What Tranny to use
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Senior User
Joined: Feb 2002
Posts: 433
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From: Breckenridge, Minn.
What Tranny to use
My son has a 68 F-250 that was him. It has a 390 and manual tranny with granny low four speed. He wishes to put a tranny that will get him better mileage during the next few years while off to school. What types of transmissions can be considered? We aren't going to get rid of the old equiptment but wish to get something that will serve well until he can get out of school and proceed with restoring the truck when he can better afford to do so. Any help would be appreciated.
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Lead Driver
Joined: Apr 2001
Posts: 6,175
Likes: 21
From: Texas
There aren't many optios for the 390 (FE motors).
I think even the few 5 speeds you can get a bell-housing for are still 1:1 in top gear. Not helping with mileage any.
You can get adapters to run other transmissions that never came behind FE motors, like the A0D automoatic with OD or even ones like the NV 4500 truck 5 speed or even the T56 6 speed. But these are pricey.
You can also get an aftermarket OD unit to attach after your tranny, gving you twice as many gears. Again, not cheap.
The cheapest option is a gear change for the rear axle. With a 68 F250, you probably have a Dana 60. 4.10:1 gears were popular. You could go down to 3.55 or even 3.30s. You'll give up some hauling power. You should see what gears you have now.
hope this helps...
I think even the few 5 speeds you can get a bell-housing for are still 1:1 in top gear. Not helping with mileage any.
You can get adapters to run other transmissions that never came behind FE motors, like the A0D automoatic with OD or even ones like the NV 4500 truck 5 speed or even the T56 6 speed. But these are pricey.
You can also get an aftermarket OD unit to attach after your tranny, gving you twice as many gears. Again, not cheap.
The cheapest option is a gear change for the rear axle. With a 68 F250, you probably have a Dana 60. 4.10:1 gears were popular. You could go down to 3.55 or even 3.30s. You'll give up some hauling power. You should see what gears you have now.
hope this helps...
Posting Guru
Joined: Dec 2001
Posts: 1,668
Likes: 3
From: Lincoln USA
If he wants an automatic the cheapest would be to find a C-6 with an FE bellhousing. He may have to move the rear cossmember and use the mount for the C-6, along with shortening the driveshaft. Then if, as your post implies, he wants to switch back to the T-18 (which is probably what he has now) he is going to have to swap it all back again, spending more money.
You can buy a lot of gas for the money he'll be spending.
You can buy a lot of gas for the money he'll be spending.
Post Fiend
Joined: Jun 2002
Posts: 13,873
Likes: 3
From: Atlanta GA
All my C-6s had a 1:1 ratio in top (third) gear, same ratio as any granny transmission that will fit in without an adapter. About the only option worth doing is changing the rear ratio as someone mentioned. Other then that, you get to the point of diminished returns, how many miles do you have to drive to make a change worth it? You have to drive MANY miles to make even a small $1000 rear end change worth it. At the most, I think you are lucky to hit 15 mpg highway and I would consider 12 mpg doing well.
Posting Guru
Joined: Oct 1999
Posts: 1,188
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From: yes
it may be almost as cheap to try to find a 9" from a wrecking yard in the gear ratio you want and put it in the truck then you could also swap center sections for different gear ratio's if you wanted to. My 68 with a 360 and 5 speed gets 13 right now. it's final ratio is something around ~2.80 and it needs a tune up
Junior User
Joined: Jun 2002
Posts: 62
Likes: 0
From: Mid-Eastern US
Keep the 4 speed and get a 3.30 or 3.25 chunk for the rear end depending on type(DANA or 9"). Changing trannies won't help especially to an automatic. Most manual trannies get better mileage. Had 3.70 in my 9" and put the 3.25 in and nearly doubled the fuel mileage. Good luck.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
Save the kid some bucks and just put some big *** tires on the back and maybe rejet the carb down abit. Put in a K&N Air cleaner, some good plugs & wires and to save more gas put on electric cooling fans..Use a cool air intake tube and not that hot engine air going in to the carb. And a Hotter coil.
Wire the heat riser open if it's has one. Many guys will shoot this down
..old school days we read the books plus learm a few tricks.. my 2 cent
orich
Wire the heat riser open if it's has one. Many guys will shoot this down
..old school days we read the books plus learm a few tricks.. my 2 cent
orich
