Hi Everyone,
I have changed the drive/driven gears inside the transmission of my 2008 Impala, 4T65E. Will I need to change anything in the tune file to accommodate this change?
Printable View
Hi Everyone,
I have changed the drive/driven gears inside the transmission of my 2008 Impala, 4T65E. Will I need to change anything in the tune file to accommodate this change?
Yes. You will need to change it in Transmission>General>Gear Ratios. You would need to change the gear ratio's in BlueCat if you intend to use that as a trans tool.Quote:
Originally Posted by Trevyr2041
Thank you for your reply. I am not familiar with BlueCat? I have HP Tuners MPVI3. I do want to note that this is a racing application so I don't really care if the speedo is off....
How do I figure out the correct gear ratios to input? I installed a 33T drive gear and a 37T driven gear with a 3.29 differential. The gears I took out were 35drive, 35 driven.
Driven/Drive=ratio
37/33=1.1212...
So your ratio is 1.12
Easy way to get it in your head is if the drive is smaller than you go slower. If you go slower your numbers get higher.
If you are in 3rd gear, straight through, no multiplication than the engine will turn 1.12 turns every time the driveshaft only turns once.
Inputs.
4T65e gear ratios are
rev gear 2.38:1
1rst gear 2.96:1
2nd gear 1.63:1
3rd gear 1.00:1
4rth gear 0.68:1
New Gear ratios
rev gear 2.38:1 * 1.21 new ratio 2.66:1
1rst gear 2.96:1 * 1.21 new ratio 3.3152:1
2nd gear 1.63:1 * 1.21 new ratio 1.825:1
3rd gear 1.00:1 * 1.21 new ratio 1.12:1
4rth gear 0.68:1 * 1.21 new ratio 0.7616:1
Easy peezy. :)
@TheMechanic, thank you for the explanation! My drive gear is 33T and the driven gear is the 37T so my ratio is .892, but I get the point. I changed the ratio in the tire/gear wizard to .892 and it changed my shift schedules. Which method is preferred?
Forgot to add. So you can get a feel for what it will be like.
Diff gearing
3.23 diff gears would appear to change to 3.90's
3.73 diff gears would appear to change to 4.51's
I have a 3.29 diff. Do you recommend the tire/gear wizard method or changing the gear ratio method?
You can't fix it with the tire gear wizard because you didn't change the differential/final gearing.Quote:
Originally Posted by Trevyr2041
It can only be accomplished at the Transmission>General>Gear Ratios. You will need to input them all with the math I provided you. You didn't post the tune so I can't help you with that.
As to the tire and gear wizard, since it is a transverse the only thing you could reasonably do is change tire size.
Awesome, thank you for your help!