I wouldn't worry about running the highway if you have 3.55s. If you have stock size tires then thats about 2200 RPM at 55 MPH and 2600 RPM at 65 MPH. If your tires are bigger than stock, those numbers are lower.

 

Ok thanks for the advice, I have 33s so I should be alright

 

Cool! That changes those numbers to like 2050 @55 and 2400 @65. Good highway RPMs. Should get pretty good MPGs on the highway.

 

I have a 7.3L diesel with 3.55 gearing and 35" BFG AT KOs. Before the tires I had worn out 32s and ran about 2500 rpm at an indicated 55 mph getting about 16 mpg. After the switch to 35s I run about 2300 rpm at an indicated 55 mph and I'm getting close to 20 mpg, 18 mpg with a motorcycle or two in the back. Also, the "55 mph" indicated with bigger tires in my case is closer to 65 mph. Note that all these mpg guesstimates are based on highway figures.. 90% of the driving I do is cruising at 2300 rpm.

To sum up my findings since switching to 35s.. Not only do I get better mpg and higher speed, I'm putting less stress on the engine because I don't rev as much. With all the driving I do I save about 20 a week in gas with the bigger tires. That means each tire pays for itself in a little over 3 months, balanced and installed.

I hope this might help someone out! If I made any sense that is..

 

Makes sense. I'd love to find a good IDI truck and set it up like that. I'll probably end up getting a ranger as a second truck though...25 MPG highway on gasoline (~20% cheaper than diesel where I am) in a Ranger is hard to argue with.

 

Get a car and get in the 30s

 

But then you'd have to drive a car... ha! Oh and I forgot to mention I have a 4 speed with overdrive so that definitely contributes to my efficiency. I would like to get a newer ranger with a 5 speed for a daily driver though.. 2 wheel drive as well. (Never thought I'd say that!) Times are rough..

 

I'm driving a car right now while the truck is down... Getting between 26 MPG (traffic) and 40 MPG (cruising in OD at 50), and averaging around 32 MPG total.



Yeah, not loving driving a car right now... Can get almost as much MPG out of a Ranger, and you get to sit higher and have a bed and a little bit of towing capacity.

Exactly what I'd like. Probably a 3.0 V6 or maybe even a 4-cylinder (not sure if I'd take the tradeoff in power vs MPG...). Wouldn't mind doing a small lift on a Ranger and slightly bigger tires (maybe 31s)

 

Yeah , it's like a mini truck for when you can't drive your big truck!

 

Yeah, pretty much, haha. Doing a small lift with bigger tires may also help the highway gear ratio. Especially if it doesn't have the tall 3.08 gears.

 

Was debating whether or not to get a new radiator for my engine since it'll be fresh, but I just pulled the trigger and did it. The old one seemed to be cooling okay, but it's the original one to the truck so it's 25 years old with about 140,000 miles on it total so it's definitely not perfect anymore. If there's any build-up in the radiator, I don't want any of it in my fresh and clean engine.

Got Autozone to order me a stock replacement aluminum one. Also got 20% off, so it only came out to $112.73. Should be in tomorrow.

The stock one is painted also, and I always felt like that wasn't the greatest for heat...

 

Isn't your truck a 460 now and before a 351? Wouldn't the radiator make a difference then? I am trying to remember if that was your truck or not.
Trav

 

Yeah, it used to be a 351. Radiator is the same for 351 or 460 in these trucks though.

 

oh ok then because when I looked at our 89 F250 351s radiator it looked smaller then our 89 F350 460 or are previous 93 F250 460s radiator so I wasn't sure.
Trav

 

Difference between F250 and F350 maybe? Or possibly the difference between 4x4 and 2x4? Or maybe one of them was swapped out at some point. It's the same according to all of my local parts stores.