Newly Finished Project Drivetrain Problem
 

I finally finished my '66 GTO , original tri-power engine, M20 transmission and rear end. all rebuilt .

Something is locking up, at low speed it can actually chirp the tires. I haven't had it on the road yet but around the parking lot it shifts poorly and binds up somewhere. it can be hard to get out of gear. when it binds up you can break it loose by forcing it with the engine. does it in both forward and reverse.

I jacked it up and ran it and it's weird, doesn't always do the same thing but sometimes when you try to shift from one gear to the next the wheels stop like you hit the brakes. sometimes they don't. the rear wheels do turn more that they should when idling in neutral.

I've checked all the fluid levels and I checked the linkage adjustment. if it was the brakes or real axle it seems like it wouldn't be hard to shift out of gear, the clutch seems fine. I'm thinking the transmission but how can it do this? I'm stumped

Might be that the trans is not lined up well enough to center the input shaft in the pilot bushing.

Tell us the history of the transmission. If it is seizing in the input bearing, that would be a direct link between the engine crankshaft and the rear end, though the mainshaft of the transmission. Did somebody rebuild the trans? If so, they may have a gear flipped around backwards so it is locking up on the mainshaft gears instead of freewheeling when not engaged.

If the input was binding in the pilot bushing wouldn't it be hard to get in gear? especially reverse? it goes into revers with no grinding.

The original transmission came with the car but wasn't in it when I bought it. the owner had it since 1967 but he's passed so I couldn't ask him anything . I had a good mechanic put a kit in it, but who knows what could have gone wrong. with the rear jacked up you can easily turn the driveshaft everything seems great. you'd think if it was seizing it would at least be stiff all the time, when wheels are turning in neutral you can stop them by hand. the transmission does get stuck in gear though, you either have to mess with it or just power through and break it loose.

This is a real tough one, I can't really think of what would bind up hard enough to chirp the tires, yet move freely after breaking loose. just for grins I'm going to pull the brake drums and rule them out. I can't imagine what it would be they're all new . and how would they make the transmission stick in gear .but I'm grasping.

So I don't know what the problem is , but I know where it is.

With the rear on jacks I have determined there is something locking up and sometimes between shifts the rear wheels stop for no reason.

I managed to get it to lock up and I shut the engine off and removed the drive shaft. the rear end turns and the transmission is stuck. I can shift through all the gears except 2nd but that could simply be the position of the gears. this is with the engine off.

I'm not sure if misalignment could cause this, seems odd it would be intermittent. but if it is the cause if I loosen up the transmission bolts and move it should unlock I assume. if it doesn't it has to be inside the transmission and I don't know what or why.

I guess either way I'm pulling the tranny.

Disconnect the shifter and put the tranny manually in a gear? (3&4 in neutral and 2 in gear, 1 in neutral)

Shifter out of alignment?

:confused:

The levers are lined up perfectly and the drill bit slips right through. but I will try.

Right now the transmission is seized but I can shift it with the shifter to every gear but 2nd.

Many years ago I had a '66 442 with the Hurst shifter that was very loose and worn. It would lock up during shifts and lock the rear tires. I'd push in the clutch and move the shift lever again and it would shift into the next gear properly. Eventually it locked up at speed and broke some teeth off a gear, losing 1st and 4th.

Not common but possible. Drain the trans fluid and remove the side cover. You may be able to do this in the car. Make sure the synchronizer sleeves are facing away from each other. The sleeves have a taper and a flat side. The taper sides face away from each other. If one is reversed, which is possible, this condition can happen.

Here is a pic showing sleeves.

Does it roll freely in neutral?

Thanks for the suggestions.

It does roll freely until it locks. right now it won't roll so I pulled the drive shaft. I'm going to get und unhook the shift lever to see if I can shift it out of gear. it's in neutral now and the linkage is in adjustment.

It seems like it's sticking in 2 gears, but the fact I can shift to every gear except 2nd would suggest it's not.

The backwards parts theory may have some merit. sometimes it chirps the tires when it locks up, sometimes it just binding and pops loose.

I've seen side cover detent springs come off, and jamb in 2nd and 3rd at the same time locking the transmission in 2 gears. This does lock the output shaft.

