Grinding in Reverse

I have a 90 with 4" lift and 31's 242, aw4, d30/d35

I'm gonna be doing some work on my rig in the next couple weeks....One thing I need to address is a grinding noise I get while accelerating hard in reverse. I have been wheeling my truck mild to moderate over the past year, once a few months ago I was recovering someone in reverse while I was tugging I got a really loud sharp grinding sound. It sounded like like gears stripping over teeth. Now in reverse I get the same sound but only if I need to back over something. Everything in foward gears is fine, this noise happens in 2wd and 4wd.

Another thing to add that might be related is a noise when I shift into 4wd . It is a clicking or thumping noise that is consistant with the speed of the drive shaft.

Any ideas??

Thanks

-Mike

i have the same problem... i dont know what it is let me know if you find something and ill do the same.

I wish I could find some information on this but I have found nothing, on this site or anywhere else on the net. I do not know much about transmissions, but I wounder if it worth swapping out the tranny just for the reverse gear. I just swapped in 2 new axles hp30/8.25 so the diffs are ruled out.

NP242's are far from trouble-free.. maybe pull a fluid sample and see how nasty it's getting in there. Also on both 242's and 231's a quick back and forth twist of the front output yoke shouldn't cause any chain slapping type sounds.

How about your u-joints?

All new u joints less than 1000 miles ago....

Also on both 242's and 231's a quick back and forth twist of the front output yoke shouldn't cause any chain slapping type sounds.

Click to expand...

I'll check that out...thanks for the info.

It's the transfer case hitting on the diagonal crossmember/protector. The transmission/engine mounts have possibly sagged allowing contact between the two. Should cause no harm in the short term except for difficult de-selecting of 4wd.

Have someone (with park brake firmly applied and foot on brake pedal) shift vehicle into reverse while you are looking at the gap between the transfer case and crossmember under car. You will see the gap decrease and you can imagine with engine twist under gas, the tranny will tap away at the member sounding like a grinding. Replace rear transmission mount and inspect engine mounts LH one in particular due to temperature from the extractors (or in my case leaking original headers melting rubber mount). J.