I need to lower my RPM, considering regearing

[akoldnav]

I am considering regearing to get longer legs on my 1988 F-250 C-6 4X4 with a Banks Wastegated Sidewinder. I don't expect to pull anything heaver than a 1500 lb boat trailer. The local gear shop will change both differentials to 3.73, 3.54 or 3.08. I am thinking about going to the 3.08. Does anybody here have experience with this , or similar, high gearing?

It is at least $1000.00 less expensive to regear than to buy and install an aftermarket overdrive.

What do you all think? I would hate to do something that somebody has already tried and found unacceptable.

By the way, I am new to posting here, but I am a regular poster on TDS as hweaver.

akoldnav

 

[94f450sd]

welcome to the site.i dont think you want to go to the 3.08s.what gear do you have now?3.73 is probably as high as you want to go.i know the gas job chevies with 3.08 in them were total sleds.what size tires are you running?

 

[Mike]

By the way, I am new to posting here, but I am a regular poster on TDS as hweaver.

akoldnav

Welcome to OB, glad to see you come over and find out what we have to offer. You'll find some of the best info available in print or on the net right here in IDI land.

Why do you want to regear? Mileage or?

Mike

 

[towcat]

welcome!
caution on the 3.08 I have that rear in one of my f250's and it can cause all sorts of grief with twisting up a driveshaft when I was loaded heavy once. You never know what you may put your truck up to in the future, but the 3.08 will severely compromise your options. don't get me wrong, the feul economy was unreal but I knew I couldn't carry anything in the bed.

 

[shorthair]

i wouldn't go that low but 3.55s with a zf5 does work well for me even towing a 31' TT & grossing 14,000+ i just have to drop a gear or two up hill. with my tires i'm only turning 2000 @ 65 mph.

 

[budtoh3zo]

3.55 are what i run in mine, With the 4 speed at 70 mph im turning 3000 i think and get about 16 mpg

 

[akoldnav]

To answer some of the questions: The truck has 4.10 ratios now. My tires are 255-85-16s. I recently drove the truck from Fargo ND to Anchorage AK and I had to hold it to 60 mph because of engine rpm and at that speed it got 12.5 mpg. I was hoping to lower my RPMs and increase my fuel economy. I have a 90 F-350 to haul heavy loads, so I am pretty confident I will not have much of a load at any time.

Is there a gear ratio between 3.55 and 3.08 that can be installed in these trucks? Thanks for the replies.

akoldnav

 

[towcat]

To answer some of the questions: The truck has 4.10 ratios now. My tires are 255-85-16s. I recently drove the truck from Fargo ND to Anchorage AK and I had to hold it to 60 mph because of engine rpm and at that speed it got 12.5 mpg. I was hoping to lower my RPMs and increase my fuel economy. I have a 90 F-350 to haul heavy loads, so I am pretty confident I will not have much of a load at any time.

Is there a gear ratio between 3.55 and 3.08 that can be installed in these trucks? Thanks for the replies.

akoldnav

If you have another truck for the heavy haul, then go for the 3.08's. Rumor has it that there are 3.23's floating around but I have yet to find one all these years. I've traded out the 3.08 under four trucks now, it gets shoved under whichever truck is supposed to be the mileage getter. If you already have a 3.08 rear, go ahead and use it. Outside of my '92, the rest of my fleet is non-turbo, so yes, its a little laggy off the line but holds its own at highway speeds. One other thing....if the C-6 does ever croak, consider replacing the C-6 first gear with the E4DOA first gear. The multiplication goes from 1.75 to 1 up to 2.75 to 1. You'll get out of the hole better but the downside is a big drop to second.