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Doug's 70 AMX Build

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DoughertyAMX View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DoughertyAMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/16/2018 at 5:56pm
I meant the spider gears in the twin grip carrier as pictured.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Apr/16/2018 at 6:16pm
Originally posted by DoughertyAMX DoughertyAMX wrote:

Well cleaned off the rear end differential cover and found a C stamped there.  Just what I was afraid of, a 2.87 ring and pinion.  

Think I'm going to go 3.31.  If any member has a set of 3.31's I'm interested, or I can just buy a new set.

Be careful - C only means that is what the factory installed and intended. 
My 70 was stamped with C - very clearly a C - but the gears inside were 3.15
The original purchase invoice for the car has a line item added:
Gear ratio      ----    $10

Yup - before the car was even picked up from the dealer, when it was brand new, it had 3.15s dealer installed. I counted teeth and verified. 

Yours was likely not changed like that, but hey, who knows.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1970390amx Quote  Post ReplyReply Direct Link To This Post Posted: Apr/16/2018 at 6:51pm


Originally posted by DoughertyAMX DoughertyAMX wrote:

So does anyone have experience replacing the spider gears in the AMC 20 locker?  I have found two teeth broken off one of the spider gears.  Will this kit work?

https://www.summitracing.com/parts/cwa-j8120326/overview/


what you have pictured is an factory open diff, no clutches. The spider gears are easy to change.

I forgot to look at what gears you were looking at, no they will not fit they are for a late twin grip




Edited by 1970390amx - Apr/16/2018 at 6:54pm
1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/16/2018 at 8:52pm
Interesting thread.  A suggestion if I may, fabricate a Sheet Metal Panel to install in the trapezoid shaped hole between the trunk and passenger compartment.  Been a long time since I did it... 90 degree bends on vertical side edges fit nicely into existing "Z" bends in existing side uprights, where I attached the new panel with some screws through holes added to the "Z" bend flanges, about a 1" wide "kick-out" flange lip along bottom edge forward lays on top of axle tunnel and another rear facing approx 1" flange along the top.  Did / does wonders for a quieter cleaner and SAFER passenger compartment and meets track requirements IF doing a trunk mounted Battery, which should be mounted crossways left to right, NOT longways front to back like so many do on the rear passenger side...

Edited by PHAT69AMX - Apr/17/2018 at 2:54pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1970390amx Quote  Post ReplyReply Direct Link To This Post Posted: Apr/16/2018 at 9:16pm
carrier to the right and in the back is a factory twin grip used up to 71. It is a two piece unit that instead if a pin to hold the small gears in place it has a cross and four small gears with two larger gears that spline to the axles. Front carrier I think came out of a hummer with 2;73 gears. It is a thorsen torque limiting carrier, no clutches.
1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1970390amx Quote  Post ReplyReply Direct Link To This Post Posted: Apr/16/2018 at 9:21pm
Carrier at left is a newer Detroit locker. On right is better picture of power lock twin grip used in 70 amx
1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DoughertyAMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/17/2018 at 5:54am
Originally posted by 1970390amx 1970390amx wrote:



Originally posted by DoughertyAMX DoughertyAMX wrote:

So does anyone have experience replacing the spider gears in the AMC 20 locker?  I have found two teeth broken off one of the spider gears.  Will this kit work?

https://www.summitracing.com/parts/cwa-j8120326/overview/


what you have pictured is an factory open diff, no clutches. The spider gears are easy to change.

I forgot to look at what gears you were looking at, no they will not fit they are for a late twin grip



Thanks, so what I have is not a twin grip rear end correct?

Also, you say these gears are easy to change.  Any idea where i can get a set ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DoughertyAMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/17/2018 at 5:55am
Originally posted by billd billd wrote:

Originally posted by DoughertyAMX DoughertyAMX wrote:

Well cleaned off the rear end differential cover and found a C stamped there.  Just what I was afraid of, a 2.87 ring and pinion.  

Think I'm going to go 3.31.  If any member has a set of 3.31's I'm interested, or I can just buy a new set.

