rear gear ?
Thread Starter
|
Junior User
Joined: Sep 2015
Posts: 71
Likes: 0
rear gear ?
Hello, my 67 2 wheel drive pickup came out original with a manual transmission but when i bought it the transmission had been changed over to a automatic (C6) but the rearend gear for the manual transmission still in it.Cant find a tag on it. Everything works fine but i now have the truck back together and Im going to have to change the rear gear because running 65 to 70 mph Im turning around 3800 to 4000 rpm. On the manual transmission trucks did they offer more than one gear ratio ? and what gear ratio are most of you guys running with the 390 C6 combonations ? I had my motor completely gone thru with everything new except crank and block.I would like for it to turn around no more than 27 to 3000 rpm at 65 mph. Any sujestions on what gear to use without killing the take off ? And what was the more common gear that ford used with the automatis trucks in 67 ? Thanks
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
Hello, my 67 2 wheel drive pickup came out original with a manual transmission but when i bought it the transmission had been changed over to a automatic (C6) but the rearend gear for the manual transmission still in it.Cant find a tag on it. Everything works fine but i now have the truck back together and Im going to have to change the rear gear because running 65 to 70 mph Im turning around 3800 to 4000 rpm. On the manual transmission trucks did they offer more than one gear ratio ? and what gear ratio are most of you guys running with the 390 C6 combonations ? I had my motor completely gone thru with everything new except crank and block.I would like for it to turn around no more than 27 to 3000 rpm at 65 mph. Any sujestions on what gear to use without killing the take off ? And what was the more common gear that ford used with the automatis trucks in 67 ? Thanks
Remember, these rigs were built when 60 MPH was the norm... and these were built to work. Crappy aerodynamics because again, these are workhorses.
Do you have a tachometer? A 4.11 rear gear is what I was guessing but if you're really turning 4000 RPM then like 5.38.
No tach? Then you're providing bad information....
Senior User
Joined: Feb 2015
Posts: 294
Likes: 1
My 3.70 gears with 30" tires is about 3000 at 70 mph by GPS ( about 75 on the speedo). You must have really low gears, or really short tires! I ran 4.11's in a car with 26" tires for a short time. About 3700 at 70. It was a pain on the highway, but man it would scoot from a redlight!!
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Hello, my 67 2 wheel drive pickup came out original with a manual transmission but when i bought it the transmission had been changed over to a automatic (C6) but the rearend gear for the manual transmission still in it.Cant find a tag on it. Everything works fine but i now have the truck back together and Im going to have to change the rear gear because running 65 to 70 mph Im turning around 3800 to 4000 rpm. On the manual transmission trucks did they offer more than one gear ratio ? and what gear ratio are most of you guys running with the 390 C6 combonations ? I had my motor completely gone thru with everything new except crank and block.I would like for it to turn around no more than 27 to 3000 rpm at 65 mph. Any sujestions on what gear to use without killing the take off ? And what was the more common gear that ford used with the automatis trucks in 67 ? Thanks
3.25-1 will keep you in that 2500 to 2300 rpm range at 60 MPH ( 26 to 28" tire size)
3.50-1 will keep you in that 2700 to 2500 rpm range at 60 MPH ( 26 to 28" tire size)
Should give you a base to start from. 3.00-1 Gear sets are pretty common in the wreckers in cars from the 70's
Lead Driver
Joined: Jul 2011
Posts: 8,678
Likes: 191
From: On the Edge of the Desert
Originally Posted by matthewq4b
3:00-1 will keep you in that 2300 to 2100 rpm range at 60 MPH ( 26 to 28" tire size)
3.25-1 will keep you in that 2500 to 2300 rpm range at 60 MPH ( 26 to 28" tire size)
3.50-1 will keep you in that 2700 to 2500 rpm range at 60 MPH ( 26 to 28" tire size)
Should give you a base to start from. 3.00-1 Gear sets are pretty common in the wreckers in cars from the 70's
3.25-1 will keep you in that 2500 to 2300 rpm range at 60 MPH ( 26 to 28" tire size)
3.50-1 will keep you in that 2700 to 2500 rpm range at 60 MPH ( 26 to 28" tire size)
Should give you a base to start from. 3.00-1 Gear sets are pretty common in the wreckers in cars from the 70's
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
If you have 10% converter slip in a stock TC time to replace it, it should be 4% to 7% for a stock TC, 10% is getting on the lose end of things even for high stall drag converters.
