Which is worth more, M-20 or M-21?

65sssd · Poncho Master!

Which is worth more, M-20 or M-21?

68sd · Canadian Poncho Superstar!

i thought m-21s had close ratio gearing?

65sssd · Poncho Master!

I think your correct. The M-20 has a higher first gear (256) that makes it better with highway gears ( less clutch riding), but is a little high for gears like 4.11's. The M-21 would be more suited for 4.10, 4.11, etc. I don't know which is stronger or if they are valued the same.

4SPEED427 · A Poncho Legend!

The strength would be the same on both. Only the M22 is tougher by virtue of gear design.

65sssd · Poncho Master!

So what kind money for each or are they valued the same. Somebody wants to trade a M-20 for a M-21. The M-20 suits my needs more.

4SPEED427 · A Poncho Legend!

I'd say it's a tossup. It used to be I thought a 21 had more value because it's harder to find. Now it seems more people think fuel economy so the gear ratios are in the lower 3's (3.08/3.23/3.31 area) and for that a 20 is certainly superior.

Same old story, supply and demand. For myself I'd likely still pay slightly more (not a lot) for a 21. Still tougher to find.

I would have a tougher time giving up a trans I know the condition of for one I don't know the condition of.

427carl · A Poncho Legend!

you got that right biggrin

87 player bird · Poncho Master!

yep, if you have to rebuild it , it's hard to find good parts for them. u.s gear is not bad but be careful as a lot of the replacement parts now are made in china. be careful and actually check the part's carefully if it needs a rebuild:)

2drpost · Uber Guru

M20 with it's lower 2.52 1st gear is 'worth' more.

M21s were installed in higher hp cars with lower(3.73 and up) rear gears.

be sure of the condition of it before trading. evileye

65 SD L79 · Canadian Poncho Superstar!

M 21 would be worth more to someone building a car and the M 20 worth more to some one restoring a car back to factory. Same thing if you had a 12 bolt in your car and factory was a 10 bolt. A strait trade for the correct 10 bolt would be worth it.

455gto · Poncho Master!

I sold my M 21 for $1,500. That's with the hurst shifter,pedals and linkage.

65sssd · Poncho Master!

The trouble is making sure of the condition. Besides checking bearing slop on the input, output, and seal surfaces, I'm lost. Any advice?

4SPEED427 · A Poncho Legend!

It's hard to explain how they should look but the condition of the brass syncro rings is important.

The reverse gears on Muncies are often eaten up badly and that is next to impossible to see without taking it apart. A bit expensive to replace, too.

65sssd · Poncho Master!

Yeh, thats the problem. I have bought transmissions blind before and just hoped that the would shift right, but they have to be cheap. I already have another M-21 that pops out of gear and makes some brutal noises. Sounds like I should keep my driving M-21.

4SPEED427 · A Poncho Legend!

Does it pop out when you are off the throttle in 4th gear only?

65sssd · Poncho Master!

2nd gear when you get off the throttle.

2drpost · Uber Guru

they're not that difficult to o'haul.
original parts are readily available, syncros, bearings, gskts, on ebay and suppliers etc...

87 player bird · Poncho Master!

I had to redo mine after I lost reverse

Lemans64 · Poncho Master!

There's a few places in Vancouver that carry all the parts. I did mine with no issues, have a dummy shaft for cluster shaft as well. Did some mods to accept a seal bearing in the front, hardly leaks at all, LOL. Mine did the same popping out of 2nd, new gear and shift collar and all is well. Make sure u use the right oil with it as they don't like the new gL5 gear oil or synthetic. Sorry got tied up this weekend.

-- Edited by Lemans64 on Saturday 4th of April 2009 09:14:42 PM

65sssd · Poncho Master!

I know I can't hurt it anymore anyway. I'll probably give it a go on that one. Still on the hunt for a 64-65 M-20. The speedo is on the drivers side of the trans for easy identification.

RacerRick · Addicted!

IMO - they are worth about the same. I don't even bother with muncies in general, because Super T10's are cheaper and stronger than the garden variety Muncie M20 and M21, and they bolt right into the same place.

I just picked up a nodular iron cased ST10 for $450 and it needs nothing. I specificall got one with the deep 3.42 first gear since I am running a 3.08 in the back. I have put 500 ft-lbs through an identical transmission to the one I just bought with no problems. There is one in my turbocharged camaro.

65 SD L79 · Canadian Poncho Superstar!

Are these trannys all the same no matter what they were installed in? Olds, buick, chev or Pontiac. Just the vin stamp would say what it came out of? The chevy by the numbers book shows the case changed after Feb. 65 so If you have a late year 65 build, It would be different?

-- Edited by 70 SS ACADIAN on Thursday 9th of April 2009 03:32:23 PM

65sssd · Poncho Master!

My buddy had a 81 Z-28 that had a tranny like that, but I heard they were weak. I could be wrong about the stength. I know he had a sincro problem. Plus I have never found one. Can you post the info and pictures that I need to identify one. Thanks Paul

65 SD L79 · Canadian Poncho Superstar!

ebay item 230335014959 went for $ 455 is this the tranny you need?

Beaumont4008 · Uber Guru

65sssd wrote:

My buddy had a 81 Z-28 that had a tranny like that, but I heard they were weak. I could be wrong about the stength. I know he had a sincro problem. Plus I have never found one. Can you post the info and pictures that I need to identify one. Thanks Paul

The munci trany's have a 7 bolt side cover and the Borg-Warner T-10's have a 9

bolt curved bottom side cover.

-- Edited by Beaumont4008 on Friday 10th of April 2009 11:30:20 AM