gear ratios

F

Fred Hanks

Member
I just got my '49 F-1 on the road & after going to 15'' wheels my speedo is off a lot thus in order to keep up with traffic I have to run high RPM's .....
My rear end ratio is 3.92, has anyone changed ratios in order to CRUSE @ a lower RPM thus not beating my 239 to death???
 
15's as such shouldn't be a problem obviously some are taller than others. What size are you using?

L78-15's or 8.20-15's are about the tallest you can get, or 235-75-15's if you want radials.

Mart.
 
The Dana Spicer 41 rear axle is harder to find lower ratios. The 50 & later Dana 44 was used for so many years that there is still a lot of stuff available for it. An example is the Merc-O-Matic rear ratio adopted in late 1950 with 3.31 & 3.54 to 1 ratios. The Merc guts will go right in an F1 Dana 44 rear axle.

Another option would be an overdrive trans but it may have to be converted to remote control shift (three on the tree).
 
Look for an F150 3 spd with OD, Weld up a 49/51 passenger car bell housing aAND YOUR GOOD TO GO.
 
I just thought of something. Dodge trucks have a 5 on 51/2 bolt circle with a 16" wheel, I have a set that will drop a 3.3 gear t0 a 3.0. Kinda tall, I'd loan them to you for a try out, drop the gear to a 3.6
 
With a Dana 44, what would he need to change to a ratio the other side of the case break (3.92?)? Does he have to find a Mercomatic rear? Is not possible to use a newer (easily available) carrier? I understand that the F1 and F100 and Merc rearends had 19 spline axles and later axles had more splines. Can you fit the 19 spline side gears in a later carrier?
Martin.
 
It is all about the carrier diameter. The Dana 41 could only fit the smaller 5 5/8" carrier but the Dana 44 had the 6 5/8" bolt circle carrier. The parts book lists two different carrier part numbers for each different housing but I don't know what the difference is since they each use the same bolt circle diameter characteristic of the Dana 41 or Dana 44. There might be different ring to pinion dimensions between the lower ratio sets and the higher ration sets since that is how they are listed in the parts book. This could be compensated for by an aftermarket ring & pinion manufacturer but you would definitely have to know what carrier dimension the aftermarket parts were designed to work with.

The F1s used the higher ratio gears so I'd look into something closer to those units like the 53 F100 pickup to start out with. A call to a supplier for pickup & trucks might be a good start to find information for those questions. The late 50 & 51 Mercs with Merc-O-Matic would be a bolt in for an F1 since the only difference in the axle housing is the spring locators. Other than that, they are interchangeable according to the old Hollander Interchange Manual.
 
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The difference in the carriers either side of the case breaks is the placing of the machined area that the crown wheel bolts to, this is in a different location relative to the pinion. I'm trying to find out if you could use a latter carrier to get the desired ratio, rather than having to find a Mercomatic carrier.
I know this relates to a Dana 44, not a 41 but I've seen 53 F100's with a 41, 50 Merc with a 44, 51 F1 with a 44 And so on. It appears that the rule "this year has this axle" wasn't adhered to by Ford, no surprise their. Also the chance that a previous owner has fitted a 44 in place of a 41 is quite high.
If the original poster could put a pic of the diff cover here, we could see what rear it's actually got.
Don't want to tell him you can't get better ratios 'cus it's a 41 when it's actually a 44 and much easyer to get stuff.
Martin.
 
The larger the diameter the less rotations per mile. A 75 series in the 15 inch is probably as large a diamater as it practicable. A 16 inch could use a lower profile to get the same affect. The larger diameter 16 inch tires would have more affect.
 
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