91stormvet

Hi,
Does anyone know if I can swap in a 9.75 diff, 3:73 ratio in place of my 8.8, 3:73? My truck is a 2007 XLT extended cab. I have replaced rear once already with a junk yard part, that is now making noise again. Was never a good part from the start. I came across one that is from a 2008, same ratio, but it's a 9.75 posi. Local junk yard tells me my only option for my truck is one out of a 2007-2008 truck. Can someone shed some light for me if this is the case. I'd be looking at $1500 from junkyard, or $500 for the 9.75 from Craigslist. Would obviously like to save that kind of cash. Seems the rotors and brake pads are the same from both rears, which is nice because I just put new premium pads and rotors on it last week. Then tore rear end up pulling a trailer. Lol. Any info would be greatly appreciated.

Thanks,
Tim

gone postal

IIRC the driveshaft yokes are different, you'll need a new shaft, otherwise you're fine.

91stormvet

Thanks for the info. The guy selling the diff on Craigslist has the complete truck. Only issue is, it's a crew cab, so I'm going to assume that shaft is longer than the one on my extended cab. But I'm pretty sure locating another shaft will be much easier and cheaper than having a 2007-2008 specific rear diff shipped from elsewhere, as no local yards have one. Already spent $1200 on this job a couple years ago, and that rear was a piece of crap! I should add that my truck is a 4.6, is the shaft the same slip yoke out of the transfer case?

Thanks again!

bassJAM

If your differential is making noise, it might be better to just open it up and see what's going on in there. Could be bad wheel bearings, or a clutch pack going bad if you currently have a limited slip, or you could need new gears.

Personally I'd rather just replace a broken part than swap in an entire new rear-end, especially if it meant trying to get a 9.75" to fit.

SteveLord

I’d rather have just spent the money on fixing it and not chancing it with a swap like that.

lutter5-0

Was the original not rebuildable?

91stormvet

Considered fixing it, but with time constraints, much easier for me to swap out than tear down and fix. I know the risk of the new used rear being bad, but if I get another year out of it, I'm happy. Plan on a new truck soon. Plus, I do a lot of local towing, and the 8.8 just didn't hold up to my driving style. The original rear was serviced by me and proper gear oil used, so it wasn't neglect on that level that killed it at 120k miles. Second rear looked good inside the pumpkin, was supposedly 50k on it, but exterior condition was crap. It's still kicking, but pinion is sloppy and starting to hum pretty bad at 180k, which the math puts it at about same life span as my original. I'm hoping the 9.75 give me a little more life, especially since my nephew usually winds up buying my hand me down trucks. Obviously I need to make sure all fits, and rear is what the guy says it is when I go check it out. I'm sure I will get the responses of " I have a million miles on my 8.8 and no problems" which I'm sure is the case. Just hasn't been my luck.

Eric Kleven

I'd think as long as wheel base and back-of-trans are the same, you'd be able to swap driveshafts along with the axles.

91stormvet

Just wanted to give an update in case someone is considering this swap.
Everything went great! Only issue was the driveshaft, but not because yokes were different as stated above, but because of the length. I had to have mine shortened by an inch and half. Other than that, everything was bolt on. Brakes,rotors, shocks, and ABS plug all the same. All together, got a great condition rear diff and new u-joints and shortened shaft for $700 total. Wish I went this route the first time I changed it. Thanks for all the input.