Bottom line: The rear differential cover is poorly designed and is easily damaged leading to a total loss of fluid when off road. The lowest point of your ground clearance is the differential cover, not the differential. The cover has a ridiculous lip that extends past the outside diameter of the differential. You don't have to "hit a rock" to have the problem. All you need to do is scrape a rock and your SOL. The differential housing is aluminum, the diff cover plate is thin steel. The lip on the cover plate is facing forward, as soon as you scrape a rock it bends the plate backwards and your truck bleeds to death on the trail. It does not take much at all to make this happen. How do I know? I have done it three times!
This is not a bash my truck thread. I love this truck. I'm going to take the time to share my grief and help you with solutions. This is however about a poorly designed rear end. The problem should not be there. Unfortunately I now know more about this differential than I ever wanted to know. I will share some of that here and my expensive solution. It's been ugly.
- The rear end was retooled in 2019. There is almost no aftermarket parts or protection available for it
- I believe almost every Silverado from 2019 up has this problem. All you have to do is look at it and feel it. If there is an 1/8 inch lip extending past the bottom of your differential that is what I am talking about. It seems benign until you find out how it grabs a rock and peels right back to break the seal
- I have some tips for you when you go off road
- I finally found someone to fabricate a one off skid plate for me as nothing is available aftermarket
- New gear oil is rare and anything but the new stuff voids you rear end warranty. The world has run on 70-90W gear oil since cavemen invented the wheel. GM formulated a new SAE 75W-85 gear oil for these new rear ends and is very picky about it. It's part number, ACDelco LV Gear Oil SAE 75W-85 API GL-5 10-4122. I can only find it at dealerships and not always in stock. GM techs have told me quick lubes and such will put the wrong stuff in and they can tell what's in there and GM will void the warranty.
- BTW, the entire bottom of your plastic fuel tank is also exposed under the truck
- GM is obviously aware of these things. It is rumored to be fixed on the 2023 ZR2 Bison Edition. AEV Bison is the collaborator that built skid protection for the Colorado ZR2
I know most of you guys are not rock crawling in Moab, UT, please believe me all it takes is to scrape any rock and it bends the cover easily. First photo is the blood trail. We were on Fins and Things in Moab. I heard the scrape so we stopped and checked to be cautions. I was shocked to see my truck bleeding to death in remote desert, gear oil was running out. I grabbed a hatchet and beat the hell out of the bent metal cover as quickly as I could. That stopped almost all of the leak. Next I did a field repair with JB Weld. That was an amazing temporary fix. I had it in my tool box, will never leave the road without it again. Not sure how much gear oil I had left so we exited the trail early and went into town for oil and more JB Weld. I am glad to say that with new oil and our field repair we were able to complete the entire Fins and Things trail the next day.
View attachment 3517View attachment 3518
JB Weld field repair and a hatchet saved the day. Yes I am hard on this truck but it's a great 4wheeler.
- I recomend this in your tool box when off roading a Trail Boss
- Hammer
- JB Weld
- Proper Gear Oil
View attachment 3521
Thars the problem right there. Soft steel that bends back and does not take much to leak.
View attachment 3522
See how it extends past the housing. I thought about grinding it but that not a good solution ether.
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I had to have someone custom fabricate a skid plate to slide over rocks. That wasnt cheap or easy to find.
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We did it without using the cover bolts.
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Its 3/16 steel
Anyway, I just wanted to give you guys a heads up. Be careful with your clearance and carry tools.
@vesepilot with your skills this is a project I would definitely recommend for you. Let me know if you want more info. I started from scratch and there is a lot more to it. The only aftermarket item available is someone just released a thick aluminum cover. I talked to them and it extends past the pumkin too. No one makes skid protection. I talked to three race shop fabricators that looked at it and blew it off. Too busy for the job.
Kind Regards,
Steve
