My 48 ford f1 has some stump pulling gears in the rear end. Stock as far as I know. Truck has a 3 speed manual and at 35 mph it is spinning about 3000rpm. I was hoping to get the truck up and running so I could take to work a couple days a week but I don't see how I could ever think of going even 55 mph in it without sending a rod thru the hood! And thoughts on how to find out what gear I have in it? Tag somewhere?
Rear End Gear?
- Thread starter mustang8
- Start date
JSeery
Member Emeritus
You can count the teeth on the ring gear through the fill plug. Mark one of the teeth and count the teeth through one full revolution of the gear. IF the gears have never been changed, the ratio numbers should be stamped on the housing, tooth count is stamped on the lower front part of center section .
I have never used this method, so no idea how well it works! But might give it a try:
(from Ford Flathead V8 http://www.btc-bci.com/~billben/reargear.htm)
JimC: 5/31/2000 - 8:16:04 AM
RE: ratio
Jacking one wheel up and turning the engine over by hand will let you determine the ratio. Make a chalk mark on the bottom of the tire and crank the engine over exactly 2 revolutions. Also, make sure all the slack is out of the system when turning the engine over. Then measure the rotation on the tire. It will be plus or minus one turn, but accuracy with these measurements is critical. Take this tire rotation value, divide it into 1 (in other words, find its reciprocal), then multiply it by 4. This will give you a pretty good ball park of the ratio, which can be compared with known ratios (4.11, 3.78, 3.54) to see which one comes closest. For example, I recently went through this with my car and found the tire rotated slightly less than one turn for 2 engine turns, so I used a tire rotation value of 0.95. Dividing this value into 1.0 gives you 1.05, and multiplying 1.05 by 4 gives you 4.20. So I figured the rear end ratio was 4.11. I then used this method on a friend's car before he pulled the rear end out. I got about 1.05 tire rotations for 2 engine rotations, which figures out to a rear end ratio of 3.8. When the gears came out, sure enough, they were 3.78.
1) Jack up one rear wheel and chalk-mark the 12 o'clock position on the tire. (Make sure the slack is out of the drive train)
2) Hand crank engine 2 complete turns.
3) See where chalk mark on tire ends up.
A) Between 11 and 12 o'clock, ratio is 4.11
B) Between 12 and 1 o'clock, ratio is 3.78
C) Between 1 and 2 o'clock, ratio is 3.54
Edit: corrected typo in original document, 4.54 to 3.54 per Marts catch.
I have never used this method, so no idea how well it works! But might give it a try:
(from Ford Flathead V8 http://www.btc-bci.com/~billben/reargear.htm)
JimC: 5/31/2000 - 8:16:04 AM
RE: ratio
Jacking one wheel up and turning the engine over by hand will let you determine the ratio. Make a chalk mark on the bottom of the tire and crank the engine over exactly 2 revolutions. Also, make sure all the slack is out of the system when turning the engine over. Then measure the rotation on the tire. It will be plus or minus one turn, but accuracy with these measurements is critical. Take this tire rotation value, divide it into 1 (in other words, find its reciprocal), then multiply it by 4. This will give you a pretty good ball park of the ratio, which can be compared with known ratios (4.11, 3.78, 3.54) to see which one comes closest. For example, I recently went through this with my car and found the tire rotated slightly less than one turn for 2 engine turns, so I used a tire rotation value of 0.95. Dividing this value into 1.0 gives you 1.05, and multiplying 1.05 by 4 gives you 4.20. So I figured the rear end ratio was 4.11. I then used this method on a friend's car before he pulled the rear end out. I got about 1.05 tire rotations for 2 engine rotations, which figures out to a rear end ratio of 3.8. When the gears came out, sure enough, they were 3.78.
1) Jack up one rear wheel and chalk-mark the 12 o'clock position on the tire. (Make sure the slack is out of the drive train)
2) Hand crank engine 2 complete turns.
3) See where chalk mark on tire ends up.
A) Between 11 and 12 o'clock, ratio is 4.11
B) Between 12 and 1 o'clock, ratio is 3.78
C) Between 1 and 2 o'clock, ratio is 3.54
Edit: corrected typo in original document, 4.54 to 3.54 per Marts catch.
Last edited:
Mart
Well-known member
Easier is to jack up and mark one rear tyre.
Jack up one rear tyre. In Neutral, turn the tyre two complete revolutions while counting how many times the driveshaft turns. If a closed driveline (early ford), in top gear turn the engine counting the revolutions until the tyre has done two full revolutions.
The number of times the engine or driveshaft turns equals the axle ratio.
Mart.
PS I like the method at the end of J Seery's post, it saves effort and you don't have to watch two things at once. Please note a typo, though, the last line should read 3.54 not 4.54. I might try that method next time. It also assumes Early ford ratio's too, not necessarily the case with an F1.
Jack up one rear tyre. In Neutral, turn the tyre two complete revolutions while counting how many times the driveshaft turns. If a closed driveline (early ford), in top gear turn the engine counting the revolutions until the tyre has done two full revolutions.
The number of times the engine or driveshaft turns equals the axle ratio.
Mart.
