tranny swap 4 lower rpms

[R.Smith]

I have a 390 c6 combo in my 70 F2fitty that I drive daily. As you can expect I spend about $80 a week for gas...mainly because my sweetie lives 30 highway miles away and the 390 at 2500 rpms isn't very thrifty. What options would I have for installing a tranny with an overdrive? Also, a friend has a New Process 5 speed top loader that's hooked up to a late 70's 390 he says I can have. I've also noticed that some of these trucks also came with a Borg Warner manual overdrive.

Opinions and advice welcome.

[HIO Silver]

By far the simplest thing to do is change your rear gear for a 3.00 or 2.80

NP 5-speed top loader? What is that?? Are you sure its not a New Venture?

An AOD, AODE, or 4R70W swap is possible... be resourceful and you may escape for less than $2000.

Manual... my plan is a QuickTime bellhousing and a short-shaft TKO-500 trans through Modern Driveline... http://www.moderndriveline.com/
The TKO-500 comes with a 0.68 OD gear so with 4.11 it equates to a 2.79 rear gear. About $4,500 for a totally new system.

[ToughOldFord]

I've always heard that 3.55s are as low (numerically) as you can go in a Dana 60.

Isn't there an adapter plate for the Zf 5 speed to the FE? I think I came across a site recently that was talking about them, if I find it I'll post it here. A ZF would be a good way to go.

[ToughOldFord]

Here we go:

Ford FE Block

Adapters are available to use the ZF trans with the FE Block.

http://www.high-impact.net/transmission ... 5&6spd.htm

Of course, it'd be nice to actually see one.

[averagef250]

I port fuel injected my 390 and swapped in an NV4500 5 speed and gained maybe 1 MPG on the freeway. 95% of my driving was freeway and the mileage was pretty fair, around 14 MPG at 60 MPH with 4.10's and 35" tires with a carb. In town was awful, it could suck a 1/4 tank when it was cold to drive 5 miles to town and back.

Don't think you'll see any kind of gains from dropping your RPM's like you think you would. Dial it in to run at 2500 and it'll do just as good as it would with an overdrive.

Newer vehicles with EFI and computer controlled timing, long runner intakes, blah, blah, can run 65 @ 1800 RPM and be efficient doing it.

C6's suck a lot of power/efficiency. I'd say if the parts were free you would probably see some gains by switching in a 4 speed.

Thermostatic clutch fans are great mileage adders if you don't have one and ignition system/overall engine condition make notable differences too.

There's a lot more to mileage than just RPM's.

I don't really do any gas engine stuff anymore, but the same rules apply to diesels. Guys lug the heck out of them and don't get the number's they're looking for. I've run some diesels on their governor, actually past, at 3000+ for entire tanks of fuel on long trips and got great mileage considering the speed and mass going down the road with an overall efficient setup.

[BobbyFord]

Why not just move the girl into your place?

[ToughOldFord]

I just got a ZF that I'm going to put up to the 6.9 in my '85, I should see some gains with that setup. But true, not all engines are the same, I have no clue how a FE would respond to OD. I do know when I went from 4.10s to 3.73s in my '69 I dropped 200 rpms on the freeway and saw zero difference in fuel economy. And Dustin's right about the C6, it is a heck of a good auto, but it is a power pig.

Here's the breakdown on my 69 in my attempts to get some fuel economy:

Bought the truck, '69 F250 C6 360 4.10s.
6 MPG

Major tuneup, cap wires, plugs, rotor, points, condenser, all fluids and filters, set timing (was at zero degrees!), replace transmission modulator, old one had been bad for so long the #4 plug was fouled heavy with AT fluid. The PO owned the truck for 15 years and I swear he did nothing to it but drive it, but that's another story. And rebuilt the carb.
8 MPG

Added protinix ignition & flame thrower coil.
Swapped out the 4.10s for 3.73s.
Installed a fan clutch.
8 MPG

Pulled the 360. Dropped a 390 in with a mild cam, 4bbl intake, and 4bbl Holley carb.
8 MPG

Swapped out the C6 for a NP 4 speed.
9.5 MPG

And that's where I am today. Never did break the double digits with the thing.

[ToughOldFord]

Why not just move the girl into your place?

Now who's dipping into the moonshine?

[BobbyFord]

Why not just move the girl into your place?

Now who's dipping into the moonshine?

[michael69]

Why not just move the girl into your place?

$80.00 a week is alot cheaper than what it will cost him if she moves in. Don't ask me how I know

[STROKER69]

If we could find a 1969 Mercury Cougar Elimanator 9" two speed rear chunk. I think it was somewhere in the 65% overdrive range. I was hoping some one would comment on this or question me about it. I saw this gear set up in an old old performance magizine from 1969 that was advertiseing the Cougar. this setup will fit into a regular carrier and looks like a quick change facing foward. It has two pinion shafts with the top pinion being the one that the yoke hooks to and the lower shaft being the O>D> shaft and a cable operated lever on the side. I have tried to research it more on different web sites to no avail.Maybe one of you wed gurus could find out more about it and post it.PLEASE I think it is a neat setup, and be nice if some one still made something like it for the 9'' in our Bumps.