Hey guys, would changing from 4.10's to 3.55's make a big difference on pulling with my truck. I usually only pull about 8,000lbs at most and run highways alot. Would this really make a difference when pulling, besides using 1st a lot more.

 

It will make a big difference. Think of it as a lever, you have one 3.55 long, and one 4.10 long, which will lift the load easier? Obviously the longer lever. You will give it up in daily fuel economy, but with it struggling under load, you may not notice a lot of change when towing, except that it does a better job at it.

 

My 355 gears are a little lacking pulling hills, but without an overdrive I would slow down too much going 410.

 

How hard is it to change over from a 4.10 to 3.55's?

 

I am wanting to go from 4.10's to 3.55's, so what I want to know is, how much of a power loss on pulling will I feel, and will I gain in fuel mileage.

 

If you're going to change your 4.10, why don't you go with like a 3.73? It's a compromise that will still allow you to tow comfortably. That's probably why Ford no longer uses the 3.55 with the diesels to begin with.

 

I just bought an '89 F250 with ZF5 and 3.55. Before I bought it I towed my trailer with tractor from my home to my place in the country. I had to drop into fourth on a few hills, but no big deal. I averages 14.5 mpg round trip pulling about 7,000 lbs both ways. My neighbor I bought from put a lot of highway miles on it unloaded and got as much as 22 mpg (tailwind?) but 18-19 is normal. I can deal with dropping to a lower gear once in a while.
Brent

 

rstcso--I agree, dropping a gear everyonce in a while ain't a big deal for me, plus with fuel prices, I think its worth it.

 

Firemarshal,
I am quite satisfied with my 3.55's towing lots heavier than you are wanting to.
I am up in the WV mountains. I am wanting to get an overdrive for my 3.55 gears.

Bad thing is don't you have a 4x4?
The cost of changing the gears in both ends are gonna take a long time to recover, even with a several mile to the gallon increase.

 

unless you do all the work yourself Its going to cost alot. I don't recomend changing them yourself because if the ring and pinion isn't set up just right it is going to cost you even more in the end. I would not go to 3.55s unless you are going to a 6 speed transmission.

 

I bought an 87 4x4 with the 6.9 and 5 spd that had 3.55's. It had a bad rearend so I bought one from a local yard on the cheap. It has 4.11 and l/s. I wanted it for the l/s and the price ($50). I already had a 4.11 for a dana 50 IFS so I swapped it in. It made a big difference in slow speed where I use the truck a lot off-road. But I think it killed the fuel mileage. The truck used to get 15 no matter what and 18-20 on a good day, now I'm thinking it only gets about 11 or so. I'm still working on getting a good mileage run out of it.

I wouldn't do it over again if I had the choice. Now I have to go with a big tire to get the rpms back down when and if I ever get a chance to turbo it. As for pulling power I think I liked the 3.55's better. I could use third and really wind it up, now third is too low and fourth is too high. Now it feels like I am geared too low all the time, the engine really has to wind up to get speed, whereas before it ran low rpm all the time and I never noticed that the topend of the rpm range was dead from 2800 and up.

If I had an auto I don't know what I would think. I believe that if I had an auto, I would pony up for the turbo before I did the gears. I think that 4.11's make it wind up too high for the N/A diesel.

 

I have a 7.3 5 spd in a 1990 Cab and Chassis 4x4, not sure of the milage but it got about 450 Km on the rear tank, that was with 4.10 gearing and a very tired 7.3 (4 Litres of oil in 4 days) and burning extremely black (b4 the new IP). So good or bad i don't know but hope it helps.