Trans won't shift into 3rd after VCM Cal.

[nitrousgp]

Alright, so I have the GM 3.29s gear set in my car and a stock diff. My VCM used to have the settings for 2.93 gears, and it didn't act irregular at all even though I was getting an Incorrect Gear Ratio code. So I edited my settings for 3.29s and now the trans won't shift into 3rd, OD, etc. 1st and 2nd are fine. Do I need to adjust my TCC settings? I have a 3750 stall.

TIA,

Gabe

[John_F]

Do your numbers look like these?
This is the only way I've been able to get the gearing changes to work properly and not throw the incorrect ratio code.

[nitrousgp]

John, aren't all those values (aside from calculated tire and gear) factory spec.?

Mine looks like this currently:

Tire size: 25.7
Calculated Gear: 3.29
Calculated Tire: 17.29

VSS Pulses per Mile: 23540
VSS Pulses per Rev - Trans: 9.1172

Final Drive Ratio: 1.000
Trans Revolutions/Mile: 3838.7693

Now that I look at it, I believe my calculated tire and trans rev/mile are way off.

[nitrousgp]

I used the formula (gear x 63360)/(3.142 x tire height) and got 2851.4978 as my new Trans Revolutions/Mile value. This seems a little better and it calculated my tire to be 25.71.

[John_F]

I used the stock tire size of 25.82 and 3.69 gear ratio (even though they're 3.29). This was the only way to get the speedo and HUD to show right and not throw the P0730 code. I've done this on 3 different cars with 3.29 gears and it works perfectly. One guy even had a GPS setup and it matched with what his car said.

[John_F]

even though I was getting an Incorrect Gear Ratio code. Gabe

How long were you driving around with the code on or disabled in your PCM?
If you just deleted the code and kept driving the car you may have damaged the channel plate gaskets. When the code is thrown it defaults to 100% line pressure all the time.

[nitrousgp]

Aright John, I just wrote the VCM with the same values in your screen and the car wasn't running right. It would shift too fast out a first and WOT downshifts never occured.

My question is, why the hell can we change gearing in the VCM if it's still going to throw codes?

[John_F]

Try loading stock shift mph and WOT shifts and see what happens.
As far as why it doesn't work right, who knows... I asked the same thing months ago and was told it would be looked into. Haven't heard anything though

[shor0814]

I know this is an old thread, but I am completely confused.

I thought the stock tire size was 26.6, not 25.7 so when I pull up a stock GTP file, I see 25.82.

I pulled the stock gearing for my GT, and this is what I get below,

I have an L67 swap, and need to know if this will work for the GTP's with 3.29's? I am asking because I am using a GTP binfile and need to put my GT trans/speedo settings back into the GTP bin.



Hope this helps someone, because it will help me in the end.