I had a '97 F350 cab/chassis flatbed dually 4wd with the 7.3 Powerstroke and E4OD auto trans, 4.10 gears and 235 tires. I loved the truck and would still be driving it today, had it not burned down in a fire, a year ago today. It served me well for the 4 years that I got to use it.
I towed 20,000 lbs combined weight with that truck a few times in the mountains in southern California and Arizona. It was no picknick.
I often wished for 4.56 or 4.88 gears. The 4.10's were just not enough gearing. The 7.3 likes to run in the 2500-3000 rpm range when towing heavy. 4.10 gears, even with short 235 stock size tires, wasnt enough gearing to make it rev enough in 3rd to pull the hills. So, it was down in 2nd alot at 40 mph.
My engine was all stock, 235 horsepower rating. The old body trucks dont have intercoolers like the Superduty body trucks have. Not sure how much that really makes a difference, since the '99-'02 7.3's didn't have much higher HP rating than the old body trucks had.
I didn't have a power chip or any exhaust or intake mods. The truck was very heavy when not towing anything, weighed 13,000 lbs by itself. Since it was so heavy all the time, I left the engine stock, to keep its reliability.
I did have alot of transmission work done to the truck. E4OD's have no engine braking when going down hills. That's scary. I had the trans fully rebuilt and modified valve body, heavy duty torque converter and electronic programming, also had the turbo waste gate programmed to close when dethrottling, to use as a sort of exhaust brake. All this did help alot with descending hills when towing at 20,000 combined.
I think if you do alot of power modifications to the engine and build the tranny up right and also, most importantly, change the axle ratio to 4.56 or 4.88, you may be get reasonable performance from the truck with that heavy trailer. It will not be great, but should get you by.
I really do like the 7.3 Powerstroke engine era. Very simple engines that are very reliable and reasonably powerful, for their time.
I replaced my burnt down 7.3 F350 with another great International engine, in a much bigger truck. I now have an '01 International 4800 (33,000 GVWR) crew cab 4x4, with a true medium duty commercial diesel engine, the DT466E inline-6, with High Torque output rating (850 lb/ft @ 1400rpm, 250 hp).
I'm very happy with the truck and engine. It goes down the road every day at 20,000 lbs GVW and pulls more on trailer without breaking a sweat. The 5.38 axle gearing and 5 speed Allison MD3050 tranny help too. :)
The tranny acutally has 6 forward gears inside it, but is programmed to only use 5. The 6th double overdrive gear is electronically unavailable. Some day, I intend to have the Allison dealer reprogram the tranny so I can use 6th gear and comfortably cruise at 65 mph around 1800 rpm, instead of the 55 mph at 1800 rpm that I cruise at now.
