Me again. Have a 1980 f150 4X4

For tires I'm either going with 33x12.5r15 Mickey T's, or 35x12.5r15 Mickey T's on a 4in RC Lift Kit.

Which size would you go with?

I was wanting to know if anyone would recommend re-gearing? If so what gear ratio would you recommend?

I'm going for a look like that truck.

 

This is the truck from this post?

https://www.ford-trucks.com/forums/1...l#post16838006

A worn out recently freed up 351M?

Stick with 31's.

Yes you have to regear both axles, and if you have it done, expect $400+ for gears plus as much as (or more) $400 labor per axle to do the job.

 

As 85e150six4mtod said, yes you have to regear both axles. You can't use 4WD if the ratios don't match. And yes, it's expensive. He said about $800 / axle, it might be closer to $1000. Unless you do it yourself, but if you have to ask, you probably can't.

As to what ratio you should have, it depends on what you want. I had 33" tires on an '85 F-250 with a 351W and a 4 speed (no OD). The 3.55 gears I had in that were pretty good. Then I had a '95 F-150 with 351, E4OD trans, 33" tires and 3.55 gears. With the stronger engine that 10 more years of development brought the 3.55 gears were great for me there too. But I don't like an engine screaming and I don't mind if my truck can't keep up with sports cars or if I have to downshift occassionally.

So if it were me I'd probably go with 3.55 gears with 33s, and probably 4.10s with 35s. But others would prefer 4.10s with 33s and 4.56 with 35s.

But my bottom-line advice (pun intended) to anyone considering changing tire size and axle ratio is hold off on regearing until you see how it works with the old gears. If you like it OK you've saved yourself maybe $2000. And if you don't like it you'll know why you are spending all that money.

 

You did the blah-blah emo-gee in your post, but you really did need to keep going. Your engine size, the transmission and the gear ratio you have now will determine what decision needs to be made with oversized tires.

 

For 33s, I'd leave the gears alone and just know you'll be down a bit on power. For 35s I'd absolutely regear to 4.10.


Gears and installation is not not cheap, but I also added lockers at the same time.

 

With a 4" lift you're in the 35"-37" range. If you don't want to run larger than 33", just keep it stock as 33"x12.5" fits fine on a stock height F-150. Spend your money on lockers before anything else, you'd be amazed at how much a stock height truck with decent 33" tires and lockers will go through... More than a lifted truck on 37" tires but no lockers unless the water is over the hood or you're getting stuck on the frame, then that's a different problem requiring larger tires.

What gear ratio is in it now? I ran 38.5"x15" tires with a stock 351W and 3.55:1 gears, it was fine. Slow, but fine. Used low range more off road. Eventually swapped it to a 460 making north of 400 HP and 550 ft/lbs as it sucked towing with a 351w (even with stock size tires. 3.55:1 gears are ideal for an all around truck unless you're towing very heavy, as you can keep RPM reasonable on the highway without getting into double overdrive. If it's slow or won't do what you want then you have a power output problem, not a gearing problem.

 

I think the above statement needs clarification. 33" barely fits a stock height truck, and will rub when any load is put in the bed, and will rub in the front when turned sharp in a parking lot unless aftermarket wheels are used.

 

Yes it will rub the radius arms at full lock with 12.5" tires, 10.5" maybe not. Either way it's minimal reduction in turning radius which a lift will not fix. I never had rubbing issues in the rear even fairly overloaded, though mine was a stepside so possibly more clearance in the rear.

 

Thanks for the help guys, I wanted to do 33's but it put me off because of the lift and gear change. The truck has 3.00 gear and the 14 code axle. If the gear change isn't really that helpful I would pass it up along with the lift and put it into fixing something else. The truck has 225/75-15's on it and it makes em look like gokart wheels, as long there's no damaging rubbing then I will probably go 33's.

 

33's and a 3.00 gear? That's going to be bad. If you have a automatic you had better put a oil cooler on it. If you have a manual you may get to use 4th once in awhile.

Get one of these guys to run the numbers for you in a speed/rpm calculator.

 

It's not only at speed & using 4th gear it is taking off from a dead stop.
That is where you would need to slip the clutch, not good, and puts a lot of heat into the ATF needing a LARGE cooler.


There is a post on gearing & RPM with a ZF swap in here so you can partly under stand what is going on with gearing even if it is with tranys & rear gears or for you rear gear & tire size (how tall they are) but it shows you the math to figure it out.
Dave ----


edit: found the post most is on the first page but read the full post. https://www.ford-trucks.com/forums/1...rpm-chart.html