Automatic transmission fluid and differentials

[gooffeyguy]

I think the HDC is Heavy Duty Cooling.

If you have an auxiliary trans cooler mounted in front of the radiator, that would be HDC and require an additional 2 tenths of a quart

 

[Bagherra]

Welcome. Diffs are easy; scraping the old gasket off is the hardest part. I’m a fan of LubeLocker reusable gaskets myself. No more scraping off paper and no messing around with RTV.

Where did u find these? Went there website and it's all d*cked up...

 

[OR VietVet]

Listed at Summit Racing: https://www.summitracing.com/search/brand/lubelocker?GroupBy=ProductName

 

[alpha_omega]

If summit/jegs doesn’t have them, you can always use the OEM ACDelco gaskets. They are reusable as well, so long as they are in good shape and cleaned up prior to install.

 

[Bill 1960]

Where did u find these? Went there website and it's all d*cked up...

I bought mine on Amazon.

 

[alpha_omega]

I used AMSOIL Severe gear 75-90 in the front and rear diff. The rear diff gasket is reusable and bolt torque is 27ftlbs. Just fill until it starts coming out the fill hole. When you have the cover off there is a magnet stUck to the bottom of the housing that needs to be cleaned as well as the cover. Just like the video I spayed the inside of the case and all the gears down with brake cleaner. I wanted to remove the black film. It will mostly drain but there was a little left that I just soaked up with a rag. I let the case air out for about 30 min just to make sure the brake cleaner evaporated completed. Maybe a little OCD.

The front diff is drain and fill only. Just remember like others have mentioned to remove the fill plug first. It can be frozen to the case being a steel plug. I sprayed mine with wd40 while worked on the rear. Your going to have to remove the plastic shield under the engine to do the front. I did spay brake cleaner in the fill hole and worked the plastic tube around to get it cleaned out. It ran black for a while then cleared up. This time I waited a bit then squeezed some gear oil in with drain plug out just to make sure there wasn’t any sitting brake cleaner. Again fill until just starts to come out fill plug

The transfer case take ATF fluid and it’s the same. Drain and fill. Do take note when removing the fill plug first if you get a lot of fluid coming out. If that happens the seal between the transfer case and transmission is shot. I don’t think you’ll have a problem being new but just something to watch for.

if you go with AMSOIL get the squeeze packs of gear oil for the diff’s. Also get the correct quantity for the transfer case as well in ATF. It makes the job sooo much easier IMO.

Great explanation (other than autocorrect changing spray to spay…haha). If people think thats OCD then I guess you and I have something in common. Other than the WD-40 on the plugs, it sounded like a reply of everything I do for my fluid changes. Even down to the brake clean followed up with a little clean fluid to flush it out.
A couple things I would note is to ensure you clean off the threads and the ends of your drain/fill plugs since they are usually magnetic and may be holding some shavings. The transfer case drain/fill plugs occasionally need to be re-coated. I use Parmatex Thread Sealant #80632. Don’t go crazy with the stuff and don’t drop the axle drain plug for your John Deere tractor into the container. It’s a mess to fish out of the bottle. Ask me how I know…I dare you.

Gear Oil is some smelly $h*t, especially used gear oil. Wear some nitrile/rubber gloves, long ones if you’re not proficient at what your doing. And buy either a transfer pump, a screw on hand pump, or the twist cap with a long hose. The latter two are not the best option, but they work in a pinch. Careful though as the tops don’t secure the greatest.

 

[swathdiver]

Thank you all for the info. Using amsoil's site to get specification and capacity, it mentioned the following:

Automatic Transmission, 6L80 Initial Fill..........6 quarts
Automatic Transmission, Total Fill
6 speed W/O HDC 6L80..........12.2 quarts
6 speed W/ HDC 6L80..........12.4 quarts
Differential, 8.6 RingGear Rear..........4.2 pints
Differential, 9.5 RingGear Rear..........5.5 pints
Differential, 9.76 RingGear Rear..........5.5 pints
Differential, 8.25 RingGear Front..........3 pints

I scanned my QR code containing my RPO code and it showed the following:
2019,TK15906,11,18,06,WHTXVW, AG2 AN3 ARL AXP AYQ CF5 CJ4 C6H DD8 DL3 EF7 FE9 FHS GU4 G80 G9K H2X IO6 I19 JD9 KG4 L83 MAH MYC NP5 NTB RC4 RKX RUF TC2 UDD UHN UQA U2K V8D WMK ZW7 Z82 Z88 4AA 4SA 6SH 7SH 8X2 9X2,464C

I'm assuming since my yukon is a 5.3, it doesn't have HDC (which i assume is hill descent control?) I cant find anything about ring gear for the differential or should i just resort to doing 75w-90 all around for the differentials and just top it off until it starts pouring out of the fill plug. Also, I know the rear requires a gasket but I want to make sure the front is simply draining and filling with no need to take any pans off like the ATF and rear differential.

Thank you again.

K2s use 9.5 or 9.76 12-bolt Salisbury rear axles. The 5.3s get the 9.5 and the 6.2s get the 9.76. The rear gasket on mine does not require adhesive to reseal and is re-usable.

 

[12iotman]

I finished changing out the oil in the differentials and the transfer case. Finished the atf flush and refill.
Now after putting everything back together, I’ve noticed red transmission fluid slowing dripping off the bottom plastic trim covering the front differential. I checked the transmission line running to the radiator that I had used to flush the system and that doesn’t seem to be the issue. I also checked the bottom plastic trim and could not find where it may be coming from. I did note while refilling the transmission through the dipstick, I may have overfilled the funnel resulting in some fluid running down the engine but I don’t think it should be this much?

I didn’t take out/off anything besides that transmission line running to the radiator. There is no leak around the transmission pan or transfer case.

Any suggestions?

 

[Rocket Man]

I finished changing out the oil in the differentials and the transfer case. Finished the atf flush and refill.
Now after putting everything back together, I’ve noticed red transmission fluid slowing dripping off the bottom plastic trim covering the front differential. I checked the transmission line running to the radiator that I had used to flush the system and that doesn’t seem to be the issue. I also checked the bottom plastic trim and could not find where it may be coming from. I did note while refilling the transmission through the dipstick, I may have overfilled the funnel resulting in some fluid running down the engine but I don’t think it should be this much?

I didn’t take out/off anything besides that transmission line running to the radiator. There is no leak around the transmission pan or transfer case.

Any suggestions?

Put some paper towels or something under your truck there when you park it overnight and monitor if you have a drip or if it was a one-time thing from the fill process.

 

[Jeff_]

These are great videos. I watched them before doing mine. I reused the gasket for the trans and rear end. No issues 20k miles later.

(6L80)

(8L90)

(differentials and transfer case)

This was a fantastic help, thanks for posting these. I used these today when I changed my trans fluid and filter. Both front and rear diffs. And transfer case fluid.