BubbaJ191

Hey all, been prodding around the forums for a little while here, but posting for the first time. I did search for these questions not only around the forums, but on my own as well, so forgive me if I'm rehashing things. I bought this 2007 Chevy Tahoe LTZ flex fuel a little over half a year ago and I have done some repairs to several components that were broken on purchase. Now I realized that I should've done all the preventative maintenance awhile ago, but better late than never so I'm going to change all the fluids out which led me to the reason why I'm posting.

So, first off, I checked the rear differential fill plug and had some decent shavings on it. Unfortunately I don't have a picture of it, but I'm going to crack it open, spray it out with some brake clean and inspect it to see what kind of condition its actually in (Hopefully nothing concerning towards a rebuild quite yet). So I was doing research on which gear oil to put in and whether or not I have a limited slip differential or not. Checked my RPOs and I have a g80 rear end which shows up as "G80 - AXLE, REAR, POSITRACTION, LIMITED SLIP". I know there's a lot of controversy with the g80s whether its LS posi, or locker which was confusing as ****. So I was looking at standard ACDelco grape drink to do both the front and the rear differentials, but I'm getting mixed answers whether it has the additive in it or not. (10-4128 being the gallon of lubricant 75w-90) Or I could just go with some Valvoline Synpower that already has the additive in it, opinions and recommendations are definitely welcome. Also, been hearing that most people are putting in 75w-90 in the front differential nowadays even though it calls for 80w-90 for the 1500's? No big deal if this is the case, just curious about low temperature operation whether it would be more/less wear and tear, or completely irrelevant, just wanted to hear what people think about that. I would prefer to just buy a bunch of the same, but it's not a problem either way. Also, going to do the transfer case with the Auto Trak II Formula.

That's all for the differential questions, which leads me to the classic AFM situation. I knew going into the purchase about the AFM catastrophe in these 5.3s, so I got the OBD2 range chip which was much less extensive than the physical delete with the lifters. I might do that later if I have more extensive work to do in the future, but I have to tune the ECM after the delete, correct? Anyways, it's chugging oil out of control. I'm going to buy the replacement valve cover with the PCV blocker plate on it (Dorman - 264-965) and then clean out the PCV hose to make sure its clean. So just making sure I'm on the right track with all of this, not sure if there are any other steps I should be taking, so let me know if I'm missing something here as well please and thanks!

Lastly, I haven't gotten out there and looked myself, which I will, but i heard that there aren't many zerk fittings on these trucks. They developed a lifetime enclosed (100k miles?) grease free maintenance? Seems not ideal to me, but I was reading since most people over grease or under grease that was their solution? And that the U joints are still greaseable but that's about it? I don't know, but any general quick info on that would be appreciated as well, I'll get underneath and see myself soon enough, but any information is nice.

Other than that, I was just planning to replace everything else to start fresh. Brake fluid, tranny and filter, coolant, power steering, already did the engine oil of course.... And then everything else that was mentioned above... Any other thoughts of something I'm forgetting or that I should add to the list, by all means, let me know.

I'm real happy with this Tahoe and I want it to be happy, healthy, and around for awhile. Glad to be on the forum with all of you.

repairman54

Don't use a LS lube in the rear diff. G80 rears don't need it as it's not a ''posi'' in the old sense.
I use M1 in my diff's that does not have LS on the bottle's label.
100k miles on my '11 5.3 with the range unit plugged in. Zero issues. at 138k miles total now. Physical AFM delete requires a reprogramming of ECM.
Very few greaseable parts, basically watch for wear / looseness and replace with a quality greaseable part.
If it's chugging oil it was neglected by the previous owner and may have internal issues. I've had mine from 35k miles. Barely use a 1/2 qt. between oil changes done by the monitor which averages 6k to 7.5k miles depending on summer/winter.
It's only had full synth. fluids since being in my care. My truck sees tow duty with boats, cargo trailers, etc.

BubbaJ191

Alright, good to know about the diffs, I'll just pick up some Mobil 1 75w-90 for both front and rear then, appreciate the info. "Chugging out of control" might be a bit extreme (reading back on what I said), but it is consuming more oil than it should be and I had been reading about the oil going into the intake through the PCV over time if you don't replace the valve cover.

And thanks for the info on the grease fittings as well Repairman54.

Any other advice or instruction is appreciated.

repairman54

You didn't mention how many miles are on it. Plugs should be done at 100k miles. Use AC plugs for zero issues. I would also change the O2 sensors, with GM ones, closest to the engine as they degrade as the miles add up and, in my truck, I got back a few MPG with fresh ones. The front O2 sensors regulate fuel mixture and fresh ones will help keep the cats healthy for a long time.

BubbaJ191

Ah sorry, yea it's sitting at 150k or so, so definitely need to just revamp everything since I don't have full prior maintenance history. Start with a fresh slate is my plan so I'll go ahead and change out the plugs and the O2s. I guess the air filter as well I need to take a look at, other than that, I think that's about everything now? I know I keep saying this, but anything else you think of or recommend is greatly appreciated and once again, thanks for the plugs and O2s advice Repairman54. I just did the plugs on my other vehicles... I guess I kind of overlooked them on this Tahoe as I was spiraling down the fluids and maintenance hole, especially with that differential research.