What's the general concensus on 33's and stock gearing ?

Also - on a side note - on a 4" lift - will the driveshafts need to be lengthened ?

Thanks, Dan

 

Your drive shafts will be fine with 4". I can only speak to 3.55 gears and 33" tires but it seems just fine on my Bronco. What gears are in your truck?

 

3.88's


Dan

 

3.08s you mean?

 

What motor is in your truck?

 

33's are O.K. with a V8 and stock 3.50/3.55 gears. If you have the 3.08 gears, you might feel a tad sluggish. And no need to lenghten the driveshafts with a 4-6" lift.

 

I drove my 92 with 3.55's and 33's and the passing and hill climbing power was non-existant. I guess if you don't mind pulling to the slow lane and taking a week to get up the hill, its fine. Fuel mileage gets noticably worse too. But it still drives just fine.
In the Ford 8.8 3.55's were stock with 4.10's being a factory option. I've never even seen 3.88 available for the Dana 44, Ford 8.8 or the 9" rear end. And 3.08's will be worse than 3.55's.

 

the only size tire i'll run my 1/2 tons on are 33s i find them to work just fine 351w, in one 300 I6 in the other

 

Is there a way to decode from the Vin what axle ratio is in the truck - or is it on a tag somewhere ?

Thanks, Dan

 

There is a sticker in the drivers door jamb. Tell us what the alphanumeric code is in the axle portion of the sticker.

 

How bad will 35X12.50X15 tires be with 3.55 gears? I do have some performance modifications to the engine, will it be enough with these gears?

 

I'm with greystreak, when I put the 4" lift and 33s on my 94, power went out the window and gas mileage through the floor. 4.10s fixed it up nicely.

 

I third greystreak and broncobob's comments. The 33's on my 93 with 3.55s, power and hill climbing feel like I am dragging anchor.

There should be a metal tag attached to the rear end with some numbers and letters stamped in it. Look at the lower row of numbers on the tag for example: “3L55 9 75.” These numbers signify a gear ratio of 3.55:1 (the “L” between the 3 and the 5 means it has a limited slip) and the “9 75” means it has a 9.75-inch ring gear.

 

Well, with the 33" tires, the 302 and AOD transmission it's not exactly drag racing material now. But, I'm hoping when I get done with the new engine it will have a little more power. Flat top pistons for a little more compression, new cam for more torque, headers, and possibly a larger throttle body. Does anyone think this combination will be enough for the 35"s and 3.55 gears?

 

Ok, here it is in a nutshell. A smallblock V8 (i.e. 302/351) hit optimal torque/power band somewhere between 2300-2800 RPMs. (I believe a recent thread listed the 302 as having peak output of 270 ft./lbs. @ 2400 RPM). This is the range that you want to keep the engine in when doing these calculations. The following is a list showing the changes that each nominal tire diameter makes to the RPM range when you change tires but NOT gears.

Engine: 302/352

Axle gear ratio: 3.55:1

Tranmission in OD/3RD (1:1 or direct drive in most automatics)

Vehicle speed: 60 MPH

Engine RPM with 235/75R15 (stock tire): 1728/2534 (a bit low in OD but thats to be expected since you don't pass or climb hills in OD. The 2534 is right in the middle of the power band as you can see).

Engine RPM with 33" tires (31.8" nom.): 1575/2311 (OUCH! Undercutting the optimum on the jump back to third... there goes the MPG because you will have to hammer it).

Engine RPM with 35" tires (33.6" nom.): 1491/2187 (Forget about passing or climbing hills here. Even when the jump back to third is made you are still only turning about 2200 RPMs which is way low).

Yes, the difference of a couple hundred RPM's does really make that much difference. And yes, I realize that P265/75R15's were optional tires from the factory. The numbers for 265's are as follows 1637/2401 respectively.