Used Truck purchase

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Good Day,

First post here on BITOG, I recently purchased a used 2008 Silverado QC Z71 LTZ w/ 5.3L, 3.73 gears, and 184K miles. I have been enjoying the truck and have performed an oil change already using Penzoil platinum high milage 5w-30 and a Fram ultra synthetic filter. I would like to change all fluids in the truck, I have looked in the manual and see Trans fluid should be Dexron 4, but for the differentials it listed different viscosities. The trans fluid looks a little brown, I would like to do remove the pan drain, and change the filter then refill, but I have read that this can be detrimental on high milage autos, the 4L60E specifically. Is it a waste of time or would I be asking for trouble by dropping the pan and replacing the filter and refilling? What is the recommended type and weight gear oil recommended for these trucks? Are there any MPG gains to be had in going with amsoil in the differentials?

Edit: I forgot to mention the coolant, this truck has red coolant? The manual says dex cool and it should be good for 150K miles. I'd like to flush it, but I thought dexcool was orange??

Looking forward to your thoughts. Also, I haven't ever had a UOA performed on my vehicles but have a Lexus with 293k miles I would like to do one on.
 
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Yes, I would do a pan drop & filter change and fill with any approved Dex VI. I would also change the transfer case fluid...mine looked absolutely black at about 80k miles. IIRC, I used 80W90 in the front and 80W140 in the rear diff, both synthetic.
 
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Have a 319k awd 05 XL Denali and a 205k 03 Sierra 2wd both since new. Nah nothing can go wrong if you drop the pan and change the fluid and filter. You could remove the trans line and remove more fluid and since you don't know if the fluids been done so I'd do that. YouTube tutorials explain it better than i ever could on here.

If it had regular 50-70k fluid changes you wouldn't need that. You say broken down but how brown is it. What color is the oil on a white paper towel. And as for the diffs I'd just keep using thin gear oil unless you're towing and or having diff issues like excessive metal, Wont prevent a failure but it'll prolong it a bit. 85w-140 has a kc40 of like 330 while 80w-90 is 140 so there is a big difference if you do sub 30 minute runs since the fluid is more restrictive. Now the transfer case needs a different oil but I believe they updated the spec so you'll have to check on yours. the front diff would be just fine on the 90 grade.

I have 319k on the original diff that is slightly worn and i do a lot of long drives so it best suits me to use something thicker. But if you don't drive a ton and don't have some diff wear like i do is just use that 90 grade. I'll probably need to get at least some parts replaced in my diff before 400k. Not a full rebuild but some things should be changed next time I'm in there.
 

Infosponge

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Thank you both for the replies! My daily commute is roughly 30 miles of highway driving, I do not tow, but I believe the previous owner did, truck is equipped with an auxiliary trans cooler and airbags, previous owner said trans fluid hadn't been touched since 113k miles. Regarding the fluid color, it was brown on a white paper towel. I could probably snap a pic on lunch if you're interested?
 
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Thank you both for the replies! My daily commute is roughly 30 miles of highway driving, I do not tow, but I believe the previous owner did, truck is equipped with an auxiliary trans cooler and airbags, previous owner said trans fluid hadn't been touched since 113k miles. Regarding the fluid color, it was brown on a white paper towel. I could probably snap a pic on lunch if you're interested?
sounds like the perfect time to do fluid and filter then
On the coolant how red are we talking? ive heard some mention dexcool may look a little pink but its supposedly orange. If in doubt do a full flush with water and then select the coolant of your choice.
 

Infosponge

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sounds like the perfect time to do fluid and filter then
On the coolant how red are we talking? ive heard some mention dexcool may look a little pink but its supposedly orange. If in doubt do a full flush with water and then select the coolant of your choice.
It's very red, like looks exactly like the red in my Lexus which is regularly flushed. I've seen the pre-diluted toyota coolant look pink, but this is much darker. I will add that to the list and get some Dexcool.
 
