Jump to content

Gear swap from 3.08's

CenTex5.3

By CenTex5.3
in Engines & Drivetrain

Recommended Posts

CenTex5.3 Enthusiast

CenTex5.3

Posted
Posted

So I got blessed with the 3.08 rear axle in my truck. I did a quick search and didn't find what I was looking for so, has anyone had experience going from 3.08 to 3.42 or 3.73's in our 14-15 trucks.

 

I'm wondering how much mpg variance there is between the two. I average 13mpg on E85 and 16-17mpg on 87, and about 20mpg on 87 on the highway.

 

 

Any input?

07Softail Senior Enthusiast

07Softail

Posted
Posted

If going from 3.08 to 3.42 you will have to change carriers and there are no 3.73's available for the 9.5's unless you go with a conversion hack job which uses old style 14 bolt carrier and ring and pinion set. Or do what I did and get a whole 9.76 axle with the 3.73's in it.

 

RT

Dan1220 Enthusiast

Dan1220

Posted
Posted

Check out east coast gear supply. They have everything you need and they sell kits specifically for our trucks.

 

Many will tell you to go to 4.10 if you're spending the money to do it.

 

I am in the same boat with 3.08s. I am not ready to put an aftermarket tune in the truck though, due to warranty concerns

LongrangeLauber Senior Enthusiast

LongrangeLauber

Posted
Posted

hmm, good to know. I searched complete rear axles and they aren't cheap. I have a set of gears out of an 04, but don't think they're interchangeable

 

So I was looking at these http://www.summitracing.com/parts/mgr-gm9-5-342/overview/. those won't go in without changing parts other than the install kit?

Correct, they are for the 14 bolt. I did a write up about a year ago regarding regearing these new trucks. Nothing available for the 9.76" rear, and the 9.5" uses the older style 14 bolt gears and you have to get a new carrier, yoke, seal, bearing kit, etc in order to get steeper gears in these new rear ends.

 

I wish Yukon would just step up and make a direct replacement ring and pinion set for these trucks. A lot of people are lifting them so then they join a forum such as this one and start looking around for other mods and want to do a regear eventually. It only makes sense IMO

silveradosid Senior Enthusiast

silveradosid

Posted
Posted

i looked at gm parts, if you want 3.42 it is a 1000 bucks for crown and pinion for front and back. i am thinking of this because i have 3.08's. just waiting to hear from dealership if it would void the warranty if i do this my self

TJay74 Senior Enthusiast

TJay74

Posted
Posted

Make sure to account for a custom ECM/TCM flash as well, speedo will be a ways off which will throw the shifting off as well since it is based on rpm's and speed to determine the shift points.

CenTex5.3 Enthusiast

CenTex5.3

Posted
  • Author
Posted

Check out east coast gear supply. They have everything you need and they sell kits specifically for our trucks.

 

Many will tell you to go to 4.10 if you're spending the money to do it.

 

I am in the same boat with 3.08s. I am not ready to put an aftermarket tune in the truck though, due to warranty concerns

4.10 will be too much gear, I just want that little extra uumph at the drag strip and city driving. I'll reprogram with the Tech2 so warranty shouldn't be an issue, except for the gears themselves.

Correct, they are for the 14 bolt. I did a write up about a year ago regarding regearing these new trucks. Nothing available for the 9.76" rear, and the 9.5" uses the older style 14 bolt gears and you have to get a new carrier, yoke, seal, bearing kit, etc in order to get steeper gears in these new rear ends.

 

I wish Yukon would just step up and make a direct replacement ring and pinion set for these trucks. A lot of people are lifting them so then they join a forum such as this one and start looking around for other mods and want to do a regear eventually. It only makes sense IMO

Thanks for the info, do you have a link to the writeup? I didn't find it in a search.

 

 

So does anyone have a link to the carrier we need to go at least 3.42s? I've looked at several sites and they don't show anything on it.

07Softail Senior Enthusiast

07Softail

Posted
Posted

Go to the AAM website they have an exploded view of the axle assembly with GM Part numbers. FWIW the only difference in the 9.5 and the 9.76 is the pinion bearings are larger on the 9.76 that's it all of the other parts have the same exact part numbers.

 

RT

CenTex5.3 Enthusiast

CenTex5.3

Posted
  • Author
Posted

Could you elaborate on the tech2 and not voiding the warranty? What is it?

It's the factory scan tool. My shop has one, and a friend of mine is a tech at GM and told me that it's capable of reflashing the ECM to change the gear ratio to 3.42 or 3.73. I'll know for sure when the time comes though.

Go to the AAM website they have an exploded view of the axle assembly with GM Part numbers. FWIW the only difference in the 9.5 and the 9.76 is the pinion bearings are larger on the 9.76 that's it all of the other parts have the same exact part numbers.

 

RT

Ok I gotcha, I need the carrier from a 9.76 to get the steeper gear.

