Hello, I'm new here and just bought my 1st jeep Sunday. It's a 96 XJ with 141,500 miles lifted 6.5 inches on 33x12.50 procomp Xterrain tires AW4 trans and C8.25 rearend NP-242 TC. The jeep needs quite a few things in the near future that will make a good winter project. The trans will be swapped for AX-15 and a junkyard C8.25 eventually. But, until then I would like to have it for trail rides and i need to drive it there.

So, to start with the problem. When I accelerate The trans has a strange vibration when I apply more than adequate throttle. Under light acceleration the trans shifts slow and without authority. While under stress during that vibration the Jeep seems to loose momentum while the throttle stays constant. This happens in the 2hi, part time, and full time. However, at speed, the Jeep handles hard acceleration quite well and shifts are smooth. I do have another AW4 transmission that the guy threw in along with a new rad, starter, and motor. I had thought about swapping the transmissions out for a while until I can find a manual trans. I just cant diagnose this one as this is my 1st jeep. Thank you for any advice.

 

f you have a good AW4 just replace it and your good to go transmission wise they are a very good auto trans. The other part about vibrations may be in the drive line. It does have an SYE doesn't it and the differential shimmed properly.

 

could be bad mounts

 

No, it does not have a SYE. The driveline angles are very high and the thought had come to mind that it could be the U-joints. My Xterra had a bad U-joint and did have some vibration but it was only at certain speeds never durring acceleration.

 

It feels like something is slipping. Could the lack of a SYE cause that?

 

You need an SYE, a proper Drives haft to match and either shims or new perches to get the correct pinion angle.

T-Case drop is not an option at your lift height.

As previously stated...tranny mount should be given a long hard look, but don't stop there. You may want to spend a few minutes under the hood and take look at your motor mounts as well.


And finally...Welcome to CF !

 

Thank you. I have a great idea...I need to go to the junkyard today. Do you think I would be able to find anything laying around that may help? I was there yesterday for a steering shaft and found a nice NP-231 TC under a 95 two door. should I grab that while I'm there and order the SYE for that TC? Also what am I looking for as far as a proper drive shaft?

 

Installing an SYE can be done under the rig, but it is easier on a bench. Having a spare build as you have time makes sense.

Finding parts for a lifted rig in JY is often a matter of dumb luck.

Some folks use the front shaft from AW4 equipped XJ when they install an SYE. I prefer a larger diameter driveshaft, just like what your rig came with from the factory. Yes they are expensive, but I like the piece of mind that comes with 'em.

 

4wheel parts has a store here in Indy. They have a SYE for my NP242 for around 180.00. Online, Rough Country has their CV rear drive shaft for around 280.00 as well as tom wood's. What should I look for with these shafts? Again thank you.

 

Ok, so I got this done yesterday. I bought the kit RE1801 for $180 as it came with the parts to use for a 231 in the future for the later swap. The difference in cost was $80 so, why not??? I went to the 4Wheel Parts store here in Indy to grab a set of shims $35. I went to the junkyard and found a xj with the AW4 which had a recently replaced front drive shaft $50. Started the truck, put it in reverse and touched a Sharpie to the output shaft 1.25 inches from the start of the splines. Cut it while it was still in reverse and that made a nice cut. Also while still running i took off the burrs. Drilled and tapped the shaft starting with a 3/16 steel bit $8. Used Spicer pt#211229X $60 with a new Spicer U-joint $8. I have yet to install the shims but when I put the fuel to it, it goes like it should. The shims will be installed within the week. Its much quieter but still makes a little noise. The T-case drop was welded on by the last guy so that's a job for a cut-off wheel, how fun . Did I leave anything out? Thanks for all of your help!

 

The hack n tap is holding up well so far. No strange vibes to report after 200 miles.