Vibe when off the gas???

Did the 9"/D44 ford axle swap on my MJ. Running the standard slip yoke rear d-shaft and a 231 t-case. When i'm on the gas there are no vibes, but as soon as I let off i get a nasty vibe sound that seems to be coming from the backend of the t-case. Angles look good. Actually the joint at the diff. looks to be right in line with the d-shaft. I know the two joints are supposed to split the difference as far as operating angles go, but, the joint at the slip yoke doesn't look too stressed either? I know, just go SYE. I'm saving up for the D300 swap so I don't wanna put any cash into the 231. thanks, judd oh yeah,
spring over, 2" blocks

You need to get the angles the same at both ends to verify that it is not that.

If you fix that and it still is there then replace the u-joints.

Michael

With a conventional driveshaft, the standard answer is to run your pinion ~1° lower than the output shaft, ie xfer-case shaft at 5°, pinion at 4°.

Laying under mine, it looks like the pinion and driveshaft are pretty much in line, but when I measure, the angle finder says otherwise. You really should measure your angles to be sure. Angle finders are dirt cheap, usually <= $10.00.

Your pinion may be so high that under power, it goes into a "camel-back" position, cancelling out the u-joint angles. That would explain what you are experiencing. This is a valid way to run the angles, but the high angle pinion can end up causing oiling problems for the pinion bearing.

hmmm... i'll measure them again this weekend. Kinda sucks though. when we welded the whole thing up the angles worked out great, now it's really noisy and i'm afraid to get on it too much in fear of breaking another ujoint... judd

It's not always a matter of angles. Could be your slip yoke has a sloppy fit, driveshaft out of balance or you might have a bad pinion bearing.