Help! Transmission gears won't engage

[Mr. 350]

1969 Corvette, 350 cu.in., Muncie 4 speed
I have spent the last 15 months rebuilding this car literally bumper to bumper. I have rebuilt 2 or 3 other engines before this one and helped with others but transmissions are out of my league. The trans worked fine before I removed the side cover to replace the leaky gasket. I had trouble getting the forks back in and when I let out the clutch the gears do not engage. I can moved the gear shift through the gears but it stumbles. The clutch and clutch peddle seems to work OK. The Muncie is the later version and the pin in the side cover CANNOT fall out. I installed a new flywheel, new roller pilot bushing, and new clutch disc. I reinstalled the same Zoom pressure plate I replaced several years ago. If I can't find a solution I'll have to pull the trans, rent a truck, and take it to a transmission shop. I hope someone out there has a solution. Thanks in advance.

 

[toobroketoretire]

The last time I had a Muncie apart was about 6 years ago so I'm a little rusty on the topic. But I seem to recall the forks have to be inserted facing a certain direction because the fork itself is offset from the shaft. As your trouble started the moment you had the cover off it indicates you installed it wrong. I seem to remember it'll partially lock in two gears if it's installed wrong. I suggest you take the cover back off and look it over.

 

[Mr. 350]

Thanks for the input, toobroke.

The last time I had a Muncie apart was about 6 years ago so I'm a little rusty on the topic. But I seem to recall the forks have to be inserted facing a certain direction because the fork itself is offset from the shaft. As your trouble started the moment you had the cover off it indicates you installed it wrong. I seem to remember it'll partially lock in two gears if it's installed wrong. I suggest you take the cover back off and look it over.

You are waaay ahead of me because this is the first time I have ever opened a transmission. I bought a full gasket set for the tranny but after pulling the cover and seeing all those gears I replaced only the cover gasket. However, before I remove the side cover again I need more detailed info. Going from memory the fork ends appeared to be slightly different lengths and thickness. Which end goes up? Also, just inside the cover on each linkage is an oblong pivot or weight. The shaft of each fork slips into one end of the pivot and the (outside) linkage bolts screw into the other end of each pivot. Should the pivot be up or down? Thanks again.

I did retire on April 2nd.

 

[Mr. 350]

Fyi

You are waaay ahead of me because this is the first time I have ever opened a transmission. I bought a full gasket set for the tranny but after pulling the cover and seeing all those gears I replaced only the cover gasket. However, before I remove the side cover again I need more detailed info. Going from memory the fork ends appeared to be slightly different lengths and thickness. Which end goes up? Also, just inside the cover on each linkage is an oblong pivot or weight. The shaft of each fork slips into one end of the pivot and the (outside) linkage bolts screw into the other end of each pivot. Should the pivot be up or down? Thanks again.

I did retire on April 2nd.

The following website may help anyone with tranny
trouble:
muncietrans.net --- transmission ID chart and exploded view
davids4speeds.com --- excellent video rebuilding a Muncie
cobratransmission.com --- parts, pics of forks
thegearbox.org --- parts

 

[toobroketoretire]

You are waaay ahead of me because this is the first time I have ever opened a transmission. I bought a full gasket set for the tranny but after pulling the cover and seeing all those gears I replaced only the cover gasket. However, before I remove the side cover again I need more detailed info. Going from memory the fork ends appeared to be slightly different lengths and thickness. Which end goes up? Also, just inside the cover on each linkage is an oblong pivot or weight. The shaft of each fork slips into one end of the pivot and the (outside) linkage bolts screw into the other end of each pivot. Should the pivot be up or down? Thanks again.

I did retire on April 2nd.

Does it feel like it's locked in two gears at the same time? If either (or both) of the forks have an offset to one side it would lock into two gears if the forks got turned upside down. As the trouble started the moment you put the cover back on that would indicate you installed it wrong. Does your shifter feel normal? If it doesn't that would also indicate the cover got installed wrong.

 

[Mr. 350]

Does it feel like it's locked in two gears at the same time? If either (or both) of the forks have an offset to one side it would lock into two gears if the forks got turned upside down. As the trouble started the moment you put the cover back on that would indicate you installed it wrong. Does your shifter feel normal? If it doesn't that would also indicate the cover got installed wrong.

No, it doesn't feel like it is locked in two gears. The shifter does move but stumbles. I removed the cover this morning and the forks are identical with no offset. According to David West of Davids4Speeds: "If a tranny won’t engage on any gears, the problem is someplace upstream from the tranny." According to a Perfection Clutch video: if the throwout bearing is installed incorrectly the clutch will not disengage. I think the problem is with the throwout bearing and I may have installed the lip in front of that thin metal clip. I removed the clutch fork rubber cover but I couldn't see much but there is quite a bit of play. I'm going to try to back the tranny and bell out enough to see the throwout. If that doesn't work I'll have to remove the tranny. That's a looooot of work because everything must be disconnected from the engine and the engine moved forward to get the tranny shaft out of the engine. I registered the car and got my plate yesterday so I'm ready to hit the road tomorrow when my insurance kicks in! This is the LAST hurdle. Wish me luck. Thanks for your help.

