Author Topic: Muncie and Rear Gear Combination  (Read 2069 times)

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Offline Bam Martinez

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Muncie and Rear Gear Combination
« on: November 18, 2013, 02:47:44 PM »
I am currently in the process of installing a 1968 Muncie M20 Wide Ratio into my 81 T/A. The final drive (or rear axle) has 3.08 gears.

Now my question is, would this be an alright combination?

I've had a few people tell me that this is too tall of a combo. I wouldn't think it would be seeing how the previous trans in this car was a TH350, which has just about the same first and last gears as the Muncie. And I've read somewhere that these Wide Ratio M20s were specifically built for Final Drive Gears that are 3.08 or lower.

Regardless, I just kind of want another persons opinion so I don't ruin a perfectly good 4speed.

Also, I almost forgot to say that this setup will include a plain built SBC 350.

Offline LilSki

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Re: Muncie and Rear Gear Combination
« Reply #1 on: November 19, 2013, 05:39:20 PM »
You should be fine as long as it is indeed an M20 wide ratio. The 1st gear is 2.52 on those and when you multiply it by 3.08 you come to 7.76:1. I am running a close ratio M21 with a 2.20 1st gear with a 3.42 rear gear and that comes out to 7.5:1 and I have no issues getting going in 1st gear.
Kevin
79 Trans Am: (77 nose), WS6, M-21, 461, Hotchkis TVS, PTFB Contol arms. 
85 Trans Am: Vortec 350 w/LT1 cam/T56, TPI conversion w/Megasquirt II.

Offline jonathonar89

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Re: Muncie and Rear Gear Combination
« Reply #2 on: November 19, 2013, 08:52:20 PM »
I'm definitely going an oddball route.  Purchased a 2.73 rear to go behind my 2.64 ST-10 4 spd.  7.21 first gear...hopefully won't be too bad.  Tire size is a factor in that equation too.

Offline chicagobob

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Re: Muncie and Rear Gear Combination
« Reply #3 on: April 09, 2020, 01:01:11 PM »
would a m20 work in a 81 TA with a Pontiac 400, 308 rear?