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How to ID a Twin Grip

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billd View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Dec/17/2010 at 4:04pm
1970 TSM, page 11-1 ->   (as well as 1971)
 
"All 8 7/8" axles will have the AXLE RATIO CODE stamped on the differential cover housing flange"
 
................. exactly where mine is. So mine is correct - in the correct location - according to the AMC 1970 TSM.  "cover flange". The C is on the cover, on the flange of the cover. Not on the differential housing.  So if it ended up on the housing, that wasn't according to the book  ;-)
 
The smaller axle code is on a tag "affixed to a differential housing cover screw".
 -------------------------------------------------------------
Now wait - the 1974 TSM states:
"The axle ratio identification code is located on the axle tube housing boss, adjacent to the dowel hole".
THAT's what a lot of you are talking about................ next to the DOWEL hole on the axle housing/tube itself. (the axle tube housing is the case middle part of the differential, the bit the axle tubes press into, so the code is on the cast axle tube housing where it's been machined for the spreader)
 
 


Edited by billd - Dec/17/2010 at 4:12pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Dec/17/2010 at 7:26pm
Originally posted by billd billd wrote:

1970 TSM, page 11-1 ->   (as well as 1971)
 
"All 8 7/8" axles will have the AXLE RATIO CODE stamped on the differential cover housing flange"
 
................. exactly where mine is. So mine is correct - in the correct location - according to the AMC 1970 TSM.  "cover flange". The C is on the cover, on the flange of the cover. Not on the differential housing.  So if it ended up on the housing, that wasn't according to the book  ;-)
 
The smaller axle code is on a tag "affixed to a differential housing cover screw".
 -------------------------------------------------------------
Now wait - the 1974 TSM states:
"The axle ratio identification code is located on the axle tube housing boss, adjacent to the dowel hole".
THAT's what a lot of you are talking about................ next to the DOWEL hole on the axle housing/tube itself. (the axle tube housing is the case middle part of the differential, the bit the axle tubes press into, so the code is on the cast axle tube housing where it's been machined for the spreader)
 
 
The 1972 TSM says the same thing as the 1974 TSM......(I have both the 1972 &1974 TSM's)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMC instigator Quote  Post ReplyReply Direct Link To This Post Posted: Dec/17/2010 at 7:44pm
71 is the last for it to be on the cover flange, then it swaps to the dowel hole flat spot. I have seen some 70 and 71 models with it on the dowel flat as well big cars only though. As the cars get newer, the letter gets smaller too. Sometimes I have seen them with a half faint letter from them being stamped by a worker that didn't hold the punch straight. So you have to clean with wire brush and look closely. Especially if you live with rust. SH
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Dec/17/2010 at 7:49pm
Originally posted by AMC instigator AMC instigator wrote:

71 is the last for it to be on the cover flange, then it swaps to the dowel hole flat spot. I have seen some 70 and 71 models with it on the dowel flat as well big cars only though. As the cars get newer, the letter gets smaller too. Sometimes I have seen them with a half faint letter from them being stamped by a worker that didn't hold the punch straight. So you have to clean with wire brush and look closely. Especially if you live with rust. SH
That makes sense to me..............I guess when I get the rear end out of my '72, I will have to look very closely again.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Dec/18/2010 at 12:44am
>>Sometimes I have seen them with a half faint letter from them being stamped by a worker that didn't hold the punch straight. So you have to clean with wire brush and look closely. Especially if you live with rust. SH <<
 
Oh, yeah, for sure! I've seen a few of those.... even on the chassis behind the steering sector - the VIN can be very hard to read. I've got some number stamps and if you don't hold 'em perfectly straight, especially on hard material, a 0 might end up like a C
I've not looked in other TSMs, I'm limited on those in the 70s, but suspected that it was a change in the "official" place after roughly 71 or 72. That pretty much matches the "majority" of what I remember. Of course, someone in a hurry can stamp it just close, or maybe someone not familiar with the change, etc. - of a bit hung over from the last holiday.........
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mchaggis Quote  Post ReplyReply Direct Link To This Post Posted: Dec/18/2010 at 4:58am
So I guess I'll need to get under it again and have another look on the cover. 
If I do find it what are the codes?  I guess they're on here somewhere but after a quick look I haven't found them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Dec/18/2010 at 8:39am
Originally posted by mchaggis mchaggis wrote:

So I guess I'll need to get under it again and have another look on the cover. 
If I do find it what are the codes?  I guess they're on here somewhere but after a quick look I haven't found them.
In the TSM.    I think AMC used the same codes for years.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Dec/18/2010 at 8:58am

AMC REAR AXLE DIFFERENTIAL RATIO INFO

from illustrated parts manual section Group 9.050-1

Illustrated is the general location of the rear axle
Ratio Tag used on all cars except 1970 thru 1972 10-80.
These cars have a stamped code on the cover flange.

"J" = 19/45 = 2.37
"G" = 13/43 = 2.73
"H" = 15/41 = 2.73
"C" = 15/43 = 2.87 ... 68/70 V8 ... 320 9610 (Use 448 6156)
"F" = 13/40 = 3.08
"B" = 13/41 = 3.15 ... 68/70 V8 ... 320 9609 (Use 448 6155)
"A" = 11/39 = 3.54 ... 68/70 V8 ... 320 9608
"E" = 12/43 = 3.58
"D" = 11/43 = 3.91

Dealer Installed .... Group 19 ... Performance Ratios:

"?" = 11/41 = 3.73 ... 19.950 ... 448 5749
"?" = 11/43 = 3.91 ... 19.950 ... 448 5750
"?" = 10/41 = 4.10 ... 19.950 ... 320 8546
"?" =  9/40 = 4.44 ... 19.950 ... 320 9854
"?" =  9/45 = 5.00 ... 19.950 ... 448 6587

9.003-1 = rear end housing

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Post Options Post Options   Thanks (0) Thanks(0)   Quote steeters Quote  Post ReplyReply Direct Link To This Post Posted: Dec/18/2010 at 10:48am
Are there any rules about the ratios and the LSD?  For example, if you order a 3.54 ratio is it mandatory that you have LSD?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mchaggis Quote  Post ReplyReply Direct Link To This Post Posted: Dec/18/2010 at 2:51pm

Thanks for the info.  The reason I'm trying to find the code is to identify the carrier.  I've been told different story's over the years about what ratio carriers fit what gears.  I think mine is a 3.15 but it could also be a 2.87 and I'm about to order a set of 3.73 but the vendor has asked me to identify the current ratio before he ships the new set.

What is the real story? 
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