anybody know if the 9.75 posi rear would be a direct replacement for an 8.8? my clutch pack is going again(3rd time) and i can get a 9.75 from the salvage yard(same 3.73 posi) . visually it looks the same . my truck is a 2004 4.6 4R70 and the new one is from a 2005 5.4 4R75. thank you if anyone can help me out.

 

You can't just change out the innards, they won't fit. You would have to change the entire rear axle assembly complete with differential, housing, and all.

 

I think he's talking about the entire rear axle, not the ring gear/diff internals. How much are they asking for it, I'm trying to find a salvage yard with an F150 around here. Where is a good place to look. I'm pretty sure it will bolt right up, just take measurements on where everything bolts to on your truck (driveshaft, shock mounts, leaf mounts, etc).

 

Just FYI, Josiah, I have considered buying 4 different 3.73 'posi' rear ends for my truck in the last year. Up near San Jose one went for 400 bucks, whole rear end. I was too busy to drive up to get it. Another is still for sale in Rancho Cucamonga, he was asking 1000, and was negotiable. I won't pay that much.
One on eBay went for 450 bucks, but shipping was too much, from Virginia, and there is a possible on eBay right now, but I don't know the gearing.

http://cgi.ebay.com/ebaymotors/2006-...QQcmdZViewItem

I'd get one, if I could buy it fairly local (Southern California) for say 500-600.
Got a spare front differential 3.55 brand new in my shop, but it's a non-posi 8.8 new from a 2005, and thus no use to me.
Chris

 

After having both lsd rear ends; in different trucks... The 9.75 unit feels great, where with the 8.8 seemed like the only time it would lock both wheels would be a second after the right wheel lost traction.

Go to the dealership and measure up drivelines, everything else should be the same.

 

Just morbid curiousity here - What exactly are you doing to burn up three limited slip diffs?

 

. . burning out from dirt to pavement.

 

I honestly think it was the install was not done correctly. Each time the dealer replaced it, a few hundred miles later it would start to whine. I do kind of abuse it on the back(paved)roads Lots of slow speed sweepers with full throtle exits. Should have keep my old 2wd '97

 

The ford dealer probably skipped the limited slip additive, that stuff's expensive, but I bet that's the problem!!!