3.55s or 3.73s

[Tedb]

What are you uys running and wich do you think would be the best with torqshift powerstroke combo. I am sure the 3.55s would be a little better for mileage but not sure how the would be with the auto transmission.

Thanks
Ted

[LRTMatt]

If you have the 20" tires the 3.55 will not give better economy and will be a gutless wonder. The 3.73s are plenty enough with the taller tire. Actually the height difference of the 20" wheels/tires makes the 3.73 act exactly like 3.55 gears with stock sized tires.

If you are only looking at 17 or 18" wheels then the 3.55 won't be too bad to deal with unless you tow at maximum GVWR.

[slowleak]

just curious, what would rim size have to do with gearing?

[1999F350]

rim size doesnt matter tire diameter does.

[Tedb]

I was just curious if anyone had any experience with either setup on an 08. I understand how the ratios are affected by tire size. I guess wheel and tire weight may affect power and mileage also. I just figured that with the power of the 6.4 3.55s would be the way to go. We have a 97 5speed with 3.55s and it will do about anything you need it to. Just keep it out of OD once you get it rolling with a heavy load.

Ted

[Cat_Rebel]

I don't think you can order a new truck with 3.55s so it would have to be swapped. Assuming 4x4 that means front & rear ring & pinion = not really cheap. A 3.73 to a 3.55 isn't too much diffrent like a 4.10 or 4.56 is to a 3.55 gear. Nice thing about 3.73s too is thaty you can tow alot, run larger tires & still get good MPG.

[skylinedan]

A 3.55 would.nt be a bad combo considering the 5 auto has a slightly lower first gear, but if you tow I would go with the 3.73 any day. I have driven 3.73 and 4.10 s both and I will take a 3.73 over them all. with the 3.73s if I have to drop to drive I,m not killing the motor like the 4.10 does. You will pull harder from a stop with the 4.10 , but I think your millage is gonna be better with a 3.73 over all with stock hight tires.

Dan

[POWERSTROKER]

I've heard of a few guys getting 18+ with the 3.55's, as said above the Torque shift tranny does have a lower first gear, so unless this is gonna be tow truck more than a DD, the 3.55's should be just fine.

[LRTMatt]

Originally Posted by slowleak

just curious, what would rim size have to do with gearing?

The rim itself has nothing to do with it but the size of the tire placed on those rims at the factory is a huge factor!

Cat, the 6.4 trucks are available with 3.55s now. Ford went to that option in an attempt to help with the fuel economy complaints everybody has about the 6.4s.

[F350DRW1]

Originally Posted by Cat_Rebel

I don't think you can order a new truck with 3.55s so it would have to be swapped. Assuming 4x4 that means front & rear ring & pinion = not really cheap. A 3.73 to a 3.55 isn't too much diffrent like a 4.10 or 4.56 is to a 3.55 gear. Nice thing about 3.73s too is thaty you can tow alot, run larger tires & still get good MPG.

They are coming STOCK with 3.55's. Job 3. No need to order. Its a Ford band-aid to try and get the mileage up.