Need advice on a problem w/ ride AFTER lift....

[tiger9297]

This may be kind of tough to explain by typing but....... just installed 3" TC springs w/ 4" blocks on '90 K5. I have a high frequency (fast) vibration at high speeds but I'm pretty sure (99%) this is from my U-joints. I am changing them today. However, at low speeds, and I mean 10 mph there is a low frequency vibration (really more of a "shake" than vibration). It feels like when you just begin to roll and have VERY aggressive knobby tires (my tires are new Firestone LeMans (on/off road) and are NOT aggressive at all). I can't figure it out. If the tires were out of balance it would not be noticeable at this low speed, and this goes away when you get above 20 or so mph. Could bad U-joints be causing this type of "shaking" at such a low speed? Everything with my lift has gone great and the truck rides very well other than this. If I need to provide more info. let me know and I certainly appreciate any input. Thanks.

 

[74757685k5]

i have the same problem too. i think its my rear drive line angle.or maybe slip yoke.

 

[tiger9297]

I don't know, which is why I made this post, but if it were the drive line angle wouldn't this still be present at high speeds? Also, I know this doesn't necessarily hold true, but everyone I have talked to says that if you go w/ a 4" lift or less that driveline angles are no problem. Like I said, I simply don't have the answer.

 

[jekbrown]

what front axle do you have? What steering correction devices did you install when you lifted it? have a steering stabalizer?

j

 

[tiger9297]

Everything on the truck is stock. The only thing I changed as far as steering goes is the pitman arm. Any ideas why it's doing this?

 

[primr87]

if the block is tapered then make sure u have it in the right way(the pinion should be pointed up more than stock) if that is correct u could try lowering the t-case by romoving the crossmember bolts and moving the 4 bushings so that they are in between the frame and crossmember. this can help rear d-line anles but it also increases the angle on the front d-line. this is assuming that u have a rear driveline vibe.

 

[tiger9297]

the blocks are in correctly. thanks for the suggestion though. i'm open to anything. will an increased driveline angle make vibrations like this? especially at slow speeds then going away at high speeds?

 

[Kiqman]

Bad Caliper

Had a problem kind of like yours...turned out to be a bad brake caliper. Next time you get out of your ride check to see if either of your calipers is super hot. A lot of times a bad caliper will almost pulsate with slow or speed. Different kind of vibration than a u-joint just like you said. Hope maybe that helps...also could be a bad rear axle bearing or bad brake line to a front caliper.

 

[tiger9297]

Had a problem kind of like yours...turned out to be a bad brake caliper. Next time you get out of your ride check to see if either of your calipers is super hot. A lot of times a bad caliper will almost pulsate with slow or speed. Different kind of vibration than a u-joint just like you said. Hope maybe that helps...also could be a bad rear axle bearing or bad brake line to a front caliper.

Thanks for the advice. I'm actually going to put brakes on this weekend too so I will check that as well.

 

[Blue85]

I've had the same problem, in varying degrees, ever since I lifted my truck. I thought it was a worn slip yoke, but since then I have changed to a fixed yoke and the problem didn't go away. It did get better, though and I attribute that to the longer driveshaft, which reduced the angles. I also had a worn Transfer case to crossmemeber mount once and replacing that didn't change anything. Getting rid of the block and going shackle flip also helped, but it is still there just a little bit.

Your problem could very well be axle wrap. When you accelerate, that block will give you more wrap than you had before, but the problem is compounded by the fact that the U-joint angles are also bigger. The stock rear springs are very soft (which is a good thing for ride). You might have someone watch the pinion (from a safe location) while you brake torque the vehicle to see if the pinion is walking up much. If that pinion angle changes while you accelerate it can cause a vibration.

My advice is to get an angle finder and make sure the pinion is parallel to the T-case output. Sometimes the lift companies sell you the same block no matter what wheelbase you have, so your setup may not be quite right.

 

[tiger9297]

This is why I love this site. I really appreciate the help. I will try to check all of those things over the weekend. I don't want to lose driveability in this truck. It is in pristine condition and I drive it alot. It HAS to drive VERY well. If I were to go to a longer driveshaft where would I buy one, and how much would that run?

 

[Derf00]

Assuming that none of this was present before your lift, I will almost guarantee that it is you drive line angle. You can try lowering your transfercase which will help your angles a little. Every K5 reacts slightly different to a lift. Just because someone else's didn't vibrate, it doesn't mean yours won't. My '90 did. You might check you u-joints to see if they are hitting the stops on the yokes.