[dusty_usmc]

I installed a 4" lift on my 01 tj and it drove great. I did some pretty hard offroading (in my rookie opinon) and when i got back on the road it had a lot of vibration. My friend posted about this for me, and we have narrowed it down the the rear driveshaft. I already replaced the U-joints, and have tried my friends driveshaft in place of mine, so I know it is not warped. I talked to some folks at a drivline shop and they said it was due to the angle on the driveshaft after the lift. If that is the case then: 1. Why didn't it vibrate until I took it offroading? And 2. If i do need the SYE and CV driveshaft that I've been reading about, does anyone know where to get one cheap? I would really appreciate the help. Thanks.

[girly04LJ]

Have you checked the front drive shaft?

[dusty_usmc]

the front is fine. I removed the rear drive shaft and drove it around in front wheel drive. It runs fine, no vibration, unless I have the rear driveshaft installed. On that note, it doesn't vibrate until I'm going about 30 mph.

[girly04LJ]

Did you check tires for balance? You may have lost a weight.

[girly04LJ]

If it is the rear drive shaft a slip yoke eliminator is a good idea anyway. I like the new extreme short shaft kits. They are more money but I think it's worth it.

[dusty_usmc]

I know its not the tires because when I remove the rear drive shaft the problem goes away. The few people I've talked to have said that I need to reduce the angle on the rear drive shaft. I was just here to find out if there was an easier way than buying the Slip Yoke eliminator and cv driveshaft because the cheapest I've found of those are about 500$.

[john NC]

you could drop the transfer case and/or install a MML

you may need both with a 4" lift

[dusty_usmc]

The lift came with the spacers to drop the tranny/transfer case skid plate/mount. What is an mml?

[john NC]

motor mount lift, raises the motor 1" which in effect lowers the back of the TC to help with pinion angle. plus it gets your oilpan further from the rocks

i run a brown dog mml, but M.O.R.E.'s bombproof mmls get great reviews as well. you could also do a jks bmml (budget motor mount lift) if your mounts are in good condition, they just add a 1" spacer under the motor mounts

[dusty_usmc]

Sounds good. That'll be step 3 of my troubleshooting process. Thanks.

[john NC]

you're welcome

[Jeepster83]

having the vibes at around 30 MPH does sound like the driveline. the SYE would really be the best way to get rid of the vibrations. it can be expensive but its worth it in the end. sometimes spending a little more now will save you a lot more later. the MML is a good idea though. however, theres more to it than just installing it. a BL (body lift) is recommended but not entirely necessary. when you install the MML the fan will contact the top of the radiator shroud so thats where the BL would come in. but you can just move the shroud up a bit to clear the fan. by running the MML/SYE you can get rid of the t-case drop kit getting your ground clearance back. to put it lightly - youve opened up a can of worms (not in a bad way). once you start modifying you Jeep, you never stop. if it were me, id go with the SYE and MML and be done with it. also a BL would allow you to run a belly-up skid plate giving you even more ground clearance. it makes your skid plate almost flat with the frame rails.

[dusty_usmc]

Thanks. I just wish it wasn't so damn expensive i broke the bank for the lift/rims/tires; I didn't think I would have to spend money fixing it too.

[bigjim in vegas]

I did the jsk mml and it solved my driveline vibes for now. I do plan to do a sye in the near future.

[Scotch740]

Maybe you have a bent rear output on your TC? Hard to Diagonse over the web but I would check that out. IF it was working before hand then not after wheeling sounds like its not due to the angle. Although most need a SYE and CV shaft at your height anyways. A SYE would replace the bent rear out put anyways and its a good thing to do. There are lots of stock TC outputs available due to people upgrading to a SYE so if thats your problem you can probably get off cheaper.