined shaft coming out of the gear box where the pitman arm bolts up has lateral play when you move the steering wheel. You can't feel it bump in the steering wheel, all you would notice is a little extra play that shouldn't be there. When you crawl under the truck and look the shaft is rocking back and forth in the gearbox.

I'm assuming (we all know what assume means!) that the shudder in 4wd is from torque being applied across this new found weak point at the gear box. It would be hard to feel this in the steering wheel since it is a lateral force on the shaft and not a rotational force.

I'm taking it in tomorrow morning to see if the dealership will replace it under warranty as I took my truck in for warranty work a while back (door lock actuator went out) and brought the loose steering feel to their attention, they "checked" it over and aligned the front end. I am out of warranty now but he said that since it was on the service write before and the problem is related then there should be no problem with covering it under warranty.

Since I'm not sure if this is causing the shudder or not, I will have to keep yall posted after the gearbox issue is solved! :thumb:

 

[coker6303]

Are you referring to the intermidiate shaft?? You would fell a clunk and vibration in the floor pedals and steering wheel. It's one GMT800 issues that never got resolved i have removed my shaft twi0ce and filled it with grease and put it back in in just 40K miles

I thought GM solved this issue on the new body 2007.5+??

 

[Big Block 88]

Maybe an LMM owner will chime in but as far as I know the steering issue is still there. I know my buddies 08 LMM has the steering clunk from the intermediate shaft