Swap rear 3.08 gears for 3.42

[HeidiHoe]

Hello all, I just picked up my PPV. It has smaller tires than the civilian models and I have a set of 275/55R20 michellin defenders to replace them. To keep the computer happy and maintain an accurate speedo I would need to change the 3.08 gears to 3.42. Question is should I purchased a new gear set and all the related bearings and seals or swap out the entire rear with a rear end from a wrecker yard?

 

[gooffeyguy]

What size tires are on it now? As long as the overall tire diameter stays pretty close you'll be ok.

As a cheaper alternative to a rear gear change, Just about any handheld tuning device (Diablo, etc) will allow you to input tire size so it will adjust the speedo and trans accordingly

Sent from my SM-G930V using Tapatalk

 

[OR VietVet]

Welcome to the forum from Oregon. What @gooffeyguy said about tire diameter and the reprogramming. If you choose the other way, a low mileage entire rear diff is pretty easy to swap out and bleed the brakes on.

What surprises me is that a PPV would have such a high 3.08 gear in it.

 

[iamdub]

What surprises me is that a PPV would have such a high 3.08 gear in it.

It's cuz of the 6L80.

 

[HeidiHoe]

What size tires are on it now? As long as the overall tire diameter stays pretty close you'll be ok.

As a cheaper alternative to a rear gear change, Just about any handheld tuning device (Diablo, etc) will allow you to input tire size so it will adjust the speedo and trans accordingly

Sent from my SM-G930V using Tapatalk

What size tires are on it now? As long as the overall tire diameter stays pretty close you'll be ok.

As a cheaper alternative to a rear gear change, Just about any handheld tuning device (Diablo, etc) will allow you to input tire size so it will adjust the speedo and trans accordingly

Sent from my SM-G930V using Tapatalk

The tires used by law enforcement people are winter rated uhp tires sized 265/60R17. Also, according to a large GM service center, the PPV tahoe's computer is locked and they can't make any changes so going the civilian tire size would through off the speedomter at the least. Swapping the gears and tires would match the original set up

 

[HeidiHoe]

It's cuz of the 6L80.

The 6L80 first gear is 4.03, combined with the rear gears of 3.08 and a relatively small tire makes for decent acceleration.

 

[gat0r]

i doubt the ECM is locked. that sounds lazy on that "service center's" part. more likely they dont want to figure out what all the upfitter may have done.

will be interested to hear update on that.




eta:
the mechanic & a serv writer at my dealer tried to tell me my ECM was locked b/c of callaway. they would have to mail ECM back & forth if anything was to be done to it.

that was all B.S., i have worked w/ Blackbear to tune mine. no issues.

 

[iamdub]

The 6L80 first gear is 4.03, combined with the rear gears of 3.08 and a relatively small tire makes for decent acceleration.

Right. That's what I was telling Ron in that reply. It can have such a high rear gear and not be a slug off the line because of the 6L80's low first and second gears. 3.42s would make it noticeably stronger off the line.

 

[gooffeyguy]

I think a Tech2 can change the tire sizes.

Maybe post this over in the PPV/SSV section and see what those who own these say.

Sent from my SM-G930V using Tapatalk

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics, please.

IMO, a tune would be the best option for you, and you will get the additional advantage of getting your TCM tuned for better transmission shifting performance.