Be careful - C only means that is what the factory installed and intended. 
My 70 was stamped with C - very clearly a C - but the gears inside were 3.15
The original purchase invoice for the car has a line item added:
Gear ratio      ----    $10

Yup - before the car was even picked up from the dealer, when it was brand new, it had 3.15s dealer installed. I counted teeth and verified. 

Yours was likely not changed like that, but hey, who knows.

Bill, yeah I took the cover off to specifically count the teeth and sure enough it is a 2.87, then I also found the broken teeth off one of the spider gears
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1970390amx Quote  Post ReplyReply Direct Link To This Post Posted: Apr/17/2018 at 1:49pm
I would say to find a new set of gears to post an add in the wanted section, or buy a new limited slip carrier and install it
1970 390 4speed Bittersweet shadow mask AMX
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/18/2018 at 1:28pm
Some old questions from throughout posts...
I'm "AMX Jones-ing" since selling mine April 2014, owned since 1985...
Sorry if "too much information"....

- Top of right front fender......
? Motor on hoist kinda got away from'em?

- Did ya check for a "gap" or "hole" between panels
outside the glass, directly rearward from the bottom rear corner
of the small fixed side glass, trim, and rubber, on both sides ?
My '69 had a dime sized or so "hole" right there on both sides
between where panels came together that I sealed with silicon.
Water could would did get down in there everytime washed or in rain...

- Be careful Washing or Waxing the Car of the THE DRIP RAIL TRIM ENDS!
Mine was Razor Sharp at both ends of the DRIP RAIL Stn TRIM.
I got cut on it only one time... the 1st wash...

- Firewall Pass-Thru Plate, extra holes handy for aftermarket gauges...

- DynaMat is what I'd use, modern, gotta be better than "jute"...

- Small Vertical Interior Side Panels behind seats:
Have no picture, iirc mine were masonite, which seems ok, but...
that sure does not seem "good" to use if any moisture.
Eddie Stakes PlanetHoustonAMX sells them....

- Hood Latch, drawing from parts manual...

- Carpet front top edge, iirc my '69 Carpet hung on the 4 Plastic "T" Plugs.
Then was further retained by the Left & Right Plastic Kick Panels.
I did not go as far as thehaving the Dash and/or "jute" being removed....

- Carb, I'm a Holley Guy and nothing compares to the performance of
a properly set-up DoublePumper if Punch It & Blast is "your deal".
And these guys gotta be tired of hearing this from me, but...
Proper SECONDARY Idle Speed Butterfly "Park Position" is CRITICAL.

- IF a "fair weather" only car, would block off the Intake Exhaust Heat Crossover.

- Distributor: Any decision on a path of action, recurve original?

- Brackets, Alternator, P/S, etc, Did you get install dwgs or Diagrams?

- I myself prefer the early Script style 1x1 above the trunk lid, nice.

- Opinion here: Pinion Angle, mine seemed "backwards", and had New Leafs.
I installed Aluminum Wedge Spacers to "correct" Pinion Angle, see dwg...
imho Pinion should point slightly down at rest, then with load
it can rotate up ever so slightly towards straight...
Mine stock pointed slightly up so would the go further up under load...
Angles should be equal and opposite, Trans Tailshaft & Rear Pinion.

- What's your opinion on suggested Steel Panel between Trunk & Cabin?

- Gonna go with a group 19 Brushed Stainless Chin Spoiler?

- Boy if the NOS Carrier that guy has in your Wanted Ad is
the "Right One" would think could hardly go wrong getting that
other than the big bucks for a Posi Carrier....
which then kinda "pushes" a person towards one piece axles...
Ha Ha the "snowball effect" is a vicious monster to avoid!

- Borg Warner Automatic Kick-Down Switch, reckon you're aware
there is an Electronic Kickdown Switch under the dash that is
actuated by an extra "Rod" on the gas Pedal Linkage...
At least there was on my '69 with an BW M-12 Automatic Trans.



Here's a vintage underhood picture of a brand new 1970 AMX 





Edited by PHAT69AMX - Apr/18/2018 at 1:40pm
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