What gears for a c-4?

[KiltedBanshees93GT]

I'm planning some rear end work on my '66 once the '93s tranny swap is done and it becomes the daily driver. I was wondering what gears are most popular for the first gen stangs/c-4 cars. The car is quick off the line (can chirp second when in tune), but gets wound out too fast. I currently have 3.25's and would like to go higher, but I know with this tranny , she'll be at like 3k @45mph. How do you guys deal with it? build the motor for more power and then go for lower gears?
Eventually I want to swap in a 5 speed, then its 3.73 city, but is there anything I can do now as a stopgap?

J

[hobgoblin351]

I'd try 3.50's. I'm running 3.89's in mine with an FMX and it screams on the hwy. I'll eventually either get an overdrive tranny or drop the gears down.

[Rev]

I use a 3.25/1 in my '66 coupe with the C-4. I don't want to spin more than 3000 @70 mph when cruising. I do use a TCI Breakaway convertor that's supposed to stall at 2500. Mine actually stalls at 2800 because I have a little extra torque down low .

For a street car, be conservative on the cam. Build the engine for good low end torque with 5500-6000 peak power.

The thing to remember is you can't have it all. With the C-4 and no over drive, I would stick with 3.25's and try to aim for good low end torque and a mild torque convertor.

Rev

[KiltedBanshees93GT]

What stall speed would be best given the combo I'm running? Would going to a higher speed converter and a lower gear (3.0/1?) allow a lower crusing rpm without loosing the kick off the line? The way the car is setup seems to be more toward the top end, so a new converter might not be a bad idea.
Thanks for the responses,

J

[Rev]

Don't go to high on the stall. At RPM's under the stall, the convertor is slipping some to multiply torque. If you have the stall over the RPM that you cruise at, then the convertor is slipping almost all the time. That creates alot of heat due to inefficiency and will make mileage worse as well as wear out the trans quicker due to high heat. I think around 2500 or so is a good stall speed for a moderately modded street driver. Actually, even after the converor has "coupled" at the stall speed, an auto tranny still slips some anyway (5-10% probably.

Rev

[tireburner163]

go with 3.73's or 3.90's and just drive slow

But then again I'm a drag nut


-Josh, aka the tireburner

[KiltedBanshees93GT]

ok, silly question, what is the stock stall speed on a c-4? (I know this is an inexact question due to model's etc (and I dont know where/when mine came from), but a guesstimate would give me a starting point.

Thanks,

J

[Rev]

I think most stock c-4's use a convertor that stalls around 1500-1800 RPM with a stock 289-302. You can do a brke stall test to get an idea. Just hold the brake very hard and stab the the throttle for about 5 seconds and watch the tach to see how high it goes. Don't do it much as it is hard on the trans clutches etc. It will give an idea as to what the stall speed is. Again, I wouldn't do this much.

Rev