SabrToothSqrl

Well last night was fun.

Changed the Transfer Case fluid, and both diffs. 94,000 miles, never changed before.

DEXRON VI, and (on mine) 80W-90 in the front and 75W-90 in the back.

(Manual says use synthetic on the rear) I used synthetic for both as that's what advance auto had.

Started with the transfer case. Fairly easy. I think it was a 15mm or 17mm bolt top and bottom. Removed top first to verify I could fill it. Removed bottom. Both were not very tight to the transfer case, so keep that in mind when re-tightening them. There's a torque spec I'm sure, but it's not a freaking head gasket here. Fluid came out brownish red. Drained into an oil pan collection. I didn't use my normal wheel blocks to raise the vehicle as I assume it had to remain level for the fluid levels to be on spec. Holy cow for a Tahoe this thing is low to the ground.

I then cleaned off both plugs with a paper towel, the lower had a good sludge of metal parts and ATF, almost pretty looking. Cleaned them up spotless. Replaced the lower plug and used a small harbor freight hand pump to pump 2 quarts in. It took about 1.9 to fill it, so I think it worked well.

Moved to rear diff
yea, with the vehicle on the ground, you aren't getting that diff cover off. Maybe I could/should have used a floor jack to lift the tahoe up (axle on ground), but hey, hindsight. I was never going to remove that cover...

Harbor Freight pump in hand (I use two pumps, one for dirty oil out, one for clean in), I sucked the diff fluid out. It was a 3/8" ratchet to remove the plug, which again contained a spiffy coating of metal flakes.

Fluid was a deep brown most likely from 94,000 miles of use and towing a 6,000 lb trailer.

Replaced with shiny new yellowish fluid. Took damn near all 3 qts I bought. Maybe 2.5

Now, the really fun one... the front diff is 5" off the ground, the top plug is a HUGE odd looking plug/cover thing 17mm I think, and the lower plug just to be... different? was 13mm.

That was interesting laying on my back hands overhead to do this. It was nice to have two plugs though, makes draining a lot easier. Why doesn't the rear have two plugs?!

Removed the top one first (always want to make sure you can fill the damn thing), cleaned that up. Removed the drain plug, which again, had this pretty silver goo on it. (they are magnets, I'm aware).

Anyway, this came out like it had some water contamination. A thinner grey oil looking liquid poured out. Put the drain plug back and pumped in 2.25 qts of fresh oil.

So, hopefully she's good for another 100,000 miles

My driveway has some new interesting oil stain patterns, but whatever right?

fishing nut

Thanks for the right up. When using synthetic did you go with Mobil 1.

SabrToothSqrl

CastrolTransmax Dexron VI (ATF) Automatic Transmission Fluid
ValvolineHigh-Performance 80W-90 Gear Oil
Mobil1Synthetic Gear Lubricant LS 75W-90

{tpc}

Sorry Sabr, I forgot to mention when doing the rear diff, its probably better to remove the spare. Gives you a lot more access. When I did mine, I did it with the vehicle on the ground. There is a lot of room to remove the cover that way as well...but if you weren't going to do it anyways, might be an unnecessary step. And yes, I don't know why no drain and fill plug on that one.

As for the color on the front...maybe its just because it is/was original fluid? Mine was normal color, but I know work had been done up there and I had a leak...which I fixed temporarily by adding fluid to get me through the winter, until I could replace a seal.

I think by having someone else do your tranny and filter in there, your doing yourself a huge favor. If your doing that. I would be specific with the dealer about what you want done in that case and then take a paint marker or a sharpie and mark a couple of the tranny pan bolts. Just so you know they actually did what they said they would do.

The other stuff you did though is way fun in comparison!

SabrToothSqrl

doesn't yours have the drag link across the back axle? Mine's a 2009 1500 Tahoe, and the rear has a metal bar crossing right behind the diff, within 1" of it...? The suspension looks really similar to the one the my wrangler had. 4 links and a drag link to center the axle. The older ones and I think the 2500 use leaf springs. Stronger, but harsher ride. leaf springs would leave the rear diff much easier to access. Of course if I threw a floor jack under the ball hitch and jacked the truck up 6" it may also have been easier. The car's either getting lower or I'm getting fatter.

I would have gotten pics if I wasn't covered in oil and grease under the car...

Yea, after summer (towing) I'll get the transmission filter changed and fluid changed out.

{tpc}

I'll be honest and say I don't know what a "drag link" is. I know that there was something metal, I almost thought it might have been a brake line that crossed near the top of the diff and one of the diff bolts had a bracket attached to it and the bolt. I just kind of moved that out of the way and above the diff cover...carefully, when I removed the cover.

I don't think you did wrong by not removing the cover, I was just interested in what it looked like in there. Mine was pretty clean, and having the cover off allowed me to soak up a bit more fluid, but no "huge" benefit. Cleaning both sides of it wasn't easy after what was probably 195k miles...I don't think it had ever been removed.

I really was tempted to spray in some brake cleaner and clean everything out inside of there, but in the end I felt that with whatever mechanicals are in there, I don't know if I could mess something up, so it was just a wipedown that it got.

Put the transfer case plugs back in was fun too, because the spec lists a very small amount if anything for the torque as I remember, but I know you don't want to go crazy on them cause they can crack. I would bet the dealer has them....but what if they don't? Then you are out of a truck for a bit.

The trans pan...some actually drill a hole and fashion a plug in it (with the pan removed) for easier draining. I didn't do this, but I feel I've given this truck 10 times more love than the previous owners so she is just going to have to live with it lol.

SabrToothSqrl

Sorry, Panhard bar



describes a 4 link suspension with a panhard bar, some jeep guys call them a drag link.

https://en.wikipedia.org/?title=Panhard_rod

this bar passes RIGHT behind the rear diff.

Yea, I would have liked to have seen inside the rear diff, but other than a visual check, I don't see a huge advantage unless for example you have a contamination issue...

Offroading my wrangler would result in yearly diff fluid changes due to the possibility of water intrusion. So I'd pull the cover to make sure I got every last drop, as oil floats on water.

I raised all the vent lines when I lifted it, but still it's pretty demanding off road use.

in2pro

It looks a whole lot like this... and like {tpc} said, yes for sure take the spare out of the way, jack it up on jack stands and you will likely have enough room to sit under and right in front of the diff to do the servicing ( its what I did)

SabrToothSqrl

Not bad. I'm not gonna mess w/it for another 100,000 miles

I see the weights that swing out and lock the diff in that photo.