transmission swap ?

Beach66Bum · Mar 9, 2011

Wanting to know what's involved in changing my 4-speed with the bo-low to a regular 4-speed. The truck is a extended cab 1983 F250 two wheel drive with the 351 windsor. The gearing is so low with the combination of rear end and tranny. Would it be a direct bolt up if the donor came from the same year/style/etc. Thanks smilieFordlogo

1985 Ford F-150 · Mar 9, 2011

Be better to do a 5 speed swap.

Fellro · Mar 10, 2011

Unless you are going to an overdrive, not a lot of point in swapping to essentially a car transmission. If you don't need to start out in lo, then don't, start in 2nd. The lo is for towing or heavy loads. I don't know of any truck transmissions that have a higher geared 1st that would be similar to a car that are worth putting in.

Beach66Bum · Mar 10, 2011

Hi. Thanks for the input. I never start in first unless on the farm in the fields. The truck is so low geared that on a level surface I can start in third with out any lag !! On the highway the tach reads close to 2800 rpm's at only 55 MPH. Did Ford have different gearing for trucks that would only be used for logging or in my case airport use. I need to install flashing school bus lights everytime I leave from a stop... LMAO Great truck, but man is it low geared

Fellro · Mar 10, 2011

You should have an axle code on the door jamb. Look at the axle code and let us know what it is, and as long as it hasn't been changed, it should be what the tag says. It is possible to have 4.56's in it, more common would be 4.10's, but I don't believe they spin that fast that soon, don't recall for the moment, and don't have the time to look into it.

Beach66Bum · Mar 11, 2011

the sticker says C2 for the axel code and trans code says F. thanks.

Fellro · Mar 11, 2011

Looks like a limited slip 4.10
http://www.drivetrain.com/parts_cat...do_i_have_in_my_ford__is_it_posi.html#RPOCODE

Fellro · Mar 11, 2011

Well, if you run the numbers through a gear ratio calculator, the rear gears likely have been swapped, as the RPM's are close to 2800 with 4.56 gears and 245/75/16 tires. I am guessing on what you have, 235/85 16's will bring it down a bit. 9.50 16.5 is very close to 245/75 16's.

Beach66Bum · Mar 12, 2011

Thanks Fellro. Yes the truck came with that size tire on it. (I've had the truck for 6 months) I want to get the factory size back on (235/85R16) as you noted. How much would that drop the rpm's down.

DNFXDLI · Mar 12, 2011

Here is a handy link for rpm calculations:

http://www.csgnetwork.com/multirpmcalc.html

Fellro · Mar 12, 2011

It only changes about a 100 RPM.
http://www.ramblerman.com/blazer/gearcalc.htm

Beach66Bum · Mar 12, 2011

DNFXDLI said:
Here is a handy link for rpm calculations:

http://www.csgnetwork.com/multirpmcalc.html

thanks a lot for the link !! looks like the rpm's will drop about 179 with the numbers I put in. The tires on the truck have to go.(wrong size,load range, etc.) I might even pick up a mpg. smilieFordlogo

Beach66Bum · Mar 12, 2011

Fellro said:
It only changes about a 100 RPM.
http://www.ramblerman.com/blazer/gearcalc.htm

thanks a lot for the link, really has help !! I'm going to change the tires. They are wrong for the load range of the truck, the size and even the tread.
(245/70R16 General Grabber UHP's directional tread pattern summer use)

Beach66Bum · Mar 15, 2011

Got the new tires on. Made a big difference. They're 265/75R16 load range E. Must say they look really good too !

Fellro · Mar 15, 2011

Same height as 235-85 16's, but wider.

Beach66Bum · Mar 16, 2011

The tires it came with were 245/70R16. (The diameter difference is 29.50 for the 245, and 31.7 for the 265) so when I drove it home, i really noticed a big difference. Has a taller stance too.

Fellro · Mar 16, 2011

Those are even shorter than the 245/75 I was expecting... so it will make a definite difference...

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