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when i got my lo mile but older 2011 fronty SV i changed ALL fluids to Redline except the oil 10-30 quaker state ultimate durability fake synthetic + mpgs increased 2-3 in Pa summers driving mostly local short to med!! real synthetics work IMO!!
 

AZjeff

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AFM has been turned off since 113K. I am aware of the AFM issues, but still not sure what your suggesting.

Kaboom. If it's gone 184k chances are it will go 300k but of course who knows. A coworker bought a new 2008 5.3 Silverado and neglected it from day 1, OCs when he remembered and always at a quick lube and it was still doing fine last I knew over 150k. Luck of the draw. You could disable the AFM the day you brought a new truck home, run good oil on short OCIs and still have it break.
 
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Infosponge

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Kaboom. If it's gone 184k chances are it will go 300k but of course who knows. A coworker bought a new 2008 5.3 Silverado and neglected it from day 1, OCs when he remembered and always at a quick lube and it was still doing fine last I knew over 150k. Luck of the draw. You could disable the AFM the day you brought a new truck home, run good oil on short OCIs and still have it break.
Ah ok. I thought he/you were saying the AFM would be somehow related to the red coolant. Previous owner claimed to do his own oil changes with mobil 1 full syn 5w-30 at 3500 miles with a wix filter. I stay on top of my oil changes also. I'm hoping for the best.
 
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Thank you both for the replies! My daily commute is roughly 30 miles of highway driving, I do not tow, but I believe the previous owner did, truck is equipped with an auxiliary trans cooler and airbags, previous owner said trans fluid hadn't been touched since 113k miles. Regarding the fluid color, it was brown on a white paper towel. I could probably snap a pic on lunch if you're interested?
That sounds good enough. If you're in a time and effort pinch a drain and fill would be fine. If you've got the time and energy the line disconnect and pump out would be better.
 
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that red coolant sure sounds weird to me. If i were you id definitely opt for a full flush for safety on that one. And 70k since the last tranny service is right in line to get that done, seems like you're in a good spot to keep this thing ticking for a while to come bar something catastrophic from previous ownership.
 
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I would also do all the things mentioned by zrxkawboy. I mean, as long as you are buying a new truck, you might need to change a lot of things there, even if it's in a good state. I recommend you be cautious about it and don't fall for all the shiny things when you find a truck that you'd like to buy. I have a friend who is buying and selling old trucks. He is giving them a cosmetic repair and selling it for double the price, though it's still in a terrible state. I would recommend all the guys who have old trucks to find proper truck buyers uk who won't scam people like that.
 
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Change the ATF and filter then do it again in 5000 miles.

I had issues in my 08 4.8 2wd with the trans pan clearing a crossmember, think I undid a mount to jack it for that last 1/4 inch.

Also get the coolant and it wouldn't hurt to do the PS and brake fluid either.
 

Infosponge

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To update, I have done a drain and refill on the coolant and the color looked normal compared the new coolant. I have ordered a new trans pan with a drain plug,a wix filter and valvoline ATF that meet the proper dexron rating. I have the differential fluid for 1 differential, just need the remaining fluid and a rear gasket then I'll be ready to perform that job. So far I've got about 2500 miles on the penzoil platinum high milage and it looks clean still but has darkened in color a bit. OLM show about 80% iirc. I have also replaced the battery in the truck. The truck has a Volant air intake, they offer a few high priced options on there site, but I'm sure I could find a similar sized filter to work as a replacement. Thanks for the tips/help.
 
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Watch the video on transmission fluid flush from 1ROAD on youtube.

If/when your 4L60E needs to be repaired, I'd find the best independent trans shop around and talk to them. Make sure they use the "bulletproof" 4L60E rebuild kit. That, along with regular trans service, will last far longer than the rest of the truck. Don't take it a dealer and let them sell you a 100k mile transmission rebuild for the same or more money as what I've described above.
 
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