help confirm axle size and gearing options

FirstAscent · January 31, 2019

Hey everyone, coming from a Tundra I'm not familiar at all with the Silverado's, from what I've searched/read on here it sounds the the stock diffs are 9.5" (not the 9.76) for the 5.3L 8spd with 3.23, is that correct?

are these sizes the same as 2018's where as any gearing options available from previous gen would be available for the 2019's as well?

I've been looking into potential gearing options after I go to 35's but will wait until next week after they are installed to see if it warrants a regear, we'll see how the 8spd handles it and the affect on mpg.

For what it's worth I have the Silverado 1500 High Country with 5.3L V8 8spd and stock 3.23 gears.

Thanks everyone!

newdude · January 31, 2019

17 hours ago, FirstAscent said:

Hey everyone, coming from a Tundra I'm not familiar at all with the Silverado's, from what I've searched/read on here it sounds the the stock diffs are 9.5" (not the 9.76) for the 5.3L 8spd with 3.23, is that correct?

are these sizes the same as 2018's where as any gearing options available from previous gen would be available for the 2019's as well?

I've been looking into potential gearing options after I go to 35's but will wait until next week after they are installed to see if it warrants a regear, we'll see how the 8spd handles it and the affect on mpg.

For what it's worth I have the Silverado 1500 High Country with 5.3L V8 8spd and stock 3.23 gears.

Thanks everyone!

5.3 with the 8 speed gets 3.23 as the standard ratio, that is correct. 3.42 is the optional ratio, but is only available with NHT Max Trailer Package.

The diff sizes are the same as 2018, however I'm not 100% on if the gearsets interchange. I say this, because GM uses two manufacturers for the axles now, either in house GM, or AAM. Both also use two different fluids. The RPO build sheet can determine the source of the axles, both front and rear on these trucks.

Edited January 31, 2019 by newdude

L86 All Terrain · January 31, 2019

2019 High Country would have the 10 speed trans, even as a 5.3L right? Good call on waiting to install the 35's before deciding to re-gear. People are stuck in the mindset that they need to go from a 3.08 gear to a 4.10 or 4.56 gearset to turn larger tires like they had to with their old late 80's 3 and 4 speed transmissions (and 190hp engines). With more gears and shorter spreads, the effects will not be as drastic because the transmission takes care of the "dead spots" where your old truck's would just lay down on the converter and seemingly do nothing with larger tires. A 35 is a big tire, and it may warrant a re-gear, but you should only have to go up a size or two to get the effect your after. A 3.42 would probably be just about right. But like you said, put your tires on then decide.

OnTheReel · January 31, 2019

5.3 will have the 8 speed in the HC. 10 speed is exclusive to the diesel and the 6.2 regardless of trim level.

As as I understand it:

3.23 is 9.5” and could be made by AAM or GM.

3.42 is 9.76” and is AAM.

FirstAscent · January 31, 2019

12 minutes ago, L86 All Terrain said:

2019 High Country would have the 10 speed trans, even as a 5.3L right? Good call on waiting to install the 35's before deciding to re-gear. People are stuck in the mindset that they need to go from a 3.08 gear to a 4.10 or 4.56 gearset to turn larger tires like they had to with their old late 80's 3 and 4 speed transmissions (and 190hp engines). With more gears and shorter spreads, the effects will not be as drastic because the transmission takes care of the "dead spots" where your old truck's would just lay down on the converter and seemingly do nothing with larger tires. A 35 is a big tire, and it may warrant a re-gear, but you should only have to go up a size or two to get the effect your after. A 3.42 would probably be just about right. But like you said, put your tires on then decide.

Not necessarily. I have the High Country and it is 100% an 8spd 5.3L. And yeah for roughly $2k (parts/labor) to regear I'm definitely going to wait to see what I think after the 35's are on. The 8spd should definitely handle it better than a 6spd but I will definitely see how it feels and how much of an affect on mpg I lose.

3 hours ago, newdude said:

5.3 with the 8 speed gets 3.23 as the standard ratio, that is correct. 3.42 is the optional ratio, but is only available with NHT Max Trailer Package.

The diff sizes are the same as 2018, however I'm not 100% on if the gearsets interchange. I say this, because GM uses two manufacturers for the axles now, either in house GM, or AAM. Both also use two different fluids. The RPO build sheet can determine the source of the axles, both front and rear on these trucks.

Thanks for confirming. So the 2018's had the 9.5" diffs then right? I also don't have the RPO build sheet so I'll have to do some research on how I can track that down.

