Results 1 to 4 of 4

Thread: AMX Rear End

  1. #1

    Default AMX Rear End

    I've got a guy who wants to give me what he thinks is an AMX posi rearend from 67 or 68. 12 bolts on the differential cover but I haven't seen it yet. What am I looking for to prove it's from an AMX? Any pictures?

  2. #2
    Join Date
    Jun 2008
    Ketchikan, Alaska


    There was no '67 AMX for starters. You'd have to measure the width and mounts to see if they are from an AMX/Javelin. The AMC 20 is a fairly common axle.

    Here is a good article with some broad details, but an interesting section on the differential.
    The Model 20, an AMC design with an 87/8-inch ring gear, enjoyed a long life under Kenosha cars--it was used through the end of AMC V-8 production in 1979. AMC engineers made it simple to identify the axle ratio inside the pumpkin by stamping one of four codes from the factory on the differential housing cover flange. An A-code refers to a 3.53:1 gear ratio, B-code to a 3.15, C-code to a 2.87 and a D-code to a 3.91. Stakes said that dealers offered four additional gear ratios: 3.73:1, 4.10:1, 4.44:1 and 5.00:1. AMC made a limited-slip differential, called the Twin-Grip, available as an option. Apparently, nothing apart from the build sheet can identify a Twin-Grip-equipped car.

    Reeves said Model 20s "are hamstrung by the splined hubs on the ends of the axle shafts. If kept properly torqued, these axles can take a good bit of extreme abuse, but most serious performance drivers replace the splined shafts with solid one-pieces units."
    Last edited by MR2Di4; 06-24-2008 at 12:52 PM.

  3. #3


    I grabbed the rear end and took a few pictures. Supposedly from a 70 AMX that had a 390. It didn't have the cover plate so not sure what ratio without counting the teeth. Based on wheel rotation, it appears to be the twin grip. Approximately 52" from backing plate to backing plate, and about 44" from the center of one mount to the center of the other side. You can see some pictures here....

    Does it look right for a 70 AMX?

  4. #4
    Join Date
    May 2005
    Gresham, OR 97080


    I don't want to hijack this thread, but the following quote, from MR2Di4's Quote,..... well, it grabbed my attention:

    Quote: (?Quote:?)
    "AMC made a limited-slip differential, called the Twin-Grip, available as an option. Apparently, nothing apart from the build sheet can identify a Twin-Grip-equipped car."
    I thought that there was a sticker in the trunk and/or a tag at the filler plug

    I have a '73 Matador 2dr Hrdtp that has that little Chrome Sticker Label in the trunk, Stating something to the effect of 'Warning the car is equiped with a certain differential and caution should be taken while one side of the car is jacked up and the wheels are spinning..' I don't know exactly what it says at the moment nor do I know what year AMC started using them. I was fairly certain that it was a Twin-Grip indicator though??

    Also, Just last week, while I was helping determine the ratio on a '70 MD Javelin, I noticed that little stamped metal Washer/Label at the fill plug. I while I didn't read it this time, I seem to recall, again, that it states something to the point of ' Use a special gear oil additve for positve locking differenentials' or what-not.

    Am I mistaken recoallating (Mis-Re-remembering??) on to what both those little labels indicate?
    I'll have to take a closer look at each of them. Also AMC might not have started to use them until '70 (Filler Label) or '73 (chrome Trunk sticker)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts