Help With Ordering Shims... Hey Kert?!?!

[nvrenuf]

I've got a horrible rear driveshaft vibration and need to order some shims to try and fix it. I realize ultimately I may need a CV type driveshaft but I have plenty of other things that I need to spend $500+ on right now so if I can fix it cheaply....

My rear t-case yoke = 4°
My rear axle yoke = 11°

Difference = 7°

Now my understanding is I need the rear axle to be ~2° down from the t-case to compensate for upward wrap during acceleration.

I think I need 9° shims. I see Kert offers shims in even increments - 8° or 10°. Which size should I get?

I should also note that I'm currently using a Zero Rate both for lift and 1" offset of the axle position. Is it possible to get an EZ Inch with an angle and still use the axle offset?

 

[ChrisPerry]

Why not cut and turn the spring perches. Same price and you'll get the angle set exactly where you want it. If you are careful about how you place your welds you can reuse the perches when you get the CV driveshaft.

 

[nvrenuf]

I don't mind reworking the perches as a final fix but I would like to see if turning the pinion down will correct the vibe before cutting and welding on the housing a bunch (and avoid an expensive cv driveshaft purchase when I have a new 1410 assembly already in it).

 

[nvrenuf]

hello..?

 

[ChrisPerry]

I would go with the 10* shims. With the big tires you probably have a fair bit of axle wrap even under partial throttle. IMHO I don't think using an easy-inch with a wedge that big are a good idea, but Kert will be the expert on that.

 

[nvrenuf]

IMHO I don't think using an easy-inch with a wedge that big are a good idea, but Kert will be the expert on that.

I agree completely that stacking the 2 isn't a good set up, I just want to verify what it'll take to stop the vibe. Assuming the shim works, I'm hoping Kert can make an angled EZ Inch for a final fix.

 

[blazinzuk]

I have never been a fan of the 2* down to compensate for axle wrap. Mainly because I don't care if my driveshaft vibrates a bit under acceleration. I want it to run smooth at speed.

I have simply used the same idea that if I use a 2* down to compensate for wrap that under cruise conditions it will be 2* off perfect. So why not use one that sets it correct and be 2* off under acceleration.

Has worked for me up to this point. So I would get the 8*

 

[cybrfire]

Missed this one...

I'd probably go with the eight degree. The 2 degree for wrap is speculation anyway. Reality is you could use either one and eliminate the vibration. Generally speaking if you are within a couple degrees of perfect you won't feel or hear anything.

You have a single joint on both ends of the shaft correct?

 

[nvrenuf]

Yeah, I'm using a standard single joint type shaft.

 

[Blue85]

Those angles explain the vibration, so this is a route worth pursuing. What you didn't post is your current driveshaft angle. Once you get to 10-12 degrees in the joint, a little vibe becomes inevitable.

I agree with others saying to go with the smaller shim (8*). The more shim you put, the weirder the center pin and U-bolt business gets. Plus the U-joint angles get more severe. If you need that extra 2* down for acceleration, then it should be downright dreadful right now.

I would rather have a little vibe at low speed, where it matters less, than a vibe on the freeway. Usually the little vibe/bounce you get on takeoff is coming from spring wrap anyway.