CHECK YOUR DIFFS...

davester · November 5, 2025

alldata.com has the full service manual for your truck. SEMA25 for 25% off right now...

Chuck FB · November 5, 2025

5 minutes ago, davester said:

alldata.com has the full service manual for your truck. SEMA25 for 25% off right now...

I have heard of that system but I am referring to an actual complete manual that is purchased and is downloaded and saved, a one time purchase rather than permission for a specified time to be allowed to view it.

davester · November 5, 2025

gm doesn't license it for one-time purchases like that.

Chuck FB · November 5, 2025

30 minutes ago, Pryme said:

If I recall, the rear bolt was magnetic.
can’t help with specs. Newdude should be able to though.

I can't swear by it now but at the time I removed my check plug, I didn't get the impression it was magnetic to look at from what I am used to seeing with highway tractors etc with a bonded on magnet but I also didn't touch a steel object to the face of the plug to test it either. On older GM diffs so not a proper comparison but they typically had a magnetic donut of sorts that was placed in the bottom area of the diffs casting.

JW2024 · November 5, 2025

16 minutes ago, davester said:

alldata.com has the full service manual for your truck. SEMA25 for 25% off right now...

Thank you. Works out to a decent price for 1 year.

Edited November 5, 2025 by JW2024
Spelling

Chuck FB · November 5, 2025

Just now, davester said:

gm doesn't license it for one-time purchases like that.

It would not be through GM, its some other source from what I gathered.

davester · November 5, 2025

The info would come from GM (through some intermediate company that licenses it from GM), unless you get something like a Hayne's.

fondupot · November 5, 2025

I have the alldata.com GM tech manuals for my 2024 Silverado 2500HD and also for my 2021 GMC Yukon. I find them to be an invaluable resource when working on my vehicles. I used them too on my previous 2019 GMC Canyon and 2022 Silverado 1500. Great info on them

And since this thread is about diffs. I'm gonna drop this video here.

Couple Highlights:

The diffs no long have drain plugs. (BOO! GM). The fill bolts are not magnetic. But the covers have a magnet attached to them.

The diff fluids have a range of "fullness": Rear Differential Approx. Minimum Capacity 3.17 quarts - Fill to 0.0"-0.4" below fill port. Front Differential Approx. Capacity - 1.9 quarts - Fill to 0.0" to 0.24" below fill port.

I used 75W90 Mobile Delvac front and rear. Been running great for several thousand miles.

T-Case is simple. Dexron VI fluid. Has both fill and drain plugs. Fill er up til it spills out.

Edited November 5, 2025 by fondupot

Chuck FB · November 5, 2025

5 hours ago, fondupot said:

I have the alldata.com GM tech manuals for my 2024 Silverado 2500HD and also for my 2021 GMC Yukon. I find them to be an invaluable resource when working on my vehicles. I used them too on my previous 2019 GMC Canyon and 2022 Silverado 1500. Great info on them

And since this thread is about diffs. I'm gonna drop this video here.

Couple Highlights:

The diffs no long have drain plugs. (BOO! GM). The fill bolts are not magnetic. But the covers have a magnet attached to them.

The diff fluids have a range of "fullness": Rear Differential Approx. Minimum Capacity 3.17 quarts - Fill to 0.0"-0.4" below fill port. Front Differential Approx. Capacity - 1.9 quarts - Fill to 0.0" to 0.24" below fill port.

I used 75W90 Mobile Delvac front and rear. Been running great for several thousand miles.

T-Case is simple. Dexron VI fluid. Has both fill and drain plugs. Fill er up til it spills out.

That was an excellently presented video that gave all the torque specs as well as where the magnets are located these days in the GM diffs, actual oil volumes experienced in refilling to the full level, cover bolt loctite use, oil level spec which has been discussed here and so forth. So it appears the front diff cover gasket is reusable even though GM lists it as a one time gasket. I had searched before on youtube but had not come across his video or your channel, this will certainly help anyone else on here with any unknowns.

I will say though I would caution the use of teflon tape on a tapered plug that goes into an aluminum housing and even more so if it has a thin walled aluminum boss that protrudes from the body of the aluminum cover, teflon in the tape form allows for a much lower torque value on the plug for how hard/deep its actually forcing itself into the tapered hole and has caused aluminum cases to crack at the hole if there isn't enough aluminum thickness to hold up to that stress. Using a liquid teflon or other non curing type plug sealer would be the safer bet.

