Gear Swap In 2009 Sierra With Traction Control

[clintg]

I have a 2009 Sierra 2x4 that came with 4.8L V8 and 3.23 gears. When I bought it, I didn't have any towing requirements, but now that I have a travel trailer, the 4700lbs towing capacity is insufficient. Even when within all the weight restrictions, the truck just can't handle the tow.

 

So I ordered a new set of 3.73 Yukon gears for the truck, and then started to look into what it will take to get them installed. As it turns out, the actual install is quite inexpensive. The computer programming on the other hand is turning out to be the issue. The reason I chose the 3.73 gears is that they were a selectable option when building my truck online and it is listed as an option in the user manual.

I know that I have to update the computer with the new gear ratio, or else I will have a traction control light on. I found some scan tools that can make this change, but was told by the service advisor that they will void the entire warranty on the vehicle. If GM is able to change the gear ration (with a new VCI number?) then the warranty for the vehicle will stay valid, just the rear end warranty will be void (This is fine since Yukon gear is warrantied for life).

The service rep is going to check with Techlink to see if they can issue a new VCI number for me.

My questions are:

- What should I expect from Techlink/the dealer?

- Is this standard procedure for GM?

- Is there any reason that they would not issue a VCI?

- If they do say it's not possible, is there anything I can say to encourage them to look into it further (I have a history of being told possible mods are impossible)?

- How much does this usually cost?

- Should I have them re-program the module before changing the gears to make sure they can actually do it?

- Is there anything else I should be concerned about with this mod?

When I started looking into this mod, the service rep told me to just sell & buy a new truck, I'm starting to think this might have been easier.

Thank you.

[Stevens03]

Thats nuts.... A gear swap isn't difficult. The dealership should be able to program the gears easy enough since it's a gear ratio GM offers. Most places only charge around $500 to do a gear swap and you'll have no more than 1 hour labor from the dealership.

 

If they can't do the reprogram, it's because they don't have a tech that knows how.

[Zembonez]

I went from 3.23 gears to 3.73 gears without ANY reprogramming and all went perfectly well. I did then go with a Black Bear tune and at that time corrected my speedo calibration. Everything else has been 100% fine. The truck does not "know" you changed the gears...

[clintg]

I went from 3.23 gears to 3.73 gears without ANY reprogramming and all went perfectly well. I did then go with a Black Bear tune and at that time corrected my speedo calibration. Everything else has been 100% fine. The truck does not "know" you changed the gears...

 

 

that would be great if i didn't have to deal with reprogramming. From what I read, the traction control system will throw some codes if the truck is not reprogrammed. Does your truck have traction control?

[Zembonez]

I went from 3.23 gears to 3.73 gears without ANY reprogramming and all went perfectly well. I did then go with a Black Bear tune and at that time corrected my speedo calibration. Everything else has been 100% fine. The truck does not "know" you changed the gears...

 

 

that would be great if i didn't have to deal with reprogramming. From what I read, the traction control system will throw some codes if the truck is not reprogrammed. Does your truck have traction control?

 

I do not have traction control. I see the point there. The control module will "see" a difference in RPM vs Speed. and trigger a light.

 

Fire an email to Justin at Bleck Bear and I bet he has an answer.

[J-man67]

I would of went with 4.10's personally. Anyway, BlackBear Perfomance can tune the truck for new gears. Also, for dealer worries, purchase a new pcm/tcm combo to swap back into the truck during warranty work.