60 T-10 speeddometer drive gear?

[William B.]

In my 60, I will be using a 4:11 rear gear, and I am not sure if I need a different main shaft gear in the T-10 transmission that drives the speedo plastic gears? The car previously had 3:70's.
I had a problem with a 67, I had purchased, previous owner had changed the rear from from a 4:56 to a 3:70 and could not get the speedo to read correctly. Had to change the drivin gear and then could insert the correct plastic gear, but that was a muncie, are the T-10's the same? If so does anyone have a part #?

[Edward J.]

Re: 60 T-10 speeddometer drive gear?

William, there where only two drive gears in the trans. I believe one was from the 3:08 to 3:50 range and the other was 3:70 TO 4:56 . I think in some of the vender catalogs they speed it out for.

[Joe L.]

Re: 60 T-10 speeddometer drive gear?

In my 60, I will be using a 4:11 rear gear, and I am not sure if I need a different main shaft gear in the T-10 transmission that drives the speedo plastic gears? The car previously had 3:70's.
I had a problem with a 67, I had purchased, previous owner had changed the rear from from a 4:56 to a 3:70 and could not get the speedo to read correctly. Had to change the drivin gear and then could insert the correct plastic gear, but that was a muncie, are the T-10's the same? If so does anyone have a part #?

William-------


IF you remove a GREEN, 22 tooth DRIVEN gear, then you can replace it with a YELLOW, 24 tooth DRIVEN gear without the the need to change the DRIVE gear and it should provide correct speedometer calibration with 4.11:1 rear gears IF your tire OD is about the same as stock.

The yellow, 24 tooth driven gear for your application was GM #3708143, but it's long-since GM-discontinued. However, I think it's available in the aftermarket. This is a gear for 1960 and older which is different than 1961 and later. The 1961 and later DRIVEN gears are still available from GM.

[Joe L.]

Re: 60 T-10 speeddometer drive gear?

William, there where only two drive gears in the trans. I believe one was from the 3:08 to 3:50 range and the other was 3:70 TO 4:56 . I think in some of the vender catalogs they speed it out for.

Edward------


There were only two COMMON DRIVE gears. However, there were other UNCOMMON DRIVE gears. The one used for 4.56:1 rear gear applications was one of these uncommon gears. The DRIVEN gear used with it was steel, not nylon as most of the common applications used.

[Joe L.]

Re: 60 T-10 speeddometer drive gear?

-- was the bullet different ?.

Wayne-----


Yes, the 1960 and older FITTING ("bullet") was different and longer than the 1961+.

[Wayne M.]

Re: 60 T-10 speeddometer drive gear?

Wayne-----


Yes, the 1960 and older FITTING ("bullet") was different and longer than the 1961+.

Joe -- I cancelled my post because you were more accurate in your info than I was.

[William B.]

Re: 60 T-10 speeddometer drive gear?

in the trans I am using is a steel driven gear with 24 teeth, I believe it had a 4:56 rear behind it.
I just ordered a new drive gear and a driven gear for a 4:11, from a transmission vendor. Most everybody in the parts stores did not know what I was talking about.
Thanks everyone for all the helpfull replies.

[Wayne M.]

Re: 60 T-10 speeddometer drive gear?

Wayne -----Yes, the 1960 and older FITTING ("bullet") was different and longer than the 1961+.

Now I'm a bit confused. 1st thumbnail below is of two NOS 3860329, 20-tooth driven gears (2.36" OL), compared to a 24-tooth yellow plastic gear (2.20"OL). But the longer steel gears part number relates to a '61-up service, per the P&A catalogs.

Second thumbnail (upper) is another 20-tooth steel gear from eBay that came as a used set with the 6-tooth drive gear. I assume by deduction that this shorter 2.185" OL gear is the earlier #3845071, listed in the P&A catalog as for '57-60 Corvette w/4.56. Notice the 4 flats on the '329's versus the 4 grooves on the '071 ?'.