Muncie trans question

[althomas55]

 Speedometer stopped working ,( M-21) thought cable crapped out  pulled the speedo cable checked it out and not broken ! removed speedo bullet put finger in tail shaft and felt gear inside to be way forward of where bullet gear could engage it ,and can slide it back and forth quite far .Once or twice prior to speedo quitting I thought I heard a strange zingging ,whining type noise and slight vibration in the shifter handle but dismissed it as the radio, ( except for shifter vibration yesterday,vibration lasted couple seconds then quit ) as all seemed well with gear shifting and driving , no shaking,clunking,crashing or any other abnormalities ! In my 63 years never had a trans. apart and was curious as to why this gear could slide forward ( towards engine ) so far ? Do I possibly have a big problem brewing, does the tail shaft slide off easily as a turbo 350 does , or do I need to bite the bullet and yank the tranny  ? Thanks in advance for any insight !

[bcmiller]

What year is the transmission? On the later ones - after 67 I think? can’t remember for sure - there is a clip to secure the speedo drive gear.  The ones with a clip are the plastic or nylon type drive gear. I would have to look that up.

It’s almost always easier - at least for me - to pull the trans and work on it while on the bench.

[althomas55]

 Car is 68 but not sure of the trans year as car was in pcs. when I got it, car is not original , started life as a 6 cyl. now a 468 resides under the hood, 342 corporate gm 10 bolt rear with the 4 speed doesn't seem to lack for power , fun to drive , not so much fun to work on anymore !

[67jeffreyt]

In my Muncie group I believe it's just a press fit and the tail shaft gear can move, I will share your post in the group, the founder of the group is a professional Muncie rebuilder as his regular job.

[Tx-Z 302]

In my Muncie group I believe it's just a press fit and the tail shaft gear can move, I will share your post in the group, the founder of the group is a professional Muncie rebuilder as his regular job.

id sure like to join a muncie group?

[z28z11]

My '69 M20 broke the clip under the shaft gear, and proceeded to jam the reverse selector with the remains of the clip. Goofy design to be sure - the spring clip fatigues over time, and becomes a problem. You'll have to pull the tailshaft housing to correct it. There are several options to replace if the gearset and clip are like my '69's problem including ones like this :

https://www.ebay.com/itm/MATCHING-SET-ALUMINUM-MUNCIE-POWERGLIDE-SPEEDOMETER-SPEEDO-GEAR-COMBINATION-KIT/192617012588?hash=item2cd8de5d6c%3Ag%3AWw8AAOSwal5YG1BZ%3Asc%3AUSPSPriority%2137087%21US%21-1&_sacat=6028&_nkw=Muncie+speedo+clip&_from=R40&rt=nc&_trksid=m570.l1313

Not terribly difficult, but a pain in any case. My gear was metal, not plastic, and I reused it. Clip was sourced from GM, and yes, you'll really need to pull the trans as it will need some wiggling to clear the tailhousing from the reverse gear selector. Do yourself a favor and don't try to drive the staking pin out of the reverse shifter boss on the tailshaft - the (tapered) pins are usually frozen in place by this age, and you'll bend them or mangle the tailshaft housing if you try to pound them out. With a little creative wiggling, you can disengage the selector from the slider and pull the tailshaft housing clear. Actually a fairly quick process, discounting the fact you have to pull the trans.

Regards,
Steve

[67jeffreyt]

Craig's response, and the Muncie group is on Facebook, anyone can join, Craig Wright is the founder of the group.  It is Muncie 4 speed & GM manual transmissions buy sell trade, but it's a tech forum group.

[67jeffreyt]

A lot of responses on this forum are very informative too, sounds like a lot of great advice here also

[althomas55]

Thanks for all the responses, looks like I'll be pulling the trans. not what I wanted to do but was fairly sure that would be the case , not as concerned about the speedo issue as I am about the vibration felt in the shifter handle a couple times makes me envision something jamming up and destroying the tranny while I'm going down the road 60 mph !