Gear Swap for 14 Sierra

CTHM732 · February 9, 2015

The thing is the 3.73 is tied to the NHT(max tow) option. Which I dont think there is a lot of them out there. My buddy actually dumped is 07 last year because it needed a whole new axle and rear end, I think he said it was about 4 grand fix to do so.

I was told by the salesman when I bought the truck that the 3.73's were rare in a 5.3. I actually purchased my truck in VA where it's definitely horse country and max tow is needed. Unfortunately, most are with the 6.2's. You are correct that the max tow is tied to 3.73. If they're making it they should provide the ability to place into another vehicle. They'd just rather you trade in and buy another one.

nards444 · February 9, 2015

I was told by the salesman when I bought the truck that the 3.73's were rare in a 5.3. I actually purchased my truck in VA where it's definitely horse country and max tow is needed. Unfortunately, most are with the 6.2's. You are correct that the max tow is tied to 3.73. If they're making it they should provide the ability to place into another vehicle. They'd just rather you trade in and buy another one.

I think with the NHT option there isnt a whole lot sitting on the lots, it has to be ordered, which I did that and it took 5 weeks to get it. I know your stuck in conundrum, but adding up pros and cons I think your best off living with it or trading in.

GRN69CHV · February 9, 2015

I was at the dealer this morning on another issue. Had it two for two very busy weeks, already put 1165 miles on it, all over the road miles. Passenger rear is sitting 1" higher than the driver rear. Front is equal height side to side, so truck is sitting twisted. While there we touched on the gearing. They have a large inventory with both 3.08's and 3.42's, with most being 3.42 gears. Told them I was very dissatisfied with the way it won't hold 6th gear or V4 mode at all. We're going to get past the twisted frame/suspension deal first, truck is scheduled to go in the shop for frame measurements Thursday morning. As an experiment, I've been running it around in M5 which just about duplicates a 3.73 in 6th gear with the exception of the V4 mode. Rural driving it's a lot more responsive, on the highway, while responsive, it's definitely harder on fuel. Considering I only plan to run stock tires and doubt I would ever tow anything over 5k-6k, 3.42's would be more than adequate to maybe address things. Was told if the frame is twisted, they'll replace the truck. Either way, doubt I'll do a 3.73 gear swap.

CTHM732 · February 10, 2015

Sorry to hear about the frame. I had that happen to me years ago with a Dodge pickup.

Have you thought about potentially tuning the truck? I've had mine at the dealer twice for recalls where reprogram was needed and I think things changed when they messed with computer too. I'm considering tuning mine to get better acceleration.

Big Whiskey · February 10, 2015

To the OP....it's probably not worth the cost of a gear swap. I looked into the same thing when I was unhappy with the performance of my '06 Silverado. It was going to be very expensive to have the dealer do it (so I could keep my warranty). I just lived with it as long as I could...didn't sink any more money into it...and traded it off after a couple years. I suggest you do the same. Getting a tune and driving in M5 at speeds under 60 mph may help make things more livable for you.

I was at the dealer this morning on another issue. Had it two for two very busy weeks, already put 1165 miles on it, all over the road miles. Passenger rear is sitting 1" higher than the driver rear. Front is equal height side to side, so truck is sitting twisted.

The last 5 GM trucks I've owned didn't sit completely even at each corner. Every one was different. Many guys call it the 'Chevy lean.' It's pretty common. I doubt it's the frame. Most likely the springs. Measure it with a full tank of gas or an empty one and it'll be different, haha.

GRN69CHV · February 13, 2015

We got the "lean" straightened out. Took it in, pass rear corner was sitting 1" high. Put the truck on the lift for about 2 hours while looking everything over and back and forth discussions with myself (I waited in the lounge area) that they couldn't find anything that looked damaged. Let it down - it was level. Took it out for a couple mile test drive, brought back inside the shop to remeasure, was still level. Only thing we could think is bushings might have been binding, thought was letting the suspension go to full extension may have let it settle.

Back to gear swap. For now, I'm doing nothing. Have been driving it in M5 which with the 3.08 gears it just a tad more gear than it would have with the 3.73 in 6th gear. Truck is a pleasure to drive like this. So, I think my next move is going to be either a tuner or the Range Technology V4 disabler plug-in. Leaning to the Range unit and see how the motor handles that deep overdrive in V8 mode.

