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Gear Change

I have a 1952 F1 with the 215ci six. Three speed on the column. Need to have a lower rpm high mph. Is it better to change the gearing in the rear end or change the transmission. Would like to cruse at 55-60 instead of 40-45. I believe Randy's Ring and Pinion has the rear end gearing. Is the a 4 or 5 speed transmission that would bolt in. Thanks


Flatheads Forever
Welcome to FTF!

There are a couple ways around your situation. If you want to keep it stock, Randy's gear set would probably get that done.

I went a different route by swapping the stock rear for a 57-72 9" Ford differential with 3.50:1 gears. This is almost a bolt-in exchange with your stock axle. I can go into more detail if you decide to go this route.

The trans swap is a bit more involved - you'll have to change the crossmember and the only 4 spd that would help is an OD. The mid-80's Ford has been adapted by some guys. The more common swap is the T5. There are adapters available... but I'll let somebody who is more familiar with the 215 talk about that.
Very interested in the differential swap. What is the almost part of the bolt in exchange. Have not done any of this type of work but am very mechanically inclined. What where the before and after driving results in your case. Thanks


Flatheads Forever
My original axle was the 4.27 ratio...anything would have been better.
With this one I can cruise easily at 62 +/- all day long. Have driven it across country.

The almost: You need to do something with the shock mounts and mounting at the spring perches as the stock tubes are 2 1/2" and the 9" is 3. I used plates from any later truck and bought new U bolts at NAPA to fasten it together. The shock mounts I ground off and re-welded to the tube in line with the upper mounts on the truck.
The only other issue is the driveshaft. The 9" pinion is approx 1 1/4" shorter than the Dana/Spicer 41. Mine was easy cause it has a slip joint in the shaft so I was able to purchase a longer front yoke. If you have a light duty 3 spd you will need to have the driveshaft lengthened.


Tin bender
The 9" rear end swap is a popular way to go, but not the only one. I swapped in a 9" with 3.00 gears, because I had it laying around. It improved highway speeds but the wide 3 speed trans ratios made it harder to drive with the taller gears. In other words, with only 100 hp, it was a dog.
Since then, I have installed a 5 speed OD trans which makes the truck more drivable and fun. See my thread here...

Bottom line, your 215 isn't gonna pull super tall gears, but a compromise ratio would be around 3.50 to 3.75 as Tim said.

What ratio does the truck have now? If it has 3.92's, then 3.50's aren't gonna change much.
How tall are the tires? sometimes going up a size or 2 can bring the rpms down some.....
Have the stock 3.92 gears now. Randy's ring and pinion suggested a 3.08 All the parts total up to about $450 to use the existing Dana 44 rear end. Is the truck still going to be drivable with this set up or am I wasting my money. For now I wouldn't mind a lack of power as long as I'm not burning up the clutch or damaging something else by doing it. My main goal is to be able to go down the road at 55-60mph to get from point A to point B


Tin bender
Your truck should easily go 55-60 mph with the 3.92 gears, unless your tires are really short. Just push down on the gas pedal, LOL.
Seriously, it may sound like it is over-revving, but it really shouldn't hurt it.

with a 29" tire at 60 mph your rpm would be 2725
with a 27" tire.........................................2927

I don't think you would be happy with 3.08's. The 215 will not be happy either.
Just my 2 cents though....
I think your right after doing lots of research and getting information from yourself and others. I should probably live with it the way it is or sell it and buy one the work has already been done to. I'm not experienced enough or have the time to do what it would take.


Ford Truckaholic
I have the same issue in my 52. However, I get a shimmy at above 45mph. This is likely due to the old bias ply tires on it now.

I'd like to get better gearing as well. I've looking into Randy's instead of replacing with a 9" rear. What about getting taller gears like a 3.50 instead of the 3.08? Will that help much? I'm running original 6.50x16 size wheels/tires.

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