Cherokee guru's...I have the typical thud after takeoff from a complete stop (doesn't do it from a "rolling stop"), and I usually do all work on my vehicles, but I had it in the shop this morning for a tire swap to new rims and had them look at it. I don't think they really did anything because all they told me was that my rear diff jerked when put in gear...well, okay, but that's not what I asked about. I did have them grease the splines (as noted on here in other threads), but it still makes the thud.

So all that being said, would the thud have anything to do with the rear diff? From everything I've read on here, I don't think I've read that. Lots of advise on checking trans mounts being loose (mine are tight), hung rear drums, u-joints, and such, but rear diff?

I can live with it I suppose, but would rather get it working properly. Like most others, if I coast off the brake before adding throttle, it doesn't make the thud noise...

 

my thud was bad u-joints in the drive shaft with them replaced its gone

 

I vote u-joints as well.

 

I wonder if they actually removed the drive shaft and greased the splines or if they just used that needle tip on the grease gun I've heard about... I can't imagine being able to grease it properly with out removing it...but who knows....maybe it is the u-joints..... there are some good videos on youtube on how to do u-joints...they are by expert village I think it is, they are for a ford but I'm sure it's the same difference...

 

u joints fixed mine also. Same thing would thud from a dead stop, or from going reverse to drive

 

Thanks!! Looks like u-joints are next on my list then...

 

Might I also suggest checking the engine mounts? We have had several cars of various makes and models in our shop complaining of "mystery thuds", and a LOT of them have been a bad engine mount or two. Just my two cents worth...

 

a good 2 cents motor mounts and trans mounts are highly overlooked when diagnosing thuds

 

Thanks guys, I'm gonna put it on ramps this weekend and I'll check those too.

 

you can pop the hood and stand off to the side of the vehicle while someone else in the driver's seat puts it into gear and see if the motor mounts are bad.

the motor will move way more than you think it should if they're bad.

 

with the parking brake off and it in park on level ground. Kneel down beside rear tire and rock tire front to back....... watch the u joints, pinion where it enters the diff and also watch and see if the rear diff itself twists a lot.
I had one of mine doing that and it turned out to be that the springs were weak and letting the diff twist when torque was applied to it from a dead stop. New HD springs from quadratec fixed it.

 

Now that I actually did do last night when I was removing my hitch. I laid on the ground next to it while rolling the rear tire and the rear diff did twist a little bit. Don't know how much is normal tho...

 

Was gonna suggest the u-joint as well since I had that issue on an old XJ, but was surprised to read that bad rear springs would cause this as well.

Guess I need to pony up and order a new set......although I wanted something with about an extra inch of ride height in the rear. You guys think with new HD springs, I'd see this kind of "lift" in back?

Also, should I get new front coils so all is fresh?

 

I had a thud caused by a bad wheel cylinder. The shoes would grab when at a complete stop and pop free when I started moving.

 

Consider the t-case mount as well. Had an issue with the t-case shifting about. I think it was more so around low speed corners, but acceleration from a dead stop would do it too.