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TB has serious flaw when off road

PHXPHOTOG

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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.

20210805_113648.jpg
20210805_074040.jpg

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
20220614_094144.jpg

Thars the problem right there. Soft steel that bends back and does not take much to leak.

20220614_094346.jpg

See how it extends past the housing. I thought about grinding it but that not a good solution ether.

20220710_151751.jpg

I had to have someone custom fabricate a skid plate to slide over rocks. That wasnt cheap or easy to find.

20220710_152224.jpg

We did it without using the cover bolts.

20220710_151835.jpg

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
 
I was more worried about the stupid long shock brackets on the rear than looking at the diff cover. The diff cover has been an issue for a long time on GM trucks. I'm pretty sure almost all of the covers extend past the housing and have always been steel. I didn't know about there being no aftermarket covers for them. I put an ARB cast iron one on my 08 Avalanche when I had the rear end rebuilt. The gas tank was also a source of concern to me since it's plastic and there's a little extra piece of plastic at the front edge that is maybe supposed to add some protection, but doesn't look like it will do much. I hope AEV releases the skid plates to purchase they are using on the ZR2 Bison and Sierra version.
 
AEV offers all of the armor they make for the Colorado ZR2 at very reasonable prices. Hopefully they will do the same for Silverados.

Steve
 
That custom skid plate looks great, and that's good that you used shackle fasteners instead of the diff cover bolts. Nice color, too.
Another solution may be an aftermarket diff cover, although these are kinda pricey:

From Banks:

And various brands from Summit:

Off-road people like Matt and Rory like the Banks covers. Matt really likes the Yukon diff cover he recently installed, but I checked and they don't make one for our trucks.

edit: Actually, IIRC it was off road recovery guy Casey Ladelle who installed a Banks diff cover recently.
 
Last edited:
Another solution might be to make "banana clips" ... these are banana-shaped steel reinforcement pieces, which would be installed under the existing diff cover bolts. I had to fabricate and install a pair of these on my Rutan VariEze Lycoming engine, surrounding the Main Seal. Because these airplanes mount the engine backwards, there is a potential for the Main Seal to pop out of the case.
 
This is all great information.. I’m planning a long off-road trip for next spring.. Something to get done before I go..
 
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.

View attachment 3523
I had to have someone custom fabricate a skid plate to slide over rocks. That wasnt cheap or easy to find.

View attachment 3524
We did it without using the cover bolts.

View attachment 3525
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
This is the kind of post that makes forums like these pure gold. Thanks for the time and details.
 
This is the kind of post that makes forums like these pure gold. Thanks for the time and details.
Thank you for the props. This was so important I felt it was necessary to explain the whole thing. In late August we are going back to Moab then up to Colorado to do the entire Alpine Loop. A 10 day overland style trip to include Ouray, Silverton, Lake City, and Telluride.

Steve
 
Hey guys I was wondering if anyones had any updates to this thread as far as aftermarket support? I took a 101 off-roading course this past weekend and had a blast. I was very pleased with the truck overall, but as described above the instructors also shared the same concern with the rear differential. From searching online the only place I have been able to find that offers anything for underbody skid plates for 4th gen is ASFIR, but its only for the 2500/3500 series trucks. Ive reached out to them in regards to potential future products. Another company that was suggested was Purple Cranium. Their rear diff guards look like spider webbing over the rear cover, and use the existing cover bolts. Any pros or cons to this?
 
AFE has aluminum covers for both the GM and AAM axles. I picked one up the other week but haven't installed it yet. Going to wait till the weather warms up as I want to paint it as well since it's the raw finish. https://afepower.com/vehicle-platfo...&afe_product_sub_category=75&c=6375&is_ajax=1

I'm also waiting for AEV to release their Silverado ZR2 skid plates as stand alone parts. I just checked their website and still nothing listed for Silverados. They have parts available for the Colorados.
 
AFE has aluminum covers for both the GM and AAM axles. I picked one up the other week but haven't installed it yet. Going to wait till the weather warms up as I want to paint it as well since it's the raw finish. https://afepower.com/vehicle-platfo...&afe_product_sub_category=75&c=6375&is_ajax=1

I'm also waiting for AEV to release their Silverado ZR2 skid plates as stand alone parts. I just checked their website and still nothing listed for Silverados. They have parts available for the Colorados.
Will the aluminum cover extend past that lip that hangs down for protection or is it the same diameter?
 
I can tell you the skid plate I had fabricated is working for me. This is what it looks like now.

20230207_104025.jpg
20230207_104331.jpg
 
I need a skid plate like you had made, does the person or shop have any interest in building more? I would definitely buy one like yours.
He is a kid that works at a shop. He fabricated mine from scratch in his garage. He said he can't do quantity but now that he did all the preproduction on mine maybe he will do some. I will ask him, If he is interested I'll put you in touch.

Steve
 

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