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Vibration from lift.........found solution..i think

tiger9297

tiger9297

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Have a '90 K5 w/ TC 3" front springs and 4" blocks in rear. Vibrates at slow and fast speeds. Someone referred me to "Tom Wood's Custom Driveshaft". They told me I needed to have a new shaft with a CV joint up front (behind transfer case). Angle difference b/t slip yoke and shaft is 9 degrees, and b/t shaft and pinion is 4 degrees. Has anyone tried this? I want my truck right and don't mind spending the $450 he quoted me, but wanted to get some input before I did it.
 
a 3inch lift "shouldnt" cause any vibrations at all, i have 8inch springs and zero rates and the thing drive sweet.....no vibrations.
 
bigbadchev84 said:
a 3inch lift "shouldnt" cause any vibrations at all, i have 8inch springs and zero rates and the thing drive sweet.....no vibrations.
Click to expand...

Well, that's what I was told when I ordered this lift kit. BUT, it does vibrate badly. I have replaced both U-joints but it's no better. I am new to this whole "drive line angle" thing, but I'm told that the front and rear U-joints need to run within 3 degrees of each other so one can offset the other's vibration. Like I stated earlier I have a 9 degree difference up front and a 4 degree difference at the rear. NOT good. I guess I could use shims to rotate the rear axle down about 3 degrees. That would get me to 7 degrees at the rear and slightly more than 9 at the front for a difference of 2+ degrees. But this will increase the angle of my driveshaft even more. It will also increase my front angle a little but I don't know how much. I'm just thinking the CV joint may be the way to go. Any input is greatly appreciated.
 
I just bought an 83 Jimmy with 6 inch lift and it vibrated at low speeds.
I was looking through lift kits on the net and noticed alot had a kit to lower the transfercase. I just got some 1 1/2 square tube and added it between the frame and the crossmember. It took care of the vibration :cool1: something is not quiet right if your 3" lift caused vibration though.

not to insult you but the rear blocks are positioned correctly? thicker part facing the rear?
only thing I can think of ..............good luck
 
fatboy said:
I just bought an 83 Jimmy with 6 inch lift and it vibrated at low speeds.
I was looking through lift kits on the net and noticed alot had a kit to lower the transfercase. I just got some 1 1/2 square tube and added it between the frame and the crossmember. It took care of the vibration :cool1: something is not quiet right if your 3" lift caused vibration though.

not to insult you but the rear blocks are positioned correctly? thicker part facing the rear?
only thing I can think of ..............good luck
Click to expand...

Thanks for the reply and I'm not insulted at all. Sometimes the simple things are what we overlook. However, the rear blocks are positioned correctly. The problem ( I think) is the angle on the front U-joint which is 9 degrees. I honestly don't know how you could avoid this though. If you raise the truck (doesn't matter if it's 3" or 8") that angle WILL increase. NO way around it. Is anyone running a CV joint on their truck?
 
I am running a CV , I don't have blocks though , just a shackle flip . I have seen some local trucks on blocks with lift vibe . Mine vibed hardcore from 5 to 45 , like the whole truck shakin' apart .

Regardless of the lift method and angle of rear joint , with a Blazers wheelbase , lifting the truck makes the angle of the joint at the case suck .

Some have had good luck , some have not .

You need either a CV with the pinion pointed straight at the transfercase , OR both front and rear joints angles equal if on blocks or springs .

Now my buddy with Suburban on blocks never vibed , but his shaft is a lot longer .
 
when i had my 3" TC lift i didnt noticed any vibrations but i would eat U joints like every 4 months. now i got a 6" and i still dont have vibrations but go through u joints much faster
 
I really don't think you need a cv shaft with only 3" of lift. It would be better to correct your u-joint angles.
 
when you replaced your u-joints did you put the slip yoke and driveline back exactly? maybe it is out of phase? is it a bad vibration or just enough to know that it is there?
 
I'm 99% sure that I put the slip yoke back in the same way it came out. I'm not sure that would be the problem b/c it was vibrating before I changed the U-joints which is why I changed them. I thought the vibration may be caused since they were now running at a different angle after having run at that same angle for 15 years. Anyway, it is just as bad now as before. Someone said earlier that I should just correct my driveline angles. THAT is what I'm trying to figure out. I don't see how I can correct the angle at my T-case enough to equal the angle at the rear. That is why the CV joint seems, at this point, to be my only solution. Like I said I never dealt with this issue before which is why I made this thread. I knew I could get some reliable info. from the people here. This site is well worth the small amount that a membership costs.
 
tiger9297 said:
Angle difference b/t slip yoke and shaft is 9 degrees, and b/t shaft and pinion is 4 degrees.
Click to expand...
You identified your problem right there. 5 degrees difference must be like riding in a paint mixer :grin: . Shim your pinion down 4-5 degrees and you should be good to go. I would definately try this $20 solution before shelling out several hundred for a C/V shaft.
 
I should mention, too that if you do end up going with the C/V shaft, you will still need those shims, just installed in the other direction.


BTW, if you can, bolt the shims to the spring pack with the center bolt like they were part of the spring so that they can't get spit out.
 
I'd definitely slap a 5* shim in there. Don't worry yourself too much about increasing the angle at the pinion to match the angle at the t-case. TONS of people are running 6"+ of lift without a CV and have had no vibration problems. It's most important that they match, not that the angle be as slight as possible.
 
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