I just bought a 1971 f-250 4x4 with a 360. I'm trying to find if I can swap the 4 speed manual transmission, with a 5 speed or anything with a overdrive. Driving 50 mph and the motor is screaming

 

davyhyde Welcome to FTE and the Bumpside forum

Sorry dude a very bad econo purchase choice. All these old Fords are ***** at the pumps, but a 3/4 ton heavy duty 4X4 sucks it big time.

Don't know how long you have had the truck, how in love you are with it or whether you need 4X4 but a 2wd F100 will be some better.

Now if you have a heavy wagon to pull up into some rough terrain, it's a good choice.



John

 

Sounds like you have some pretty low gears in there, like a 4.10 or so. Changing the rear gears to a higher gear, such as a 3.50 or thereabouts will help. Can't really offer any advice on tranny swaps, though.

 

Thanks and I've had the truck for about 3 months now. I am more of a 4x4 guy. Plus growing up we had a 72 high boy for a farm Truck that I always wanted to fix up, so when I saw the truck I fell in love. It's not my everyday vehicle, just more of something to play around with. It just would be nice if I could drive it on the highway without people cussing me for going 45 mph.

 

I was thinking of changing the gears, but I didn't know if it'd help that much being the tranny is geared so low.

 

Also if I did change the gears would I have to change it in just the rear or the from differential too being 4x4?

 

Not being a 4x4 guy, I don't know for certain but if it were ME I'd do both, just to keep both sets of tires moving at the same speed. Of course most situations where 4wd would be used there would be slippage from snow or mud, so it may not matter. But me personally I would do both.

 

2wd guys, those 250 4wds use Dana gears that have to be swapped on both ends and not that many choices.

Best he can do is suck it up and drive it. Oh and don't worry, you can run it up to 65-70 with no fear. It will be drinking more but not damaging anything.

Try it and see.



John

 

to answer the transmission question- not really.
there are swaps, but they're aftermarket, and will cost you several thousand dollars.

 

Hi and welcome to FTE. If you are only getting 45 mph on the highway with your truck you are more likely running 4:56 gearing in that truck. That is a pretty standard gear ratio for the older Ford 3/4 ton 4wd trucks. If you post up your vin tag here with all information maybe someone with a book to interperet your numbers will be along to help you figure out what you have there. This is assuming the gearing is still the same as what the truck came with when new. If you can find out what you have for gearing find a tire gear calculator on the net and find out what size tires you can run to effective raise that gear ratio. I run 3:50 gears in my 65 4wd with a 352 and I can drive at least 60-70 with out the motor wanting to jump out from under the hood. I dont have a tach on it but it doesnt sound like it is straining to stay put. Good luck with it.

Edit.... Just reread my post and thought I would also add that in my truck I have a 4 speed trans it is an NP 435 with a dana24 TC these should be similar to what you have in your truck. My tire diameter is close to a 7.50 x 16. Tire diameter is close to 31 inches.

 

Look into the ZF5 or a TKO-500/600. A swap into a 4x4 requires more work to mate up the t-case plus a front driveshaft.

.. or consider a Gear Vendor unit but limit usage only when in 2WD.

 

After talking to a few people. I think the easiest way is to put bigger tires. I was told if I put 38's on it I'd gain as much speed as putting 373 gears in it