2018 3500HD Tranny/Rear End Maintenance

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So my 2018 Silverado 3500HD (6.0 Gas) is at 32k miles. It mostly gets driven around town and a few highway trips....mostly unloaded. So far, the most I've ever pulled a 14' enclosed trailer with two garden tractors in it. 90% of the time my truck is empty. 5% of of the time there is a 800 pound garden tractor in the bed. So, for a 1-ton truck, it's living an easy life. What do you think is the best schedule for the tranny and rear end?? I think the rear-end is due for a drain and fill. That should get rid of all the break-in debris. But for the Tranny (6L90E), I was thinking I'd have the dealership do a complete fluid exchange in the near future. And then in around 60k miles, I'd drop the pan and change the filter. I would probably just do drain and fill's from 60-200k miles and then change the filter again at that time. What do you think of this plan?? Lastly, what about fluids?? Would you stick with AC Delco DEXRON-VI or do you guys prefer an aftermarket fluid for the transmission and transfer case?? What about the front and rear differentials??
 
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Sounds like a good plan. I'd argue that if you're capable of doing the tranny service yourself, why not just do it yourself, rather than the dealer? Pan drop, filter replacement, then do it again at 60k. Every 30k for the diffs sounds good, I've been using Mobil1 but I imagine Amsoil would be better. For tranny fluid I just use DexlV. You should probably do your transfer case if you have one.
 
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Originally Posted by Railrust
Sounds like a good plan. I'd argue that if you're capable of doing the tranny service yourself, why not just do it yourself, rather than the dealer? Pan drop, filter replacement, then do it again at 60k. Every 30k for the diffs sounds good, I've been using Mobil1 but I imagine Amsoil would be better. For tranny fluid I just use DexlV. You should probably do your transfer case if you have one.
I think getting rid of all the fluid now is a good idea.... Getting rid of all break in clutch material. The filter will be good for another 30k, and then drop the pan and change the filter and freshen up fluid with 4-5 quarts from the pan drop. Most friction material should slowly accumulate from them on.... So fresh fluid every 30k will keep everything in decent shape for awhile.
 

dnewton3

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The tranny is a fairly decent unit. I'd advocate for just a drain/fill now and then every 50k after that. Dex VI is a good fluid and holds its vis well. The diffs only need a decent GL-5 fluid. Assuming you have the G80 locking diff, you'll need a fluid with some FM in it to help with clutch operation (yes - there are clutches in this particular design of the Eaton "Gov-Lok" unit.
 

4WD

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AC Delco Dex VI is reasonable when ordered by the gallon. Check a few websites. Think Mobil made lots of it and P66. I used Mobil 1 in Eaton diffs the longest … but about 4 years back I started getting Delvac 1 from Summit Racing and have used in 3 GM LT's to date.
 
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The 6L90E holds about 12.5 quarts. I did a pan drop, filter and fill on my 2017. It took 6.5 quarts. That was at 30,000 miles. GM says change it every 45,000. Most guys are adding 5.5 to 6.5 quarts after a pan drop, so you do get a bunch out. Mine was nice and clean at 30,000. So I got half of it out. Ran it the rest of the summer and I am now at 32,000 miles. Next oil change I will pull the drain plug and swap another 6 quarts. Should stay really clean like that. Not interested in having the dealer mess with it. If I feel like it I will do what I did what the old truck and pull a cooler line and flush it that way. I pull 7800lbs about 3000 to 4000 miles a year. Truck may get a total of 5000 miles a year on it. This, as I have been told, is basically the same rear diff I had in my old 02. I just run Mobil 1 75W-90. I did the fluid once at 23,000 miles and then again at 55,000. I will probably just do it at 45,000 in this truck.
 
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