I know the usual thud that happens when you push the gas after the torque converter kicks in, but imagine this about 5x harder at various speeds. I can usually make it happen around 35mph, but not any lower or higher than that. It's not every time I hit the gas, but pretty frequently. Sometimes at lower speeds and higher speeds it happens, but I can't do it on purpose outside of 35mph.

-I checked the drive shafts for play, the rear one is solid and the front one has a very slight bit of play, but I think that's due to the yoke in it. So I don't think I need new u-joints.

-I cannot physically see any fluid on the transmission dipstick, but the little eye hole has fluid in it and it was fine when my dad and I changed the fluid in the summer. I haven't seen any leaks either.

-My transfer case does seem to leak a little, but when I changed the fluid it was a fine color and the level was not super low. It hadn't been changed for years before then, and that was also in the summer. There is just a drip at the bottom of the case, it honestly doesn't even fall after a minute or two of watching (unlike my oil). The 4 wheel drive still works fine, and it was rarely used throughout my jeep's life.

I'm stumped on what this thunk can be. The transmission shifts fine, no weird noises, the transfer case doesn't get super hot like there would be a ton of friction in it. My next step would be to take off the rear diff cover and look at it, but i'm not really sure what to look for other than metal shavings. Does anyone have an idea of what this could be? Thanks a bunch for any replies to this. My jeep is 100% stock as far as the drive train goes. No lift either.

 

take a look at your Transfer case mount. My guess is it's shot which could be part of the problem.
Do you have any lift? The SYE could be off or the drive shaft could be a little long after the lift.

 

No lift, but I will take a look at the mount. Thanks! I also noticed it will shift into gear pretty hard sometimes. Between reverse and drive usually. I park on a fairly steep hill when I go to my girlfriend's house (Pen Argyl was literally built on the side of a mountain), could that be putting a greater amount of stress on the tranny and everything when shifting from park to reverse or drive? I know it has to affect it a little, but would it cause damage? her parents never had trouble with their cars doing that. But then again, I own a jeep. I love it to death, but it's a pain. haha.

 

I had the same clunk when shifting to drive. It didn't happen all the time. It went away after I changed the tcase mount.

If you change the mount, also change the two motor mounts at the same time. All 3 mounts are fairly simple to change.

Use pb blaster on the tcase crossmember bolts and on the two bolts holding the mount to the tcase. You might have to use heat for those two bolts. Be careful because they can snap and you DONT want to deal with that headach.

The motor mounts are simple. Just losen the bolts and put a jack under the oil pan. use a piece of wood inbetween the two - just to make sure you don't damage the pan. Raise the jack and the bolts should simply slide out.

Best of luck.

 

I have a tranny crossmember, not a t-case one. Do you mean the tranny mount?

 

Yeah, same thing. Should be the only crossmember and right under the transfercase.

 

The mounts are all fine, it ended up being the rear most u-joint. I must've looked right over it while I tested the others. I'll probably pick a new one up from autozone tomorrow and put it in this weekend. Thanks alot man!