dv69vet

Hello to all out there.I am new to this forum and am in need of some information please.
I own a 1969 350/350 cid, hurst 4 speed, 4.10 gear differential with original tire size tires and I am in the process of swapping out the differential to a 3.08 gear differential.
I do a lot of highway/open road driving and that is why I am going to the 3.08's.
I have looked in my corvette manuals and don't find any info on this subject.
I am reading a lot of info on differential swap outs and can not find information on original driven/drive gear pairing for my original setup or the new driven/drive gear setup I am going to.

I need to change the driven/drive gears for my setup to make the speedometer read correctly.

Can you tell me what driven gear/drive gear combination came with a hurst 4 speed,3.08 diff gear, original size tire car?

Hopefully I have explained this correctly.

Thanks in advance....Dennis

corvgreg

http://www.stl-vettes.com/65Vette/GearCalc.htm

71VetteLover

The formula for calculating speedometer driven gears needed is:

Number of drive gear teeth (8) times rear axle ratio (3.08) times tire revolutions per mile (734) divided by 1001 equals 18 teeth on the driven gear.

So assuming you are running the stock GR70-15 tires you'll need an 18 tooth driven gear when using a 3.08 rear axle ratio.

dv69vet

Sorry, my transmission is a M-21 4 speed manual transmission and I don't think a 20 tooth Blue driven gear goes into a manual trans....it is shown in chevy manuals as an automatic trans driven gear....I am probably wrong. Would a black 20 tooth gear be the one I need for a M-21 manual trans....

Does anyone know what drive gear comes from the factory in a M-21 trans with 4.11 gears, large (8 tooth, 1.84 dia.) or small (8 tooth, 1.76 dia.)?

71VetteLover

You didn't plug the right numbers into that formula. You need to plug in the 3.08 gear ratio and the 27.4" tire diameter and it'll show an 18 tooth driven gear..........not a 20 tooth. And the 1969 Muncie used the larger 1.84" plastic drive gear.

dv69vet

Thank you sir....told you I was wrong.
That was the info I needed.
I have been on the forum many times and the wealth of knowledge that is here is amazing.

dv69vet

Well I bought the brown 18 tooth driven gear and it turns out that the gear is the small type driven gear. My drive gear seems to be a small gear also cause the driven gear spins inside the tranny with no meshing up with the drive gear.

Now, is there a large driven gear used with the smaller drive gear for a 4 speed manual transmission?

If not, where do I get a large 8 tooth drive gear and can I just take the tail section off the tranny instead of taking out the whole tranny to change the drive gear?

Now I did use the speedo calculator and it gives me an error stating that a small driven gear can not be used with a small drive gear.

thanks.

71VetteLover

Is this what you want: http://www.ebay.com/itm/MUNCIE-4-SPE...item51e66ef515