Thread: rear ratio

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What would be a good gear ratio behind a 350 crate engine with a 700 R ( for a daily driver ) 1949 ford F-1 ? My motor has 202 heads with a mild cam and headers ...

why are you putting chevy powerplant in ford truck?

3.50-3.70

depends on what you want. i run a 4:10 with my 700r4 and that gives me a little more bottom end, the 3:50-3:70 would give you a little more road gear.

With the price of fuel fluxuating so much these days and not knowing where it's going to end up, the 410 gears are a little to much if you want fuel economy. Mid 300's as Techinspector suggests is a good highway combination for a TH350 Turbo..
Take into account that you're going to be running an overdrive tranny which, if you go with too low a gear ratio, ( below 370 ) the end result could be that the engine rpm's will be too low for the torque converter to function properly and vibration in the drivetrain may occur.

with a 373 gear and 28in tall tires, pretty much the same set up as yours, my truck did not like 55-65 mph.loves 100mph+.but the darn truck floats at that speed.

I have a 700r4 in a T bucket and a 3.73 gear, with 26 inch tires.
In OD 1700 rpm is 60mph. I wish I had a 4.10 rear.

I had a 350 Chevy with cam, headers, and 4 bbl. in a 27 T roadster, only I was running a Turbo 350 automatic transmission and an 8" Ford rearend with 3.55:1 gears. The combination worked great, but I always thought I would have liked a bit more bottom end torque to the tires. If you are going to run an overdrive transmission, you can afford to go a little heavier on the rearend ratio, maybe 3:70 as techinspector 1 has indicated. I think that your top end and gas mileage would suffer too much if you ran 4.11:1 gears.

With the overdrive, you can run lower gears than on a 3spd and maintain lower rpm's at highway speeds but your also defeting the purpose of the overdrive gear if you go too low, and being that, depending on your tiresize but I'm shure your not gonna go extremely tall with the tires, a 3.73 would work well, 4.11 would get you out of the hole a little quicker but your going to reduce the effectiveness of the overdrive gear.

As I said earlier and confirmed by others, using a 3:73 gear with an overdrive tranny, the rpm's will drop below 2000 rpm at 60 mph thus causing torque converter overload trying to maintain engine speed and a noticeable shudder in the drivetrain. I'd recommend a 350 Turbo for the 3:73 ratio and a higher 4:10 with the O.D. to keep your rpm's up at 60 mph, unless of course you want to drive at 100 mph whenever you go.

i get over 20 mpg with my lt1- 700R4 and 4:10 gear. not bad i dont think.

I just came in from driving the T. at 50mph with the converter locked it is cruising at 1250 rpm. With the converter unlocked about 1700. I have a 2500 stall with a lock up. The lock up will only work in OD and has its own switch on the dash. Mine could really use a 4.10 gear.

Originally posted by RPM
I just came in from driving the T. at 50mph with the converter locked it is cruising at 1250 rpm. With the converter unlocked about 1700. I have a 2500 stall with a lock up. The lock up will only work in OD and has its own switch on the dash. Mine could really use a 4.10 gear.

sounds like you are lugging the motor, may take more gas.

Yes you are right it does lug the motor. I don't lock the converter till at least 55-60 mph.

Thanks for the ratio reply !! I'm sure I'll have more tech questions later !! Is anybody going to Old Town Spring Tx rod run this weekend ? What a run !!!!