Shdwdrgn said:
I have HPTuners and have spent a lot of time fine-tuning my shift points... I'll have to go through all that again once the new gears are in, plus apparently getting the dealer to do a reprogram so my speedometer is corrected. I think I calculated my speedo is going to be off by 19% after the gear change. I'd love to learn more about tuning in HPT, but it seems like everything is this huge trade-secret that nobody is willing to discuss, so I have to just keep playing with different tables and see what affects they have.
Finding the G80 option took a bit more digging, but my 3.42's have the G80 and it handles well. I'm running 30.6" tires, and its just too much for these gears. Sometimes I can get up to around 18mpg on the highway, but I used to get 22. Its curious that you get better mileage at certain specific speeds... makes me think there's some kind of resonant harmonic where everything runs better, which in turn suggests that something is out of balance?
I did not think even the dealer could fix your speedo if before 2006.
There are a few guys on here that seem pretty knowledgeable on HPT, have you asked around here?
I think it has zero to do with balance. I think it has to do with the torque convertor being locked up and not popping in and out like it used to. I also think that it is my driving style and how everything fits together. I never use cruise control. Barely ever go more than 1/2 throttle and am good at coasting.
50 on country roads works better than 45 or 55. Everything just kinda clicks and it rolls along nicely.
65 on hilly highways seems to give good mpg and not too much shifting. even if 3rd is needed, it does not kill the mpg.
78 on the nice flat open highway and it sails along pretty good. Stays in lock-up and rpms are not too high but not too low that I do not have torque for the little grade changes.
Just my sweet spots I have found, but they can vary. Its a matter of knowing the truck. A simple change in weight of my tires changed things. Same height and basically same width, but new set-up is 20 lbs less per corner and I can honestly tell. Helps to run a chalk test and run the max PSI with flat pattern wear as well.