[AMX guy]

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

[steve25]

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

[geeteeohguy]

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.

[AMX guy]

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.

[AMX guy]

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.

[johnta1]

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?

[AMX guy]

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.

[android 211]

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.

[mgarblik]

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.

[mgarblik]

Here is a pic showing sleeves.

[Holeshot71]

Does it roll freely in neutral?

[AMX guy]

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.

[Sirrotica]

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.

[AMX guy]

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.

[AMX guy]

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

[Sirrotica]

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.

[64speed]

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

[AMX guy]

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.

[AMX guy]

another

[tstroud]

Originally Posted by AMX guy

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.

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