Mattb
06-04-2003, 02:35 PM
Here is my set-up: '85 4runner, stock rear driveshaft, approx. 5-6" lifted Alcan rear springs, no drivetrain lift.
I recently installed some new springs in the back of my 4runner, which were a couple of inches taller than my old springs. Following this, I started to get a moderate amount of driveline virbration between 35-45 mph. Based on this, I did some research and determined my pinion was tipped up a bit too high and that I needed to shim the springs to bring the pinion and t-case flanges to where they are parallel. Based on the measurements (top to top of flanges was 11/32" longer than bottom to bottom), I bought some 5 degree shims.
After installing them, the difference between the flanges was less than 1/8" with the pinion being tilted down just a bit too much. Even though the measurements between the flanges are much closer to parallel, the vibrations are now much worse, and I can feel what I think is the u-joints binding a bit when I transition from load to coast. I also feel and hear a grind through the t-case when I coast at freeway speeds.
I spoke with one driveline shop, and their opinion was with my current set-up, I had exceeded the working angle of the u-joint. On this basis, they recommended a CV rear.
At this point, I am going to check the u-joints to make sure they are good condition and consider going to a shorter shim (or to no shim if it truly is a u-joint working angle issue). Before I went through that exercise or considered buying a new drive shaft and re-doing the rear perches, I thought I would ask here on the board if anyone had some relevant advice. Thanks.
I recently installed some new springs in the back of my 4runner, which were a couple of inches taller than my old springs. Following this, I started to get a moderate amount of driveline virbration between 35-45 mph. Based on this, I did some research and determined my pinion was tipped up a bit too high and that I needed to shim the springs to bring the pinion and t-case flanges to where they are parallel. Based on the measurements (top to top of flanges was 11/32" longer than bottom to bottom), I bought some 5 degree shims.
After installing them, the difference between the flanges was less than 1/8" with the pinion being tilted down just a bit too much. Even though the measurements between the flanges are much closer to parallel, the vibrations are now much worse, and I can feel what I think is the u-joints binding a bit when I transition from load to coast. I also feel and hear a grind through the t-case when I coast at freeway speeds.
I spoke with one driveline shop, and their opinion was with my current set-up, I had exceeded the working angle of the u-joint. On this basis, they recommended a CV rear.
At this point, I am going to check the u-joints to make sure they are good condition and consider going to a shorter shim (or to no shim if it truly is a u-joint working angle issue). Before I went through that exercise or considered buying a new drive shaft and re-doing the rear perches, I thought I would ask here on the board if anyone had some relevant advice. Thanks.