I have a 4x4 91 for parts, it happens to have 3.08 ratio rears.

My grey 93 has about 250k miles on it and the springs are looking sad and its starting to sound like it needs new kingpins. I'm thinking about getting a new set of springs and roll the 3.08's under it.

I would expect my fuel mileage to increase with my OD Lockup trans and the trans has been built with a decent after market converter.(probably going for one of Dave's in the spring)
But I do tow every once in a while, typical load is 2 5500 lb. tractors plus 5000 lb. trailer. Gross combined right around 23,000 lbs.

Should I or Shouldn't I, that is the question.
Anyone have a similar setup out there running around?

Thanks,

 

It would be awesome for highway mileage, but that's a lot of weight. Unless you run at high speed a lot I don't think it would be worth sacrificing the towing performance.

 

Yeah, what Dave said. That isn't a good combo for heavy towing at all.

 

You could use the the gear section from an NP203 to give you an underdrive. Apparently that is the hot ticket right now. The NP203 gear section was practically unbreakable, and I tried!

 

Holsteinman put an OD in with his oem 3.07's. I'm sure he'll chime in. Just don't get rid of your current axles. You may have to fall back on them if the 3.07's let go. You can't get gears or a carrier for it anymore, and the houseing can't be interchanged. Sounds like a good project. Just check out your guide pin and lock pin for excess wear.

 

What would the RPM be in Direct with 3.08's?? Could you drop out of OD when towing, and still maintain your desired speed and mileage...and also save the tranny a bit too!

Chris

 

i wouldnt do it if your going to tow. but running empty down the interstate they would be great

 

When I get my other tow vehicle straghted out with the knock (hope its an injector) it has, then I'll probably put the 3.08's under this truck.

 

i say cash in and sell them...

 

If you are going to tow heavy I would not do it. Unless you are going to drive 70mph and above a lot I'm not sure it would be worth it. My brother and I both have D250's his has 3.54 gear rear gear and a 518 tranny and I get about 2-3mpg better than him at 70. If we both would drive 75+ I thing the difference would be more. With the od off driving at 55 and him still with od on I do not get any better mpg than he does. I do love it on the highway. At 75mph you will be at about 1700rpm (depends on tire height) and to drive slower I almost have to set the cruise. The truck would love to do 80 if I let it. To me 65 is about the slowest I like to drive in od.

For me going to an od tranny when I had a chance was a no brainer as I already had 3.07 gears. I really don't think I would put 3.07's under my truck if I already had 3.54's and an od tranny. I will put it this way if my rearend takes a dump I'm not going to watse much time looking for a 3.07 rear.(even though I love it on the highway)
Good Luck, Paul