And that is why it was range and not exact numbers.
Trending Topics
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
Truck tires are more in the range of 28 to 30 inches in height. Adjust the calcs above accordingly.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
ru67, Sounds like the truck may have come with the small 240 6 in it. Couple suggestions, get a app for your phone that will give you correct mph. I think I have both digiHUD and car performance. Both can use gps for actual miles per hour. The other is to get a bud and on your garage floor or very level ground hand roll the rear wheel 1 complete revolution while counting the revs of the driveshaft. The bud is just for safety and help with the counting. I like using a Sharpie to make makes on both. Since this is reverse action it gives you the actual count for your correct ratio your truck is set at.
John
John
Lead Driver
Joined: Jul 2011
Posts: 8,678
Likes: 191
From: On the Edge of the Desert
Originally Posted by matthewq4b
If you have 10% converter slip in a stock TC time to replace it, it should be 4% to 7% for a stock TC, 10% is getting on the lose end of things even for high stall drag converters.
And that is why it was range and not exact numbers.
And that is why it was range and not exact numbers.
As another baseline, with 2.75s and 31" tires, with a locking TC. I run right at 2000 @ 65.
Lead Driver
Joined: Jul 2011
Posts: 8,678
Likes: 191
From: On the Edge of the Desert
Originally Posted by jowilker
ru67, Sounds like the truck may have come with the small 240 6 in it. Couple suggestions, get a app for your phone that will give you correct mph. I think I have both digiHUD and car performance. Both can use gps for actual miles per hour. The other is to get a bud and on your garage floor or very level ground hand roll the rear wheel 1 complete revolution while counting the revs of the driveshaft. The bud is just for safety and help with the counting. I like using a Sharpie to make makes on both. Since this is reverse action it gives you the actual count for your correct ratio your truck is set at.
John
John
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
In dealing with a vehicle that's nearly 50 years old, anything could have been done/changed on it. 3rd members are one of those things that isn't terribly difficult to change out for some other 3rd member with a different ratio.
Unfortunately, when something like this is messed with, many people are too lazy to put that little gear ratio tag (that specifically goes with the particular 3rd member) back on the stud before installing the nut.
Doors can be changed too, which would make the info on the warranty tag bogus.
If either of these things are not known to be original to the truck, there's only one sure way to verify what the rear end ratio is with 100% accuracy --and that's to pull the 3rd member out of the housing, count the number of teeth on the ring gear and the number of teeth on the driving pinion, divide the number of teeth on the ring gear by the number of teeth on the pinion and you'll have your exact ratio.
Unfortunately, when something like this is messed with, many people are too lazy to put that little gear ratio tag (that specifically goes with the particular 3rd member) back on the stud before installing the nut.
Doors can be changed too, which would make the info on the warranty tag bogus.
If either of these things are not known to be original to the truck, there's only one sure way to verify what the rear end ratio is with 100% accuracy --and that's to pull the 3rd member out of the housing, count the number of teeth on the ring gear and the number of teeth on the driving pinion, divide the number of teeth on the ring gear by the number of teeth on the pinion and you'll have your exact ratio.
Senior User
Joined: Apr 2006
Posts: 323
Likes: 1
The final drive gear on the manual and the c6 is the same so the engine will turn the same rpm with either tranny. I'm doubting your turning that many rpm's. I'm guessing your speedo may be off. That's a lot of rpm for 65-70mph. You would need a 4.56 or so to turn that.