How do you build a fast truck?

When you find me a fast set of rears for these SQHP rockwells let me know, nothing faster than a 3.55 was ever produced for this housing, and even finding the parts to rebuild the current diffs to that ratio is almost impossible as the parts are considered obsolete and are not made anymore.

Let's not turn this thing into one setup it better than another, that is not what the guy asked.

 

The thing is Dave, is all the RTLO's are already turned around inside, they have a reverser in the shift tower on the right gate to give it a normal shift pattern. So someone would have to reengineer the back box to Direct/Over rather than the Under/Direct as they are now, in order to get any taller than the .73.

Good to see ya, around again!

 

Depends on the motor. The C13 ACERT in our T600 peaked at 1450rpm (403rwhp) and held within 5hp to 1600rpm then fell off.

 

If y'all ever had your trans out and checked the difference to turn the input shaft by hand in direct vs. OD you'd see why they say low ratio rears and stay in direct for MPG.

 

FWIW I used to think my little 359 is fast, will it do triple digits you bet dragging a loaded cattle pott if you want. How fast will it go I'm not sure hope it is never documented. My set up could use some improvement I am sure but it suits me. Gets close to 6 MPG which was my goal. To answer the thread title question horsepower to pull long legged gears is the key to a fast truck. Like I said I used to think mine is, till I seen a fast truck not in person but didn't have to to see when you kick a fast truck it gets to the triple digit mark lots quicker than mine.

 

I run east of I-35 so about the only example I can really share would be Monteagle, only a couple of miles. On 6% close to 80k I would probably be in high range, either 1H or 2L (7 or 8 counting from the bottom), somewhere around 30 mph. Once in a while I'll come up on slower company trucks and usually just drop another gear or two and follow. The extra minute or two to be gained by passing isn't worth over-stressing the truck to get around.

My truck isn't running any special tunes or modifications. It's stock. But comparing it against the one I traded (a fleet spec FL I'm certain had a leaky CAC making it worse), the main benefit to bigger power isn't being able to race up mountain grades. I'm sure there's many that can and will do that, but I'd venture not many. The bigger value is keeping more momentum on rolling terrain.

That tends to add to the illusion of a fast truck if you happen to be the guy in a 62 mph fleet rig and I pass you at the bottom of a little hill after coasting up to 75-80 on the way down. I'll still be back down to 60 or so and dropped a split by the top of the next rise but you're too far back to see that. And I'll still get 6.2 - 6.4 mpg doing it.