truck transfer case and differential service intervals

[Keith Hughes]

Tow vehicle question (please delete if not allowed): We tow our 2021 Montana 3121RL rig with a 2021 GMC Sierra 2500 Diesel 4WD truck. This is the first time we’ve owned a truck and want to keep it properly serviced. The truck will be 3 years old later this month and nearing 30,000 miles of which 13,000 are towing miles. The owner’s manual recommends the transfer case fluid be changed every 45,000 miles but there is no mention of if/when to change the front and rear differential fluid. The dealer is recommending both differentials and the transfer case be serviced every 30,000 miles. I’m inclined to go with the owner’s manual maintenance schedule but am concerned that it is silent on if/when to service the differentials. Thoughts and recommendations?? TIA!

[prndl]

You might want to join the Duramax forum. Lots of people there with information on your truck. They will be able to answer your question.
https://www.duramaxforum.com

[BB_TX]

My dealer has often recommended certain services be performed earlier than the manual states. But the dealer has a financial incentive to do the work earlier and more often. I figure the manufacturer knows what works so I go by the manual. And never a problem in the many many years of driving many many vehicles. Don’t think the manufacturer would be wanting their vehicles to get a reputation for failing early.

[scottz]

Go by the service intervals in your manual. Ford considers towing to be severe duty, so that changes some of the intervals; check your manual. Some mfgs do not require differential fluid change unless submerged in water.

[Rotnjonny]

Good morning. If mine, I would follow the manual for the transfer case service intervals. In my experience, if you are not towing the majority of the time, it wouldn’t fall under the severe duty category

For the differentials, I would follow the same maintenance schedule that you follow for the transfer case. In many applications, it is the same fluid specification for the diffs as the transfer case. Sometimes they are using a different additive (friction modifier)

YMMV

[mlh]

I would do exactly what the manufacturer says to do. Who would know better the dealer or the manufacturer? Now let me think.
Lynwood

[drjjj]

2015 Ford F350 Super Duty Platinum. I have always been a fan of synthetics as I had a good friend who ran the fuel testing lab at Southwest Research here in San Antonio for over thirty years and he has told me that the Royal Purple products surpassed everything else he tested. I changed all my differential, transfer case and transmission fluids to theirs at 60K and will probably be dead before they have to be changed again. Use their oil as well. I also do not trust the truck computer regarding oil changes. At 5K complete change and 10K filter change and top off. Just my $.02.

[mlh]

I have a friend who owns a Ford van with 580,000 miles on it. He changes the oil every 15,000 miles. He uses regular oil not synthetic. It’s the 5.4 engine not a great engine to begin with. It’s never been rebuilt and doesn’t use any oil. Sure synthetic is better but do you need it. I use synthetic to but I’m not sure you need it. I certainly wouldn’t change oil more frequently than the manufacturer recommends.
Lynwood

[Keith Hughes]

Thanks everyone for the feedback. I ended up getting the transfer case and differentials serviced at 30,000 miles which is in between the service interval in the owner's manual for normal vs severe truck usage.

[bshgto]

Originally Posted by mlh

I would do exactly what the manufacturer says to do. Who would know better the dealer or the manufacturer? Now let me think.
Lynwood

I get my advice from these guys. My "go to" mechanics, they know everything.

[mlh]

Those guys are good. If you don’t believe me just ask them.
Lynwood

[Ram Montana High Country]

I had a dealer that thought diesel oil should be changed every 3,000 miles ... when asked about service manual saying 15,000 - they thought it was wrong ... some dealers don't know ...

[77cruiser]

About the worst place to go to get your truck serviced is a dealer.
Bought mine with 79K on it, it had 11 oil changes done at the dealer it was sold at.

That was the only thing, don't think a grease gun had ever touched a fitting. Diffs were never done trans.
Got it a jam on the road & had to go to the dealer for some things, she tried pushing the service on me. Fuel filter $200, diff & trans $700, Nope just did it last week.

[BB_TX]

Lack of scheduled services being performed is more likely due to owner declining those services rather than the dealer not choosing to perform them. Dealers have financial incentives to perform those services more often than actually required rather than not at all. But those dealers are certainly likely to charge more than other places you can get the work done. And considerably more that do it yourself if you are so inclined, and able. There was a time I did all my own maintenance and repairs, sometimes significant repairs. Those days are long gone.