C:1 Speedodometer gear 4:56 Gears

[Gene #39090]

Can anyone tell me the color or tooth count for 4:11 gears? 60 series tires but not revelant.
Thanks,
Gene,
fuelie1962@aol.com

[Doug Flaten]

Re: C:1 Speedodometer gear 4:56 Gears

Seems to me the tire size is relevant since you are not talking stock tires. The attached website has a lot of information regarding calibrating speedometer based on gear ratio, tire size and speedometer driven gear tooth count.

http://www.classictruckshop.com/gears.htm

[Joe L.]

Re: C:1 Speedodometer gear 4:56 Gears

Gene-----

Assuming stock or close-to-stock tire diameter, you require a pair of gears which were discontinued by GM MANY years ago. The DRIVE gear is of GM #3845079 and is a 6 tooth steel gear of 1-59/64" OD. The DRIVEN gear is also a steel gear of 20 tooth count and of GM #3845071.

My recommendation to you would be to factor in whatever tire size that you're using (if it's significantly different than stock), determine what DRIVE gear that you have currently installed and then select a COMBINATION of a DRIVEN gear compatible with your DRIVE gear AND a speedometer adapter of the appropriate ratio to produce an accurate speedometer reading.

[Mike M.]

Re: C:1 Speedodometer gear 4:56 Gears

joe: when i put my 57 FI back together in the late 80's , no one had the correct drive and driven gear for the 4.56;1 pumpkin i wanted to run. I found both in an old 55 chev pass car that had a 2345 and O.D.. Speedometer was within 2% of actual speed( I knew it had to be near perfect because that dastardly fellow from lyle, wash was the P>V> judge. It passed. Mike

[Tom B.]

Re: C:1 Speedodometer gear 4:56 Gears

I'll be darned Doug. I didn't know that chart was there and I'm a moderator for the '67-'72 forum (Basketcase). Maybe I should look around more.
Tom

[Gene #39090]

Re: C:1 Speedodometer gear 4:56 Gears

Oops I guess I should have put in that I am running a Super T10 not stock T-10, the tires are not a big factor because I will be changing from 60 series BFG Comp TA's to dog dish hubcap and stock 5.5" or other 6" rims that look stock with itty bitty tires when I can. So stock speedo gearing numbers are what I am looking for. Thanks for the quick responses.
Gene Layne

[Joe L.]

Re: C:1 Speedodometer gear 4:56 Gears

Gene-----

With a Super T-10, I think that you are going to have to go with an adapter to get a correct speedo reading. The adapters are a bit expensive (about $75-100), but they are a very quick and easy means of correcting speedometer calibration. With them, you can actually get a more accurate reading than you usually get with an available drive and driven gearset. Adapters are how "certified" speedometers which are part of "police packages" used to be accomplished by the car factories.

[Dennis C.]

Re: C:1 Speedodometer gear 4:56 Gears

Gee Whiz # 14, can you help me find the correct speedo gears for my '57 with factory 4.88 RPO ratio...

[Mike M.]

Re: C:1 Speedodometer gear 4:56 Gears

SUGGEST YOU PUT A WINDSOCK ON THE ANTENNA AND JUDGE SPEED WITH IT(AS NONE OF YOU CARS IN THE PAST WOULD HIT 50 MPH) MIKIE