Tune with gears?

[Kyle2k]

So I have an automatic and I am aware that a tune is required for proper shifting if you change the rear gear ratio. However, I intend to get other things installed later this year and I was wondering if I can go without the tune if I keep it out of WOT for the time being? Thanks in advance!

[The Stig]

you have to get the speedo tuned after swapping gears. Totally different than the tranny tune

[Kyle2k]

Originally Posted by stieger

you have to get the speedo tuned after swapping gears. Totally different than the tranny tune

I could care less about the speedo, I swear I heard someone say the transmission needs to be tuned to shift properly on the auto though?

[klatterblast]

I think shift points , it will hit the rev limiter before it shifts I think. Not 100% sure though. You could tap shift and be good . Or just take it easy no full throttle shifts in D or S in the lower gears. Speedo will log more miles than it should.

[toml_pa]

Originally Posted by Kyle2k

I could care less about the speedo, I swear I heard someone say the transmission needs to be tuned to shift properly on the auto though?

If you don't change the gear ratio to match the gears in the calibration (tune), you will constantly get ABS brake related Diagnostic Trouble Codes (DCTs). This is because the computer constantly monitors each wheel's speed (RPM) and expects the reading to be within a certain range. The range it looks for is determined by several factors such as gear ratio, transmission gear, and engine RPM. If the programmed gear ratio is incorrect, wheel speed will be outside the range and you will get DCTs. The transmission control module also uses wheel speed along with other factors to determine when to shift into a lower or higher gear. If the wrong gear ratio is in the calibration, wheel speeds will be out of range and the transmission will not shift at the correct time. So you are correct that it will not shift properly. Personally, I would only drive the car from the gear shop to the tune shop to have the correct ratio put in. With the DCTs and screwed up shifting the car's driveability is going to suck. I would try to find a tuner who is willing to work with you. Explain your plans and see if you can work something out.

[IndeedSS1]

I wouldn't drive it until the transmission has been tuned to match the gears. Depending on how it reacts you could break hard parts. I had gears done on my Impala SS. For a very short period of time the tune wasn't exactly right and when it shifted it felt like I had dropped in a really big pothole. The speedo calculations were slighly off.

[swiftkart]

I hear the manual 6 spd doesn't need retuning, is that correct? Does it relearns after a gear swap on the manuals and corrects the speedo for you? Sorry to thread jack, but I'm thinking of changing the gear in my LS3 and was wondering the same thing.

[MA2010SS]

Originally Posted by swiftkart

I hear the manual 6 spd doesn't need retuning, is that correct? Does it relearns after a gear swap on the manuals and corrects the speedo for you? Sorry to thread jack, but I'm thinking of changing the gear in my LS3 and was wondering the same thing.

You will have to adjust the calibration in the tune for the gear swap, via HP Tuners, SCT, EFI Live etc

[Kyle2k]

Hrmmm, okay, because the tuner is about 200 miles away and I don't really want to spend an extra 400 for a programmer when I'm going to get an a custom dyno tune less than a week later, but I guess if I have to....

[swiftkart]

Originally Posted by MA2010SS

You will have to adjust the calibration in the tune for the gear swap, via HP Tuners, SCT, EFI Live etc

Thank you!

[tonetone]

Been considering a gear swap myself and had the same question.

LPE has a set of 3.91 gears and the product information section says:

"Manual transmission vehicles do not require ECM calibration changes to correct the speedometer. Automatic vehicles will require ECM calibration changes to correct the speedometer."

I'm no expert just pasted what's on the site

[MA2010SS]

Originally Posted by tonetone

Been considering a gear swap myself and had the same question.

LPE has a set of 3.91 gears and the product information section says:

"Manual transmission vehicles do not require ECM calibration changes to correct the speedometer. Automatic vehicles will require ECM calibration changes to correct the speedometer."

I'm no expert just pasted what's on the site

Any vehicle when you change the ring and pinion to a different ratio will throw the speedometer off regardless, olden days you would change the speedo gear in the trans, now you will have to adjust within the tune the calibration of the speedo via HPT, SCT, EFI Live etc, hope this helps