rippinbyu

Looking to refurbish my 53 year old M-21 as the clutch bearing appears to be going (Making wining sound when pedal is release and "alt" light comes up like something is grounded for 1-2 seconds).

Looking at: *New flywheel (possibly light weight steel).
*Ram dual clutch
*Hydraulic throughout bearing and master cylinder
*New pressure plate

Anyone have any suggestions on what worked well/reliable with the Olds BB and M-21s?

Thank you,
Chad

MI68442W30

Chad ,are you sure there isn't something going wrong with the alternator or voltage regulator or a loose belt? just asking. anyway in my opinion you are over thinking this and unless you are racing your car or your engine is well over 450 horse none of what you want to do is necessary ,and I have never had a throwout bearing make a whining noise on any of my 4 speed cars but it is easy to replace and by all means while you are in there replace the clutch/pressure plate and flywheel if needed with a quality set and you will have no issues for many years. the factory setup works flawless in both of my 68's I drive and I have had zero problems or issues with my driver that I have been driving for 14 years now with a Weber clutch set behind a rebuilt 68 455 H/O engine and I do drive it hard and my project 68 is also a 4 speed and I will keep the factory setup on it also. the best clutches I have had are the Weber and Mcleod that performed and lasted and I will continue to use them.if you can't tell I like my 68's ,good luck with your 68

BackInTheGame

If you really feel the need to refurb/upgrade the M21, why don't you look into replacing the guts with aftermarket M22 parts? That could be FUN!

BangScreech4-4-2

While you're at it, you might want to go to the 2.52 low gear from the M-20. Your car must be a bear to launch with that 2.20 M-21.

rippinbyu

positive... alternator is restored and and new. Not overthinking it...just trying to install the latest, reliable, and driver friendly options possible without pissing off the wife. Just finished 1.5 year refresh of suspension, brakes and steering in garge to make it handle, break and steer as best as possible while looking factory correct (maybe I am in the weeds with the details). Motor might be close to 450 with rebuild and W30 cam but hasn't been dyno tuned yet...but just trying to install BEST parts possible and not cheap out...

rippinbyu

What is the first gear ratio in the M-21 v M-20?

Launches pretty hard when I stand on it with 3.91s

67OAI

The M-21 (2.20/1 1st gear) is fine with the 3.91 rear gear. The M-20 trans has a 2.52/1 1st gear. The changeout from M-21 to M-20 or visa-versa is accomplished by changing the input shaft (4th gear) and the accompanying counter gear. Now here is the rub....gear changes (percentage of drop in ratio) from 1st to 2nd, and 2nd to 3rd remain essentially the same but with the M-20 you would now have a much larger drop in ratio in the 3rd to 4th gear change! As for the comment about changing your transmissions guts out for the M-22 gears, the ratios are identical as those in your M-21; the M-22 gears are considered "strait cut" gears and are much noisier than the "helical cut" gears in the other Muncie transmissions but a little stronger, thus a very expensive way to make noise. In my opinion, keep your M-21.

BangScreech4-4-2

Agree, with 3.91 rear it's probably not worth the effort of switching low gears. If you ever go to a more "highway-friendly" rear (cut-off point being 3.42 as I believe the factory did it) you'll appreciate the lower 1st gear in the M-20 vs. your current 2.20.

rippinbyu

Thanks for the info!

rippinbyu

Ram Tech (www.ramclutches.com) is asking if it is a 10 or 26 spline input and "Is the engine internal or external balance factory"...any help??

Thanks!
Chad

RetroRanger

The spline count is the input shaft on the trans where the clutch rides older ones were 10 “newer” ones were 26 spline.

youll probably need to verify by running the numbers on the trans

notsure on the balance

BangScreech4-4-2

If the transmission is correct for your application and hasn't been monkeyed with, it should be a 10-spline. Generally speaking, 10-splines were '64-'70 and 26-splines were '70-'74. But 1968 was a long time ago, so you better run the numbers.

rippinbyu

Thanks....yeah it's original. It was my father-in-laws car. Trans was never touched.

67OAI

As stated above, trans should be ten spline input if never replaced or rebuilt. Your motor would be external balance from the factory. The M-21 trans would be fine for general use even with a 3.42/1 or 3.55/1 rear gear in most cases.