There are 2 levers with detent springs designed to keep this from happening under the side cover. You may find the trouble in this mechanism, I've seen it before, not common, but it does happen.

One time I saw the spring come off the hook on the lever, one time I saw the hook that the spring hooks to on the lever just break off.

Sometimes the levers can be unjammed and driven home, sometimes it locks tightly enough that the side cover must come off to get the transmission back in neutral. Only have I seen this happen on is Muncie 4 speeds.

:2cents:

If this were to happen would you still be able to shift gears and have the transmission locked?

0I got under it and everything looks fine. I can easily shift it to each gear , except 2nd is not going all the way, which may be it's just not lined up. all other gears shift smoothly but the output is locked. but it's locked with a little slack that sounds like it's in gear, a solid clunk as you go back and forth.

I'm draining the oil and figured I'm going to have to pull the transmission, so I just as well do it. if you think there's any chance the problem is something that may be fixed by pulling the side cover I can.

If this were to happen would you still be able to shift gears and have the transmission locked?

I got under it and everything looks fine. I can easily shift it to each gear , except 2nd is not going all the way, which may be it's just not lined up. all other gears shift smoothly but the output is locked. but it's locked with a little slack that sounds like it's in gear, a solid clunk as you go back and forth.

I'm draining the oil and figured I'm going to have to pull the transmission, so I just as well do it. if you think there's any chance the problem is something that may be fixed by pulling the side cover I can

If those springs or lockout arms aren't working correctly I could see that you may be able to shift into the other gears while second was still engaged.

The mechanism in the side cover is meant to never be able to engage 2 gears at once. If it's damaged, or a spring came off you can engage 2 gears at once locking the output shaft.

Shift forks can break also, never have seen it in a Muncie, but have seen it in truck transmissions.

Probably worth a try to remove the side cover in car to fix the problem without pulling the transmission. Even if it's not in the side cover little time lost to save a transmission R&R.

I’ve had this happen to me. The gears might be stacked meaning trying to be in 2 gears at one time.

Well as far as I can see everything looks fine. the sliders rattle back and forth a bit but the main cluster is rock solid tight. I'm wondering if the bearings on it or the countershaft are seizing.

I'll try to post some pictures and if nobody sees something obvious I guess I'll pull it.

another

I would guess you are right about a bearing seizing.
Can you tell if the countershaft is stuck or moving?

okay I pulled the transmission and I don't know what the problem is but I know where it is.

With it on the bench it turns freely and looks fine to me. but with it in neutral you cannot turn the input without the output turning as well. the sliders rattle and move and they are in neutral. there is a bit of slack between the input and output in the cluster. when you turn the cluster everything appears loose and moving freely. but something is serious wrong inside of it.

It had a kit put in it and it hadn't been used before I installed it and did the break in run on the cam. I put oil in it before starting the engine. is it possible a bearing inside the cluster was starved for lubrication during the break it? it worked fine just moving it around the shop but when I was getting ready to test drive it this all started.

Found the problem, don't know the solution.

the 1st synchro ring from the front was stuck on the hub. I took a screwdriver and popped it lose and now everything moves freely. this was a new kit with rings, should I assume they're junk and search for higher quality ones or could there be another cause?

Sometimes welding on a car can send high current through strange places and do damage... you really can't see what's going on with the surfaces while it's together could be something that's new wasn't made quite perfect

New synchros can be out of round. They need to be checked for fit. There is an excellent video on this by a guy named Paul Cangualosi at 5speeds.com. The video explains it a lot better than me. Good luck!

Before I take it to someone I'm wondering if I should check the bellhousing alignment. could it be messes up enough to cause that synchro to bind on the hub? that would explain a lot. I could use one of the alignment tools in the future anyway.

the input fits in the pilot bushing easy and it bolts up no problem. but I don't know if that means anything. also, I did something kind of dumb , I put some silicone over the spot where the countershaft pin goes just to insure it didn't leak. about the thickness of 4 sheets of paper, I wonder it that may have had any effect on the alignment?

