1988 f150 300 np435 4x4 with 3.08 gears.

I'm looking into buying some off road tires. Looking at the Goodyear MTRS 33-12.50x15. Also putting a 4" lift on the truck.

I'm curious to whether or not my current driveline will be good to turn these tires. I'm worried about the 3.08 gears. It's not a highway truck, pretty much just around town and offloading beater truck.

Will the 3.08 turn them knobby 33s ok or will have have to regear it?

 

Will it? Yes. Will it like it? Not really. Just probably will never need 5th gear.

 

It's the new process 4 speed with granny so I'm used to it being slow lol

 

3.08 gears are marginal with the stock tires IMHO. Those 33s are going to suck what little life that powertrain combination has to offer. I vote for 4.10s minimum.

 

For what it would cost to regear, you would want to go to a minimum of 4.10s but with the NP435(NO OVERDRIVE) it is going to running pretty high RPMs at any higher speed

 

I figured as much. Probably the only way I would regear it is if I found a donor truck with complete axles and swap everything. This truck however is pretty much going to turn into a woods/mud/beater truck that I also drive to work across town. I have my 89 f250 7.3l for highways trips or hauling.

 

Even more reasons why you need the proper gears.

 

Agreed. Unless it never left the dirt and you just always ran 4low

 

With 3.08s and 33s you might actually make use of your 1st gear to launch

 

I'm not saying that 33s and 3.08s is a good combination. But if you want 33s I'd try it for a while before popping for two new axles. It won't be great, but it might be very tolerable.

 

I'm going to run it awhile and see what happens. My friend has a bone yard and he might be able to sell a set of axles if they have a better ratio.

 

NothingSpecial has a good point. If you're set on 33s, do it, try it out, and if it's a $1000 problem to you, regear. I have 33x10.5 with 3.55:1 and a 5.8L/E4OD, don't think I'd be ok with any less gear myself, but you might find it tolerable.

 

Well I bought the truck off my friend for $200, used lift kit for $165, another $200+ in parts to get it running. It's a very cheap build/beater truck. Tires I figure I can put on something else when this one dies. Frame has been patched before and it has 175K miles. Not trying to spend $1000+ on regearing it if I can help it lol.

 

I honestly think you won't be much different than a zf5 that starts off in 2nd, with 3.08s you might find first gear to be usable, 2nd to 3rd will probably suck, and your 1:1 4th will be like an overdrive.

 

Did most of you that replied forget that the 435 doesn't have OD and has a 6.69:1 1st or are you all running 302s with no compression and a 500lb toolbox in the bed?


HE WILL HAVE A DEEPER EFFECTIVE 1ST GEAR RATIO THAN A TRUCK ON 29" TIRES WITH 4.10s AND AN M5OD.


He'll also have a slightly deeper 4th gear than 5th on an M5OD or ZF with 3.08s and 29" tires.


Yes he'll find himself wanting to downshift into 1st more often with 33s than 29s. Off road he can probably suck it up and just stay in 1st more.


On road performance will be fine. There will still be a big split between 3rd and 4th because it's still an NP435, it might actually move 3rd and 4th up to more useful speeds. 2nd with the 435, 33s and 3.08 is going to be only slightly taller than 1st in an M5OD with 4.10s and 29" tires he should have no problem.

I can't see why everyone thinks 33s will be too much tire for OP's truck. It should be right in the middle of what trans + tire + axle ratios are good for general use and probably a little on the deep side fuel economy.


Run the numbers before you run your mouth:
Calulators from www.4Lo.com
https://www.ford-trucks.com/forums/8...tml#post544558
The Novak Guide to the New Process 435 Transmission