Bad vibration in 4x4 under acceleration

[2003tv]

Its in the chassis the front end will shake up to 30mph then go's away if i put it in 4whd past 30mph it does't do it all

[navigator]

In the first post you mentioned that you have replaced a good number of front end parts.
Did you replace them to correct the issue or did the issue happen after you replaced them?

[navigator]

this is a wild guess because it seems like you have tried everything else...
do you have any vibration at idle when in gear?
Could it be your motor mounts? I would think they would show their issues in 2wd as well as 4wd but just thought I would ask.

[Trail X]

Its in the chassis the front end will shake up to 30mph then go's away if i put it in 4whd past 30mph it does't do it all

Did you follow my diagnosis method? I would try that, it sounds like a resonant vibration if it goes away above 30. If it is a resonance, then you will need to determine the out of balance item.

[2003tv]

I have no vibration at idle when in gear but i will look at the motor mounts so what should i look at for out of balance item

[Trail X]

I doubt its the motor mounts. Are you reluctant to go through the routine I suggested?

[2003tv]

Are you talking about this routine ??? remove both the left and right CVs, and then throw it into 4WD and drive it. That will at least eliminate or incriminate the CVs.

If you still have vibrations, then remove the front prop shaft and drive in 4WD, that will then help you determine if its in the transfer case or in the diff.

[navigator]

yup, I think that is what JD was referring to.

[2003tv]

OK I wes just checking I have not done it yet trying to find a good weeken to do it but i will let you all know when i do and what i find out

[Opeth]

My money is still on cv shaft angle. I'm not paying for a set of RCV shafts to trial and error it either, I'll live with the shimmy till I can find someone who'll make me a set for >$1,000.

[2003tv]

Where is the cheapest and the best place to get RCV shafts

[Opeth]

Where is the cheapest and the best place to get RCV shafts

http://www.rcvperformance.com/categorie ... _AXLES_ALT

$2,500 a set.... Yea, not exactly cheap and are built per application.

[Trail X]

I'm still not sure it's the CV angle. Why would that provide vibration only in 4WD? He's tried different CV shafts, taken out lift, and neither has helped.

[Opeth]

I'm still not sure it's the CV angle. Why would that provide vibration only in 4WD? He's tried different CV shafts, taken out lift, and neither has helped.

I have the exact same issue here as everyone else. Here is my thought process behind my theory.

Before my lift I had no wheel vibrations in 2hi or 4hi.

I used marks 3" lift kit with z71 springs and rear blocks. Brand new Bilstein front struts and rear shocks all installed the same weekend.

Post lift w/ stock wheels- I had a rear end vibration now that is minimal which was not there the day before. Changed pinion angle / driveshaft angle or dried u joint cup is most likely the culprit as that issue is widely known with any lifted truck.

4wd w/ stock wheels- front end now has a vibration/ side to side wobble only under acceleration, coasting there is no vibration no wobble. Thus this is a driveline/ torque issue and is coming from the front end somewhere.

Parts/fixes thrown at truck:

4 different alignments ( only thing out of whack is caster, but amount is equal on both sides and shouldn't be an issue)
New wheel bearings
New wheels/ tires road force balanced. ( some of the rear vibrations were masked by weight of tires and wheels and have to really accelerate and vibration is still there)
Flipped upper control arms.

Problem still exists, only thing changed since lift is the angle of the cv shafts. The lift is putting the cv shafts out of optimal range, same syndrome that occurs to the rear drive shaft and pinion angles. Replacing cv shafts with same cv shafts is not doing anything because they are all the same lengths. I'm wondering if even lengthining the intermediate shaft 1/2" would help push it further back into the tripod closer to where is was stock. Being lifted its pulling out wards but how much? I don't know and would require boot sacrifice to see.

[navigator]

Cody, you think it is the CVs causing the vibration. My only question is that there are a bunch of folks with the same lift, many with more lift that haven't had the vibration issues.

Has anyone tried removing the CV's as JD suggested and driven that way?

