Speedo Drive Sleave Replacement
Thread Starter
Burning Brakes
Joined: Jan 2001
Posts: 1,215
Likes: 441
From: Loir Valley Sarthe, France
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
Speedo Drive Sleave Replacement
Hi
I want to cure the small leak from the speedo drive sleeve on my ’78, and am planning on replacing the sleeve/seal assembly and the drive gear.
So, my question for those that have done this is, if I do this job without draining the transmission (auto) will I be washed away by the rush of trans fluid when I remove the exiting sleeve?
Or does not much come out?
When I changed the shifter shaft seal, almost no fluid escaped, so I’m hoping this may be similar?
Thanks.
I want to cure the small leak from the speedo drive sleeve on my ’78, and am planning on replacing the sleeve/seal assembly and the drive gear.
So, my question for those that have done this is, if I do this job without draining the transmission (auto) will I be washed away by the rush of trans fluid when I remove the exiting sleeve?
Or does not much come out?When I changed the shifter shaft seal, almost no fluid escaped, so I’m hoping this may be similar?
Thanks.
Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,335
From: North of Toronto - Ontario
I pulled the sleeve on my th400 a couple of weeks ago to change out the gear.
Lost about a quart or so. Not too bad. (about 1-1/2" in a 6" x 10" pan, can is tipped slightly nose down)
When you put the new one in, I've now heard from quite a few semi-reliable sources to put in two inner seals (the ones that run on the actual gear shaft) Not sure if yours is the same (th350/400?)
Mooser
Lost about a quart or so. Not too bad. (about 1-1/2" in a 6" x 10" pan, can is tipped slightly nose down)
When you put the new one in, I've now heard from quite a few semi-reliable sources to put in two inner seals (the ones that run on the actual gear shaft) Not sure if yours is the same (th350/400?)
Mooser
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You just need to replace the O-ring(s)/seal(s) in that speedo gear carrier. You don't need an entirely new carrier (total waste of money). Check with NAPA or other auto parts store to see if they can get a seal kit...or the individual seals....first.
You can always remove the old seals/rings and measure them to order the proper replacement parts. Some hardware stores carry small bins of O-rings labeled by the diameter and the ring section size.
When you install them, just put a light wipe of tranny fluid or Vaseline on the new seals/rings, so they will not bind or roll during installation.
You can always remove the old seals/rings and measure them to order the proper replacement parts. Some hardware stores carry small bins of O-rings labeled by the diameter and the ring section size.
When you install them, just put a light wipe of tranny fluid or Vaseline on the new seals/rings, so they will not bind or roll during installation.
Thread Starter
Burning Brakes
Joined: Jan 2001
Posts: 1,215
Likes: 441
From: Loir Valley Sarthe, France
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
Thanks guys!
7T1vette - Oh to have it so easy!
No NAPPAs here in France, or anything really similar close to home. By the time I faff about looking for the O rings (and it did occur to me to try that) it'll be cheaper to get a whole unit sent over from one of the UK's Corvette specialists!
Thanks all the same 
I was actually thinking of popping in a new gear as well, but is that maybe "overkill"?
7T1vette - Oh to have it so easy!
No NAPPAs here in France, or anything really similar close to home. By the time I faff about looking for the O rings (and it did occur to me to try that) it'll be cheaper to get a whole unit sent over from one of the UK's Corvette specialists! Thanks all the same I was actually thinking of popping in a new gear as well, but is that maybe "overkill"?
Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,335
From: North of Toronto - Ontario
Check the gear where the shaft goes through the inner seal. If it feels worn or has any marks,nicks, lines replace it.
Are you sure the leak is from the outer o-ring? Usually seem to leak on the gear shaft rather than the static o-ring
Mooser
Are you sure the leak is from the outer o-ring? Usually seem to leak on the gear shaft rather than the static o-ring
Mooser
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
I did mine on my '76 a while back (350 auto). You'll loose some fluid when pulling it but if you jack the car up on the left side, the loss will be minimal. Put a catch pan underneath the speedo connection. Once removed, I took it to a tranny shop and they replaced the 2 o-rings at no charge. I know the guy but he did the job in a couple of minutes. on reinstallation, lube the outer o-ring well with tranny fluid as it takes a little pressure to get it in. Even if you have to pay a couple of bucks for the job, its better than driving around trying to find the proper o-rings.
Thread Starter
Burning Brakes
Joined: Jan 2001
Posts: 1,215
Likes: 441
From: Loir Valley Sarthe, France
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
Thanks chaps!
Moser - I'm not sure where it's leaking exactly, I just see teh fluid around the speedo cable attachment. That's whay i was thinking I'd put in a complete new sleeve.
Jud - Thanks. I have a slight issue in that I need to drop out the exhaust (a custom bracket on the centre chassis beam) so I was hoping to put the whole car in the air. But, I may get away with it "tilted" to one side!
Moser - I'm not sure where it's leaking exactly, I just see teh fluid around the speedo cable attachment. That's whay i was thinking I'd put in a complete new sleeve.
Jud - Thanks. I have a slight issue in that I need to drop out the exhaust (a custom bracket on the centre chassis beam) so I was hoping to put the whole car in the air. But, I may get away with it "tilted" to one side!
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Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,335
From: North of Toronto - Ontario
Dollars to donuts it's leaking on the gear shaft seal.
It's a TH350 ?
The seals are literally a dollar or so each (pennies if you have a local shop)
If you still want, the TCI bullets (summit etc) come with seals installed
Mooser
It's a TH350 ?
The seals are literally a dollar or so each (pennies if you have a local shop)
If you still want, the TCI bullets (summit etc) come with seals installed
Mooser
