2008 silverado 23k miles.

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Guys, i just bought a 2008 silverado Z71 with 23k miles on it ( see pics in Vehicles thread).I changed the oil today with Synpower 5w30 and AC/Delco pf48-E. Plans are to change the Transfer case fluid with the GM Trac II as it has the Auto 4x4 feature. Also plan to Change both Differentials with Synpower 75w90 GL-5 and service the transmission by dropping the pan and replacing the filter and 5qts dex VI fluid. The differential is a locking diff with 3:73 ratio. is this a G80?? Question is...Is it too soon at 23k miles? should i hold off a while or go ahead and service it all now? Unfortunately the previous owner (first onwer) lost the manual so im not sure of the severe duty schedule. Thanks!
 
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Just FYI the 2009 owner's manual is available here. I don't think that there should be any major differences (they are both second generation - but I could be wrong).
 
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The rear diff can get nasty pretty quick. My used truck had 60K and it was silver gray. The next change out was golden. Change it out and it will be good for a long time. The rest of the boxes can wait if you want but I start fresh when I buy a vehicle.
 
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Originally Posted By: donnyj08
Guys, i just bought a 2008 silverado Z71 with 23k miles on it ( see pics in Vehicles thread).I changed the oil today with Synpower 5w30 and AC/Delco pf48-E. Plans are to change the Transfer case fluid with the GM Trac II as it has the Auto 4x4 feature. Also plan to Change both Differentials with Synpower 75w90 GL-5 and service the transmission by dropping the pan and replacing the filter and 5qts dex VI fluid. The differential is a locking diff with 3:73 ratio. is this a G80?? Question is...Is it too soon at 23k miles? should i hold off a while or go ahead and service it all now? Unfortunately the previous owner (first onwer) lost the manual so im not sure of the severe duty schedule. Thanks!
1) G80: G80 is the RPO code for locking differential. You will find a GT4 code in your RPO list to indicate the 3.73 ratio. 2) Too soon: If it were mine, yes. My 2006 has 46,500 miles on it and has the factory fill in my transfer case and transmission. My diffs would still be factory fill but they have been serviced for seal leaks. However, do what makes you comfortable. 3) Service Intervals (these are for my 2006, I doubt a 2008 is any different but check the many online manuals to be sure): Trans - 50,000 miles for severe service otherwise 100,000 miles, Transfer - 50,000 miles (no severe service difference), Axle - As per usual no service interval regardless of severity. I do intend to change my trans and transfer case at the 50k mark, next year. I only replace the diff fluid upon service (i.e. axle seals etc.).
 

donnyj08

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thank you. I did see the GT4 code in the glove box. I also have the window sticker that stated the axle as a 3:73 ratio and locking . I may just check them through the fill hole for right now to see how it looks.
 
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Originally Posted By: Tabor
Just FYI the 2009 owner's manual is available here. I don't think that there should be any major differences (they are both second generation - but I could be wrong).
Biggest difference that affected the 09 vs 08 trucks was the roll out of the six speed transmission in most GM truck in 2009. (They had the six speed in higher trim levels in prior years, but they became commonplace in 09) Also the 3.73 rear became less popular and the 3.42 became the most common rear end in the 09+ trucks due to the two extra gears in the transmission.
 
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Nice truck! We run these in our fleet and do not service the trans until at least 30k miles or more. Note that the trans generates the overwhelming majority of its debris during the first part of its use so an early trans change is NOT inappropriate if you plan to keep it long term. After the first one, which should always service the filter, too, you can then greatly extend the interval as Dex VI is a long term fluid.
 
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Originally Posted By: donnyj08
Guys, i just bought a 2008 silverado Z71 with 23k miles on it ( see pics in Vehicles thread).I changed the oil today with Synpower 5w30 and AC/Delco pf48-E. Plans are to change the Transfer case fluid with the GM Trac II as it has the Auto 4x4 feature. Also plan to Change both Differentials with Synpower 75w90 GL-5 and service the transmission by dropping the pan and replacing the filter and 5qts dex VI fluid. The differential is a locking diff with 3:73 ratio. is this a G80?? Question is...Is it too soon at 23k miles? should i hold off a while or go ahead and service it all now? Unfortunately the previous owner (first onwer) lost the manual so im not sure of the severe duty schedule. Thanks!
I wouldn't use the auto 4x4 feature. Put it 4 high if you need 4x4. Otherwise leave it in 2. Death to many transfer cases around here using auto 4. Also are you sure it's gm trac II for the tran case? Dealer told me Dex 6 on mine.
 
