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OK, I just got done putting my finger on the drive gear in the trans. I can move the gear with my finger. Meaning I can turn the drive gear around while it is on the shaft.Is that supposed to move with my finger? I thought it wouldn’t be that easy. So is that normal that it moves with my finger? As far as what it looks like, it looks OK to me. Here are a few pictures. Sorry they are kind of dark. I wouldn’t think that gear would be worn out because the car only has 50,000 miles on it, but what do I know? Seems like the speedometer gear is OK too because I put the cable in it and there’s no play and it turns the cable fine. Is it possible that the drive gear is back to far? If so, why would that happen and what do I do about it? Can I move the gear closer by just pulling on it?
Hey, I need to apologize to headssu.p. , Melwff, 4-vettes, Racer, bmotojoe, Melting Slicks, and VbGod1 My drive gear is not moving at all. I was wrong. My apologies to all of you. Thank you for helping me. I am sorry. Just wanted to say that. I ordered a new speedometer gear and a new bullet. So hopefully that will work. Thank you all again and once again, please accept my apology.
Gary
Last edited by garykuter; Jun 6, 2025 at 12:20 AM.
OK Gary, you have a 77 with a BW Super T10. Correct?
you say the speedo drive gear spins on the shaft with your finger and almost no effort?
WOW!
From the Genuine GM 1977 Unit repair manual, showing that speedo drive gear. See how it's driven with a splined shaft and retained with a snap ring on both ends.
it should turn with the output shaft of the transmission. And ABSOLUTELY no other way. If it's that stripped that it spins with your finger.
Yes mate. Your pulling your transmission.
Gary, just to be clear. You are working on a 1977 Corvette with the original 4 speed manual transmission, correct?
This should then be a Borg Warner Super T10 Transmission. Correct?
And you stick your finger in the hole and can spin the speedo drive gear with your finger without the driveshaft moving? Correct?
Gary, just to be clear. You are working on a 1977 Corvette with the original 4 speed manual transmission, correct?
This should then be a Borg Warner Super T10 Transmission. Correct?
And you stick your finger in the hole and can spin the speedo drive gear with your finger without the driveshaft moving? Correct?
I wouldn’t actually say spin it but I can move it. Yes this is a 77 Corvette with the original tranny, but I think its a Muncie M 21 Because mine is close ratio.
Gary, just to be clear. You are working on a 1977 Corvette with the original 4 speed manual transmission, correct?
This should then be a Borg Warner Super T10 Transmission. Correct?
And you stick your finger in the hole and can spin the speedo drive gear with your finger without the driveshaft moving? Correct?
The speedometer was working with the old speedometer cable, but it would sometimes fluctuate, but would work fine. Anything under 60 miles an hour was fine. But the cable was loose so was the bullet when I first started to change the speedometer cable
You have a 1977 Corvette? Yes?
it's pretty easy to see if it's a Borg Warner or if someone has changed it out to a Muncie. You stated it's a low mileage car. So unusual that someone would have changed the gear box. But it's certainly possible.
At any rate. The transmissions are different. However. You should not be able to turn that gear with your finger no matter what.
You have a 1977 Corvette? Yes?
it's pretty easy to see if it's a Borg Warner or if someone has changed it out to a Muncie. You stated it's a low mileage car. So unusual that someone would have changed the gear box. But it's certainly possible.
At any rate. The transmissions are different. However. You should not be able to turn that gear with your finger no matter what.
no one has changed out the transmission. I am the second owner and I know the first owner who bought this car from the dealership here in Las Vegas. Pretty simple just to Google a1977 Corvette and ask what transmissions were stock that year for the manuals. and you’ll see what I’m talking about
The retaining clip that locks the gear in place went AWOL.
But where did it go?
I think I would buy a long reach magnet and go through the speedo port. Start fishing for the clip on the bottom of the tranny.
You do not want that clip interfering with gearing.
Slight possibility the clip is still in position on the shaft and the plastic drive gear is shot / stripped.
Likely you will have to remove the driveshaft, and tail housing to get at the drive gear. If your speedometer is spot-on then buy a duplicate number of teeth gear.
If speedo is off by a few mph then shop for smaller / larger tooth.
The tail housing removal will require jacking up the trans slightly after loosening the mount. Use a brace to support the weight (engine+trans).
Not a fun job, but doable.
The retaining clip that locks the gear in place went AWOL.
