Another rear axle ratio question
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Elder User
Joined: Sep 2003
Posts: 587
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From: Augusta, ME
Another rear axle ratio question
I picked up a 9 inch rear this weekend from a 68 half ton truck, and will be putting it into my 51 F1 whenever the project gets to that point. I've searched and read some of the posts throughout the ford-trucks website, and got a lot of ideas, but I want some final suggestions before I sink more money into the new gears.
What I have: 51 F1, engine will be the flathead slightly bored and pretty well stock innards, holley 390 4 bbl to breath, Mallory dual point distributor and offy finned heads, compression about stock or slightly increased. Trans will be stock 3 speed. Tires will be the 235/75/15.
What I want: To be able to drive on the highway at 65 without getting run over or screaming the motor, but able to take off on a hill without burning the clutch out. This will NOT be a work truck, but I do plan on driving it a lot, long trips included.
The axle I got has 3.7 gears, and look pretty worn. I am thinking 3.25 gears will be my best bet for all around driving. Have any of you got something close to this set up and what are your suggestions? Also, if I go to 3.25, should I consider the 11" clutch as well?
What I have: 51 F1, engine will be the flathead slightly bored and pretty well stock innards, holley 390 4 bbl to breath, Mallory dual point distributor and offy finned heads, compression about stock or slightly increased. Trans will be stock 3 speed. Tires will be the 235/75/15.
What I want: To be able to drive on the highway at 65 without getting run over or screaming the motor, but able to take off on a hill without burning the clutch out. This will NOT be a work truck, but I do plan on driving it a lot, long trips included.
The axle I got has 3.7 gears, and look pretty worn. I am thinking 3.25 gears will be my best bet for all around driving. Have any of you got something close to this set up and what are your suggestions? Also, if I go to 3.25, should I consider the 11" clutch as well?
Elder User
Joined: Jul 2003
Posts: 785
Likes: 6
From: Columbus, Ohio
Hey man -
When you're ready to get rid of the 3.70 ring and pinion, let me know. I'm going back to a stick shift in my truck, and need to get some 3.70s again.
What's the back lash on them? If it's still around .010" I could prob use them. If you find the gears you're after, I'll take the old ones.
Let me know....
When you're ready to get rid of the 3.70 ring and pinion, let me know. I'm going back to a stick shift in my truck, and need to get some 3.70s again.
What's the back lash on them? If it's still around .010" I could prob use them. If you find the gears you're after, I'll take the old ones.
Let me know....
Lead Driver
Joined: Oct 1999
Posts: 6,776
Likes: 553
From: Kalispell, MT
Scott, do you have the HD 3 spd floor shift or the regular 3 spd on the column?
The HD unit has a first gear ratio of 3.71:1
Standard unit first gear ratio is 2.78:1
I have a 9" with 3.50 rear gears and I run the flathead at about 62-65 mph without strain. That works out to about 2400 rpms. With my HD tranny ratios I could even go with 3.25's. If you've got a standard tranny, 3.25's might be pushing it a bit.
The HD unit has a first gear ratio of 3.71:1
Standard unit first gear ratio is 2.78:1
I have a 9" with 3.50 rear gears and I run the flathead at about 62-65 mph without strain. That works out to about 2400 rpms. With my HD tranny ratios I could even go with 3.25's. If you've got a standard tranny, 3.25's might be pushing it a bit.
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Elder User
Joined: Sep 2003
Posts: 587
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From: Augusta, ME
Tim, thanks for the info, that's a good bit of difference between the HD and my light duty column shift first gears.
Sixoh, sorry, but I think these 3.70s have lived their life. I haven't measured backlash but can see a lip worn onto each tooth, pretty well used up I think. The junkyard I got the axle at had the truck up on a forklift, torched off the u bolts to get the axle off, then took the truck over and dumped it over on its side on a hill. Pretty well summed up the gear condition!
Sixoh, sorry, but I think these 3.70s have lived their life. I haven't measured backlash but can see a lip worn onto each tooth, pretty well used up I think. The junkyard I got the axle at had the truck up on a forklift, torched off the u bolts to get the axle off, then took the truck over and dumped it over on its side on a hill. Pretty well summed up the gear condition!
Logistics Pro
Joined: Oct 2002
Posts: 4,489
Likes: 5
From: Valley Center, CA
Daryl sold me a very good set of 3.00s out of his 59. I now have the 3.50s that came out of the 78 Lincoln Versaile 9" in pretty good condition setting on the shelf. They are not as low as 3.70s, but close. If anybody's intersted I would let them go real cheap.
John in Sacramento 
John in Sacramento
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