57 4 speed speedometer driven gear

[Larry O.]

Could someone please tell me which gear would be the correct one for my 57 with a 4 speed and a 4:11.
Thanks,
Larry T. Omps (52152)

[Gary C.]

Re: 57 4 speed speedometer driven gear

Larry, moved your post from the Help Forum to the Technical Forum. Gary....

[Larry O.]

Re: 57 4 speed speedometer driven gear

Gary,
Thanks, I am having some difficulty navigating the website. Any help is greatly appreciated.
Larry

[Terry D.]

Re: 57 4 speed speedometer driven gear

Larry

According to my 67 parts book it takes a 24 tooth yellow gear. Part number 3708143, if you need one I will look in my spare parts as several years ago I bought a bunch of different gears from a going out of business Chevy store.
Terry

[Mike M.]

Re: 57 4 speed speedometer driven gear

if i recall correctly, the 4.11 and 4.56:1 differentials require the same drive gear(on the tailshaft) and a seperate driven gear for the 4.11 and the 4.56. as i recall, both the drive and driven gears for these two differentail ratios require STEEL gears. the parts books will contain the info you need. don't use a drive gear for the 3.08 thru 3.90 rears with a driven gear for the 4.11/4.56 as the teeth won't mesh. mike

[Wayne M.]

Re: 57 4 speed speedometer driven gear

.....According to my 67 parts book it takes a 24 tooth yellow gear. Part number 3708143 .....

I get same number in my July '65 P&A30; described as 56-60 CORVETTE w/4.11 axle, (24 teeth) (nylon) (solid yellow). In the big pic I show the steel 20-tooth 3860329, with 6 tooth drive 3845079 which is described as for Corvette '61 thru '67 w/4.56 axle, but the shaft is longer than the other 20-tooth steel gear next to it [see thumbnail, below], and a variety of shorter plastic gears for the C2-C3 manual trans. Note the 'flats' and the splines near the steel gear shaft ends.

So this raises the question; are there two 'familes' of driven gears, longer shaft for the '56-60 cars and shorter for the later ones ? Is it because of a different length "fitting" (or bullet) which supports the driven gear ? Measured one I have from a '65 and it's 1.79" O.L.

[Joe L.]

Re: 57 4 speed speedometer driven gear

Larry

According to my 67 parts book it takes a 24 tooth yellow gear. Part number 3708143, if you need one I will look in my spare parts as several years ago I bought a bunch of different gears from a going out of business Chevy store.
Terry

Terry and Larry----


Yes, the GM #3708143 is the gear that I come up with, too. It's a yellow, 24 tooth, NYLON gear. It was discontinued without supercession in November, 1982. However, an aftermarket replacement for this gear should be available from transmission shops or specialty speedometer parts suppliers.

[Ray K.]

Re: 57 4 speed speedometer driven gear

Larry---

I agree with the other comments that the #3708143 24 tooth yellow gear would be the correct choice. An alternative would be #3738400 which is a 25 tooth gear natural in color and is listed for full size pass cars with O.D. and 4.11 ratio. These earlier gears (55-60) are longer at 2 7/8" versus the '61 and later gears such as the 24 tooth 3860347 which is 2 1/8" long. The longer gear requires a longer fitting #3708147 or 3748533. This should mate to a 3708144 "drive" gear inside the transmission.

Ray

[William C.]

Re: 57 4 speed speedometer driven gear

I'm with Ray, I've seen the longer fittings used in the early cars. Per the '63 Parts book, 2 5/8 inch length used thru 1960, part number 3708147 except 1960 4 speed, then switched to 1 7/8 inch length part #3775589 in '61, leaving the question of what was used in '60 an open item. Very noticeable difference and the speedo cable will not connect and drive properly with the short driven gear in the long fitting.

[Larry O.]

Re: 57 4 speed speedometer driven gear

Thanks Guys,
You have been a great help.
This is the first time I have used this site. It is EXCELLENT!
Thanks,
Larry T. Omps
Winchester, Virginia
540-247-4400

[Wayne L.]

Re: 57 4 speed speedometer driven gear

Since the 1960 T10 uses the 7B tail housing, it takes the shorter driven gear.