I have a 1977 Ford F250 2WD and I have 4:11 rear end gears, I was thinking on going with 3:55, what are your thoughts on this folks? Is 3:55 a good choice, I want gears that are better for the highway.

thanks

BigRed

 

Auto or stick ?

 

My truck is an automatic.

 

I have a 1978 F100 with 400 motor and FMX tranny. Tyres are 235/75/15 and run a 3.55 rear diff. Seems to run on the highway agreeably, but still has good bottom end torque.
Craig

 

If you have an FMX, it was swapped in from a passenger car.

The ONLY F Series trucks to have an FMX were 1973/77 F350's with 300 I-6's.

The original and only A/T for your truck is the C6.

FMX = 14 trans pan bolt holes / C6 = 17 trans pan bolt holes.

 

3.55 will run good on the highway.

 

I have 3.55s in mine (with a 460) and I LOVE it!
Good luck getting the speedometer right.

 

Thanks for the information about the FMX Bill. I had read that FMX's were used in F350's but did not know the engine used. Yes, I can confirm that my tranny is an FMX since I obtained it from a passenger car. I obtained a big block bell housing for an FMX from the USA. Put a shift kit in and works like a dream.
Craig.

 

Hi everyone, where is a good place to buy rear end gears in the Calgary, Alberta area?

 

I've got 3.50s in my F150 with a 460 and I think they are perfect. I don't feel the need for OD at all with 33 inch tires, but I do have the granny low and low Range if they are too high for something.
Also my dad has a 1979 full time auto F250 with a 429. It has 3.55s and are great with the automatic trans as well. I would go for it. The speedo shouldn't be that big of a problem. I know on 80s/90s Mustangs there is a chart to get the correct speedo gear so I would assume you could find something similar to obtain the correct speedo gear.
Ive never heard of an FMX in a truck, and I had no idea they were offered from the factory, interesting. Speaking of things along those lines. A C4 auto trans has a removable bellhousing. I have a bell housing to put a C4 behind a 460! Not something you see every day. I had a project that never got finished where I was stripping a 1981 Mustang to be as light as possible and I was gonna use a junkyard 460 with a C4 (lighter and uses less power than a C6) and see how fast I could go for extremely cheap. I still have every thing just never materialized, got too much else going on. My bell housing came from a car that would have had a 351m or 400. I don't think a C4 actually ever came behind a 460.

 

The plastic speedometer DRIVEN gears (at the end of the cable) are the same from 1960 thru today for cars & trucks, so are available from Ford.

The prices range from $2.00 to $3.76...each.

16-17-18-19-20 & 21 tooth gears are offered.
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No C4's were used with 400, 429/460 or FE engines.

Some 1975/79 passenger cars with 351M's used the C4.

Other Passenger Car / F100/350 / Bronco / Econoline engines with C4's: 2.3L I-4 // 200/240/250/300 I-6's // 3.8L V6 // 255/260/289/302/351C 2V/351W.