I also have 9.75 with drums!

 

I have had the same problem with mine, although I had a locker, grenaded the rear and broke both axles, just because an ear broke off of one clutch got caught in the spider gears and ripped everything to peices. So that being said, please buy a good set of clutches for the rear..

Adam

 

I broke the rear end again.

1st time the factory diff came apart and went through everything. Replaced factory diff with auburn, 4.10 gears.

2nd, 3rd, and now the 4th time, pinion tooth broke off. Had two different mechanics do it so it's not a setup issue. This time the auburn posi has given out and it's just an open diff. Also one of the axle shafts was very scored, to the point where it needed to be replaced.

So I found myself a 99 9.75 rear end out of an f150. In 99 Ford put them in some trucks, and in 2000 they started putting them in all of them. 99 still had drum brakes. Discs would have been nice, but I didn't want to get too difficult with the swap, as time and cash were tight.

There were a couple of minor issues not worth mentioning, but the axle was pretty much a straight swap. I still need to get a set of 4.10 gears for the 9.75 put in, but I got one with a factory limited slip. The abs works, brakes were exactly the same, etc. The only hard part was fitting the truck in my garage (it barely fits and you have to go under the truck to get from one side of the garage to the other), then getting the truck high enough to get the axle in and out from underneath it. And of course, the axle is heavy, which makes things interesting.

Took a few pictures here of the difference. The 9.75 is much bigger.

 

jayntguru,

Did you shorten the drive shaft?

JMC

 

The nose was a little bit longer but everything seemed to fit ok.

 

I shortened my drive shaft. I measured the length of the flange on the diff to the output shaft when the 8.8 was still installed and the when the 9.75 was in place. The difference between the two measurements was removed from the drive shaft. I cannot remember how much it was but it think it was just a little over 1 inch.

JMC

 

I need to look into that, haven't driven the truck a bunch but I will check ASAP.

Is there a reason you had the shaft shortened as opposed to getting one from a 9.75" rear end truck?

 

Just curious. After you had your diff rebuilt did you break the new gears in properly? I have heard too many stories of people who get their truck regeared or something and then go out mudding the next day and break them. I recently blew my rear diff and replaced it on my own with posi (had an open diff before) and it was so hard for me to drive 500 miles without doing donuts or heading out to the mud pit. Also I'm confused: JMC mentioned to you that you should swap your 8.8 with a 9.75, but your signature says you have a 9.75... Am I missing something?

 

jayntguru,

Ford never made a driveshaft for the M5OD with a 9.75 diff drivetrain.

JMC

 

jiggle,

Read post #18.

JMC

 

I just went out and checked after my drive, and I need to have the shaft shortened, working on that now.

 

Yeah I don't know how I missed that. I guess I didn't realize there was a second page before I replied.

 

Hate to break in here, but could someone replace the rear 8.8 with a 9.75 on a 4x4 truck, without having to replace the front one? Or would you have to replace them both? Thanks.

 

My 03 came with an 8.8 in front and 9.75 in back.Just make shore the gears are the same.

Phil

 

Cool .