I have been noticing a disturbing trend in my driveline lately. It's gotten to a point of good consistency, now, so I'd like help in trying to diagnose the problem. If any of you can give me some pointers on what parts to check (and possibly how to check them), in order of likeliness, I would appreciate it greatly!
My Jeep: 1997 TJ I6 4.0L, 4" lift, 33" tires, D30 front, D44 rear (w/limited slip), AA SYE kit (installed myself), brand new CV front and rear driveshafts (front installed < 6 months ago, rear installed w/SYE kit in October-ish). Still original AX15 and NP231.
The Problem: Whenever I first start from a stop, and often when apply the gas after a shift (especially in 1st through 3rd gears), I am getting a small but noticeable "thunk". I can't so much hear it, but I can feel it both through my seat and through my pedal (I can feel it when riding as a passenger in my jeep as well). This thunk also occurs when I let off the gas pedal quickly while in gear, especially noticeable in lower (more torquey) gears. It has become a futile battle of me trying to match my engine RPMs EXACTLY when shifting, and pulling the clutch out VERY slowly, in order to try to get the thunk to not occur; I am successful probably 40% of the time when I try this. So, it seems something is loose in my drivetrain or in something that has tension under forward and rearward drive direction, and thunks when extra power is applied, or if a deceleration force due to engine braking occurs. BTW, all of this is happening in 2-high mode.
What should I check? So far, I've put the t-case in neutral and tried moving both the front and rear driveshafts. The rear had negligible play (pretty close to none); the front had quite a bit more play (but I have ruled that out as the cause since it is not even engaged at the transfer case end when I get this problem). Could this be control arm related? I have brand new teraflex adjustable rear control arms on it (installed at the time of my SYE kit), which I've kept greased properly... I haven't tried prying on them yet to see if they are the issue.
Thanks in advance for any advice or suggestions!
/Bob