jeepin4fun

I'd like to start by saying I've searched quite a bit. I bought this jeep about 2 months ago. I've been going through it replacing stuff and one thing I replaced was the tranny mount. After I put it in I'm now getting a grinding and jerk when feathering the throttle above 35 mph. I put new u-joints on the rear and still the same. I also put anti seize on the slip yoke and no help. When going over 60 it sounds like a chainsaw is cutting away at the drivetrain!

I'm going to do a sye and put in a front ds in the rear but I don't have time or the parts and I'm going on a 200 mile trip next Sunday for Easter.

Will I be safe driving it?

Is it the stock slip yoke making the horrible noise? I noticed a little bit of play in it.

Bonus question - Will a stock front drive shaft fit in the rear with a 4"+- lift without having to shorten it? What's the lowest lift you can have before having to shorten?

96 4.0ho auto np231 d30 c8.25 d lockers front and rear. was told a 4" lift
I also changed the rear diff fluid to like 140-85 and put in new fluid in the t-case. If that makes a difference.

Thanks

VTJeep

Try removing front DS and see if that does it. You should be good at 4" and a front DS setup. Anything over the 3-3.5" height seems to start needing a little help. Also consider axle shims, 3* would be enough.

jeepin4fun

I'm new to lifted vehicles so I've still got alot to learn. I just read up on the shims. The shim (fat side to the front) angle's the front of the rear end up to re-leave some of the angle in the drive line correct? Where can I get these shims? Off road place I assume.

Do you think I'm safe driving it next weekend with the bad grinding or should I shim it before I go?

Thanks for the help!

jeepin4fun

I went outside and looked and a 2-3 degree shim would make the rear diff and drive shaft be in a straight line. Is the goal of shimming to make the only angle in the drive line at the slip yoke?

cruiser54

How are the engine mounts?

jeepin4fun

As far as I can tell there good. How good I don't know. If I had a jack big enough I would have changed them out. Any good way to tell if there bad? I cant move the motor by hand.

cruiser54

Look at them. Is there rubber missing? Is the center bolt in the middle of the mount or below?

jeepin4fun

I will take a look at them tomorrow and see what shape they are in. Could they cause the grinding in the rear?

cruiser54

Probably not, unless they're causing your exhaust to ride on the trans/transfer case crossmember. Look at that, too.

jeepin4fun

I looked at the exhaust but couldn't find anywhere it could be hitting other than at the very rear its about an inch from the leaf spring mounting point. It sounds way worse then the exhaust banging against something.

Along with the noise I can feel a jerk in the drive line. When going from R to D there is a bang underneath. I figured it was the u-joints but it wasn't.

Thanks and I'll add some aftermarket motor mounts to the HUGE list of stuff to do...

cruiser54

U-joints are a real possibility then. A flashlight, grubbies and a willingness to look and learn are your friends.

jeepin4fun

I just replaced both rear u joints last weekend and no change. And put anit-seize on the slip yoke.

cruiser54

Diff taking a dump maybe?

jeepin4fun

God I hope not. I'm going to try and shim the rear like VTJeep suggested and see if less angle helps. Read alot about bad vibes without a sye.

cruiser54

That and/or a transfer case drop or SYE.