Hi All,

I have a 1967 with a 12 bolt posi with 3.73 gears and a 350 (350hp) with a Turbo 350 with 2500 stall. I run at appr 3350 RPM on the highway at 65 and was looking at putting in a 700R OD tarnny. I talked to a rod shop owner builder and he said he would not make that change as he would go with a 3.08 instead. He also said I would be going down the highway at 65 MPH with RPM's only at 2200 RPM? That seems to go against all of the RPM calculators with that setup. I also have 26.1 tires. Anyone have any comment's on this?

Thanks

 

a 700r4 built right will handle your car and should put you at about 2k at 60. 700r4 is the same trans as th350 with overdrive gear added

 

If you go with a 200r4 you have better gearing and the same overdrive and you don't need to cut the drive shaft. Same length as the th350 so no cost in shortening the one you have.

 

If you go for the OD trans, THM200-4R would be my choice also, you may have to install a stock torque convertor as a looser one, higher stall rpm, would not be 'locked up,' thus heating up ATF more than it is designed.

 

I think what you are asking for is this. Since you are comparing RPM and speed on the same car with no other change other then the rear ratio we have everything we need. First we make a formula.
RPM / Rear ratio /(all other drive info)= 65 MPH
First we need to solve for (all other drive info)
3350/3.73/65=13.817
So now we can replace the rear ratio in our in our above formula
3350 RPMs / 3.08 /13.817= 78 MPH
2200 RPMs / 3.08 /13.817= 52 MPH
2766 RPMs / 3.08 /13.817= 65 MPH

You need to find another shop. This guy is clueless; forget he is poor with math. Who would recommend a cruising RPM below your stall point? Your car is going to feel like a dog with 3.08s in there. While everyone else in the free world is going to taller rears and over drives you are going to be cutting edge by going back to what the factory installed in 67?

 

YAV8 so what would the driver shaft length be with the 700R4? TIA

 

The TH350's case length is 21 5/8 inches. Depending on the tail shaft housing, its overall length can either be 27 5/8 or 30 5/8 inches. The 700R4's case length is 23 3/8 inches and its overall length is 30 3/8 inches.

 

craby I know you put up a lot of numbers. But I dont even know the length of the stock drive shatf on the first gen cameros.

 

All 69's are 49.56" from center of u-joint to center of u-joint.
Small block 67-8's are 49.96".

 

Camaro 69 Thanks for the info. It is greatly appreciated.THANKS