Okay, I got a very good deal on a Hypertech and programmed it in this evening. I set it for 87 octane, stock top speed limiter, stock rev limit, stock shift points, increased shift firmness, and adjusted for tire size. The first thing I have noticed is that the throttle response from either gentle or quick acceleration is definitely smoother and quicker. No more flat spotor delay as you mash the pedal.
The online calculators I found for determining tire height do not match up to the height I got for mine by measuring the rolling circumference and dividing by Pi. I used the closest setting the programmer had tomy actual measurement for adjusting the tire size. Now here's a question for anybody who has the correct answer. Is there a chart/formula for determining the rpm's per mph based on tire height or circumference? The chart in the Hypertech manualis for a 30" tire height and my 235/70x15's came out to 27.25".
I know that the only way to tell what would be the best shift points would be to run it through the traps, but this truck will never set tire to a dragstrip. So that's my story and I'm sticking to it.

 

722 revolutions per mile per tire size calculator that swartlkk posted a while ago...

not sure if that's what you're looking for, but it shows 28" diameter for your 235/70's

 

No, that's the revs of the tire per mile. I'm talking about how many engine rpm's per mph based on tire height, but thanks.

 

That all depends on the gear you are in and the rear end ratio your truck has...

 

Exactly. That's the way the chart from Hypertech is broken down, but the tire height they use is 2.75" taller than mine. I don't know how much that would skew the figures they show.

 

The 4L60E has 1st through OD ratios of 3.06, 1.63, 1.0, and 0.7.

4.10 gears, your final drive ratios to the wheel are 12.55, 6.68, 4.1, & 2.87 1st through OD respectively.

3.73 gears, 11.41, 6.08, 3.73, & 2.61.

3.42 gears, 10.47, 5.57, 3.42, & 2.39.

3.08 gears, 9.42, 5.02, 3.08, & 2.16.

So from there, you would have to then convert the circumference of the tire in inches to miles and RPM to RPH (revs per hour), etc. Or just use the tires revs/mile (722 for 235/50R15) and back factor to the engine revs per mile. So in 3rd (1:1) and 3.73 gears, you are looking at 2693.0 revolutions per mile (722 tire revs per mile x 3.73 rev engine to 1 rev tire = 2693.0 engine revolutions per mile).

 

Ow! I'll have to work that out tomorrow. Thanks, Kyle.

 

I did notice, that with the Hypertech installed, it's a little easier to stall out the truck when in the low RPMs...

It takes more throttle to keep it above 600 when letting off the clutch, lol.

Other than that, though, she works good, mileage seems to be pretty good so far...

 

did u get a mpg gain

 

Not a problem withmy automatic.

No change (might be the right foot).