Hey fellas!

Im thinking about driving my truck out to work. It’s about 11 hours of 90-120 km/h the whole way.

I hate are running this thing over 90km/h it sounds so high in rpm (tach doesn’t work. Have no actual clue). But then again I’m a diesel noob. From what I know it sounds like diesels love to work and work and work so maybe this ain’t so bad.

I dono. What do you guys think? Anyone drivvvve their trucks or is this a bad idea.

 

I'd say a tentative yes, because I don't know much about your truck. Personally, I'd do it in my truck, but even with my overdrive I'd keep it below 65mph (105kph) mostly to be easier on the drivetrain, and to help fuel economy.

As to the rpm, via throttle it will not rev high enough to damage itself, as it is limited to 3200rpm. However, it can rev higher if going down a hill or something. Others on this forum might say that these motors are completely fine running for hours at high rpm, but I always feel like the motor is not having much fun going that fast. But I'm not the pro, and those guys might be completely true.

 

Not sure on year, gearing etc?

My 5-speed '93 with 4.10 gearing runs around 2500 at 75. It sounds a little fast, but I did that for about 9 hours straight one way, and a few days later another 9 hours back. It did just fine.
I think it would prefer an extra gear and get those RPMs down to about 2K, but it'll handle it fine.

 

Depends on the truck.
Mine did CA, NV and ID in one 12 hour run sitting on the overloads going 90ish for the majority of the run. Also moved 350 miles across the state going 95mph through snowstorms with everything I owned in the back. High RPMs the whole time, and topped off a lot of oil, but no problems otherwise.

 

She’s an 85 6.9 with a 4 speed. Far from a highway truck.

 

with that 4 speed, you will be limited to around 110-120 KPH top speed.
it will do it with no problem, but it will also sound like it is ready to blow up.

 

If it is well maintained I see no issuw with it. I have taken my van on multiple long trips and wouldnt hesitate to do it tomorrow. Currently has 240k miles.

 

Depends on the ratio in the pumpkin and tire size as well. With a 4 speed and 3.55s you can get up there, with 4.10s and stock tires you're really limited before you top out on RPMs.

Mine is an 86 6.9 NA with 4 speed, with 4.10s and had military 37" tires on it (that brought it back closer to stock 3.55 ratio). Even close to 3.55 it was screaming in the upper end of the RPMs, but EGTs held good.

 

agreed Taylor. not knowing rear gear ratio and tire size, it is a guessing game. that is why i said around 110-120 KPH top speed.

my 88 7.3 with 4.10 and 37 tires will top out at 129 KPH, or 80 MPH

 

I drove my truck from Springfield to OKC the day I bought it. I also took it down to Dallas one weekend when I was scrounging for parts. I keep it at 65 mph whenever I'm on the highway and it seems to do ok.

 

They will govenor out and you will be fine. I ran my old 91 at govenor lots. I told my machinist whe. He was doing my guides that seats didnt get hammered out because I always ran it at the govenor, it would pull till 3850 and just stop cold than.

 

I'd like to see that. Really goes to show just how durable these motors are.
For comparison, my truck has a zf5 and 3.55 rear and I cruise at 55mph at about 1600rpm. Nice and low. But one time going downhill I actually got it up to 85. But then I start to worry about exploding u-joints and stuff like that. Which brings up the point of if other parts of the truck are able to survive the stresses of high speeds. Just too keep in mind.

 

I can't speak for the mechanical condition for your truck, but I wouldn't hesitate to drive mine across the country right now.(After an oil change... it's about due. Lol) I routinely drive mine at 75+ mph (~125 kph). Admittedly, the 3.55's and 37" tires keep the rpms down around 2200 even at that speed.

 

What is the point of owning a vehicle if you ain't gunna drive it. My motto is: if I own it, it's going to get used. A lot.

With respect to your question, these engines can last long miles. I've driven my IDI to Prudhoe Bay, Newfoundland, Hudson Bay, Fort McMurray, Yellowknife, Los Angeles, Wisconsin, New England, Labrador, the southwest states, pretty much every single state and province. Every July, I put on 10,000-13,000 miles per roadtrip, usually lasting 2-3 weeks. Heck, I drove 2000 miles last August with my 6-year-old just to see an eclipse for fun. So 11 hours is nothing. Just keep the R's under 2100 and you'll be fine.

 

That, without an overdrive, is the challenge. Even with 3.55s, 2100 is barely 90 km/h. At 120, you're up in 2600 RPM territory. Engine will take it, but your sanity might not.....