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Discussion Starter · #1 ·
Just had my 07 Classic Siverado into a dealer for warranty replacement of a leaking transmission cooling line crimp fitting. I have only 30,000 mi. on the truck. They suggested changing the rear differential fluid and transfer case fluid at a cost of $340. I asked what they based this on when the book has no interval. The only justification was that they thought it was a good idea. Am I getting taken for a ride? I did pull a 10,000 lb. horse trailer mostly on the hiway for approx. 2,500 mi. of the total mileage. I have been conservative with the Allison transmission and flushed and changed at 10,000 and 25,000. Thank you for any advice.
 

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It is something that should be done as regular maintanence yes! Especially since you pull a horse trailer. Should you have the dealer do it at $340.00 hells no! If you can do it yourself you will save a ton of money on it. Do the front diff while your at it.

Do it yourself for about 75.00 in quality fluids. It is real simple stuff both have drain plugs and fill plugs. Its a 15 minute job for each one and most of that time is spent gathering tools and catch cans and gettting under and out from underneath the truck. :D

We can help you with a top quality synthetic fluid at a great price. Especially with our DP member offer.
 

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Discussion Starter · #3 ·
Thanks. The owners manual does not have an interval on the differentials. The dealer said the interval on the transfer case was 50,000. What is a conservative interval on the differentials and transfer case, given frequent trailer towing with a loaded camper? I plan to change the transmission fluid every 25,000. Does that sound reasonable for the other boxes.
 

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Thanks. The owners manual does not have an interval on the differentials. The dealer said the interval on the transfer case was 50,000. What is a conservative interval on the differentials and transfer case, given frequent trailer towing with a loaded camper? I plan to change the transmission fluid every 25,000. Does that sound reasonable for the other boxes.
Yes for towing that is a perfect interval and it will be easy for you to have most all of your fluids on the same interval.

Put a Dual byapss on the truck and change the engine oil at the same interval as everything else 25k. and virtually eliminate the harmful wear metals and particles that cause wear in your engine.

We can get that for you at a pretty good price with our Diesel Place member offer. Less than half the price or our most popular competiton on the market.
 

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The suggested first change on the diffs is somewhere between 5 and 10 thousand to get the initial wear metals out. Some do it earlier. Then you're good to go for a while, depending on the fluid you put in.
 

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Its a secondary filter (smaller in micron than that of the regular oil filter) to catch smaller particles and soot usually.. They dont affect pressure as they are limited to how much passes through them and dont hurt anything if they do become plugged.. Do a search, i used a single amsoil bypass filter and my engine oil looks new for about 2500 miles, most diesels as soon as you check the engine oil after the oil change, the oil is black already.
 

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Discussion Starter · #8 ·
Are you suggesting that I can go 25,000 between oil changes if I install the dual bypass system? I use nothing but Mobil synthetic, I must be misunderstanding you.
 

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Possibly if you get your oil checked by a laboratory as well.. Personally i dont, i do mine simply for piece of mind and it was something to do on a saturday to keep my mind on something.. Guys do extended drain intervals with these systems, good oils and testing.. ps- simply because the oil is not dirty does not mean its doing its job, its just one of the affects of having a filter that is so fine, it can trap some of the soot diesels create.
 

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Are you suggesting that I can go 25,000 between oil changes if I install the dual bypass system? I use nothing but Mobil synthetic, I must be misunderstanding you.
Your not missing anything except the money in your pocket. :)

Yes if you were to install a dual bypass system you could go 25k or even futher but with all extended oil change intervals you should do UOA to help you determine you change interval or if you are set on going 25k you should do it to keep tabs on your engine and oil to nake sure that 25k is working for your oil and engine. It will detect other problems and warn you of them usually before a failure that would cost much more after the failure. An example is if you have coolant in the oil it will detect it when you do analysis. If caught early through analysis you could get the leak fixed before it blows into the oil thus possibly creating a catastrophic failure.
 

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Discussion Starter · #11 ·
I think I will install a dual bypass, but still change oil by the DIC message. It will be good for the ecomomy ;) I will change the differentials and transfer case now, then every 25,000. Thanks for the expert advice.
 

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Anytime. I would go further than the DIC says though thats wasting money on oil especially with a dual bypass. Your oil will still be golden at 2500 miles which is 1/4 of the dic life.

I would go atleast 15k miles minimum.
 

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HOLY CRAP.... im at 91k and havent changed my transfer case fluid ever.....i thought it was connected with the tranny fluid so thats why i havent even paid att. to it.....i know what i will be doing ths weekend
 

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Clean the magnetic drain plug real well too while your there!
 

