I have a 79 f250, 351M-C6-3.07 dana 61. It's only got 59k miles on it. The tires are 245/75/16. I want to pull a 27' fifth wheel camper that weighs 5k lbs. What would you suggest I change to help get some more power for pulling? I think I'll have to do something with the gear ratio.

 

gears first, definitely. somewhere between 3.54 to 4.10, depending on how hard you want it to pull, and what kind of fuel mileage you can accept when running without the trailer. The higher the number ratio, the more the engine has to spin, and the more fuel you can expect to use.To pull best the 4.10 would be best for highway use, the 3.54 will not have as much pulling power, but a little better fuel mileage running by itself.

 

WHAT ABOUT A 3.73?

 

3.73 is a descent compromise between mileage/freeway speed and towing power, provided that you stay with stock height tires. With a Dana 61 not being all that common an axle these days, I don't know what your ratio choices will be.

I wouldn't suggest 3.54 for towing.

4.10 would be the best but since you dont have overdrive, if you like to drive fast on the freeway you will be using more gas. I had 4.10's in my old dually with 454 engine and TH400 auto (no OD). I didn't make a habit of driving fast with it.

 

I agree, 3.73 would be best, just wasn't sure if it is available. 3.54's work, but it dogs it pretty good on the steeper hills. My father's diesel has them, and it does the job, but works it on the bigger hills, wouldn't want to try any mountains though. 4.10's give the best pull and retain some highway useabilty, but the rpm's come up above 3000 trying to run 60 or more.

 

i have a c-6 in my 79 f-150 and my brother swaped 1st and 2nd planetarys out of an e4od (i think) and i got about 11% underdrive in first and second while keepind my final ratio the same so it didn't effect my milage. It made a BIG difference pulling my car hauler from a stop, and with 3.73's it still ran well at highway speeds.

Just my 2 cents

 

Just wondering... I went from a 97 F150 5.4 Auto reg cab to a 04 F250 same specs. The 97 w/373 rears pulled my 27' fiver just fine. A tad slow on hills. I aint hooked on yet but I'm thinking that the 5.4 in a 250 might be enough mill to haul as good as with the 150 . GVW of the 97 was 5373 the 04 is GVW 6575 these are certified weights taken on the same scales. Any thoughts??

 

If the '04 5.4 is equally powerful as the '97, and the new truck weighs more, it would be similar to pulling a trailer that weighs 1200 lbs more with the old truck... So basicallly, no, the new truck will not pull as well as the old one (engine output, transmission, axle gearing, and tire size being equal). Tire size is another thing, your new 3/4 ton may have taller tires than the 1/2 ton. For pulling with a 3/4 ton and stock tires with an overdrive trans, 4.10's are best.

 

Thanks SoCal; You reaffirmed what I imagined. I do have the 4.10 tires but not much more. I have been told the '04 5.4 has a tad more berries that the '97 but me thinks that will be lost in the 250. I'll just have to give it a try and see what adjustments I can make. Thanxs for the input

 

Contrary to what other people may tell you, size does matter. If you have concerns about power get a bigger motor. problem is resolved. If you go diesel you may be able to even get good mileage to boot.

 

Thanx Doc: The Diesel is sounding better. No pun intended.The V10 is a bust. Excuse me for looking at 6.0 in the GM site. What is my punishment

 

No punishement here, all 3 manufacturers make good trucks and engines. I just prefer the Blue Oval...