Well, here's the latest fix I'm in. Right now, my truck has the 351/cruise-o-matic with a 2.75 rear gearing. I am going to put a '59 292 V8 in w/the original 3 speed trans.

I have a Ford 9" carrier available to me w/a 3.00 ring/pinion setup. These trucks came stock w/a 3.70 rear.

What's the best range for the 3 speed manual that will allow me to go freeway speed? I mean cruise there, not get there and huff. The 2.75 is too low for the manual, and I feel 3.70 is too high for a daily driver.

 

I don't know why you believe 3.70 is to high for a daily driver?
Fathers '60 F-100 had 223 I-6 w/ a Manual w/ a 3.70 & he achieved an average of 25MPG on the Fwy @ 65MPH.

 

How tall are your tires?

Use this calculator:

http://www.ringpinion.com/content/calculators/RPM.asp

Ron

 

This does not help me fore I run 7.00x15s & that Calc is not set up for my type of tire measurement.

 

They still make tape measures, don't they?

Ron

 

If my M-100 were in the Driveway instead of @ the Installers, then Fine that would work, but that is Not the Case & I Do Not have access to the Olde Girl.

 

A truck axle that I traded for had a 3.25 ratio. If I were you, I'd try out the 3.00 pumpkin and if that's still to tall, look for a F100 differential to locate a 3.25 ratio. If that's still too tall, you'll have to think about a trans swap.

Mark Silva (Madathlon) now has a 3.25 in his 60 F100 with a 223 and a 3 speed. He might be willing to give you his impressions of how well that's working for him. Previously, he had a 4.11.

 

Col Flashman This does not help me fore I run 7.00x15s & that Calc is not set up for my type of tire measurement.


what size tire are you running??? that is a rim size you posted

 

Ron, sounds like it's time for a visit to www.measureityourowndamnself.com.



Sixoh, I think you would be happy with a 3:25 ratio...

Vern

 

assuming Kansas is fairly flat 3.50 with the 292 is a good gear, ran them for years at freeway speed, 3.25 is a little high, just my 2cents, I preffer 3.70 my self.

 

Shane -

My 56 came with a 351C, FMX auto and a 3.0:1 9-inch rear pumpkin. I run 26" tall rear tires (P295/50R15). These were perfect highway gears. I cruised at 70 mph at 2700 rpm. It was pretty zippy around town too.

When I pumped the engine up to 300 hp, I also went to a posi. I changed the gears to 3.50:1 rear ratio. VERY zippy around town, but pushing it a bit for extended highway cruise and the mileage got worse. 70 mph is around 3200 rpm. Highway mileage is around 12 mpg.

Assuming that your 3-speed is a 1:1 final gear, I would go with the 3.0:1 pumpkin. You'll like it. That 292 has got plenty of torque to handle that ratio rear end. The 2.75:1 is a little tall for my taste, but the 70 mph cruise rpm would be around 2200 and mileage would be improved, if that is a concern.

My 2 cents...

 

I had a c-4/289 combo with 3.50 gears. It was making the motor run too high at freeway speeds. I now have 3.00 gears and tyhe travel at freeway sppeds is much better. For most people they would prob do fine with 3.25. Jag

 

It entirely depends on what you want to use the truck for? If you plan on highway 60 mph and over, I'd keep the higher gears. If you do a lot of city stop and go. The lower gears are nice. There is always the in between gears which would work for both Something like Jag with 3.25. Guys who run who the new overdrive transmissions tend to go with really low gears because they get the torque in 1st and high ratio from the tranny with the overdrive. If your not happy with the gears now, I try some lower ones and go from there. Remember, everytime you change the gearing it effects the speedometer reading and that needs to be adjusted. The taller tires also effect the gear ratio. Good luck.

 

3.25s here with my old flathead. I think it's about perfect.

 

Awesome! Thanks guys, I'm happy with the responses and am going to print this thread out and keep it handy! I know it's a matter of trial and error, but I usually don't get too much foolin' around time to experiment. It's "do it once and be happy with it!" most of the time.

Imlowr2 mentioned "adjusting" the speedo for different gear ratios. How is that done? My speedo runs at about 5-7mph faster than I'm really going with my current 351M/Cruise-o-matic /2.75 rear end w/215/75R14s.

I did get her on I-135n for a 76mi round trip to Salina and back the other day at freeway speed! First time on the open freeway. What a good feeling...until my stupid tailgate fell open and was flapping around. Now, I've got 2 round burn marks on my 'gate from the exhaust! *!@#&