[dvanbramer88]

I'm still not sure it's the CV angle. Why would that provide vibration only in 4WD? He's tried different CV shafts, taken out lift, and neither has helped.

I have the exact same issue here as everyone else. Here is my thought process behind my theory.

Before my lift I had no wheel vibrations in 2hi or 4hi.

I used marks 3" lift kit with z71 springs and rear blocks. Brand new Bilstein front struts and rear shocks all installed the same weekend.

Post lift w/ stock wheels- I had a rear end vibration now that is minimal which was not there the day before. Changed pinion angle / driveshaft angle or dried u joint cup is most likely the culprit as that issue is widely known with any lifted truck.

4wd w/ stock wheels- front end now has a vibration/ side to side wobble only under acceleration, coasting there is no vibration no wobble. Thus this is a driveline/ torque issue and is coming from the front end somewhere.

Parts/fixes thrown at truck:

4 different alignments ( only thing out of whack is caster, but amount is equal on both sides and shouldn't be an issue)
New wheel bearings
New wheels/ tires road force balanced. ( some of the rear vibrations were masked by weight of tires and wheels and have to really accelerate and vibration is still there)
Flipped upper control arms.

Problem still exists, only thing changed since lift is the angle of the cv shafts. The lift is putting the cv shafts out of optimal range, same syndrome that occurs to the rear drive shaft and pinion angles. Replacing cv shafts with same cv shafts is not doing anything because they are all the same lengths. I'm wondering if even lengthining the intermediate shaft 1/2" would help push it further back into the tripod closer to where is was stock. Being lifted its pulling out wards but how much? I don't know and would require boot sacrifice to see.

But have you pulled the CV's and driven around in 4hi to confirm? While everything you said has good logic, it's still just a guess.

[plaen]

But have you pulled the CV's and driven around in 4hi to confirm? While everything you said has good logic, it's still just a guess.

I'd be interested in the results of this. If he doesn't have immediate time, I can do it in 2 weeks and report back my findings.

[2003tv]

I am going to try and do it Sunday if all possible

[Opeth]

Cody, you think it is the CVs causing the vibration. My only question is that there are a bunch of folks with the same lift, many with more lift that haven't had the vibration issues.

Has anyone tried removing the CV's as JD suggested and driven that way?

It's the same situation that applies to lifted trucks, some get the vibrations and some don't. I went through this same crap with my tuner car I had, but I was getting the vibrations from being too low. I lowered my car 2.0" front and 2.5"rear. I couldn't figure out why since there were guys that were even lower than me with no issues. I went with a less aggressive drop by Eibach 1.5" and cured the problem. I also added stiffer control arm bushings by pro thane and my car was amazing after that.


I honestly don't know why this is the case, mileage could be a factor, different amounts of corrosion in suspension parts from salt v. Non salt regions, could be a multitude of things but I am still willing to put money on the angles of the cv's being the culprits, just because I've went through the same scenario before.

I've spent hours looking at the same issue on other IFS lifted trucks, most have ways to drop the diff or add shims to bring the angle of the joints back closer to factory. Obviously our platform has almost no aftermarket support and GM's stupid through oil pan design prevents us from lowering the differential to cut back on angle. So our only option I think is playing roulette with the cv's and seeing if some work could be done to them. ( e.g. Lengthining the shaft 1/4"-1/2")

Has anyone with this same issue not flipped their upper control arms?

I haven't had the time to pull mine out, I'm on vacation this week and were getting a snow storm now and then I leave for Vermont Wednesday for a ski trip.

[Trail X]

You don't have to destroy your cv boot to check the engagement. Just take off the back clamp, and pull the boot back. When you're done, just put a pipe clamp in place. But I understand what you're saying. You're guessing that the tripod engagement is such that the roller is exiting the tripod at the top of its rotation? That could be the case, but the only way to check is to pull off a boot and look. Also, if the vibration frequency is 3x the wheel rpm, then that could also suggest the tripod joint.

If that is the case, then the different aftermarket cvs could prove to make a difference, as they are never made 100% the same between the brands.