what degree of shims?

audie.a · Jan 15, 2005

I have a 93 bronco with a 8'' lift..does anyone know if im suppost to add a shim to the stock one on the rear ..i have a slight vibration..it has a rancho 4'' leaf then the stock 7 degree shim and a 3 3/4 block..the vibration is between 30 and 40 mph..i have almost tried everything to get rid of it,but cant seem to do it....any suggestions..anything would help..............

Justshootme84 · Jan 16, 2005

Simple fix is to check the angle of the driveshaft to the pinion yoke on the rear axle. IT should be zero degrees, or straight in. If this is the case and you still have the vibration, you may have enough "axle wrap" with those blocks to throw this angle off. Other causes would be an out-of-balance tire, or the rear driveshaft, either a bad u-joint, the double-cardan joint or slip joint binding on you.

audie.a · Jan 16, 2005

Justshootme84 said:
Simple fix is to check the angle of the driveshaft to the pinion yoke on the rear axle. IT should be zero degrees, or straight in. If this is the case and you still have the vibration, you may have enough "axle wrap" with those blocks to throw this angle off. Other causes would be an out-of-balance tire, or the rear driveshaft, either a bad u-joint, the double-cardan joint or slip joint binding on you.

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i have had the rear end apart trying different shims and degrees about 8 times, and as far as the axle wrap it had the same vibration when it only had the 4'' rancho lift with no blocks.i have had the tires checked and put a different driveshaft on it(from my buddies 93 bronco) and it still continues to vibrate i dont know what else to do!!!!!!!!!

Justshootme84 · Jan 16, 2005

Sounds like the ds-pinion angle thing is O.K., then? Next thing I'd try is to lower the transfer case an inch or so. I had todo that with a Rancho kit on a truck. It had the spacers in the kit, and I needed them to reduce the ds angle to the t-case.

audie.a · Jan 16, 2005

I have already lowered it 1 1/2 inches so i still dont know,and i had new gears and a locker put in it about 3 years ago and i just delt with the vibration but now its just mostly pissing me off. :angry:

Justshootme84 · Jan 17, 2005

Wow, I've come up with about evrything I could think of that might cause this problem, it must be something internal in the rear axle or drivetrain. Maybe someone else has an answer for you.

audie.a · Jan 17, 2005

thank you for your suggestions..i really appreciate it..if you think of anything else PLEASE let me know.....

dicain · Jan 20, 2005

i had a vibration and the next thing you know. boom the spider gears turned into mush.

highboy73 · Jan 22, 2005

http://performanceunlimited.com/documents/...ationguide.html
here's a chart with some things to check

Broncoholics · Feb 4, 2005

Get under the truck and grab the driveline and see if you can wobble the slide shaft. The splines might be worn out. Again do the same at both ends to see if there is movement in a u-joint. Most times its tough without pulling the driveline to check u-joints and the CV.
It could also have tossed a weight and need to be reballanced but I bet its just a u-joint, it always is. I used to go through a rear u-joint ever 6 monts until I added traction bars.
Otherwise drain the gear fluid and see if there is any metal that comes out. If you drive hard, things will wear fast. Check the torque on the pinion nut, this is a good time to look at the u-joint, pull off both caps.
When I tossed a driveline it bounced the truck 12" into the air as it bounced around and around. If you are on the freeway, hang on tight!