I just recently bought a 93 W150 Xcab with a terribly noisey 3.55 rear diff. and I am sure I will have to either replace or rebuild it very soon. I have rebuilt an 8-3/4 front dropout diff back when I was drag racing but I haven't tried one of the 9.25s before. Any info about what,where, and how would be greatly appreciated.

 

Well, I have found a small part of the noise at least. The original rear shocks were still on it and one had a shroud broken loose from the top and was rattling bigtime plus the other one was totally bad and had a loose shroud too. I replaced them and then pulled the diff. cover to look inside the beast. It actually looked very good IMO. The ring and pinion gears looked OK and there was no massive amount of metal shavings attached to the magnet in the bottom either. The pinion bearings seem fine when I lift the driveshaft up and down but there IS a lot of rotational slop when turning the driveshaft back and forth. I need to do lots more research before I tear into it so I just replaced the nasty oil in it and hoped for the best. It still make nasty noises but not as loud now.
Sure rides better now though!
I am hoping that someone knows about this 9.25 unit and can tell me if there is a nice easy backlash adjustment procedure or something similar.

Thanks in advance.

 

You need specail tool sto set backlash. There are 2 adjusting caps on either side of the diff carrier. They can only be accessed through the axle tubes. The tools we have are about 3 feet long each with a nut 5/8" nut welded on one end and the other side has a huge nut welded on it-that is the side that goes into the diff adjusters. With the tools they are very easy to work on. Good luck