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Muncie popping out of gear

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Old 10-27-2010, 10:25 PM   #1
vettepoor
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Default Muncie popping out of gear

What is the likely cause for my muncie m21 popping out of gear? On a cruise this past weekend, I had this happen twice, both times when I was in 2nd gear and coming down hills. Is this most likely in the linkage adjustment or something worse? Thanks for any thoughts.

John
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Old 10-27-2010, 11:02 PM   #2
Dan Hampton
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One of three things or a combination thereof, but in all likelihood, your slider is not maintaining its engagement with the driven gear. The best solution for this is to replace it with a torque lock slider. That will eliminate the problem. I would also purchase a new internal hub to go with the slider. Worn engagement teeth on the gear, itself, can be a secondary cause, and given that gears are relatively inexpensive, I would consider replacing it, too. Since you have it disassembled, you might want to consider replacing the hub/slider for 3/4 gear, too.

No easy way to remedy the problem but to remove the transmission and tear it down.

Last edited by Dan Hampton; 10-27-2010 at 11:05 PM.
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Old 10-27-2010, 11:05 PM   #3
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Is this something that can be done at home, or do you need any special tools to do the job?

I have the same problem on a B/W transmission.
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Old 10-28-2010, 08:03 AM   #4
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You do need to check the linkage adjustment before diving into the transmission. There is a slight chance it could be the linkage. You didn't say if you have a stock or Hurst shifter. The Hurst have shifter stop bolts to limit movement of the linkage cams and arms. If the one on the second and fourth gear is too tight the transmission gear and slider may not be fully engaging. I would check this because I believe it's often that third gear is the one that gets weak first and starts poping out of gear. Or maybe that was just my car.
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Old 10-28-2010, 08:23 AM   #5
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I doubt if it's the shifter if it's happened over time. My B-W started doing this, only on deceleration, and when I dove into the cases, found all sorts of worn parts, and did a complete rebuild. And yes, there's no real special tools required, and if you are organized you can do it yourself. It was the first one I did, and it's never given me any trouble since, 20 years ago. K
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Old 10-28-2010, 08:30 AM   #6
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Rebuilding the tranny takes care, but would make a good winter project. I did mine a few years back. This site http://www.5speeds.com/muncie.htm is great. I used his video (a tape then, DVD now) and it helped a great deal. He was always available by phone if you had a question.

Check the linkage first, though.
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Old 10-28-2010, 09:20 AM   #7
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Quote:
Originally Posted by Dan Hampton View Post
One of three things or a combination thereof, but in all likelihood, your slider is not maintaining its engagement with the driven gear. The best solution for this is to replace it with a torque lock slider. That will eliminate the problem. I would also purchase a new internal hub to go with the slider. Worn engagement teeth on the gear, itself, can be a secondary cause, and given that gears are relatively inexpensive, I would consider replacing it, too. Since you have it disassembled, you might want to consider replacing the hub/slider for 3/4 gear, too.

No easy way to remedy the problem but to remove the transmission and tear it down.
Dan is 100% spot on!
I've been building 4spds (mostly Muncies) for 40+yrs, and when the Tork Loc sliders became available, it was an excellent "fix" for many trannys (Muncies and T10s) that ocassionally popped out of gear while decellerating. Another thing that is a MUST to check whild the tranny is out, is the pilot bushing in the end of the crankshaft---------------MANY people neglect to check/replace this VERY IMPORTANT cheap part!!!!!!!!!!!!!!
The Tork Loc sliders (photo comparrison below) have an additional machined back cut at each end of the splines. This back cut serves to "pull" the slider into the small engatement teeth of the gear, thus making a more secure engagement of the gear.
But, as Dan mentioned, if the engagement teeth of the affected gear are badly worn, then gear replacement is also advised.
Personally, based on your experience/description, I think a pair of Tork Loc sliders (PLUS a rebuild kit) while you have it apart, will extend the service life of your Muncie for as long as you own the car (or live ).


Tom Parsons
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Old 10-28-2010, 09:48 AM   #8
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I had the same problem, ended up doing a rebuild and all is well.
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Old 10-28-2010, 10:04 AM   #9
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When I got my '63 some years ago, it was jumping out of second on decel.

The shift linkage was adjusted in such a way that the handle would come back too far aft in second, pinch the shift boot between the handle and console and keep it from going all the way into second.

You couldn't really feel it but the condition existed. No problem in fourth. A quick adjustment to hold the shift gate a little forward fixed the problem more than five years ago.

Maybe you'll get lucky.
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Old 10-28-2010, 10:32 AM   #10
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One last thing that you might want to think about, too, is replacing the detent spring in the side cover with a heavier spring. Larry at D & L Transmissions can provide one of those for you. GM made the change in the mid 60s (John Z might know when) but it serves to keep the shift levers more rigid and helps in preventing the shifter from popping out of gear.
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Old 10-28-2010, 11:45 AM   #11
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Quote:
Originally Posted by Dan Hampton View Post
One last thing that you might want to think about, too, is replacing the detent spring in the side cover with a heavier spring. Larry at D & L Transmissions can provide one of those for you. GM made the change in the mid 60s (John Z might know when) but it serves to keep the shift levers more rigid and helps in preventing the shifter from popping out of gear.
Every rebuild that I do on an early tranny that has the spring with shorter, lighter coils, I replace it with the heavier spring that was on later trannys.
Many years ago when the springs were available from GM, I bought 50. I'm now down to about 4-5.

Tom Parsons
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