SYE vibrations, need a pro's eye

jaredm83

Member
Joined
Sep 20, 2019
Messages
41
Location
Fresno, Ca
I have 02 wrangler 4.0 5 spd, just installed Currie 4” kit. RC SYE and RC driveshaft. New 4.56 gears and 33” tires. I’m getting a vibration starting around 25mph and can feel it mostly when I’m on the throttle. The faster I go the more intense the vibration gets. I’ve tried rear pinion angle 2 deg down, 1 deg down, straight and even about .5 deg up. None of these angles seem to change the vibration. I disconnected the front driveshaft no change. Disconnected rear driveshaft and drive in 4 hi, vibration went away. Here is a video of my yoke idling in first gear. Looks like it definitely has a wobble to it. What do you think?
 

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I have 02 wrangler 4.0 5 spd, just installed Currie 4” kit. RC SYE and RC driveshaft. New 4.56 gears and 33” tires. I’m getting a vibration starting around 25mph and can feel it mostly when I’m on the throttle. The faster I go the more intense the vibration gets. I’ve tried rear pinion angle 2 deg down, 1 deg down, straight and even about .5 deg up. None of these angles seem to change the vibration. I disconnected the front driveshaft no change. Disconnected rear driveshaft and drive in 4 hi, vibration went away. Here is a video of my yoke idling in first gear. Looks like it definitely has a wobble to it. What do you think?
You have a bent output shaft.
 
You have a bent output shaft.
Ya I was kinda thinking so. How do you recommend I go about “proving” this to the seller? Is there a way I can confirm the shaft is bent with out too much trouble? I bought the kit from Morris 4x4 and just installed it, haven’t driven the Jeep other than test drives
 
Ya I was kinda thinking so. How do you recommend I go about “proving” this to the seller? Is there a way I can confirm the shaft is bent with out too much trouble? I bought the kit from Morris 4x4 and just installed it, haven’t driven the Jeep other than test drives
If they can't tell from the video, not sure what to do then.
 
Crooked machining would be very unlikely, a bent output shaft is an easy thing to cause.
Ok, another thing I just thought of, the machining for the bolts seems to be a little off on one side vs the other. one side is easy to get a wrench on and the other side is very tight and the wrench won’t go all the way down on the bolt head if that makes sense. Just thinking out loud
 
Ok, another thing I just thought of, the machining for the bolts seems to be a little off on one side vs the other. one side is easy to get a wrench on and the other side is very tight and the wrench won’t go all the way down on the bolt head if that makes sense. Just thinking out loud
The way stuff like that is machined is very easy to have the features relative to a common datum and be true to each other offset slightly on the forging. The hole for the splines is likely machined first, then that is used to establish the seal surface so it is concentric to the splines. After that it is fixtured up off of either the seal surface or the spline hole and the holes for the bolts and yoke caps are machined so each feature has a defined relationship to a datum. If the yoke forging is slightly offset to one side won't affect that relationship typically. Emphasis on typically.
 

Got the yoke off, shaft appears to be straight. I think the yoke is bad?

 
The way stuff like that is machined is very easy to have the features relative to a common datum and be true to each other offset slightly on the forging. The hole for the splines is likely machined first, then that is used to establish the seal surface so it is concentric to the splines. After that it is fixtured up off of either the seal surface or the spline hole and the holes for the bolts and yoke caps are machined so each feature has a defined relationship to a datum. If the yoke forging is slightly offset to one side won't affect that relationship typically. Emphasis on typically.
Let me know if you can’t see the videos
 
FWIW, I had a bad yoke on my AA SYE. Tom Woods diagnosed and rectified that for me at no charge. Still singing their praises. I had wrongly thought it was the drive shaft. TW sent me a new yoke, and problem solved.
 
Another thing I noticed, is after I got the yoke off, I can pull the shaft out a 1/4 inch or so. I do t recall being able to move the shaft in and out like that with the yoke attached, is this normal? Shaft feels good in the bearing with no play though