Just purchased (2) 1999 f800 crew cab box trucks that have the 5.9 cummins 24v engine. Drove them home 700 miles threw the mountains. These things need more power. Holding 60 mph on flat ground empty is a struggle with both. 30-45 mph in the mountains. I know there must be programmers for these trucks somewhere but all I was able to find was stuff for the dodge pickup. Need these trucks to haul about 8-10k lbs of equipment and tools for work @ 70 mph.

 

Try fuel filters to start.

We have these at work, and compared to the earlier motors, they are noticeably more powerful.

What transmissions?

Having said that, they will struggle on hills, but should run up to 70 on the flat all day long.

 

Before I left town I had everything changed on the trucks including the filter.

 

As for the trans they are autos unfortunately. Guessing they are Allison's. Both shift threw all the gears just fine. One has 109,000 the other 123,000 miles. Funny thing is their vin numbers are only 2 digits apart.

 

Not sure how the "99"s are setup, but my "96" had the boost hose worn through. My truck also has a racor filter and the pump was bad and sucking air through it also.

Since both trucks are running the same, I would guess both are fine.
My "05" was an auto duramax and weighed 8k lbs and ran very good. It would run 85 mph weighing 26k easily.
My "96" f800 is also a auto, 8.3 cummins and weighs 13,5k and now it runs pretty good. It will run 67 mph downhill weighing 13,5k. Just the governor shutting it down.

We have become use too more power, smoother shifting, better ride quality, quieter cabs and more power. These older, heavier, less technological nightmares do take some getting used to.

 

You sure those aren't 12 valve motors? We have those also, and with a 4 speed auto they are really slow. They will run over 60 on the flat, it just takes some time......

 

Nope. Definatly 24v motors. Looks identical to my uncles 24v in his 01 dodge pickup. The 12v has the individual looking rocker covers the 24v has 1 big valve cover. Plus 24v came out in 98.8. These trucks are 99's.

 

Fairly cheap add on is RV275 injectors. I believe there's one place out there with a programmer that will work on a non-Dodge ISB....I just cant remember the brand.

 

On the flat are you power limited or gear bound?

Cheap medium duty trucks are likely spec'd to max out at 62 mph on the governor. Most commercial outfits don't want the liability of a 20000 lb truck going 70 with a minimum wage driver. If it isn't gear bound, it may have road speed limiting programmed in.

Have you talked to a Cummins dealer to see what you have? They can shut off the road speed limiting feature (if you have it) to allow operation at normal governed speed in high gear, or can program in a higher (EPA certified) power rating if the engine and drivetrain components allow it.

The transmission torque capacity may be an issue for increasing power, though.

 

The trucks governor is set at 77. I know this from going downhill and then staying on a flat for a bit they will hold that speed for a few miles. So they are power limited.

 

I drove a 2000 5.9 f650 i could have swore it was a 12v. It have a 7 sp spicer and 4.56's I believe. Would do 80 no problem. Could even get it up to 75 pulling a john deere 310D backoe on a 12k lb tripple axel trailer. But man that thing was a dog. Pedal to the metal all the time even unloaded lol