07Softail Senior Enthusiast

07Softail

Posted
Posted

The carriers are the same part number based on the break of the gear ratio 3.08 are different. 3.23-3.73 are the same part number carrier both 9.5 or 9.76

 

RT

CenTex5.3 Enthusiast

CenTex5.3

Posted
  • Author
Posted

The carriers are the same part number based on the break of the gear ratio 3.08 are different. 3.23-3.73 are the same part number carrier both 9.5 or 9.76

 

RT

 

Thanks for the info in this post, I think I found what I need thanks to you.

TJay74 Senior Enthusiast

TJay74

Posted
Posted

It's the factory scan tool. My shop has one, and a friend of mine is a tech at GM and told me that it's capable of reflashing the ECM to change the gear ratio to 3.42 or 3.73. I'll know for sure when the time comes though.

 

 

Your buddy is wrong on this part, the K2xx trucks don't use the Tech II to flash the modules, they are done via a laptop by connecting to the GM global system. That system uses your VIN to find the calibration for the modules in your truck, it will only flash the modules with the current programming GM has on file for your VIN for those modules. The dealer can no longer make changes to gear ratios or tire sizes anymore, that loop hole was closed out when the 2014 (K2xx) trucks came on line.

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • PhilB
      No 12v outlets in 2026 gmc Sierra

      By PhilB · Posted

      It is possible to add your own 12v outlet to your truck.  Check out this video:   I verified via GM Upfitters that pin 31 is the same on the 1500 trucks.  The wire is GM part number 84779405.   You can get the GM 12v outlet from Amazon  https://www.amazon.com/Genuine-Accessory-Receptacle-25774623-13549530/dp/B0F1H9YRGF EWAY 12 Volt Power Adapter for GM   https://www.amazon.com/EWAY-Chevrolet-Silverado-Cigarette-Ignition/dp/B0915RRW6Q/ref=sr_1_1?   I just haven't figured out a good place to put the 12v outlet in my truck.   Some people are getting USB-C to 12V adapters  https://www.amazon.com/WYMECT-Cigarette-Lighter-Socket-Adapter/dp/B0F87WNQKB/ref=sr_1_1_sspa? Not sure if they provide the correct amperage that a device like a tire inflator would need.  
    • Core-Lokt
      Wiring Help, Please

      By Core-Lokt · Posted

      Thanks; I looked there a few minutes, and I think I can find something. I really never looked there, as I thought it was stuff like PTO/aftermarket bodies/accessories like snow plows.
    • newdude
      2 speed transfer case optional now?

      By newdude · Posted

      This is a 1/2 ton thing ONLY.  All HDs 2020-2026 have the two speed transfer case, with Autotrac as an option.     1/2 tons 2019-2026, regular 4x4s come with a single speed case (no 4LO!), and trucks with Z71 ordered, or all Trail Boss trucks come with the 2 speed case.  2 speed case is also an option on WT, and is also standard on High Country.  
    • newdude
      Different requirements for oil filters?

      By newdude · Posted

      2013 5.3 still to this day calls for the PF48 filter.  Which as a 15psi bypass pressure.     There is a TSB, 17-NA-157 that talks about the PF-63 and PF-64 filters which have a higher bypass rating of 22psi.    TSB HERE - temp.xml   "Beginning in 2012, the oil pumps began to regulate main gallery feedback instead of pump out pressure. This means that the oil pump now does not begin to regulate until pressure is built up to the main gallery. This change reduces the amount of time it takes to provide oil to the engine bearing and lifters during extreme cold start conditions.  Main gallery feedback oil pump control systems are present on the following engine families which use Spin-on oil filters: Small Gas Engine (SGE), Large Gas Engine (LGE), High Feature (HFV6) Gen2 and Small Block Gen5 gasoline engines. These engines with the main gallery feedback oil pump control systems are factory built with an ACDelco® oil filters"   It also calls out what engines use those filters.  The gen 4 small blocks were not on that list (LMG, LC9, L9H, L92, L94, L20, L96).  Gen 5 small blocks use the higher pressure filter.          That all said...   Your 7045 Napa filter is the PF63 equivalent, with 22psi bypass.  You are already using the higher bypass pressure filter.  You CAN keep using it, you don't technically have to use it though.  
    • Grumpy Bear
      Different requirements for oil filters?

      By Grumpy Bear · Posted

      Do you know WHY the filter relief setting was increased to 22 psig?    When the new system goes into the second stage the pump volume ramps up considerably. It was found that the 15 psi filter bypass setting put the filter in bypass on a warm engine when the second stage was activated. Raising the filter bypass setting forced the filter to do what it designed to do. Filter. Preventing debris from circulating during high load, high rpm operation.    So next question is how did GM find this out? VLOM/lifter failures and a deep dive by Melling Corp.    Last question. Is it required? Look at it like this; a motor may be equipped with a rev limiter. But it only works if the set point in reached. That 22 psig setting only matters if the pressure differential across the filter media exceeds 15 psig during normal warm operation. Second stage kicks in around 3000-3500 rpm.    I can't answer your question because I don't know you and how you use the truck. But I think there is enough information here to let you decide for yourself. 😉

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...