post lift kit woes

[KohlTrain]

I have just finished with skyjacker 4" w/rear leaf kit. Its an 87 full size jimmy. Truck was perfect when I pulled it in my shop. Now with the system installed I have a mean vibration at all speeds and sometimes a grinding noise at higher speeds. The grinding is especially loud if I throw the auto in neutral while rollin at 55 mph. I have had the driveline out and the universals are tight and lubed. What the heck? Any suggestions? I haven't lowered anything because all the tech line guys said is not neccesary for only 4" lift. Any suggestions greatly apprecitated, I can not figure this one out. Should I change the universals anyway?

 

[perp]

is the front driveshaft rubbin the crossmember or exhaust?

 

[perp]

maybe the rear spring shims are backwards forcing the rear joint angel worse instead of better?

 

[KohlTrain]

I have the thick end of the rear leaf spring shims facing the rear like the instructions stated and the front drive is not binding or touching the exhaust.

 

[perp]

is the rear d shaft a slip yolk or a bolt yolk?
if it is a bolt yolk ( with slip spline in center of shaft ) did you maybe take the two havles of the shaft apart and re-assemble out of phase

 

[Stoner42]

Are the u-joints new? Its possible that they wore in one spot and now that the drivelines at a different angle its cycling from the worn spot to an unworn spot as the shaft rotates.

 

[crowley]

lower your trans/ t-case crossmember!!! the spacers are already provided! there on the top side of the lower frame rail, spacing the nut away from the inside of the frame. install those spacers between the bottom of the frame and the top of the crossmember, tighten the bolts up, it should take care of your problem.
please use a floor jack, and only do one side at a time!

 

[muddybuddy]

i have the grinding noise on my k5, but its with about 9" of lift. its because my driveshaft angle is real bad. you cant really hear it when u have the pedal down, but when coasting it sounds really bad. it also vibrates a bunch. so HAD driveshaft is in the future

 

[mechted]

Dont Use Those "spacers"

those "spacers" will punch some nice holes in your crossmember and render it useless if you get into any sort of flexy situation or hit anything... they redistribute any "twist-load" of the crossmember into those 2 tiny circles rather than the large flat surface and pull right through
do it right and buy some flat steel and cut it to fit (i used 1/4" steel bar from the local hardware store and drilled 2 holes for the bolts and good to go)

 

[csnutrition]

I had a similar problem with vibration after installing a 4" on 76 Blazer. I kinda thought it was something I was going to be stuck with. Luckily the shims Rough Country provides with there lift kits suck and mine shattered . This forced me buying new shims, for which I purchased 6 degree shims. Problem solved. Matter of fact this past Friday I purchased a set of BFG/replacing the TSL Bias and now I have virtually no vibration. Bottom line...get that drive line at the proper angle and you will solve your vibration problem caused by the lift kit

 

[pauly383]

Well , they make shims ( I don't really like )
You can reweld perches ( best , but we all can't do , ask a friend if you can't )
And for those of us with flips , or shimmed up , theres CV's .

If you do a all spring lift , yokes need to equal , yet opposite in angle .

If you do shackle flip , pinion points at transfercase and you run CV .

 

[KohlTrain]

Thanks for the advice. Have the next couple of days off will try to get it smoothed out by then. The vibration is so bad I can hardly stand to drive it. One good thing is the new suspension w/the nitro 8000 ( all i could afford after buying the new leaf kit) shocks rides better than it did stock! Man that old stuff must have really been worn out.

 

[wforicv]

klink

I say replace your ujoints first. When I installed my 4" lift I had the same problem. Replaced the rear ujoint and everything was nice and smooth. It is fairly safe to say you should be just fine with 4" but every truck and lift kit is different.

Eroc

 

[KohlTrain]

I installed a 30.00 t/case lowering kit. Came with some heavy duty steel spacers. Vibration is almost gone and no more grinding noise. Thanks for all the advice.