For the first time since having the gears changed from 4.10 to 4.56, I drove the truck to work. That is my usual drive and the yardstick I use to measure all upgrades/modifications since I know exactly how my truck performs on that trip. It is mostly highway, with several small and moderate hills, and one very large hill.

When I had 4.10's and 33's, I could make it the entire way to work with only having to downshift on the one big hill. The rest of the trip I could easily maintain highway speeds with no change in speed on any of the other hills. When I changed to 35" tires (still 4.10 gears), even the small and moderate hills along the way required a downshift out of overdrive. On average, I would have to down shift out of OD about 5-6 times along the 16 mile drive to work in order to just maintain highway speeds (around 55-60 on that road). Now, with the 4.56's, I once again made it the entire way with only a downshift on the biggest hill. I noticed a slight bog on some of the moderate hills (loss of about 1-2 mph), but it wasn't enough that the trans felt it required a downshift, so I kept truckin along in OD. This is probably due to the extra weight and rolling resistance of the larger tires. I bet if I had a highway tread tire, even this slight bog would be gone.

Overall, I am very pleased. Just the fact that I can now maintain highway speeds without constatntly kicking in and out of OD for small and moderate hills makes me very happy. The truck defiently is getting more power to the ground with this new mechanical advantage. RPM's at speeds up to 70 are also very acceptable. I only went as high as 70 once and for just a brief second just to see. I'll have more rpm updates at speeds over 60, but not until I have broke in the gears completely. At 60 though, I was just about 2000 rpm in OD.

 

Hey Silver, let me know what you're RPM's are around 70 mph when you feel more comfortable pushing it. Is your speedo calibrated correctly ofr the 35's?

I'm running 265X70X16's and 4.10 gears in the back and I am running right around 2200rpm's which makes me think my speedo might be off a bit.

BTW, my SCT tuner arrived few days ago, and I can't get over the difference. This thing runs like a scalded ape!

 

Yup, my speedo is correct. I'll let you know.

That's good news about the SCT. What grade fuel are you having to run?

 

Sean from KRC put a 87 tune and a 93 tune on it. The 87 pulled harder than the 93 on my superchips. The 93 is insane. The only downer is I've gotten to the point where the mods to make real gains are going to start costing big $$$.

 

SCT tuner??? what is it?

 

Thanks guys for posting your RPM's at highway speeds.... now I don't have to start a new post or PM Silver asking him dumb questiosn again... lol

 

This is THE most annoying charateristic about my truck.... I really can't wait to get gears.

 

JUST A STUPID QUESTION ABOUT CHANGING GEARS. I WAS WONDERING BECAUSE I AMTHINKING OF CHANGING MY GEARS IN MY 2000 RAM 1500 SPORT,IF I CHANGE THE REAR GEARS THEN I ASSUME I HAVE TO CHANGE THE FRONT GEARS AS WELL SO THEY MATCH. ANY HELP WOULD BE GREATLY APPRECIATED. THANKS IN ADVANCE.

 

yup, need to change both...

 

Yep you need to change both unless you never ever put it in 4wd.