Two piece drive line vib

[KBoz]

Need some advice on two piece drive shafts ...I trans at +1 and my rear end at-1 and I have as slight vib...I do have air ride ...any help?
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[rustbucket66]

I'm wondering if the slip joint is in phase. If the slip joint has been apart, say to change the hanger bearing or a u-joint, and wasn't marked how it came apart, it may have been slipped back together out of phase. The u-joint cups on the front u-joint have to line up with the middle u-joint caps. If it is out, then it can be put back together in phase. However, now it may be in phase, but it could be 180 degrees out, and the balance weight will be on the wrong side. You have a 50/ 50 chance. It might be a good idea to take the driveshaft to a driveline shop and have it balanced. Your working angles sound ok. Always mark how the slip joint comes apart, so it goes back together the same way.

[KBoz]

Well I had it re balanced cuz I had a bad vid all the time and come to find out the drive shaft that I got out of the wrecked 2000 Chevy it was bent 10 degrees and after that it helped a lot .. And playing with air ride if I ride with 80 psi all the way around it doesn't vib but if i drop to 60 the vib comes back ...I wouldn't think that much movement would cause the vib
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[rustbucket66]

It sounds like you have to change the pinion angle a bit. If it is smooth when you have it at a higher ride height, that eliminates any problems that may be in the driveshaft. When you drop it down, the angles change and you get the vibration. You can buy shims from the driveshaft place you were at, or try to make some. I think the pinion angle needs to be angled up one or two degrees. The shims go between the trailing arm and the axle mounting block. From what you describe, I think that will correct it.

[KBoz]

Would shimming the carrier help? Or would I have to do axle angle?
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['63GENIII]

I've shimmed the carrier on a couple of occasions and been successful. It was more of trial and error to get it right though. Once I had it ... no more bad vibes. I just did it in 1/8" increments till I liked it, then made a 1 piece shim to take its place

[chevyrestoguy]

It sounds like you may not have enough driveline angle difference between the trans and the rear end. At certain air bag settings, you may almost be at 0 degrees, which might be causing your vibration. As was mentioned earlier, try the shims. You can either shim the trans mount, or buy the angled shims for the rearend perches from just about any on-line vendor that deals in lowered vehicles.

If it only vibrates at certain air settings, a shim or two will get you dialed in and you'll be good to go.

[KBoz]

Ok sweet thanks for the help I'll try it and tell y'all Wat I find that works
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[KBoz]

And I have about 3/4 in shims so far on the carrier...idk pull some out or add more?
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