I would watch those gear box videos on Youtube. They are excellent. It's likely one or more brass rings are bent or warped. I do the Sharpie test he describes on all the gears and synchronizer rings now based on the video. About 1 out of three new ones are bad and can not be used. Junk parts make life tough on us. I bet you can fix this yourself. You just need a pair of really good heavy duty snap ring pliers and basic hand tools to take a Muncie apart. Very simple transmission. If you don't want to tackle it your self, PM me. I am doing 1 right now, a M22 for a guy from Indianapolis. I am in Dayton, OH.

Are there any high quality rings you can buy? I ran into problems using junk imported parts on an NP435 and luckily I found some NOS ones. I'm sure on a Muncie that's not an option.

I'll check that out.

Yes, Paul checks each set he sells. 100%. The videos are called The Muncie Tapes. On YouTube. There a 4 parts on YouTube. You can also call Paul. He’s a great guy and will answer any and all questions.

So if his current problem is isolated to the forward syncro can he not just pull the input shat out of the front and install a new part..

No special tools just remove throw out collar pull input shaft collect the dropped out roller bearings position new syncro put roller bearings in place with a touch of grease reassemble with new gaskets with gasket thickness in mind for the bearing nut to collar relation..

The easiest syncro in the trans to replace on the fly

That would be nice if it's that easy, I'll watch the videos.

I'm going to look at things harder but I'm really starting to think I have an alignment issue. this is the original engine, bellhousing and transmission so I never checked the alignment. but one ear was broken on the transmission I had welded back on, and I think I see wear on the bellhousing opening. I suspect a problem there.

This would be a good root cause...check the mating surfaces for signs of arcing or local heat damage?

I pulled the bearing retainer, and it fits snug in the bellhousing so that's not the problem.

I think I'll get some of those synchro's and order an alignment check tool.

Please help me understand how a stuck synchro caused the transmission to lock. Did it prevent the slider clutch from moving/disengaging?

If you could move the synchro with a screwdriver I doubt it would transmit enough torque to lock anything so I'm missing something....

Clearly something is wrong. I just want to understand the failure mode. This one has me curious as I don't understand how two gears could be engaged at once because of a synchro...

Here's a picture I found that helps me visualize. Where was the synchro bound up and how did it lock up the transmission hard enough to resist the engine?

https://forums.maxperformanceinc.com...1&d=1747683235

Mike

The syncro is keyed to the hub in 3 places so if syncro is locked with gear cone then its like shift collar is over all of them

does seem like the keys or syncro would bust or just loosen before locking chirping tires

ignore.. I posted before Formula's edit

doh!

Thanks for this! I'm slow and still not seeing it, but it's been a long time since I was into a transmission. I have a Saginaw in the garage, will go look.

I thought all the torque went through the slider clutch (not sure of the right terminology) that moves on the hub when the shift fork pushes it... basically locking the hub to the gear. So if the synchro is locked to the hub, I'm not seeing how the mating gear was engaged and locked if the slider was either in neutral or engaging the other gear.

I guess if the synchro was locked to the gear (the tapered face), then it would try to transmit torque to the hub.... but again, if he loosened it with a screwdriver, how could it lock the gear against the engine torque ???

hmmm...

If I hadn't seen it myself I would question it too. it actually chirped the tires.

So I talked Paul at 5Speeds, very helpful and knowledgeable. He told me with the new syncros you need to polish and fit them or this can happen. he said I should be able to put it back in and wear them in by pushing on the shifter but not putting it in gear. he said my alignment would not be the cause since it's all original equipment.

I think I'm going to get a new set of rings and fit them properly since it's on my bench right now. I want to put new gaskets in with silicone it leaks bad now anyway.

Buy your parts from Paul and watch “the Muncie tapes” on YouTube. He is a smart guy.

That's exactly what I'm doing. he explained it to me and told me to watch the video, it's exactly the problem I have, and I've never heard of it before.

He told me how to cure it and I didn't need to buy anything, but I'm going to put new rings in it and make sure they're working correct just so I know it's fixed. great guy. *

Paul wrote a book about working on Muncies. I "had" a copy, even though I'll never likely own a 4 speed car...
I'm sure the book is still in print, it's not that old...