oldwest

I own a 1996 f 150 lwb 2wd with 300 I-6 and 5 speed manual transmission. It has 2.73 open differential according to the door sticker. The rear end is making a roaring sound and may have to be replaced. If replaced, I want a rear end that will give me maximum torque/low speed pulling power such as in pulling small stumps or going up rutted dirt roads. Top speed does not matter as long as I can obtain 65-70 mph for highways. I know I need a limited slip or locker, but what rear gearing would be best for my needs? My mileage is okay now and since I only use the truck for back-forth to work (10 mile round trip) and chores I'm not really worried about mpg. I don't completely understand rear gearing ratio applications. Thanks for any assistance.

oldwest

BLDTruth

3:55 gears with a limited slip should fix most of your problems while keeping your mpg reasonable.

jkenprice1

x2 I had that exact truck. With a 3.55, you should have a real stump puller and still be good down the road.

jkenprice1

Here'a another factor. Have you thoought about bigger tires? Stock tires are 235/75-15s. I ran 31/10.5 75s. They look a lot better. The 235s are 29" diameter. The 31/10.5s are 31"s. The bigger tire size eats up some of the mechanical advantage you've gained changing gears. You might like even bigger tires. Before you decide, you might google one of the tire size calculators and crunch some numbers. If you use stock tires and 3:55 gears for a baseline to see what your rpm would be at 60 mph in 5th gear. A good place to be for what you want is 2000rpm at 60 mph. You need to know what ratio 5th gear is coming out of the tranny.

jkenprice1

I looked up your tranny. Should be a Mazda M5R2. 5th gear is .750

Chris_1

iTrader: (1)

The higher the number, the more low end torque. A real stump puller would have 4;10 or 4;56 gears but would be revved up quite a bit to reach highway speed.
Your 2:73's will have it idling down the highway but are like starting off in 2nd gear compared to 4;10's.
3;55 or 3;73 gears are a good compromise - kind of halfway down to tractor gears.

BLDTruth

Different engines obviously, but my '94 M5OD 5.0L with 31x10.5's and 3:55's sits right at 2000-2100 rpms at 60mph. So good call

But don't expect to get much better than 13-15mpg. Ever.

oldwest

Thanks guys for all the responses! The info helps a lot.

oldwest

jkenprice1

Hope all goes well. Another choice you will have is limited slip w/ clutches, a trutrac unit, or a locker unit. Good luck

frank5079

I have a '95 with a 300 six and 5 speed as well; it had a 2.73 rear too, but it was starting to make noises and was leaking gear oil. I swapped in a 3.55 unit and found it to be a better combination with the 5 speed. My take offs from a dead stop are quicker and my gas mileage on the highways are still about the same as with the old 2.73 rear...