alsxj

I have a 1990 cherokee. 4.0, aw4, np 231, dana 30 and c8.25 rear with a 3inch lift. I've had this vibration that I haven't been able to figure out. First off about year ago I blew my transmission, and after I got the second one I started noticing theses vibrations. Then shortly after I blew my t case in two. So now I'm on my second t case and trans. The vibrations happen from 35 to 55 and I got some vibes at low speeds but there not as violent as the higher speeds. When this happens the whole vehicle shakes and the vibration only happens when I have the foot on the gas. When I release the accelerator the vibration goes away. Now when this happens the engine doesn't seem to be acting up, no hesitation or anything. I know its not my front drive shaft because I don't have one in the vehicle. So far I've replaced the all u joints, motor mounts, trans mount, and front hub assembly's. I had the driveshaft balanced and checked and it was perfect. I had my tires balanced and I rotated them. I checked my trans and t case fluid all are great in color dont smell burnt and are at the right level. I know its not my rear axle because it was doing this before with my old dana 35 before I swapped for a 8.25. I don't think its my lift with the driveline angles because I had the lift for a year without any problems. So I don't know what to do know. I'm broke college student so I can't afford no shop to look at nor do I want to take it too a shop. Any help would be awesome! Thanks for reading my lengthy post. Tried to include everything I can think of, sure I forgot something. Thanks again!

The Black

Check bushings, control arm mounts and bolts. Have someone drive it for you and you get in another car and ride beside it and see if you can find something that way.

alsxj

I'll try and get somebody to drive beside me and watch. All my mounts are good, and the only bushings that are bad are my upper contorl arms.

alsxj

Okay soo still having this problem and today I had time to put the front driveshaft in and disconnect the rear driveshaft. I took it for a test run the vibration still present itself. Again between 35 to 55mph. So I've put my rear back in for now. Pretty much I think maybe its my transmission? Anyone else ever have this to there aw4? or any ideas of what it could be?

evilxj85

sounds like drivline vibs, get a tcase drop

Tural

wait, u took out the rear driveshaft and drove with just the front??? and still vibrated? have u re-checked your new motor mounts?
you could possibly have more than one issue going on. check the track bar bracket and make sure that the hole is not worn out... make sure your pitman arm is secure. check around the steering box for cracks, or damage.
if you have the time, change out your ball joints, or did u already change those out too???

alsxj

Thanks for replies guys, So yes I had only the frond ds and still vibrated, and the ujoints are good in the front. Track bar is good, everything steering related is brand new and replaced. And I did an alignment at my school. Ball joints I checked last month and were great. I'm really starting to think maybe a trans issue? Just because I've elimited the tcase, front diff and rear diff, drive shafts and steering related. Now this vibration is still speed related at 35 to 55 and it only happens when I have my foot on the gas, once it starts vibrating if I let off the gas or slip it into netural the vibration completely stops! And I never had the need for a tcase drop becase I've ran this lift on it for a good year without a problem, and motor mounts and trans mounts I checked again and both are good. thanks for your help guys.

alsxj

So nobody has any ideas? I really don't know much about automantic transmissions. I've narrowed this vibration to my tranmission and I would like to know what would cause this in the trans and where to go to next? This is my second trans and this really didnt start till after I had it installed but it shifted soo good thats what led me to not even think of it. So help me out, I got my tax refund so now I have some money soo if all else fails I can go transmission shopping. Again guys thanks for your help so far.