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I am a big fan of changing out the intial fluids when a vehicle is new; doing the diffs and t-case around 10k miles can't be harmful, and helps flush out an manufacturing remnants. After that, though, the intervals can well be extended to at least 50k miles, and sometimes more, depending upon service severity and fluid used. Don't confuse change intervals with service intervals. You might only have to change fluids every 50k miles, but you should check the level every 10-15k miles.

As a massive generalization, you can do the changes yourself and save yourself a huge amount of money. $340 is grossly overpriced.

Here's a rundown of the must-do and should-consider topics:

Diffs - must use a GL-5 rated diff fluid with the low end of the grade around 75w (or 80w), and the high end from 90 to 140 grade; all depending upon service severity and length. "Synthetic" fluids are NOT required; they are recommended - you'll get longer service life out of them. Just about any brand will suffice, but a recent test from Amsoil showed their Severe Gear to be tops, with the Mobil 1 fluid a close second. All others were not that competitive, and fell back fairly substantially. Brand wars aside, the paper was well written, well documented, and (while sponsored by Amsoil) not entirely biased. The proper stated capacity is 2 qts in front diff, and 4 qts in the rear diff.

For t-case fluid, there's a large controversy over this. I believe the proper fluid is ATF fluid based upon (former) DEX/Mercon base stock chemistry; that's what the t-case was designed for. If you choose to "upgrade" you can use s "synthetic" ATF from one of many sources. Other people choose to use 5w-30 synthetic motor oil. There was an article written by Rockland about how the motor oil supposedly resisted evaporation better; a case of mistaken facts and little understanding of tribology. However, there is no proof that motor oil either helps or hurts the t-case. I prefer to use the factory spec'd fluid in the t-case; others don't. To each his own. There is plenty of factual basis for using the ATF; there is none other than anticdotal evidence for the motor oil; choose as you see fit. Further, those that use motor oil often overfill the t-case by 50%. The stated capacity is 2 quarts; the overfill takes 3 quarts total. Again, choose as you see fit. There is no proof that the overfilling helps anything.

What is known to "help" is proper maintenance with proper fluids. Change your fluids on a regular, reasonable basis and you'll have a vehicle that lasts a long, long time.
 

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What is known to "help" is proper maintenance with proper fluids. Change your fluids on a regular, reasonable basis and you'll have a vehicle that lasts a long, long time.
Bingo!!! As always Mr. Newton very informative.
 

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Nobody is mentioning time - I will be lucky to put on 10K in a year and change every year which comes out to what the DIC recommends........

The way you guys are talking if it takes 5 years for the OP to reach 25K one might assume that is OK.......

Now somebody who puts on more that 25K a year I can see a by-pass system then......
 

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Time is the one thing that often upsets the apple cart.

GM, and about any other manufactuer, has the " xxxx miles, or one year ..." clause in their warranty. Even the vaunted Amsoil products have the "25,000 miles or one year" clause on many of their products.

The reality is that oil has no idea how long it has been in the crankcase. The things that degrade oil are corrosives and contamination. If you drive low mileage per year, but each trip is of decent length (to fully warm the engine and fluids), it is quite possible to go well past the "or one year" mark.

However, for most people, including me, it's not worth the warranty risk to extend past the one year mark, to save the money of an oil change; the risk outweighs the reward. So, we change oil at one year, as a max. I personally only drive about 5k miles a year in my Dmax. I use Rotella 10w-30 year round, and change once a year, to comply with warranty concerns.

There was a recent post over on BITOG where a guy ran 5 years, for 10k miles, on just ONE oil change in his gas powered Tundra. He then did a UOA, and everything came back fine! That really blows away a lot of myth! Still - is it worth the risk? Not to most of us.

If you drive short annual mileage, your most beneficial strategy is to run a decent quality HDEO dino oil (grade: 10w-30 or 15w-40) (brands: Delo, Delvac, Rotella, Tection Extra, Premium Blue, etc) and quality filter (brands: A/C, Wix, Napa Gold, Baldwin, Purolator, etc) and just change oil once a year. For anything around 10k miles or less, this has been proven, by many UOAs, to be an excellent route. In fact, UOAs show that for lower mileage (less than 10k miles) dino oils provide just as good wear numbers as any "synthetic" out there.

Past 10k miles, synthetics, and possibly bypass filtration, are good things to consider. UOAs are a must past 10k miles.
 
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