But where did it go?
I think I would buy a long reach magnet and go through the speedo port. Start fishing for the clip on the bottom of the tranny.
You do not want that clip interfering with gearing.
Slight possibility the clip is still in position on the shaft and the plastic drive gear is shot / stripped.
Likely you will have to remove the driveshaft, and tail housing to get at the drive gear. If your speedometer is spot-on then buy a duplicate number of teeth gear.
If speedo is off by a few mph then shop for smaller / larger tooth.
The tail housing removal will require jacking up the trans slightly after loosening the mount. Use a brace to support the weight (engine+trans).
Not a fun job, but doable.
I have no idea about the clip. Maybe it did fall inside The speedometer has never worked correctly from day one and I’ve had the car for three years now. I’m familiar about dropping the tailgate and trans. Something I don’t wanna do.
While my driveshaft was out, installed Spicer Solid U-Joints.
While the driveshaft was out, good time to change the pinion snubber.
While my tail-shaft housing was out, swapped-out the yoke seal too.
While the tranny was jacked up, great time to swap-out the rubber mount.
All that, just to change the Drive Gear.
While my driveshaft was out, installed Spicer Solid U-Joints.
While the driveshaft was out, good time to change the pinion snubber.
While my tail-shaft housing was out, swapped-out the yoke seal too.
While the tranny was jacked up, great time to swap-out the rubber mount.
All that, just to change the Drive Gear.
While my driveshaft was out, installed Spicer Solid U-Joints.
While the driveshaft was out, good time to change the pinion snubber.
While my tail-shaft housing was out, swapped-out the yoke seal too.
While the tranny was jacked up, great time to swap-out the rubber mount.
All that, just to change the Drive Gear.
so if I put the car in gear, let’s say first or second gear on manual trans. I have the M 21. Should I still be able to move the gear in the tranny with my finger?
No. That's why we suspect either the clip is gone or the gear itsef no longer can lock on to the shaft.
The drive gear is fastened to the trannys tail-shaft. And that is fastened to the driveshaft.
There is a web site that sells all kinds of speedometer parts for the tranny. I believe it's called Speedo World.
Then look for GM 4 speed products. You will see pictures of the parts you need.
No. That's why we suspect either the clip is gone or the gear itsef no longer can lock on to the shaft.
The drive gear is fastened to the trannys tail-shaft. And that is fastened to the driveshaft.
There is a web site that sells all kinds of speedometer parts for the tranny. I believe it's called Speedo World.
Then look for GM 4 speed products. You will see pictures of the parts you need.
OK, thank you but when I googled it and a website a Corvette website said that the M 21 drive gear will turn with your finger. Here is a copy of it unless they’re wrong.
It says it should turn freely when it’s in neutral. Doesn’t say anything about when it’s in gear. I don’t know I guess I can always take it back to the place that did my rear end gears a few years ago and just ask them. I’m sure they would know. But it makes sense of what you are saying that it shouldn’t turn freely. No if I put the car in reverse, I know the gear shouldn’t turn because the speedometer doesn’t work when the car is in reverse. Maybe I’ll try that. Lol.
OK, thank you but when I googled it and a website a Corvette website said that the M 21 drive gear will turn with your finger. Here is a copy of it unless they’re wrong.
It says it should turn freely when it’s in neutral. Doesn’t say anything about when it’s in gear. I don’t know I guess I can always take it back to the place that did my rear end gears a few years ago and just ask them. I’m sure they would know. But it makes sense of what you are saying that it shouldn’t turn freely. No if I put the car in reverse, I know the gear shouldn’t turn because the speedometer doesn’t work when the car is in reverse. Maybe I’ll try that. Lol.
That information is referring to the input shaft.
The gear you are turning is on the OUTPUT shaft. You should Not be able to turn it with your finger.
That information is referring to the input shaft.
The gear you are turning is on the OUTPUT shaft. You should Not be able to turn it with your finger.
is it possible to replace the drive gear retainer clip Without taking out the transmission or the tail housing? Just in case that is my problem that the clip fell or came off. I’m gonna say no to my question, but maybe you have a different answer. Thank you for your time.
is it possible to replace the drive gear retainer clip Without taking out the transmission or the tail housing? Just in case that is my problem that the clip fell or came off. I’m gonna say no to my question, but maybe you have a different answer. Thank you for your time.
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Drive Gear