 

[toobroketoretire]

No, it doesn't feel like it is locked in two gears. The shifter does move but stumbles. I removed the cover this morning and the forks are identical with no offset. According to David West of Davids4Speeds: "If a tranny won’t engage on any gears, the problem is someplace upstream from the tranny." According to a Perfection Clutch video: if the throwout bearing is installed incorrectly the clutch will not disengage. I think the problem is with the throwout bearing and I may have installed the lip in front of that thin metal clip. I removed the clutch fork rubber cover but I couldn't see much but there is quite a bit of play. I'm going to try to back the tranny and bell out enough to see the throwout. If that doesn't work I'll have to remove the tranny. That's a looooot of work because everything must be disconnected from the engine and the engine moved forward to get the tranny shaft out of the engine. I registered the car and got my plate yesterday so I'm ready to hit the road tomorrow when my insurance kicks in! This is the LAST hurdle. Wish me luck. Thanks for your help.

And the plot thickens. As you hadn't told us you had taken the transmission and throwout bearing out we never suspected anything could be wrong in the fork/throwout bearing area. When you say your shifter "stumbles" what exactly is it doing? You don't have to move the engine foreword EVER to pull a transmission out. It just has to be supported like using a bottle jack and a short 2" X 4" under the oil pan. Once the rear of the engine is supported it's just a matter of wrestling the heavy transmission out. Once it's out check the fork pivot ball stud to make sure it's bottomed out against the surface of the bell housing. I always used blue LocTite on the threads then screwed it in tight. The throwout bearing simply slides into the fork with the fork and metal clip being in the groove. The clip is there to prevent the fork from pivoting and that's its only purpose. Let us know what you find and maybe take a picture or two so we can see if something is obviously wrong.

 

[Mr. 350]

And the plot thickens. As you hadn't told us you had taken the transmission and throwout bearing out we never suspected anything could be wrong in the fork/throwout bearing area. When you say your shifter "stumbles" what exactly is it doing? You don't have to move the engine foreword EVER to pull a transmission out. It just has to be supported like using a bottle jack and a short 2" X 4" under the oil pan. Once the rear of the engine is supported it's just a matter of wrestling the heavy transmission out. Once it's out check the fork pivot ball stud to make sure it's bottomed out against the surface of the bell housing. I always used blue LocTite on the threads then screwed it in tight. The throwout bearing simply slides into the fork with the fork and metal clip being in the groove. The clip is there to prevent the fork from pivoting and that's its only purpose. Let us know what you find and maybe take a picture or two so we can see if something is obviously wrong.

Sorry, I did not specifically state that I had removed the transmission from the car but that has nothing to do with the problem. The ONLY thing removed from the tranny was the side cover and old gear lube. Nothing else changed. I did say I put in a new throwout bearing and other parts. The shifter doesn't feel smooth as I try to shift into the gears. It hesitates and I have to try some of the positions more than once to get it into position for a given gear. The fork pivot ball and the pivot ball in the side of the block for the clutch linkage is tight. Go to: http://www.perfectionclutch.com and watch the video entitled, GM RWD Clutch Fork & Release Bearing Installation on the clutch fork clip.

 

[toobroketoretire]

Sorry, I did not specifically state that I had removed the transmission from the car but that has nothing to do with the problem. The ONLY thing removed from the tranny was the side cover and old gear lube. Nothing else changed. I did say I put in a new throwout bearing and other parts. The shifter doesn't feel smooth as I try to shift into the gears. It hesitates and I have to try some of the positions more than once to get it into position for a given gear. The fork pivot ball and the pivot ball in the side of the block for the clutch linkage is tight. Go to: http://www.perfectionclutch.com and watch the video entitled, GM RWD Clutch Fork & Release Bearing Installation on the clutch fork clip.

If you're trying to shift it into all the gears with the engine not running you will have a lot of trouble because the input shaft has to be turning for it to easily go into the gears.

 

[Mr. 350]

If you're trying to shift it into all the gears with the engine not running you will have a lot of trouble because the input shaft has to be turning for it to easily go into the gears.

Thanks for confirming that. The car has been sitting in my garage the past 6 yr. and I wasn't sure. I should have the tranny out some time today. According to the code on the pass. side of tranny: manufactured in 1969, Oct., 02 day, M20. I'm not good with attachments but I'll send pics if I can.

 

[Mr. 350]

Thanks for confirming that. The car has been sitting in my garage the past 6 yr. and I wasn't sure. I should have the tranny out some time today. According to the code on the pass. side of tranny: manufactured in 1969, Oct., 02 day, M20. I'm not good with attachments but I'll send pics if I can.