PS I like the method at the end of J Seery's post, it saves effort and you don't have to watch two things at once. Please note a typo, though, the last line should read 3.54 not 4.54. I might try that method next time. It also assumes Early ford ratio's too, not necessarily the case with an F1.
rotorwrench
Well-known member
The rear cover comes off easily on a Dana 41 so it would only cost a gasket to count the teeth. It could probably use a cleaning in there anyway. The 1949 Mercury used the Dana 41 and normally had 3.91:1 gears most of the time. If you could find one of those coming out of some Merc update project, you could swap them pretty easy. The spring mounts are the only part that is different between the two so you could swap the whole thing if you swapped the spring mounts. Another option would be a later Dana 44. They are easier to get parts for.
38 coupe
Well-known member
You may have the 4.27 ratio that was optional in the F-1s. The 48-56 Ford truck forum has a lot of information about regearing your truck (one member even figured out how to put new Dana 44 gears in the original Dana 41). Forum here: http://www.ford-trucks.com/forums/forum41/
Also, have you put a tachometer on the engine while you are driving, or does it just sound all wound out at 35 mph? The stock truck fans and mufflers can make the engine sound like it is turning a lot tighter than it really is.
Also, have you put a tachometer on the engine while you are driving, or does it just sound all wound out at 35 mph? The stock truck fans and mufflers can make the engine sound like it is turning a lot tighter than it really is.
Ross F-1
Well-known member
I agree, 2500 in these old trucks sounds like they are really spinning.
Cheapest, quickest, easiest thing to do is get a 48-50 3.73 Dana 41 from someone who is putting a 9" in their truck. Totally a bolt-in and a very good overall ratio unless you are running short tires.
JSeery
Member Emeritus
I get numbers similar to Martin for that combination.
Edit: Well, we may have both been using the same calculator! I think you may be getting the correct reading. I will do some more checking, but this chart seems to have the numbers you are seeing (hard to read, but has 28" tires with 3.73 comes out 2909 rpm).
I am going to calculate it by hand and not use the online calculators! and see what I get.
Edit: Well, we may have both been using the same calculator! I think you may be getting the correct reading. I will do some more checking, but this chart seems to have the numbers you are seeing (hard to read, but has 28" tires with 3.73 comes out 2909 rpm).
I am going to calculate it by hand and not use the online calculators! and see what I get.
Attachments
Last edited:
JSeery
Member Emeritus
[SIZE=+2]Formulas for Calculating Gear Ratios, RPM's, MPH and Tire Diameter[/SIZE]
[SIZE=+2]If you wish to do the math on your computer's calculator, [/SIZE]
[SIZE=+2]To multiply, use symbol [/SIZE][SIZE=+3]*[/SIZE][SIZE=+2], to divide, use symbol [/SIZE][SIZE=+3]/[/SIZE]
[SIZE=+2]GEAR RATIO =[/SIZE][SIZE=+2] RPM *[/SIZE][SIZE=+1] [/SIZE][SIZE=+2]Tire Diameter / MPH *[/SIZE][SIZE=+1] [/SIZE][SIZE=+2]336[/SIZE]
[SIZE=+2]RPM =[/SIZE][SIZE=+2] MPH * Gear Ratio * 336 / Tire Diameter[/SIZE]
[SIZE=+2]MPH = [/SIZE][SIZE=+2]RPM * Tire Diameter / Gear Ratio * 336[/SIZE]
[SIZE=+2]TIRE DIAMETER =[/SIZE][SIZE=+2] MPH * Gear Ratio * 336 / RPM[/SIZE]
[SIZE=+2][/SIZE]
[SIZE=+1]From, Carl/Roseville[/SIZE]
[SIZE=+2]If you wish to do the math on your computer's calculator, [/SIZE]
[SIZE=+2]To multiply, use symbol [/SIZE][SIZE=+3]*[/SIZE][SIZE=+2], to divide, use symbol [/SIZE][SIZE=+3]/[/SIZE]
[SIZE=+2]GEAR RATIO =[/SIZE][SIZE=+2] RPM *[/SIZE][SIZE=+1] [/SIZE][SIZE=+2]Tire Diameter / MPH *[/SIZE][SIZE=+1] [/SIZE][SIZE=+2]336[/SIZE]
[SIZE=+2]RPM =[/SIZE][SIZE=+2] MPH * Gear Ratio * 336 / Tire Diameter[/SIZE]
[SIZE=+2]MPH = [/SIZE][SIZE=+2]RPM * Tire Diameter / Gear Ratio * 336[/SIZE]
[SIZE=+2]TIRE DIAMETER =[/SIZE][SIZE=+2] MPH * Gear Ratio * 336 / RPM[/SIZE]
[SIZE=+2][/SIZE]
[SIZE=+1]From, Carl/Roseville[/SIZE]
Jseery, that chart makes no sence. There appears to be no speed given for the calculation.
I use the same calculator I always use, I've checked the math and it's correct. Our first calculations that suggest a circa 8.3:1 ratio to get 3500 rpm at 30 are right.
Something funky going on with the F1.
Clutch slipping? Tach telling lies? Is the tach an 8cyl tach?
The maths don't lie.
Martin.
I use the same calculator I always use, I've checked the math and it's correct. Our first calculations that suggest a circa 8.3:1 ratio to get 3500 rpm at 30 are right.
Something funky going on with the F1.
Clutch slipping? Tach telling lies? Is the tach an 8cyl tach?
The maths don't lie.
Martin.