Thump/Clunk still there after installing new drive shaft
bought a used 2008 V8 4Runner 2 years ago and experienced the thumping/clunking issue around 1 month after purchase. The thumping would occur when coming to a stop, when accelerating from stop and when accelerating moderately or hard from ~20 mph.
My mechanic would grease the driveshaft during every oil change which would address the issue for ~500 miles. After reading many posts in this forum, I was confident that replacing the drive shaft would resolve the issue. My mechanic is very knowledgeable about Toyotas but even he was not certain that replacing the drive shaft would solve the problem.
One week after installing the new Toyota drive shaft, (not the Lexus part), I was happy to report that the thumping had gone away, or at least I thought so. While driving to work one morning, I accelerated moderately hard from ~20 mph and felt the thump/clunk again. I went reported the issue to my mechanic and went back to have him tighten the U joint bolts. I also learned that he replaced only the rear drive shaft. I asked if he should have replaced the front drive shaft as well and he responded by saying that he did not think that the front drive shaft had anything to do with the thump/clunk issue.
It has been more than 2 months since I replaced the rear drive shaft but given my state implemented stay at home orders in mid-March, I have driven my car ~300 miles with the new drive shaft. There is no issue when coming to a stop or accelerating from a stop but the issue did present itself again 3 days ago when I accelerated moderately hard from ~20mph.
My mechanic believes that there is some other issue with my transmission, perhaps with the differential. He has found a significant amount of rust (also know issue with this generation 4Runner) which we have covered with 3M rubber coating twice since I bought the vehicle.
I wanted to reach out to this forum and ask if anyone might know what is causing the thump/clunk when accelerating from ~20 mph. Is this a front drive shaft issue, differential or something else in the transmission?
I use my 4Runner as my daily driver and to trailer my race car to the track. I have installed an auxiliary transmission cooler, replaced the timing belt and done a full tune up since purchase. The truck runs beautifully, except for this one annoying issue. I want to address this issue given that I tow a heavy load (race car plus equipment and tools = ~6,000 pounds) 7-10 times per year, sometimes several hundred miles and over significant grades.
Any advice/suggestions would be greatly appreciated.