Edited January 31, 2019 by FirstAscent

newdude · January 31, 2019

31 minutes ago, FirstAscent said:

Thanks for confirming. So the 2018's had the 9.5" diffs then right? I also don't have the RPO build sheet so I'll have to do some research on how I can track that down.

2014-2018 they use the 9.5 for everything but max trailer, max trailer gets the 9.76. Same for 2019 T1.

Build label is in the driver door jamb, truck side of the jamb. Should be a QR code on a silver label. If you have a QR scanner on your phone, it should pull it up.

This is from the T1 quick reference sticky on here:

Quote

Front Axle Lubricant:

Supplier RPO code SU4 - 10-4091 / 19300457 High Efficiency 75W-85 (AAM)

Supplier RPO code SU5 - 10-4122 / 19368514 Dexron Low Viscosity 75W-85 (GM)

Rear Axle Lubricant:

8.6" axle - 10-4091 / 19300457 High Efficiency 75W-85 (AAM)

9.5", Ratio RPO GU5, Supplier RPO code SU7 - 10-4091 / 19300457 High Efficiency 75W-85 (AAM)

9.5", Ratio RPO GU5, Supplier RPO code SU8 - 10-4122 / 19368514 Dexron Low Viscosity 75W-85 (GM)

9.5", Ratio RPO GU6 - 10-4091 / 19300457 High Efficiency 75W-85 (AAM) - 6 speed trans ONLY.

9.76" rear axle - 10-4091 / 19300457 High Efficiency 75W-85 (AAM)

FirstAscent · January 31, 2019

13 minutes ago, newdude said:

2014-2018 they use the 9.5 for everything but max trailer, max trailer gets the 9.76. Same for 2019 T1.

Build label is in the driver door jamb, truck side of the jamb. Should be a QR code on a silver label. If you have a QR scanner on your phone, it should pull it up.

This is from the T1 quick reference sticky on here:

I see the QR code but every time I scan it (tried multiple apps) all it gave me was the VIN number and nothing else.

I just called the service department for the dealer I bought the truck at, they said they can print one off for me and "mail" it, she didn't know how to email it....really!? Luckily they aren't too far from me so I might just go pick that up, just annoying they can't figure out how to email a document haha

FirstAscent · February 1, 2019

So I ended up just driving by the dealer really quick and they print off 5 pages of codes for me

SU5 - AXLE FRT

SU8 - AXLE RR

Your above post is in reference to lubricant but does the GM notation mean that these are the GM axles and therefore probably not the same as last years gears so not compatible?

OnTheReel · February 1, 2019

The codes you have are for the new GM axles. SU4 and SU7 are the AAM. I would have to assume everything is different between them.

FirstAscent · February 1, 2019

22 minutes ago, OnTheReel said:

The codes you have are for the new GM axles. SU4 and SU7 are the AAM. I would have to assume everything is different between them.

Darn, I was afraid of that. But at least now I know all the options my truck has haha!

newdude · February 1, 2019

3 hours ago, FirstAscent said:

So I ended up just driving by the dealer really quick and they print off 5 pages of codes for me

SU5 - AXLE FRT

SU8 - AXLE RR

Your above post is in reference to lubricant but does the GM notation mean that these are the GM axles and therefore probably not the same as last years gears so not compatible?

Let me do a bit of digging and I'll see what I can find out.

newdude · February 1, 2019

So going by the numbers, the GM in house and AAM call for different gear set part kit #s. I don't have much more than that unfortunately, so there seems to be some sort of difference, but I'm not sure what.

Some of the seals and stuff though are the same however...

Edited February 1, 2019 by newdude

FirstAscent · February 1, 2019

3 hours ago, newdude said:

So going by the numbers, the GM in house and AAM call for different gear set part kit #s. I don't have much more than that unfortunately, so there seems to be some sort of difference, but I'm not sure what.

Some of the seals and stuff though are the same however...

Thanks for looking into it and trying to gather some info! I really appreciate it. It's hard to believe they'd use a different gear set even with different axles, solely from a cost perspective. I could see something minor being different like a seal or something but the main component (gears) I'd imagine were the same.

However, that is just my guess, you never know what GM was thinking when they designed it using two different manufacturers haha. I'll continue to do some research.

OnTheReel · February 2, 2019

It certainly sounds like the GM axles are somewhat of a clean-sheet design. They are on restriction from GM so if there’s even so much as a leak at the pinion seal they are replacing the whole rear end and taking the old one to do analysis. I can’t imagine them doing that if it was just a carbon copy of the AAM but who knows. I’m sure there’s a reason for everything...