Will I need a new tune??

[88Racing]

Originally Posted by JackandJanet

Lars, I went back and changed my mind. See what I added. And, I think the latter part is more correct. I think this is why he has no speed correction capability with this unit.

- Jack

Oh
So a new gear requires a new speedometer gear to compensate for them?
97xl will have to look for a speedometer gear correction kit.

Lars

[Jackpine]

Originally Posted by 88Racing

Oh
So a new gear requires a new speedometer gear to compensate for them?
97xl will have to look for a speedometer gear correction kit.

Lars

Yup! I think that is the RIGHT approach. I vaguely remember reading something about this in the not so distant past, when my brain cells were more active. And, I'd think this would be a trivial addition to a gear mod, wouldn't you? I'd be surprised if the installers of the gears, didn't include it in the work order.

- Jack

[88Racing]

Originally Posted by JackandJanet

Yup! I think that is the RIGHT approach. I vaguely remember reading something about this in the not so distant past, when my brain cells were more active. And, I'd think this would be a trivial addition to a gear mod, wouldn't you? I'd be surprised if the installers of the gears, didn't include it in the work order.

- Jack

They must have let it slip their minds also?
Good catch

Lars

[97xl]

I know I can't adjust the speedo with the programmer, needs to be done by swapping out the VSS gear. Just wondering if I'll need a new tune to make the shift points correct. Last thing I wanna do is go messing with the shifts in the programmer and make things worse. It should be liveable until I can get new tunes. Right now the speedo gear is set for stock tire size of 235/70r16 and since my winters are 255 and summers are 265 it was already off to begin with but that didn't seem to make a difference with the tune(when I had the tune made I put 255s as the tire size on Troyers order form.) Guess I'll just wait till PHP is open again and find out the details.

Thanks for the info.

[Jackpine]

Originally Posted by 97xl

I know I can't adjust the speedo with the programmer, needs to be done by swapping out the VSS gear. Just wondering if I'll need a new tune to make the shift points correct. Last thing I wanna do is go messing with the shifts in the programmer and make things worse. It should be liveable until I can get new tunes. Right now the speedo gear is set for stock tire size of 235/70r16 and since my winters are 255 and summers are 265 it was already off to begin with but that didn't seem to make a difference with the tune(when I had the tune made I put 255s as the tire size on Troyers order form.) Guess I'll just wait till PHP is open again and find out the details.

Thanks for the info.

Thanks for reminding me of the name. If the VSS gear makes your speed correct, then the shift points should also be correct. I'd say install a VSS, with the new gears, that matches the tires you use most of the time and live with the slight error that will be present with the others. Looks to me like you'll have only a 2% error between the 255s and the 265s.

- Jack

[97xl]

Ok just so I have things clear in my head...the shift points are controlled by the speedo...the VSS gear in the truck right now is the stock one so I know the speedo is off but if I change the VSS to match say my 265s that will correct the speedo error and since the shift points are based on the speedo then the truck should shift at the proper point without having to modify the tune??

[Jackpine]

Originally Posted by 97xl

Ok just so I have things clear in my head...the shift points are controlled by the speedo...the VSS gear in the truck right now is the stock one so I know the speedo is off but if I change the VSS to match say my 265s that will correct the speedo error and since the shift points are based on the speedo then the truck should shift at the proper point without having to modify the tune??

Yes, almost. The part throttle shift points are controlled by speed AND throttle position. At a fairly open throttle, the shift is delayed to a higher speed, and vice versa. But yes, having the correct VSS for the tires AND gears will make the shifts occur where they should.

- Jack