how tall of a tire with 3.55 gears

[mcghan]

i have a 87 f250 4x4 with 3.55 gears,4 speed,gear vendors over drive,dana 50 front,and i doubt that i will pull over 7000 lbs with it,more realistically i will be keeping under 4000 lbs,how tall a tire can i run,seems like anything much taller than 235/85-16 would really make it a dog for pulling,thinking 285/75 would probably be the max tire for this ratio,also probably will be going with powertrax lockrite in the front also,thanks,ps truck does have a ats turbo on it

 

[dunk]

On my 460 truck with 3.55:1 and lockers with a ZF5, D60 front and lock right in the rear I run 35"x12.5". Pulls great, spins them on the 2-3 and chirps on 3-4 shift if I so desire, and cruises at about 2000 RPM at 70 MPH. Would be nice to be a few hundred less at cruise as torque comes on strong around 1300 RPM, but i really can't complain. 12.5 MPG highway unloaded and 10 - 10.5 MPG towing about 5000 lbs, about 70 MPH for both. Truck has a 4" lift and tips the scales at about 5900 lbs.

My IDI currently just has a C6 and stock height/tires/etc. but I intend to do exactly the same with it as I did the 460 truck but likely will get a TruTrac in front. I'm a little worried about how well it'll tow in 5th as it struggles at times now even with a turbo, but I suspect on level ground it'll be fine and hills just mean drop a few gears. If it can't pull a load in 5th comfortably or hills become more of a problem I intend to do studs, exhaust porting, more fuel, more turbo until it does what I expect of it.

As for tires I think 35" is ideal for a working truck that sees a bit of everything. Big enough to get enough traction with lockers that you never get stuck unless you expect to, tall enough to keep RPM reasonable, short enough that it's not a pain to lug things in and out of the bed. Needs lift to fit a 250, might fit a 350 without lift as they sit a hair higher. 33" will clear fine though without a lift, I've run that size on some trucks at stock height and been pleased with a wide tire and a locker to not we wanting terribly for traction.

 

[oregon96psd]

In my opinion from having an 84 with 3:55's, its already to much gear for it on stock size tires. They struggle to move themselves let alone anything behind them, 4:10's and lower should have been the factory options, unless you don't mind sitting in the slow lane for a very long time on every 6% pass that you come across when towing.

 

[TWeatherford]

Have you towed 4-7000 lbs with it yet? My guess is you might be wishing for 4.10s even with stock size tires if you are on anything but really flat ground.

Auto/manual does make a difference. For my old manual truck, I loved my 4.10s. I felt like I'd be burning my clutch with 3.55s and any kind of load. I briefly had an 85 with C6 and 3.55s and Banks non waste gated turbo (put its engine in my 94), and it was sluggish on hills (granted those hills were the mountains west of Denver on I-70). I would be more inclined with taller gearing with an auto, just because starting isn't ******* a clutch, and you're losing something to slip already.

 

[chris142]

I'm running 285's. Fortunately I don't haul heavy. My trailer and 2 quads puts a hurt on it.

 

[mcghan]

I had a feeling I was looking at gear change,I don't have but a couple miles driving in it but that was the impression I was getting, I live in Colorado mountains in teller county and a trailer and two quads is what I will be hauling,looks like I will be hunting up some axels with 4.10's,if I put bigger tires on it would be better with a 4.56 gears,just regear what I all ready have?