I couldn't get the pictures I took to attach. I removed the transmission and found I put the throwout bearing in correctly. In fact, to install it wrong you would have to TRY to do it wrong! Getting the tranny out w/o moving the engine forward was difficult because of the way GM designed the rear tranny bracket. W/O the pics all I'll say is it was a cluster. There are two bolts with "blind" heads you could not see or get to easily. That's why I moved the engine forward the first time I removed the tarnny. But then I was pulling the engine anyway.

Since I have the tranny out I'm going to take it to a shop and have it rebuilt like I should have done in the first place. I have not skimped on the rebuild so far and I'm not going to start now. I will have peace of mind and I will sleep better if I have it done even though it was working OK. After all, it is the original transmission and has 84,111 miles on it.

Soooo, most likely I put the forks in wrong but it wasn't working so I had no choice. Thanks for all your help, advice, and patience. Rebuilding the engine was easy compared to dealing with the transmission. The engine is purring like a 350 should!

 

[toobroketoretire]

With only 84,000 miles on it only a new rear seal would be needed unless you or a previous owner beat the daylights out of it. If cared for a manual transmission should easily go 500,000 miles or more.

While the transmission is out take a moment to make sure the pivot ball is screwed all the way into the bell housing until it's firmly bottomed out. If fact I would take it out then reinstall it with blue LocTite on the threads to prevent it from unscrewing.

 

[GTR1999]

If the trans shifted fine before and all you did was pull the shifter linkage and cover then it should be reasonable to figure out.
The shifter forks are the same. There are 2 combs and a spring on the cover. To remove the cover & install put it into 2nd gear to allow the fork to clear the casting. If it didn't go back in the correct position then the cover would not sit flat on the housing. There is also a roll pin to locate it.

Since you have it out now you can check it pretty quick. You should be able to use a wrench on the levers to engage all 4 gears- more accurately the sliders and hubs. The only gear that engages in a Muncie or Super T-10 is reverse.

Here is one of the slider/gears

 

[Mr. 350]

With only 84,000 miles on it only a new rear seal would be needed unless you or a previous owner beat the daylights out of it. If cared for a manual transmission should easily go 500,000 miles or more.

While the transmission is out take a moment to make sure the pivot ball is screwed all the way into the bell housing until it's firmly bottomed out. If fact I would take it out then reinstall it with blue LocTite on the threads to prevent it from unscrewing.

WOW! I had no idea a transmission would last that long. A copy of my original title (which the state "confiscated" when I registered the car) shows I purchased the car 12-15-1971. I am the second owner and the car was a daily driver and wasn't abused, even though I put my foot into it from time to time, I couldn't afford to trash it because it was my only transportation. Actually, the car sat idle for half the time I have owned it. My ex-wife tried to get me to sell it. I still have the car...

I have LocTite Blue but I don't remember if I applied it but I'll take your advise and use it now.

 

[Mr. 350]

If the trans shifted fine before and all you did was pull the shifter linkage and cover then it should be reasonable to figure out.
The shifter forks are the same. There are 2 combs and a spring on the cover. To remove the cover & install put it into 2nd gear to allow the fork to clear the casting. If it didn't go back in the correct position then the cover would not sit flat on the housing. There is also a roll pin to locate it.

Since you have it out now you can check it pretty quick. You should be able to use a wrench on the levers to engage all 4 gears- more accurately the sliders and hubs. The only gear that engages in a Muncie or Super T-10 is reverse.

Here is one of the slider/gears

I think the combs are the real problem! But, I have no idea what gear it is in by looking at the combs. The cover won't sit flat.

 

[GTR1999]

Ball bearings fail, the original front bearings were known to come apart. The Bearing retainers will wear a groove on them from the throw out bearing. It's hard to put a shelf life on a mechanical item. These were pretty good trans but made for the power of the day, today guys push double or triple out of their cars and the driveline is going to fail.

If the cover is not sitting flat you know the answer. Look at my picture. The groove in the slider is where the forks have to go otherwise the cover is not going to fit. The only thing that engages the gear is the slider, in the picture it is locked on the LH side gear, the gear on the RH side is free wheeling at this point. Whether or not you need to overhaul the trans is a different question. Look for pitting or chipped teeth on the gears. Look at the brass teeth, they should look sharp, like pentagons. Look around the tapped holes for cracks.

 

[Mr. 350]

I think the combs are the real problem! But, I have no idea what gear it is in by looking at the combs. The cover won't sit flat.

I asked a buddy who is a former mechanic for a recommendation of a good transmission shop. I spoke to the owner and he said to bring the transmission in and he would help me get the forks in correctly. I took it to him this morning and in less than 10 min. he was finished and didn't charge me a dime. I had to be ABSOLUTELY, POSITIVELY sure it was right because wrestling that transmission in and out is no fun. By noon tomorrow I'll have the tranny back in and ready to roll.

Thank you both for all your help and advice.