AMC 20 Torsen Type 1
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I bought a pallet of HMMWV differentials on govliquidation.com a while ago to try and salvage some AMC20 TORSEN Limited slip differentials. I was the high bidder at $55. So $68.47 later, I owned 4 of them. I recently started the install and thought I would post some things I learned.
Most HMMWV differentials have a 2.56 or 2.73 gear ratio. Some are 3.08, however it is a "thick cut" ring gear made to fit the 2.73 and down carrier. The four that I bought are 3.08. It would have been nice to just slap on the 3.54 ring gear and re set the back lash. It's about 7/32 off. I talked to a few machine shops and there are a few options if you want to run the standard AMC20 3.08 and up gears. you can turn the carrier dawn so that the carrier bearing opposite the ring gear sits farther inboard and put a spacer under the carrier bearing on the ring gear side. Or you can have a ring gear spacer made. 7/32 looks like you could have a ring gear spacer made from the old ring gear and still have enough of the machined area on the carrier above the spacer to center the ring gear. Both options ran about $100 for labor. I chose to keep the 3.08 gears. I run 29 inch tires and it is screaming at 65.
Everything else is the same set up wise as the normal AMC 20 accept the pinion depth shims. The HMMWV AMC 20 uses a single pinion depth shim that is machined to the right thickness for that pinion. I very carefully re moved the inner bearing cup with out damaging that shim so I could use it as a starting point in my jeep M20. It produced a good pattern and I didn't use any other shims for pinion depth.
Most HMMWV differentials have a 2.56 or 2.73 gear ratio. Some are 3.08, however it is a "thick cut" ring gear made to fit the 2.73 and down carrier. The four that I bought are 3.08. It would have been nice to just slap on the 3.54 ring gear and re set the back lash. It's about 7/32 off. I talked to a few machine shops and there are a few options if you want to run the standard AMC20 3.08 and up gears. you can turn the carrier dawn so that the carrier bearing opposite the ring gear sits farther inboard and put a spacer under the carrier bearing on the ring gear side. Or you can have a ring gear spacer made. 7/32 looks like you could have a ring gear spacer made from the old ring gear and still have enough of the machined area on the carrier above the spacer to center the ring gear. Both options ran about $100 for labor. I chose to keep the 3.08 gears. I run 29 inch tires and it is screaming at 65.
Everything else is the same set up wise as the normal AMC 20 accept the pinion depth shims. The HMMWV AMC 20 uses a single pinion depth shim that is machined to the right thickness for that pinion. I very carefully re moved the inner bearing cup with out damaging that shim so I could use it as a starting point in my jeep M20. It produced a good pattern and I didn't use any other shims for pinion depth.