John_chadra1 · February 16, 2015

I don't know if this really matters, but... my 2014 Sierra 6.2 has the 9.76 rear but has 3.42s in it. I could upgrade to the 3.73 that are put in the Max tow, but i'm waiting for someone to come out with 4.10s for it.

crafferty · February 16, 2015

I don't know if this really matters, but... my 2014 Sierra 6.2 has the 9.76 rear but has 3.42s in it. I could upgrade to the 3.73 that are put in the Max tow, but i'm waiting for someone to come out with 4.10s for it.

Call Yukon, I have seen several threads were people performed gear swaps.

GRN69CHV · February 16, 2015

I don't know if this really matters, but... my 2014 Sierra 6.2 has the 9.76 rear but has 3.42s in it. I could upgrade to the 3.73 that are put in the Max tow, but i'm waiting for someone to come out with 4.10s for it.

If you get a chance, is it possible for you to snap a picture of the diff cover and post it. As I understand it, AAM is producing the rear axles for these. They recently updated the site to list both the 12 bolt 9.5" and 12 bolt 9.76", only item listed is pinion seal (same part # for both 9.5 and 9.76). I've been told the 12 bolt 9.5 uses the 9.5 ring and pinion sets from the 14 bolt 9.5 but with a new housing. Tend to think little by little parts availability will start to get listed. One detail being overlooked is, you can almost guarantee that while the housing may have been redesigned, the internals (gears, carriers, axles, etc.) are carried over from the existing parts bins. I'd lay money on it, GM did not commission an entirely new setup for production of either 9.5" or 9.76" rear axle components. Might take some digging, but those parts are already out there.

John_chadra1 · February 16, 2015

Mine is identical to the 9.5, both 12 bolt.

http://eastcoastgearsupply.com/files/PDF%20Files/gm9-5-12-bolt.pdf

GRN69CHV · February 17, 2015

If you look at the pics, the ring gear surface on the Yukon case is noticeably lower than the stock G80 requiring either a thicker ring gear or a spacer. Is this from the thread where the guy went from 3.42's to 4.56's? If so that would explain a lot. 4.56's move down to a 9 tooth pinion, 4.88's go even further to a 8 tooth pinion. Not questioning what they did to get it in there, but in hindsight it might have made more sense to have milled the spacer .182" to keep the carrier centered as opposed to moving it off center .182" and incurring the related issues at the brakes. Also, thinner spacer (or preferably no spacer is a stronger install. Last thing you want to do is space the ring gear away from the carrier in a high load application which creates higher stress loads on the bolts. Doubt this would be the case if the swap was from 3.42 to an OEM (AAM) 3.73 or even a 4.10. As for the cover not fitting, yes correct. You can see the Yukon posi case is clearly wider than the stock G80 causing interference at the flat portion of the cover.

Clarken015 · May 15, 2015

Check this one out.

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

I still want to do it, being as the truck is lifted and has 35" tires on it, it is literally sluggish.

Now I did partially rectify that, I just had a Edelbrock Supercharger installed, I'm having it dyno'd on Tuesday 5/19/15, I'm hoping they can further tune it & get some serious horses & torque.

I'll post the results when I get them.

But 3.73's sure would be nice, I haven't tried the M for towing yet, but I may have too.

Clarken015 · May 19, 2015

I still want to do it, being as the truck is lifted and has 35" tires on it, it is literally sluggish.

Now I did partially rectify that, I just had a Edelbrock Supercharger installed, I'm having it dyno'd on Tuesday 5/19/15, I'm hoping they can further tune it & get some serious horses & torque.

I'll post the results when I get them.

But 3.73's sure would be nice, I haven't tried the M for towing yet, but I may have too.

Here's the RWHP Dyno sheet, 396 HP & 416 TQ! I'll take it, but I still want 3.73 gears!

Clarken015 · June 10, 2015

Update, I've not got the truck back as I'm adding some Hawk Brake pads & slotted rotors, but the truck now has 4.10 gears successfully installed & tested. Only thing left is to pick it up from Carlton Customs in Greenville SC. tomorrow. Then back to the Dyno/tuner to adjust for new gear ratio & speedometer correction!

Cliff14Denali · June 10, 2015

It looks like a complete 9.76" axle 3.73 geared rear goes for @$2000 and the fronts 3.73 another @2000. Right now I have the 9.76" axle 3.42's in my truck.....my idea would be this. If anyone would be interested in my complete 3.42's front and rear differentials for @$3000 I would venture to do the complete rear swaps. My truck has 12,000 miles on it and zero drivetrain issues.