One thing you can try is to get the rear of the jeep on jack stands, put a dial indicator on the slip yoke, turn the driveshaft and measure the runout of the whole rear driveline assembly. If I remember correctly by Spicer standards it shouldn't have more then .008. If it's more then you can start isolating what the cause is. Yoke, SYE, driveline, Etc. Then for example say the total run out of assembly is .014. The driveline is .006 and the transfer case tail shaft/yoke or pinion/yoke is .008 you can sometimes rotate the driveshaft 180 degrees and get the two differences to cancel each other out so your total is .002. I kept rotating at the pinion, the transfer case, and the slip yoke, measuring and marking each time until I was able to get it down to .005 on my jeep. Almost no vibs now.
Re-geared, now I have a vibration above 50 mph
- Thread starter bobthetj03
- Start date
OP
I'm open to any and all suggestions. Thanks. Good idea. I had the vibes before doing the SYE. The vibes started after re-gearing the rear axle. I had the front axle re-geared a few weeks later.
OP
I did this last weekend. I was getting .006 at both yokes and .020 on the rear driveshaft.
OP
So, a phone call, and a couple of emails and I have another drive shaft on its way. I'll install the 2nd new drive shaft and re-measure run out, then try to orient the yokes and driveshaft with the highs opposing the lows. I'll put the high spot on the yokes down, and the high spot on the drive shaft up in hopes they will help cancel the harmonic. Does this sound right?
Sure
. Hell, can't hurt. You've gone this far. Not sure how hard it is to remove the tcase yokes but maybe try to clock them 90 -180 degrees and see what happens.
OP
Sure
My jeep is so god damn sensitive who knows, but I have to try anything I can. I'll mark the high spots on the yokes before I remove the drive shaft, then clock them accordingly once I remove the drive shaft. Worst case scenario, I gamble on the new drive shaft run out and have to remove it again to clock it against the yokes.
This thread is so crazy I had to make some popcorn halfway through. I can’t believe the trouble you are having. I thought for sure this was going to finally end happily ever after.
I am new to TJ’s, but not to CJ’s or YJs.
My YJ had a 2.5 OME lift with a spring over conversion. I regeared it myself from 3:73 to 456 with ARBs front and rear and the rear was a 8.8 Ford. There is absolutely no caster camber adjustments on a YJ. I ran BF Goodrich MTs the old kind. i ran it like that for years. I rode as smooth as it could with muds and a crazy lift. No vibrations whatsoever.
The reason I mention the 8.8 is that it is slightly off center but i did install a SYE kit. i guess I am suspect of the 4link set up, because seriously my pinion angle in the rear was horrible in that the driveline was not in the same plane as the rear end.
I am not really going anywhere helpful with this other than maybe it has something to do with the 4 links.
If it were me I would try removing the lift pads on the coils just to see if it is different, or at least see if the molecular structure is still good. Like you I am grasping at straws, but I have seen some worse setups drive smooth.
Also for fun check your exhaust too make sure it is solid all of the way back. I have been reading about lift kits making it impossible for the exhaust and or shocks rubbing on something. Check your ebrake cables check for anything that maybe rubbing.
Sorry just random thoughts because I can’t believe after all of this it still isn’t fixed.
i wished you lived closer because I would swap axles with you just to see if going backwards would fix it.
I am new to TJ’s, but not to CJ’s or YJs.
My YJ had a 2.5 OME lift with a spring over conversion. I regeared it myself from 3:73 to 456 with ARBs front and rear and the rear was a 8.8 Ford. There is absolutely no caster camber adjustments on a YJ. I ran BF Goodrich MTs the old kind. i ran it like that for years. I rode as smooth as it could with muds and a crazy lift. No vibrations whatsoever.
The reason I mention the 8.8 is that it is slightly off center but i did install a SYE kit. i guess I am suspect of the 4link set up, because seriously my pinion angle in the rear was horrible in that the driveline was not in the same plane as the rear end.
I am not really going anywhere helpful with this other than maybe it has something to do with the 4 links.
If it were me I would try removing the lift pads on the coils just to see if it is different, or at least see if the molecular structure is still good. Like you I am grasping at straws, but I have seen some worse setups drive smooth.
Also for fun check your exhaust too make sure it is solid all of the way back. I have been reading about lift kits making it impossible for the exhaust and or shocks rubbing on something. Check your ebrake cables check for anything that maybe rubbing.
Sorry just random thoughts because I can’t believe after all of this it still isn’t fixed.
i wished you lived closer because I would swap axles with you just to see if going backwards would fix it.
I have the same problem. Lifted 3.5" and installed SYE and Adams CV shaft with 3.07 gears. No vibes.
Installed new Dana 44 rear axle with 4.88 and an ARB. Harmonic vibes noticable above 55 and bad at 65. I emailed Adams with info and request for some advice but they went silent after the first response.
I just had the drive shaft balanced and there is an improvement but its still there.
OP
Thanks for all the suggestions folks. I'll post results when I get the 2nd NEW drive shaft.
Hey was reading about your issue, weirdly this seems to be common with no or many fixes meaning people seem to have this same issue a lot but different things either fixed it or it was never solved.
Curious, I don't think I read in this and it is getting pretty long, but have you made sure the front and rear axles are parallel? Not sure if it is anything, and I would bet if they weren't your jeep would dog walk, but thought I would mention that because I have seen other people complain that their front and rear axles fight each other and they should be parallel. I have seen where you played with pinion angle but don't remember reading anything about if you axles are parallel to the frame. Again might not make any difference and in most cars it doesn't but the wheelbase being so short on a jeep maybe it could cause a vibration.
Also Just for fun I think now that you have made all of your changes, you should see if you can borrow your friends tires again just to test all of your changes. Or see if you can get some really smooth street tires just to test, Like maybe even factory stockers?
I am perplexed, and I really want to solve your issue haha
OP
I did measure my axles for square to the frame, and they are perfect. Also made sure they were centered side to side. Part of what I was waiting on was the purchase and installation of an adjustable rear track bar. That is on now and axle is centered. As far as messing with pinion angles, I adjusted the front pinion angle as close as I could to the front driveshaft angle without making my caster angle too much. For the rear, I adjusted the pinion angle in 0.5* increments from 0* to -2*, to +2* with a test drive after each adjustment. Each adjustment netted zero change in vibes intensity. Thanks for the suggestions, and keep em coming.
They usually say (and I almost always find it to be true), the simplest explanation is usually the correct answer. In your case, I'm not sure what that is (since I suspect you've checked the simplest stuff already). But I'll bet when you figure it out, you'll kick yourself wondering why you didn't think of something so simple... I alway end up doing that.
What did you use for a reference point for centering. I want to check mine. I put a straight edge on the tire and measured the distance from the body. It showed 3/8" difference but I'm not sure the body is the best reference.
OP
I took a 4' level, sandwiched it vertical to the tire, then pulled a tape measure from the frame in the wheel well to the level.
OP
That is awesome. I measured from some point in the frame by the cross member to the axle tube. Your way seems much easier.