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Tapered axle Mopar 8 3/4 ring and pinion options
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jboymechanic
Posted 2018-02-17 10:58 PM (#558283)
Subject: Tapered axle Mopar 8 3/4 ring and pinion options



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Everything I've read suggests that ring and pinion sets are specific to the differential case (741, 742 or 489). Well, what about buying a new ring and pinion set for the tapered axle Mopar 8 3/4 (AKA 657 case)? It has a 1 3/8" pinion shaft like a 741 case differential, will gears for a 741 case fit the 657?
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mstrug
Posted 2018-02-18 6:10 AM (#558301 - in reply to #558283)
Subject: Re: Tapered axle Mopar 8 3/4 ring and pinion options



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There is accually 6 case numbers, 657 741, 985 742, 488 489. The 657 is the earliest, and basically identical to the 741. 985 and 742 are the same basically, as is the 488 and the 489. The 657/741 is also the hardest one to find gears for.

http://www.yellowbullet.com/forum/showthread.php?t=126172&page=3




The case has the number 657 on it and I am told it is the same as the 741 case. The gears in it are apparently 3.91 ratio (or at least I was told so)but are very noisey and due for replacement. I would like to change them out but I've searched and do not see anyone who sells a 3.91 ring and pinion for a 741 case. What are my options? Does anybody sell a 3.91 for a 657 / 741 case? What would the 657 case have come in? Could they have been 3.91 from the factory or did someone actual make them at some point but they have since discontinued them?

https://moparforums.com/forums/f7/3-91-gears-657-741-case-2325/




https://www.summitracing.com/search/part-type/ring-and-pinion-gears/...

http://www.doctordiff.com/8-3-4-ring-and-pinion.html

https://www.justdifferentials.com/C8-41-373-NG-p/c8.41-373-ng.htm

https://www.drivetrainshop.com/Chrysler_8_75_s/82.htm

https://www.ebay.com/i/173142518061?chn=ps
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58coupe
Posted 2018-02-18 12:16 PM (#558318 - in reply to #558283)
Subject: Re: Tapered axle Mopar 8 3/4 ring and pinion options



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The 3.91 gear set was optional in the 657 case from 57 on. If you ordered a Plymouth or Dodge 6 cylinder overdrive, it was the standard gear set.
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di_ch_NY56
Posted 2018-05-01 11:09 AM (#562611 - in reply to #558283)
Subject: RE: Tapered axle Mopar 8 3/4 ring and pinion options



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I‘m getting a 742 differential carrier /w 3.23 ratio. The original 3.31 ratio is like seeking a hair needle in a stack of hay.

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jboymechanic
Posted 2018-05-01 4:27 PM (#562625 - in reply to #558283)
Subject: Re: Tapered axle Mopar 8 3/4 ring and pinion options



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My 1960 Plymouth has 3.31 gears, stock gears in 1960 with a 318 V8 and PF trans.
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Beltran
Posted 2018-05-01 8:33 PM (#562636 - in reply to #558283)
Subject: Re: Tapered axle Mopar 8 3/4 ring and pinion options



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there is a thread here somewhere about the crossover to the more easily obtainable 8 3/4 axles 742, 488 489. These you can find lots of parts for on ebay and the local ring and pinion shop can do the work. I converted my 55 to a 742 8 3/4 from a 69 roadrunner. It has Posi as well. Only had to move the spring perches. the rest was bolt in. Oh and have a new drive shaft made. But that was surprisingly easy as well.
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Powerflite
Posted 2018-05-01 9:15 PM (#562641 - in reply to #562611)
Subject: RE: Tapered axle Mopar 8 3/4 ring and pinion options



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di_ch_NY56 - 2018-05-01 8:09 AM

I‘m getting a 742 differential carrier /w 3.23 ratio. The original 3.31 ratio is like seeking a hair needle in a stack of hay.



I have a 3.31 ratio gear set. I believe it's in a 985 casting. But shipping it to Germany would be extremely painful.
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di_ch_NY56
Posted 2018-05-02 1:17 PM (#562682 - in reply to #562641)
Subject: RE: Tapered axle Mopar 8 3/4 ring and pinion options



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Powerflite - 2018-05-01 3:15 AM
di_ch_NY56 - 2018-05-01 8:09 AM

I‘m getting a 742 differential carrier /w 3.23 ratio. The original 3.31 ratio is like seeking a hair needle in a stack of hay.

I have a 3.31 ratio gear set. I believe it's in a 985 casting. But shipping it to Germany would be extremely painful.

PM sent

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di_ch_NY56
Posted 2018-05-10 4:21 AM (#563068 - in reply to #558283)
Subject: RE: Tapered axle Mopar 8 3/4 ring and pinion options



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Location: ZH, Switzerland

I'm getting a complete rear axle out of a 1960 Chrysler Windsor (according to the pics I got). As far as I got out - if it's really a Windsor axle then the stock factory ratio was 2.93.

Happy Restoring!

Dieter

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