Diablosport Forums

Hello,

I am having a shop change my ring and pinion from 3.21 to 3.90. The question I have is this:

Since there is no adjustment in the programmer for gear ratio, do I just adjust tire size accordingly? I have used a gear ratio calculator and know that in order to fool the computer, I need to drop the tire size from 31 to 25.5 to achieve a correct speedometer reading after the gear swap.

I don't understand why the tuner does not have this parameter. Seems like kind of a lame work around to do the tire thing.

Am I missing something?

Thanks.

Sean

The gears do not affect the speedo, there is no need to adjust the ratios in the tune.

Ok, thanks a lot. Can you satisfy my inner gear head and explain this? I am not doubting you at all, I would just like to visualize how that works. If I changed to larger tires, I would need to calibrate for that wouldn't I? Isn't final drive final drive?

Thanks

Sean

Maybe I just answered my own question. Is the speed sensor in the hubs?

Yes, the speed is read from the abs rings, thus the gear ratio has no effect, just the tire height. Vettes work in this same way as well....

Thanks again.

the speed will remain the same but your shift points will probably be off a little bit now because the trans has it programmed to have 3.21s instead of 3.90s

do the 2004 rams work the same way cause i have thought of swapping gears. I thought the 04 works off the reluctor ring in the rear end. is this correct?