[Itsablurr]

Hey guys....

Looking at picking up a Muncie 4spd box. The owner says that it is in great shape except for the fact that it was jumping out of 4th gear when there is no load / decelerating off throttle.

Any ideas as to the cause of this? Cost to fix?


...and the ever-relevant question as to an estimated fair price for the tranny as-is?

Much appreciated.

 

[MEJ1990TM]

Could be just a shifter stop turned in too far, or it could be the engagement teeth on the gear are worn. It's also possible the slider is beat up. Pull the side cover before committing to buy. I would treat it like it needs a complete rebuild. No way to really know what you are getting without pulling it apart. If everything "looks" real nice I would go as high as $400 for a later style 1" pin case. Anything obviously worn/damaged and I detract from that.

 

[VinceS427bb]

Hey guys....

Looking at picking up a Muncie 4spd box. The owner says that it is in great shape except for the fact that it was jumping out of 4th gear when there is no load / decelerating off throttle.

Any ideas as to the cause of this? Cost to fix?

on one of my m21 trans i had the same symptoms and the cure was a new input shaft
this was years ago and cost was greater as the blocker rings and bearings/seals were freshened while apart.:thumbsup:

 

[Itsablurr]

Could be just a shifter stop turned in too far, or it could be the engagement teeth on the gear are worn. It's also possible the slider is beat up. Pull the side cover before committing to buy. I would treat it like it needs a complete rebuild. No way to really know what you are getting without pulling it apart. If everything "looks" real nice I would go as high as $400 for a later style 1" pin case. Anything obviously worn/damaged and I detract from that.

Thanks for the reply. I believe the assumption by the seller is that the engagement teeth are worn and the gear needs to be replaced. The seller was orig asking $425, but said he'll do $400.

What am I looking at/for specifically when pulling the side cover? Sorry, I am a bit of a novice with transmissions (though I am familiar in differential rebuilding)

Any recommended links to rebuild DIY guides?

Thanks!

 

[MEJ1990TM]

I guess $400 isn't a terrible price, but it's not that great either. A new input gear will run around $100 new, and around $65 used. No way of knowing exactly what else it will need unless until it is torn down completely. A kit will run about $160-200 depending on which one and who you buy from.

If you get the side cover off look for chipped gear teeth, flat out broken gear teeth, and wear on the engagement teeth. When new the engagement teeth come out to definitive points. Used will obviously have some wear. Later today I will post some pictures of good used, and not so good used. I am using my phone to post this now.

 

[Keith Tedford]

I have an M20 that I used for a while. It worked fine except that it would also jump out of 4th when letting off. I was told that a worn pilot bearing could do that. The pilot bearing was worn and we installed a new one when putting the M21 back in the car so I never had a chance to try it with the M20. Anyone else hear of this? I had the M21 freshened up with an bearing and synchro kit from Larry Fischer of D&L Transmissions. The M21 has worked like new ever since.

 

[MEJ1990TM]

That is about the closest to new transmission I've come across. It almost seemed like a shame to sell that one, but I had an M22 lined up for less than I sold the M21 for. Couldn't very well pass it up.

That's starting to show a little bit of wear, but perfectly ok to use. That's the transmission that's in my '71 now.

That's pretty well used and abused. The transmission still works real nice. I don't know if that's just luck, or if they can take a lot of abuse and still function. I'd be leary about re-using the gears if they start to look like that second speed gear.

 

[oktunes]

$400 might be too much if the transmission requires any kind of work. I have never had one worked on that didn't require more then what I expected. They always seem to end up costing as much to fix as they were to buy!

 

[MEJ1990TM]

That does not surprise me if you pay someone else to do the work. All the shops I know mark up their parts something considerable. Depending on the cost of parts it's usually around 35-40%. So on a $120 rebuild kit you are probably going to be charged near $160. Have to replace that input gear? Shop would probably get it for around $85. They'd probably charge you $115-$120. Then on top of it they are probably going to want $225+ to do the work. So that's $500 to have the shop rebuild your transmission.

You do that same work yourself you are looking at $205. That's subtracting the proposed shop mark up on parts, and labor. The rebuild kits I've bought have cost me around $160 after shipping, but I have seen cheaper kits that may ,or may not, include a cluster gear pin.

 

[Itsablurr]

Thanks so much for the reference pics... very helpful. I'll be seeing the lump in person this weekend, and hopefully the seller will be willing to pull the side cover off for a look at the guts.

Browsing through various fs ads for muncies are showing claimed 'good, bolt-in' used m20s and m21 trannies as low as the 5-600 realm.



Based off of that, I guess I should be looking at $350 or so if it needs a bushing/bearing/general refresh, and perhaps $300 ballpark if its showing significantly worn/scarred teeth? FWIW, it is a 1" pin trans from '67.

 

[dream66]

for a later style 1" pin case.

Pardon my ignorance. What is a 1" pin?

 

[MEJ1990TM]

Pardon my ignorance. What is a 1" pin?

That is the diamater of the pin that goes through the cluster gear. The '63-65 transmissions were 7/8".

 

[Itsablurr]

UPDATE:

Well, I got to take a look at the trans (box only, no bellhousing, shifter, or linkage) this past weekend, and pulled off the cover.

The drive gears themselves looked very nice, cluster gear looked very nice, a little bit of fore-aft play (.020 - .060 by my engineering eye), 1-2 synchros and engagement teeth looked completely mint, 3-4 synchros looked ok but with some noticeable brass shavings in the slots that the sliders run in, some worn/busted engagement teeth on the 4th (main drive) side. Selector forks showed a little bit of wear.

I'd say it would probably need a fresh main drive gear and a fresh 3/4 and slider setup. Fresh forks as a 'while you're in there'.

At $400 firm, I passed. Good move?

 

[MEJ1990TM]

I probably would have passed myself. I guess at probably around $700 in the trans by the time you got it all done right ,assuming you did the work yourself, you would be a little below the cost of buying a "rebuilt" one off Ebay. For $400 I wouldn't buy it unless all the core parts looked good though.

 

[DZAUTO]

Something that no one has pointed out so far, is the installation of Tork Loc syncro sliders instead of stock type sliders.
On most 4spds that I've built in the past, I almost always go with the Tork Loc sliders. The internal splines of the Tork Loc sliders are machined in such a way that they "pull" the syncro slider onto the syncro teeth to hold it in gear. They are an excellent method of rebuilding a tranny that has worn engagement teeth but the gear teeth are still in good, useable condition.
Also, as mentioned, a worn pilot bushing in the crank will often cause a tranny to jump out of gear. And it also imparts additional stresses on the front bearing and it very possibly will need replacing.