HPT and gear ratio discrepancy clarification?

[abc]

Working on a C5 vette and noticed original file has 3.42:1 gear ratio listed. I now for a fact the physical gear ratio is 3.15:1.
One of my questions is, do I leave what HPT has input in the file or should I correct it? Then if I correct it, what else needs corrected? If I leave it as is, as the vehicle functions as designed now, I assume I can go about my business with trans tune modifications, such as up and down shift speed/rpm changes?

[Gpreciado327]

https://youtu.be/g4J91nZFzuw?si=PXw31h6G99CLkCnv

This video explain a bit about the change process and what automatically changes when you do.

[Alvin]

Working on a C5 vette and noticed original file has 3.42:1 gear ratio listed. I now for a fact the physical gear ratio is 3.15:1.
One of my questions is, do I leave what HPT has input in the file or should I correct it? Then if I correct it, what else needs corrected? If I leave it as is, as the vehicle functions as designed now, I assume I can go about my business with trans tune modifications, such as up and down shift speed/rpm changes?

Rear end ratio doesn't really matter on C5's. The VSS is on the output of the rear end.

[abc]

Rear end ratio doesn't really matter on C5's. The VSS is on the output of the rear end.

I think I get what your saying and why but, when you input a different final drive ratio than what HPT has defaulted to it changes several other tables in the file. This leaves me wondering, what is the correct data/original data and/or what should it be?

I'm gonna watch the vid. now and see if there is any help there. Thanks for the vid. Gpreciado327.

[horsepowerguru427]

Basically, it scales some of the data for the trans and maybe other areas to compensate for the gear change, which will allow it drive and shift the same as it did before. Use the gear and tire wizard to change to your new ratio and then do your trans tuning like you normally would.

[abc]

I now understand how to use the HPT wizard but that's not my point. The point is, with the HPT default when reading the stock file is 3.42:1, do I assume the shift scaling is correct for the actual gear ratio in the car (3.15:1)? My confusion comes in when I change the gear ratio to the actual 3.15:1 the shift scaling also changes, which seems like the correct series of events, but why does it change if the actual, original gear set was 3.15:1?
Should I leave it as it was when the file was first read or input my actual gear ratio even though the physical gear set was not changed?

I have watched the vid. but it does not address this apparent bug in the software?