# Help my rear end



## Bub (Oct 11, 2020)

I just bought a 64 Le Mans to cut my teeth on. It has a 327 in it, with a 4 speed Muncie. The rear end is an 8.2 B.O.P with a 2.78 ratio. Yes, it is dead off the line and I want to re gear it but the more I read, the more confused I get. Im pretty sure I should go with a 3.23 but can't figure out if I can with my carrier. I dont want to buy both ring and pinion and also a new carrier. Can anyone tell my for sure, how low(in power) or high(numerically) I can go with my gear ratio by just replacing the ring and pinion. Can someone suggest a knowledgeable company that i can call, tell them what I have, and they can tell me what fits.im new to this game, so any help is much appreciated.


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## Rocketman269v (Oct 5, 2020)

You didn't mention if it is a posi, not that that matters on a gear change; however, it may just be more cost effective to swap out the entire rear end assembly. Where are you located?


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## O52 (Jan 27, 2019)

Toms Differentials in Idaho. 









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## Bub (Oct 11, 2020)

As far north as you can go in new york state without being Canadian. There is a P stamped on ring gear but its an open differential. Spin one wheel the other goes backward


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## maw2078826 (May 1, 2020)

3.23 & 3.42 are respectable ratios for the street...depends upon what RPM your engine will tolerate at a given MPH...tire height also comes into play. Richmond. Yukon and others make great gears & carriers...posi is definitely the way to go. Finally, get the correct speedo gear for any ratio change for your Muncie.


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## 64since65 (Dec 11, 2019)

For what little it's worth, years ago I was getting about 13 MPG with a 3.90 axle. Then the axle broke and I needed something quick so I grabbed something at the local junk yard and it turned out to be an economy axle from an automatic. (2.56? 2.93??) My new gas mileage was still 13 MPG - I'd apparently gone "over the hump". So the best gas mileage - if that's what someone is looking for - with a manual trans will definitely be somewhere in between.

I think I'd go with a 3.36 or 3.55 if looking for a compromise between gas mileage and performance. But I'm going to stay with a 3.90 posi since that's what was in mine when I got it in '67. My brother had already changed it from the original 3.36 non-posi. So rather than keeping it "production original" I'm trying to keep it "my original".

The production ratios available in '64 were:
2.56
2.93
3.08 (I believe this was the lowest available with a manual trans. Correct me if I'm wrong.)
3.23
3.36
3.55
3.90


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