Factory fill oil on diffs was 80W-90 non synthetic for many years and it was NOT the oil that made life any easier in our cold winters, horrible driveline drag and have used 75W-90 for many years now in various diffs from pickups to highway tractors. I figure with my climate challenges that I may as well stick with the 75W-85 in the front diff to allow just that much easier rolling resistance since GM approves of that fluid for the front but if I lived in a warm climate I wouldn't bother using the extra thin gear oil in the front.

Edited November 5, 2025 by Chuck FB

JW2024 · November 7, 2025

On 11/5/2025 at 4:37 AM, fondupot said:

I have the alldata.com GM tech manuals for my 2024 Silverado 2500HD and also for my 2021 GMC Yukon. I find them to be an invaluable resource when working on my vehicles. I used them too on my previous 2019 GMC Canyon and 2022 Silverado 1500. Great info on them

And since this thread is about diffs. I'm gonna drop this video here.

Couple Highlights:

The diffs no long have drain plugs. (BOO! GM). The fill bolts are not magnetic. But the covers have a magnet attached to them.

The diff fluids have a range of "fullness": Rear Differential Approx. Minimum Capacity 3.17 quarts - Fill to 0.0"-0.4" below fill port. Front Differential Approx. Capacity - 1.9 quarts - Fill to 0.0" to 0.24" below fill port.

I used 75W90 Mobile Delvac front and rear. Been running great for several thousand miles.

T-Case is simple. Dexron VI fluid. Has both fill and drain plugs. Fill er up til it spills out.

Nice video. Time to do my truck.

fondupot · November 7, 2025

On 11/5/2025 at 10:38 AM, Chuck FB said:

That was an excellently presented video that gave all the torque specs as well as where the magnets are located these days in the GM diffs, actual oil volumes experienced in refilling to the full level, cover bolt loctite use, oil level spec which has been discussed here and so forth. So it appears the front diff cover gasket is reusable even though GM lists it as a one time gasket. I had searched before on youtube but had not come across his video or your channel, this will certainly help anyone else on here with any unknowns.

I will say though I would caution the use of teflon tape on a tapered plug that goes into an aluminum housing and even more so if it has a thin walled aluminum boss that protrudes from the body of the aluminum cover, teflon in the tape form allows for a much lower torque value on the plug for how hard/deep its actually forcing itself into the tapered hole and has caused aluminum cases to crack at the hole if there isn't enough aluminum thickness to hold up to that stress. Using a liquid teflon or other non curing type plug sealer would be the safer bet.

Factory fill oil on diffs was 80W-90 non synthetic for many years and it was NOT the oil that made life any easier in our cold winters, horrible driveline drag and have used 75W-90 for many years now in various diffs from pickups to highway tractors. I figure with my climate challenges that I may as well stick with the 75W-85 in the front diff to allow just that much easier rolling resistance since GM approves of that fluid for the front but if I lived in a warm climate I wouldn't bother using the extra thin gear oil in the front.

I'm in South Carolina so 75W90 gear oil all year round doesn't hurt. I get your point about the teflon tape on the plugs, I've been doing it for years without issue. Thanks for watching.

11 hours ago, JW2024 said:

Nice video. Time to do my truck.

Thanks for watching.

diyer2 · November 8, 2025

Helminc manuals is what you want. $375 for my 2012.

Chuck FB · November 8, 2025

1 hour ago, diyer2 said:

Helminc manuals is what you want. $375 for my 2012.

I had looked that up before when I was wanting the full version of the operators manual and they didn't list a shop manual then, so now I searched again and still nothing other than the shorter or full version of the owners manual. If I go back to 2019 then they show a shop manual for that series of truck and although not any good for this truck, its 595.00 USD which is a whole other story of the gong show and rip off of my finally receiving the operators manual that in the states is 50.00. I paid around 230.00 Canadian if you can imagine for that manual because of dollar exchange and piles but a lot for importing as well as shipping. Not only that, the manual never showed up and finally I called Helminc and they traced it to Edmonton where the shipper threw the manual into the garbage because they couldn't figure out how to ship it to me because I have a rural address, Helminc was kind enough to wipe the slate clean and refund me at their expense. They then suggested I order the manual through the dealership which I did and they did receive it eventually. You have no idea how good you have it in the states where within mere days you can have a package plunked on your front step where it can promptly be stolen by the idiot following the shipping van around the city LOL.

So for now it seems there is no manual through that means and alldata would be the alternative and I have no clue what they charge for Canadians.