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donnyj08

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Originally Posted By: ChevyBadger
Originally Posted By: donnyj08
Guys, i just bought a 2008 silverado Z71 with 23k miles on it ( see pics in Vehicles thread).I changed the oil today with Synpower 5w30 and AC/Delco pf48-E. Plans are to change the Transfer case fluid with the GM Trac II as it has the Auto 4x4 feature. Also plan to Change both Differentials with Synpower 75w90 GL-5 and service the transmission by dropping the pan and replacing the filter and 5qts dex VI fluid. The differential is a locking diff with 3:73 ratio. is this a G80?? Question is...Is it too soon at 23k miles? should i hold off a while or go ahead and service it all now? Unfortunately the previous owner (first onwer) lost the manual so im not sure of the severe duty schedule. Thanks!
I wouldn't use the auto 4x4 feature. Put it 4 high if you need 4x4. Otherwise leave it in 2. Death to many transfer cases around here using auto 4. Also are you sure it's gm trac II for the tran case? Dealer told me Dex 6 on mine.
No I'm not 100% sure. Just from reading online Trac ii seemed like the choice, I'll have to research more. So the auto feature is hard on the transfer case?
 
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I havent seen a clear answer whether the auto feature is hard on the transfer case but when engaged there will be additional wear and slightly lower mpg. At some point there was a switch from the trac ii fluid to Dex VI. Not sure when though.
 
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Originally Posted By: ChevyBadger
I wouldn't use the auto 4x4 feature. Put it 4 high if you need 4x4. Otherwise leave it in 2. Death to many transfer cases around here using auto 4. Also are you sure it's gm trac II for the tran case? Dealer told me Dex 6 on mine.
I dislike the auto very much. It engages and disengages abruptly and jerks my entire drivetrain when in slippery conditions. I would not be a bit surprised if it ruins T-cases. I just run old school (either 4H or 2H hard coded in... I never use 4L no need for my driving). My truck came with the auto, I would never order it.
 
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Originally Posted By: marc1
Originally Posted By: ChevyBadger
I wouldn't use the auto 4x4 feature. Put it 4 high if you need 4x4. Otherwise leave it in 2. Death to many transfer cases around here using auto 4. Also are you sure it's gm trac II for the tran case? Dealer told me Dex 6 on mine.
I dislike the auto very much. It engages and disengages abruptly and jerks my entire drivetrain when in slippery conditions. I would not be a bit surprised if it ruins T-cases. I just run old school (either 4H or 2H hard coded in... I never use 4L no need for my driving). My truck came with the auto, I would never order it.
The auto feature on my 2012 is perfectly seamless.
 
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Originally Posted By: donnyj08
Guys, i just bought a 2008 silverado Z71 with 23k miles on it ( see pics in Vehicles thread).I changed the oil today with Synpower 5w30 and AC/Delco pf48-E. Plans are to change the Transfer case fluid with the GM Trac II as it has the Auto 4x4 feature. Also plan to Change both Differentials with Synpower 75w90 GL-5 and service the transmission by dropping the pan and replacing the filter and 5qts dex VI fluid. The differential is a locking diff with 3:73 ratio. is this a G80?? Question is...Is it too soon at 23k miles? should i hold off a while or go ahead and service it all now? Unfortunately the previous owner (first onwer) lost the manual so im not sure of the severe duty schedule. Thanks!
In regards to oil, you can use whatever oil you want. GM seems to endorse Mobil 1 and for that reason, I use Mobil 1 in my GM engine. I would recommend going to the AC Delco PF63 filter, (NON-ECORE) not the PF63E filter. The PF63 older style filter is much better built and has metal end caps and the PF63 filter will physically fit and it's about double the size of the PF48E filter you used. With the PF63 filter, you get the benefit of more filtering media over the much smaller PF48E filter. If you want a really good oil filter, go with the Amsoil EAO17 filter which is good for 25K miles or the Fram Ultra XG 10575 filter which is rated for 15K miles. In regards to the differentials...if your differentials are limited slip, I would only run the GM fluid and always run the GM limited slip additive so there is no chatter or slip. I ran what I thought was better than GM fluid in my differentials in my past vehicles only to go back to the factory stuff. The factory fluids made the diffs run quieter. You can view the owner's manual at: www.chevrolet.com It's never too soon to change the oil in a car or truck and you can change the oil out whenever you want to. After all, it's your truck.
 
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Answered my own question once I found your link to photobucket. Given what I have read, and the 2008 manual I downloaded...I would say with great certainty your vehicle calls for dex VI. Also in regards to the read diff, it has been asked many times on silveradosierra and the G80 does not need the extra limited slip additive.
Quote:
A good way to tell if you have an AutoTrak automatic transfer case: If you have FOUR buttons for the shift, and the top button is round and has AUTO 4WD: you have the AutoTrak and MUST use the AC Delco AutoTrak II fluid.
 
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donnyj08

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Originally Posted By: Scott_mi
This auto 4x4.... is it a push button or on a dial you rotate? I have seen multiple things suggesting 2008 would be Dex VI. I have a 2009 z71 with the auto 4x4 on the dial you rotate and manual calls for dex VI Can try copy pasting this for the 2008 silverado manual download....which says DexVI http://www.silveradosierra.com/2008-silverado-manual/
It is a Dial just like your 2009 has. Just saw your post! thanks for the reply! yes, i was aware it doesn't need any FM in the differentials. I probably will not use the GM fluid however as most of what i read seems to point out that it is $30 a qt for nothing special at all. I probably will go with synpower 75w90 or Amsoil 75w90. I have had great luck with both in the past.
 
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