alsxj

I have an 90 cherokee 4.0 aw4 np231 with a 3 inch lift and 29 inch tires. At speeds 35-45 I get a very bad vibration under load. When I release the gas pedal or shift it in neutral the vibration goes away. When I go to accelerate it starts up again. This vibration started happening after I had to replace my transmission. The transmission shifts smooth and fine so I really don't believe it too be the cause. Since then I've replaced all my u joints, hub assembles, had my tires rotated and balanced. I had to replace my transfer case due to it spiting in two on me. I have yet to replace worn motors mounts and the trans mount. Do a tune up and my crank senor 's wire got too close to my header and had melted a bit, seems to be working still but I'm going to replace it. So I need help. Anyone have this happen or have any ideas for me? I thought of death wobble but with it not happening at any other speeds and only when I accelerate it doesn't seem right too me. Thanks for reading and for any info.

EvilMaster

Acceleration vibrations are usually caused by the pinion angle being too high in relation to the transfer case output shaft. You may need to adjust your pinion angles.

Did the old TC have a drop kit that wasn't re-installed? Or was a new TC drop installed with the new TC?

alsxj

Never had any transfercase drop kits on before or after the new transfercase. The leaf springs I installed had shims on them but this didn't change the vibes still had them before and after.

EvilMaster

Does the vibration seem to come from the front, center or rear of the Jeep?

alsxj

Its hard to tell since the whole thing shakes but it seems to be coming from the center and front. Somewhere between the front axle and driver seats.

alsxj

Also to add to it right before this happens I hear and feel a slight grinding kind of noise coming from what seems to be the front of the trans area. Well after talking to my suspension teacher about this, seems to maybe be my torque converter maybe? I checked my trans fluid and its clean, doesn't smell, and is at the right level. So any thoughts guys? I've haven't had much experience with transmissions yet. I've been searching and will keep searching but I have't really found anything yet and would like to try figuring this out and have an idea before I start tearing the trans out since this is my only rig right now and I can't have her down for too long since I'm a full time student and I have work. Thanks for any help guys.

freegdr

jack thr rear up and support axle on jack stand pu in gear check for bent drivshaft or bent rim axle

alsxj

Done that, axle is fine, and driveshaft is fine.

freegdr

was the trans from same year jeep

alsxj

I'm not sure since the trans shop did it, I figured it would have to be pre 91 for the spines to match with my transfer case right.

alsxj

Any ideas guys??