I am going to look at a used Muncie trans this week. It was running fine when it was removed. The owner was swapping to an automatic to race the car. He said I could remove the side cover to inspect the trans. What do I need to check and what should I look for?

Matt

First off be sure there has not been a broken ear on it. Sometimes people use the bolts to pull it
in and break off a ear then weld them back on.
Then check to be sure the shifter mounting bolts
in the tail cone are not stripped. Once those check out, pull the cover and inspect the sliders, brass rings, these will show as a triangular tooth and shouldn't be too rounded off.
Besides a obvious chip a gear tooth, see if there is any pitting on them. Move the sliders into each
gear and turn the input shaft to be sure it spins freely. You also need to inspect the input shaft to be sure that a bad pilot bearing didn't chew it up. Then check the output shaft, turn the input shaft (in a gear) and see if it turns concentric, if not it may of had a u-joint explosion at sometime and bent the shaft (never seen this on a Muncie but I did on a T-10).
Slide a yoke into the tail and check to see if there is any side to side or up and down free-play
in the tail bearing (if this is bad it will vibrate real bad like a tire out of balance.

HTH.

Externally, check for grooving on the input bearing retainer/collar ($30 part). Check the threads on the case for the side cover, these sometimes are tapped out to the next size when they get stripped.

Generally the input shaft will have some side to side play. However, when you put the tranny in two gears at once, the end play should be almost gone unless the input shaft bearings w/cage is worn (17 cylinder bearings).

Internally, take of the side cover and look for excessive wear on the shift forks ($30 each). The groove on the syncro sliders that accept the shift forks should have straight grooves, ie no taper to the groove.

By sliding the syncro collars back and forth you can look at the condition of the brass syncho's.

What you can't see:
The main shaft REVERSE gear and long reverse idler are hidden in the tailshaft. Since reverse does not have a syncro, both of these gears are commonly worn ($130 for these two reverse gears).

Also in the main case the inside teeth of the two syncro sliders can be worn as well as the outside of the teeth of the two hubs that the sliders fit on. The condition of these will be hidden until you disassemble the Muncie.

Cheapest place for Muncie M-20 parts that I have found is a guy on ebay with the user ID of:
zbag522

For $25, you can't beat the information in the rebuilding video that you can get at 5speeds.com

Fiqure the front bearing is bad. They aren't expensive. Take a good look at the engagement teeth on each gear for excessive wear or chipping. If they are bad you will have to change the gear which is expensive.

Front bearing is 60 bucks from Detroit ball bearing, listen to it, it'll probably sound a little noisy like oger says figure on replacing it. The shift forks not only wear, they crack, look at them closely. Look closely for any pitting on the gears and move the hub sliders back and forth lookin at the sliders for any signs of chipped teeth, figure on replacing at least one of them and all the brass synchro rings, again not expensive items. Take a look to see if it has the larger countershaft, I believe in 67 or so they changed to a 1" shaft. Also look to see if there is a magnet glued to the bottom of the case and if there are any significant chips on it. I have also seen the reverse shifter boss crack, these are easily welded, but I would stay away from a case with a welded front ear.

Well I bought it last night. THANKS for all the info on what to check. It was running fine in the car and removed to go to an automatic. It is a M21, 67-70 maincase with 1" counter shaft. The gears are very clean (NO chips). The brass syncros are in great shape too. All the mounting ears are original and the shifter bolt holes still have great threads. On the bench she shifts good. The front bearing is slightly noisey. Not bad but I will put a new one in. All things considered I think I got a good deal for $150. Also came with the bellhousing and clutch fork.

Matt

For $150.00, I think you owe the guy an apology. Good find.

$150 was a big score, congrats!

Matt R

You might soon see "the man" pull up and issue you an arrest warrant for theft!! I gave $100 dollars for my M-20, but it was laying completely apart in an old wood crate . The previous owner tried a do it youself rebuild and gave up on it. I purchased the Muncie Basics video (which I have provided a link to) and sucessfully rebuilt the M-20. I thought the video was very helpful.

Good luck with your M-21. graemlins/thumbsup.gif

http://www.gearzone.net/

GDV350SS,

I ordered the video yesterday, should be here on Monday. The M21 is replacing a tired Saginaw 4spd. Now I need to change my rear end gears, 3.08's will be no fun with a 2.20 1st gear.

Matt

Matt, 308's may still be a little tall for your M-21. You might be replacing clutches regularly. I'd try to find a 331 to 355 gear. I have 331's with a M-20 and they seem high in certain situations but they're still OK on the freeway. Sounds like you got one hell of a deal on the trans...Good luck graemlins/hurray.gif