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Driveline Vibes After SYE

Check to see if the new yoke on your transfer case is machined centered. I recently had an issue with the same manufacturer of sye and come to find out, after about 6 months of driveline balancing, changing pinion angles, u joints, rear ends, and pouring over forums, low and behold, I found a write up on another jeep forum about a new yoke that wasn't machined centered. I jacked up my rear axle, put it on jack stands, put it in first gear and looked underneath while it idled along in 2wd. Sure enough, you could see the rear transfer case yoke going up an down while it turned. I borrowed a buddies front yoke from his 241 (I believe) transfer case that he had removed. It was identical to my new yoke from my sye kit, with exception to the seal wear. I installed it, and it drove as smooth as butter at any speed you wanted to go up to 85 mph! The guy I bought the all inclusive lift kit from called up the supplier and explained the situation. They sent a new yoke within a couple of days.
 
bonehead73 said:
Check to see if the new yoke on your transfer case is machined centered. I recently had an issue with the same manufacturer of sye and come to find out, after about 6 months of driveline balancing, changing pinion angles, u joints, rear ends, and pouring over forums, low and behold, I found a write up on another jeep forum about a new yoke that wasn't machined centered. I jacked up my rear axle, put it on jack stands, put it in first gear and looked underneath while it idled along in 2wd. Sure enough, you could see the rear transfer case yoke going up an down while it turned. I borrowed a buddies front yoke from his 241 (I believe) transfer case that he had removed. It was identical to my new yoke from my sye kit, with exception to the seal wear. I installed it, and it drove as smooth as butter at any speed you wanted to go up to 85 mph! The guy I bought the all inclusive lift kit from called up the supplier and explained the situation. They sent a new yoke within a couple of days.
Click to expand...

I'm going to check that. Never would have thought of that one!

I have the following on my list:
- Check SYE Yoke
- Replace Trans mount
- Rebuild rear diff
 
I pumped in some 85w140 gear oil and it seemed to help.

I get minor vibes starting at 60 or so (used to start at 50) and they get to be moderate vibes by 70 - still can only begin to feel them at 70 and don't get any worse up to as fast as I feel comfortable driving the jeep.

Before, you could feel them bad at 70.

I did run it about 25 miles at 70MPH.

I'm thinking the rear diff is toast. I did run it very low on oil (1/2 quart of oil i nit) and I have the pinon shimmed

If the 85w-140 can keep it together and allow me to go 60(indicated speed, really 65) on the highway, I'm going to leave it in there until I get a house with a place to work.. Then I'm going to go to the junkyard and grab an 8.8 with 4.10 gears.
 
Last edited:
Have the shaft checked for balance and being straight. If the angles are good and the joints are good, there isn't much left.
 
old_man said:
Have the shaft checked for balance and being straight. If the angles are good and the joints are good, there isn't much left.
Click to expand...

Shaft was professionally rebuilt ( new Centering yoke / ball, U Joints) , balanced and they confirmed that it was straight.

I think I might get a junkyard 8.25 and put all new brake lines and hardware in it. Or regear.
 
Just to let you know about the off center yoke. I installed the new replacement yoke that they had sent to me. It was also off center!!! It wasn't near as bad as the first one, but you could not see out the mirrors at 50 mph due to the vibrations. You could still see the yoyo effect when idling in first gear on jack stands. I put the borrowed one back in, and everything is fine. No vibes whatsoever. I have some machinist friends measureing how for out it is. Wish I had done that with the first one. I am done with rugged ridge. Wouldn't take a lot of those kind of vibes before you would ruin perfectly good pinion bearings and output shaft bearings.
 
bonehead73 said:
Just to let you know about the off center yoke. I installed the new replacement yoke that they had sent to me. It was also off center!!! It wasn't near as bad as the first one, but you could not see out the mirrors at 50 mph due to the vibrations. You could still see the yoyo effect when idling in first gear on jack stands. I put the borrowed one back in, and everything is fine. No vibes whatsoever. I have some machinist friends measureing how for out it is. Wish I had done that with the first one. I am done with rugged ridge. Wouldn't take a lot of those kind of vibes before you would ruin perfectly good pinion bearings and output shaft bearings.
Click to expand...

This is nowhere near that bad!

The front DS vibes I had were that bad when I did 3.5'' of lift and TCase drop. The DC Joint in the front DS was bad, but I thought it was the rear (which I had vibes there as well). Didn't take long for the bad vibes in the front to kill the pinion bearing in the LP30.

It's much better with the 85w-140. Tolerable, even. I'm not worried about bad things happening, but I will need to do something.
 
Got the new axle home. There's a broken bolt in the pinion yoke (going to have to put a new yoke on). Spinning the differential by hand ... it doesn't bind like mine does. There's also not as much "slop"when switching directions.
 
Miller88 said:
- Pinion Yoke is pointed DIRECTLY at TCase

Thanks in advance!
Click to expand...

? You need the pinion to be parallel to the transfer case output. If the pinion is pointing directly at the transfer case output, you'll have almost no u-joint angle at the pinion, and a "large" angle at the output. Mismatched u-joint angles are a recipe for vibration. The angles at each end need to be as equal as possible.
 
Tobey99 said:
? You need the pinion to be parallel to the transfer case output. If the pinion is pointing directly at the transfer case output, you'll have almost no u-joint angle at the pinion, and a "large" angle at the output. Mismatched u-joint angles are a recipe for vibration. The angles at each end need to be as equal as possible.
Click to expand...

Except that he is talking about a slip yoke eliminator and using a front shaft, which requires the pinion to point toward the tcase output.
 
I had vibes like this. 2000 XJ, no sye, 3" lift, 1" tc drop.

While installing the new tranny mount, I discovered one side of the transfer case cross member had a broken bolt in the frame and the other bolt had worn threads.

New tranny mount and fixed the bolts.

Now little to no vibes. I used a day star poly trans mount. In gear idling I get some vibes through the solid tranny mount.
 
So bit of a bump ... after a while. Still chasing this.

I want to avoid replacing the differential if possible. Mine isn't rusty, the one I picked up is rusty as it's from NYS originally.

I noticed that once in a while if I hit a bump, the vibes stop. Checked the trans mount and it's ... pretty much shot. If it's sitting with the parking brake holding the jeep so there is no weight on the driveline, I can grab the driveshaft and wiggle the entire engine/trans/tcase around freely. The engine mounts are also shot.

In fact, it's so bad now that the transmission hits the floor on bumps.

Jeep's going to be sitting it out for a bit until I can get better mounts in!
 
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