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model 20 answers

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tufcj View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tufcj Quote  Post ReplyReply Direct Link To This Post Topic: model 20 answers
    Posted: Sep/23/2023 at 8:39am
Also need some clarification on the carrier bearings.  They should have a +.008" preload, meaning the bearing/shim pack should be WIDER than the gap in the housing.  Otherwise the carrier will move and the tooth contact pattern will change.

Got any pics of the contact pattern, particularly the drive side?  Your "oval" should cover the vast amount of the tooth, not just the center. 

If you go to Ratech, https://ratechmfg.com/  They have a crush sleeve eliminator, which uses a spacer and shims, and is easier to get preload correct and it will stay put under hard use.

Bob
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Edited by tufcj - Sep/23/2023 at 8:45am
69 AMX
74 Javelin AMX
67 Rogue

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Post Options Post Options   Thanks (0) Thanks(0)   Quote WARBED Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2023 at 11:09pm
Do not over tighten the pinion nut. If the rotating torque figure is exceeded, a new collapsible pinion spacer sleeve must be installed. Do not loosen and retighten the nut.
59 American 2dr S/W. 70 390 AMX. 70 232 javelin. Kelvinator fridge ice cold beer storage.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WARBED Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2023 at 11:01pm
Torque on the pinion nut and crush sleeve is not a set torque value. don't know where you got 250 ftlbs you need to use a dial inch pound torque wrench. The free torque on the pinion nut should be around 22 INCH POUNDS.. don't quote me on that number. So basically, you tighten the pinion nut untill there is no slack then measure with the inch pound meter till you have the desired torque value. pinion should spin without the ring gear installed with slight resistance. You probably over torqued the assy and need to totally disassemble replace pinion bearings and start over. remember inch pounds not Foot pounds. again once tightened the pinion nut should be able to spin with around 22-inch pounds. so it takes small steps untill you get the desired settings.
59 American 2dr S/W. 70 390 AMX. 70 232 javelin. Kelvinator fridge ice cold beer storage.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1970390amx Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2023 at 2:11pm
Originally posted by rwtylla rwtylla wrote:

I just rebuilt my model 20 in a 68 amx. new pinion and ring gear bearings clutch plates, ect. I was very happy with the foot print on the ring gear, I had perfect ovals on both sides in the center of the ring gear.
my problem is it howls under a load. I really dont know what went wrong.  250 lbs of torque on the crush washer, loaded the side bearings to .008 clearence, 0075 backlash on the ring gear, axle end play is .005
any thoughts or ideas would be helpful
thanks
ROB

The spec you state on the crush washer sounds strange. It should be a very low torque measured by what it takes to rotate the pinion. Like maybe 20 inch lbs.
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1970 Amx missing most everything, or in a box
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rwtylla Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2023 at 11:18am
I just rebuilt my model 20 in a 68 amx. new pinion and ring gear bearings clutch plates, ect. I was very happy with the foot print on the ring gear, I had perfect ovals on both sides in the center of the ring gear.
my problem is it howls under a load. I really dont know what went wrong.  250 lbs of torque on the crush washer, loaded the side bearings to .008 clearence, 0075 backlash on the ring gear, axle end play is .005
any thoughts or ideas would be helpful
thanks
ROB
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Buzzman72 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/18/2023 at 11:45am
Originally posted by SC397 SC397 wrote:

I am going to put a copy of this here so that I can find it again. It shows what the 1966 Tweener AMC20 ring and pinon looks like compared to the later more common one.

Rick, did anyone ever determine if this change would work for the torque-tube AMC 20s?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/17/2023 at 1:19pm
I am going to put a copy of this here so that I can find it again. It shows what the 1966 Tweener AMC20 ring and pinon looks like compared to the later more common one.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WARBED Quote  Post ReplyReply Direct Link To This Post Posted: Aug/17/2022 at 10:30am
Moser and the rest want the original axles because AMC 20 is a semi floating design. it uses a thrust block in the carrier that the axle butts up against and shims to determine end play, so the axles have to be the exact length. Many install the axle bearing backwards defeating the thrust block's purpose. but they still use the tapered roller bearing design. You can't use a tapered bearing independently has to be used with another tapered roller bearing, hence the thrust block. 
59 American 2dr S/W. 70 390 AMX. 70 232 javelin. Kelvinator fridge ice cold beer storage.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/17/2022 at 8:25am
Originally posted by PHAT69AMX PHAT69AMX wrote:

I think it would be really helpful to know, and feel it has never been clearly figured out, explained, & documented, just WHY the 1970 ONLY Passenger Side AXLE is SHORTER than 1968 & 1969 !

There is some still even yet clearly figured out REASON WHY 1-Piece Axle companies WANT THE EXISTING STOCK AXLES SENT TO THEM in order to make & sell you new 1-piece axles...

I would really like to know SPECIFICALLY why ONLY the passenger side Axle is different for 1970 ONLY.

AND why many say the 1970 Housing is narrower... when the SAE Papers show SAME REAR TRACK WIDTH of 57.00" for all 3 years of AMX, 1968, 1969, & 1970 !

AND the Parts Book shows A DIFFERENT HOUSING PART # for 1970 only ! ????
BUT the same 2-Piece WLD Twin-Grip "Posi" Case / Carrier for ALL 3 YEARS !

Recent Parts Book "digging" appears to suggest, MAYBE...
There was a SIDE GEAR CHANGE, SIDE GEAR "RING" CHANGE, CLUTCH PACK CHANGE...

1968-69, "this" Side Gear. this "Side Gear Ring", these Clutches of this thickness, these axles.

1970, "this" Side Gear. -NO- "Side Gear Ring", these Clutches of this thickness, these Axles...

Man it's a bummer not to have a parts stash anymore of known vintage to do accurate "discovery" on.

My 1970 AMX is original and has the same width axle as my 1968/1969 AMX's.
 I just went through and measured 7 rear ends that I have and the only difference in all of these is the passenger side axle tube.
Some are at 18" inside axle flange to center housing and some are at 18 1/2"
All of the axle tubes on the driver's side measure at 17 5/8" - So all the axles on the driver's side are the same.
The spring perch cc are all the same at 43 3/8"-43 1/2"

All of these rear ends have the 18" tube on the passenger side
68 AMX - Original from my car.
69 AMX - Original from a scrapped AMX
70 AMX - I measured the one in my AMX that is original
71 Hornet - original in my car.

All of these rear ends have the 18 1/2" tube on the passenger side
4.10 gear unit out of a Gremlin but unknown if original. It does have a later casting number on the center section 3212478 vs 3186891 on all of the rest.
3.54 gear unit out of I don't know what.
4.56 gear unit out of I don't know what. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mbwicz Quote  Post ReplyReply Direct Link To This Post Posted: Jan/17/2022 at 9:33am
Dave, the gears can be swapped from your axle while maintaining the twin grip.

The other reasonable option for lowering the cruise RPM would be to swap to an overdrive transmission.


1970 AMX, one step forward, one step back. Both steps cost time and money.
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