3.42 swap for 3.73

[Leedall24]

Destroyed a G80 3.42 differential. It literally locked up at about 45mph skid hopping to a stop. No warning, except a loud howl and a loud metal to metal bang as I let off gas coming to a round about. Driveshaft and  snapped yoke laying on road. 
Ride: 2015 Silverado 1500 LTZ CREW.4WD. 35s. 6”.

GM dealer wants 7K to fix. WTF?!!

Plan: Find used complete rear axle and swap. 
Question: Can I put swap the destroyed 3.42 for 3.73? Will I need to change the front diff also? Should I go back to G80? I keep reading they are junk…..??

FYI: Just a shade tree mech here. Don’t know everything. 
Any advice appreciated. 

[Grumpy Bear]

Find a driveline shop and yes, the front diff will need regearing as well if you want to change ratios. That estimate is way out of line. Not of fan of the G80. Truetrac. That and a Yukon gear and bearings for just the rear is about $1.5-$2K. 

Edited September 30, 2024 by Grumpy Bear

[redwngr]

Fwiw, G80 is now standard on almost all trims.

On WT and Custom it is optional. 

 

Point being there are 100's of thousands of them built into GMs every year.

 

ZR2 gets the new G93 and G94 driver selectable lockers.

 

G80 suits many/most -- but other systems will be better for more extreme applications.

 

Anything can fail at unexpected times.

Certainly doesn't mean they all will.

Need to change to something else depends on what the truck is used for.

 

I've run G80's for many many years doing farm and road work without problem. 

 

[newdude]

$7K sounds like it damaged more than the rear end and driveshaft....

 

Also this should be in the 2014-2019 forum section not 2019-2025.  

Edited September 30, 2024 by newdude

[BIGDOGx]

On 9/30/2024 at 10:19 AM, Grumpy Bear said:

Find a driveline shop and yes, the front diff will need regearing as well if you want to change ratios. That estimate is way out of line. Not of fan of the G80. Truetrac. That and a Yukon gear and bearings for just the rear is about $1.5-$2K. 

He will also require his speedometer to be recalibrated or flashed to correct the gear change i believe.

 

I take it the rear pinion snapped here?? I know i did this with my 89 s10 baja, my mistake was trusting my high school auto-shop teacher when i did a rear seal on it at school. He tightened the pinion nut down without using a torque wrench and the rest is history as they say it. I was lucky to only be down the street when it let go, was able to hop it back to my house using 4wd as the pinion head binded up the main gear and the back wheels were locked. My advice is dont shade tree mechanic this unless you have the proper knowledge and tools or you will just end up spending more money in the long run!

Edited October 2, 2024 by BIGDOGx