Seriously, you live in Florida. Your most drastic elevation change is jumping a curb in the mall parking lot. Go pull grade with a loaded trailer and try to hold 85mph. Not happening.
Just trying to keep it real.

 

From what I understand with the whole 3.55 vs 4.10 discussion for towing is, it depends on what your best possible climbing speed will be assuming perfect gearing. Even assuming a perfect 100% efficient CVT transmission with The engine screaming at redline no matter what the speedometer shows, there is a limit to how fast the truck can climb any hill. This is where the limitation of the engine horse power comes in.

Generally, these trucks when not turbocharged tend to be in their butter zone when climbing steeper hills at 40-50 MPH dragging a decent load. Again, this won't apply to everyone, but as a general rule you won't find many hills in posted speed zones of 70+ MPH steeper than 5% and not many more than 10% in 55 MPH zones.

What can happen with 3.55 gears, is you get caught between gears of the transmission at that 40-50 MPH zone that the trucks were designed for. 4.10 gears pull well in 3rd at that speed (C6 trans), but 3.55 forces you do downshift or lug in 3rd. Trying to accelerate in 3rd to reach the higher Hp RPMs is futile because the truck simply doesn't have enough power to lift that much weight at that velocity and wind resistance increases too. 3.08s downshifted to 2nd gear (Again, with C6) is comparable to 4.10 gears in direct drive.

I confirmed this by driving my truck on the same 10% hill before and after the gear swap from 4.10 to 3.08 and the speed at the top of the hill was unchanged towing or empty.

Adding a turbo increases the power of the truck making the gear spread less important. But for N/A trucks the gaps between gears are what really hold you back more than the rear end ratio once you are rolling. These dead spots in operating range is what can give the impression of "lost power" for taller gears even though no change in horsepower has ever occured. Its simply harder to reach the same power you always had depending on where the gear spread powerband shows up for each gear - and where you actually want them to be.

 

wow david that is some interesting info on that! thanks a bunch! as for the climbing hills in florida, yeah bro hes got you there, go climb the hills in the rockies and then talk that 85mph noise hahaha, no serious, j/k lol

 

Even the hills around me aren't much to brag about. That 10% hill is the worst one I can find and its only about 200 meters long right at the steepest portion. Everything else on highway 19 is basically 5% and less but there is virtually no flat ground. I don't think I even took the truck over the alberni hump since the turbo was installed.

For a moment I had to think if I took it over the malahat, but then I remembered thats when I bought the saturn. *puts on guilty grin* LMAO, oh did we have fun on that trip. Took turns trying to kill the car and the truck was the chase vehicle. Oh deer, there are indeed laws against what we did that day......LMAO

Turns out a 100Hp satrun thats bone stock does move pretty well though.

 

If you took a 4.10 axle with a four speed, 3000 RPM in third gear would be 35 MPH.
Now put 3.55 gears in the same truck, 3150 in second would be about 35 MPH.

The advantage for the 4.10 axle, getting the load rolling from a dead stop.
The advantage for the 3.55 axle, you still have those upper gears for lower RPM's when the truck is empty and you are cruising.

Why do semi's have so many gears?
It gets the RPM drop between gears down to where the engine is still in the max torque band when you change gears up or down.

80,000 pounds up a 10% grade, with 13, 15 or 18 gears you have the perfect gear for the job in a semi.

 

yha,the largest hill we have in fl. is a bridge

 

Hills and mountains are very. Different things and I live in FL but it's not the only place I drive I was talking about just truck. No load

 

yeah,dont really have any reason right now to go out of state.
Dosent mean i never will !

 

Yeah I had that happen to me a while back up on the old mountain roads up north, the fastest I'd ever gotten the ole girl to go is like 75, with some coaxing. Then I tried to pass a Semi going that speed, laid off the throttle, and then floored it, hear a loud *** WHOOMP sound, and smelt diesel, and lots of it, looked in my rear view to a CLOUD of dark grey smoke, and it jumped up to about 80-85, and I blew past the semi. Never gotten her that high, with some coaxing, just seems it only works up north a bit, it was odd.

 

I went 80mph that one time because a guy on a motorcycle kept cutting me off and wouldn't allow me to merge into the exit lane on the highway. So I sped up to 60mph, he then got beside me just like the other three attempts, so I hit the brakes and as soon as he started to slow, I floored it. A gigantic tornado funnel of black gray smoke went directly from my tail pipe into his non-helmet wearing face. I thought he was going to wipe out. Next thing I knew I was going 80mph and getting off the highway.

 

Hills in Florida!

 

LOL, I got mine up to 85 back before the turbo or the E4OD. Took a while to get there but it would reach it eventually. With the 4.10 gears it would accelerate roughly at the same rate but simply hit a soft wall at 70-75 MPH (engine governor).

So far I think about 100 is the highest I've taken it. Does that sound about right for the speedometer needle being jambed against the trip meter reset button?

Seemed to take forever to get the speed back down. Only did that once and the current tires seem to shake a little at around 82.

 

ive had my speedo maxed before.... but that was when my speedo was 30mph off lol

 

These trucks are governed?

 

Engine governor...... ~3500RPM.