Gear Swap for 14 Sierra

[CTHM732]

I'll make this quick. I have a 14 Sierra 5.3 4x4 with 3.08's. I want to upgrade and do a swap to 3.73. I have been to 3 GMC dealerships, 2 in VA and 1 in GA and they have no idea how this can be accomplished. I've gotten excuse after excuse and no call back. I've even contacted the GMC 800 number to put a request in for them to contact dealer, which they do but the dealer won't follow up. I want a dealer to do it so I do not lose my factory powertrain warranty.

 

Has ANYONE here done the swap from 3.08/3.42 to 3.73 on either their Silverado or Sierra? If you have gone through this please contact me or post info in this thread. Thanks in advance.

[Yamiryder]

Yes, i've seen a couple threads where guys used gears for 07-13 trucks. Do a quick search, i don't remember if an aftermarket company is making gears for the 14+ trucks yet or not. It has been done though. Make sure you get quality gears.

 

Edit: I believe the front diffs are the same, rear axle is slightly different than 07-13 though. I THINK.

[Btuggle88]

Check this one out.

 

http://www.gm-trucks.com/forums/topic/168704-new-here-in-sc-2015-gear-swap-question/

[CTHM732]

Thanks for posting. Looks like I'm not alone. I have a feeling it's GM not wanting to offer the option of the swap. With computers running everything now I think it's handcuffing getting it done. Not to mention they'd just rather sell you another truck with what you're looking for.

[redwngr]

IIRC, the NHT 5.3 (3.73's) also come with the larger (9.76") diameter diff?

 

You'd have to change the entire axle.

[CTHM732]

IIRC, the NHT 5.3 (3.73's) also come with the larger (9.76") diameter diff?

 

You'd have to change the entire axle.

I've been told that the axles would indeed need to be replaced. I just can't get anyone to put it all together and say they can do it.

[TJay74]

You problem is not going to be the mechanicals of the swap, it will be the computer side. The dealers have no way to reprogram the ECM/TCM for the changes. They can only program those computers with what the factory calibration was for your VIN. Until GM lifts that restriction you will be stuck unless you are ok with custom tuning your ECM/TCM.

[GRN69CHV]

Just bought a 2015 Silverado DC 4x4. 5.3L with 3.08 gears. Having done a lot of gear swaps over the years it's still just a basic hand tools process. . Swapping the gears out is not that difficult of a job. I've done both GM 12 bolt and 10 bolt rears in my garage in 3-4 hours start to finish. Hardest part of the entire deal is setting the pinion depth correct and having to pull/press the pinion bearing. Typically with a new ring and pinion purchase/install I don't reuse the existing pinion bearing and just buy 2 new bearings. One gets hollowed out to allow it to slip on/off to set the depth, the other gets pressed on the pinion for permanent install once the depth is set. Backlash is set via side shims on the carrier. Two mods I always make to strengthen the rear are #1:install carrier studs instead of the bolts, #2: set up the pinion bearing preload using a solid spacer instead of the crush sleeve. Last rear I did was the 12 bolt in my Chevelle that had a 540" big block pushing right around 700 HP. Beat on it real hard at the track with plenty of street driving mixed in, never any fear of failure. For gears I've used Richmond, US Gear and Motive gears all with good luck. Never tired Yukon gear sets but heard good things about them also. I usually purchase my gear sets/parts from either Randy's Ring and Pinion or Tom's Differentials.

 

Back to the 3.08 gears. Comparing the 6L80 trans to the 4L80 , with 6L80E and 3.08 gear you would need to run a 4L80 with a 4.88 rear in 1st-3rd to get the same bottum end. I've found the truck to be very responsive and rather fuel efficient running it down the road in 4th which nets a 3.55 gear equivalent.

[gSwift]

^^Thats one hell of a first post.

[txchevy4ever]

Has 3.73 in my Tahoe and now have 3.08's in my 2015 Silverado LTZ Z71 4x4... Virtually no difference pep wise, and the gas mileage is so much better.... not apples to apples, but my take anyway.

[CTHM732]

Has 3.73 in my Tahoe and now have 3.08's in my 2015 Silverado LTZ Z71 4x4... Virtually no difference pep wise, and the gas mileage is so much better.... not apples to apples, but my take anyway.

I would think that the acceleration would be better with the 3.73. What year is the Tahoe?

[txchevy4ever]

I would think that the acceleration would be better with the 3.73. What year is the Tahoe?

I'm not saying it was not better, just that it isn't noticeable. 2006 Tahoe.

[nards444]

I've been told that the axles would indeed need to be replaced. I just can't get anyone to put it all together and say they can do it.

from what I know the 3.73 axle is different than the other gear ratios. A whole axles with gears, with install is going to run you lots of money, my guess close to 5 grand, plus you run into warranty issues. My advice trade the truck in and take a loss vs doing that.

[CTHM732]

from what I know the 3.73 axle is different than the other gear ratios. A whole axles with gears, with install is going to run you lots of money, my guess close to 5 grand, plus you run into warranty issues. My advice trade the truck in and take a loss vs doing that.

Warranty is an issue now. Even if the work is done at a dealership they will not warranty the power train if something happens. I'm going to admit, it's disappointing to know that with this new technology it's actually handcuffing the customer in what they can do with the vehicle. If it's GM parts and installed by an authorized GM dealer it shouldn't lose its warranty. Otherwise, why go to them? The only thing you need is the computer programming software which is where they get you. Like I said, not happy about that.

[nards444]

Warranty is an issue now. Even if the work is done at a dealership they will not warranty the power train if something happens. I'm going to admit, it's disappointing to know that with this new technology it's actually handcuffing the customer in what they can do with the vehicle. If it's GM parts and installed by an authorized GM dealer it shouldn't lose its warranty. Otherwise, why go to them? The only thing you need is the computer programming software which is where they get you. Like I said, not happy about that.

I agree and yeah this change would alter the warranty. Im with you, but at the same token I can almost see where the manufacture comes from as well. I can see from a business view, they probably dont want to get into the business of swapping parts and then warrantying them, if you think about it, it starts a long chain of things they probably do not want. Plus if you alter it, arent you altering it but yet the VIN doesnt reflect that change.