High pinion offset of Ford 8.8" causing vibes?

My 96 XJ has 4.5" of lift in the rear (3.5" RE springs plus RE shackles) and with a 231 and AA SYE with a new 1310 CV shaft in the rear. I swapped out the 8-1/4" about 4 months ago in favor of an 8.8. It was late when I welded the perches on and the pinion angle was a tad off. I would get vibes from 50-70 under acceleration and constant speed. The vibe would go away as soon as I let off the gas and coast. So I thought the pinion was too high. I put a 2.5-degree shim in to bring the pinion down just a bit. The vibe is still present and under the same conditions...


Do you thing the high pinion offset of the 8.8 to the passenger side could cause a vibe that won't go away? Should I try a 4-degree shim...As of now, the pinion is right at 2-degrees lower than the shaft....


Ideas???

Thanks a ton

i have never had an issue when i have installed 8.8's into yj's, and they have a much shorter rear d/shaft.
the pinion angle sounds good to me, i always set mine 2 degrees down at rest, allowing the pinion to be in line under acceleration.
i would be double checking the cv shaft to make sure it isnt binding up. i have used both custom made shafts and cut down xj shafts without issue though.
double check everything you did, assuming it was ok before the 8.8 swap and you changed nothing else.

martin

Don't guess,buy a protractor/angle finder and be sure what you need to do to get it right...

Your rear end yoke should be perfectly straight with the driveshaft,, step back and see if ur axle is pointing right at the shaft. If its even off just a little then ull get vibes. To correct your issue, your best bet is to measure out for a tomwoods shaft. They increase the angle with the double CV at the transfer case and tomwoods shafts also have 30 degrees more over stock. SO align your 8.8 directly straight with the shaft and let the CV end do whats its ment to do and thats what allows you to run a higher lift with no problems.
I can take a pic of mine tomorrow so you can see what im talking about.

With a heim jointed traction bar installed, I have ALWAYS noticed vibes from 8.8. The offset sucks.

I've solved the issue with a better stereo and suspension seats.

those of you getting vibes from your 8.8 install, check over everything again. the offset isn't that much to be causing an issue and after setting up 3 8.8s for different vehicles (1 being my own cherokee) ive never had any problems

CRASH said:

With a heim jointed traction bar installed, I have ALWAYS noticed vibes from 8.8. The offset sucks.

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Wouldnt hurt to have someone ck the balance on the new DS. Ive had one do the same thing with a new shaft and they said it wasnt balanced properly.

I was thinking on 8.8 installs....... Why not move the axle over the 1.25 to center and use a 1.25 rim spacer on the inset side, or have a steel spacer made to weld on to the axle flange ?

Rmart30 said:

Wouldnt hurt to have someone ck the balance on the new DS. Ive had one do the same thing with a new shaft and they said it wasnt balanced properly.

I was thinking on 8.8 installs....... Why not move the axle over the 1.25 to center and use a 1.25 rim spacer on the inset side, or have a steel spacer made to weld on to the axle flange ?

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Because the brake caliper is already 5/8" from the leaf spring, in my case the mounting bolt.

Sero said:

Because the brake caliper is already 5/8" from the leaf spring, in my case the mounting bolt.

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Ok, I had never noticed them being that close.

I have done this swap on another of my Jeeps. The width offset makes no difference on the 8.8 axle. Your problem is pinion angle related.

I didn't check mine with an angle finder but my pinion is just a touch down from the drive shaft so when I accelerate it lines up straight. I have no vibes with my 8.8 despite the fact it the driveshaft obviously is at an angle from the offset pinion.

as i said before, i have done @3 8.8 swaps, 2 on yj's with soa. never had any vibes setting the pinion 2 degrees down at rest. if the pinion is straight with the driveshaft, it will dive upwards under acceleration and give the possibility of vibes etc. i also never use shims and always reweld perches on a rear end, always the same @2 degrees down. again never had any vibes on other axles neither.
there is no reason the offset on a 8.8 should cause vibes, and i agree with others that have said to check d/shaft balance and pinion angle with an angle finder, not by eye!:wierd:

martin