Just changed my transfer case fluid for the first time at 115K miles. It looked terrible - black like used engine oil. Did not smell burnt though. Are these transfer cases that hard on the fluid?

 

Lots of the fluids that the factories install aren't worth a dime, in my opinion, and are claimed to be "break-in fluids". Did you change the differential fluids for their first time yourself? The first time I changed mine out was at 15K and let me tell you, that factory differential fluid that they used looked like coffee with a good bit of creamer in it and was very thin when I drained it. Really, it turned my stomach to know that the fluid that they used was that poor in quality.

Ever since, I have put in Shell GL-5 high capacity rated 80W90 non-synthetic and every time I change my differential fluid these days (just did a 20K interval and am going to bump that up to 30K this time), it comes out honey brown and just as slick as the day I put it in. Every other fluid change, I completely take the differential cover off and take a rag to the inside and wipe out any sludge build up, which other than the first fluid change, never really amounts to anything.

I'm approaching 60K on my truck now and will be doing my transfer case then. I'm surprised you waited 115K to change the fluid in your transfer case, honestly. Just doesn't seem like it should have gone that long. You're lucky for it to still be in proper working order, in my opinion.

 

Factory fill on my t-case and diffs was exactly as described above. The t-case was black and slightly underfilled when I changed it at 29k. The diffs were creamy and grayish/brown at 10k (rear) and 20k (front). Amsoil is in there now.

 

Just got done doing all the fluids recently. Sounds pretty normal to have the oil be discolored even changing them often like me. I've got almost 51k on the od right now.

NV5600 tranny - 1st change at 20k. It was dark and looked like it needed changed. 2nd change at 50k (looked same as first). Used Pennzoil Synchromesh both times.

Transfer Case - 1st and only change at 50k. Was dark and looked like it needed changed. Replaced with Valvoline ATF+4 Full Synthetic.

Front Axle - 1st change at 10k. It was dark and looked like it needed changed. Not much sludge accumulation on the magnet. 2nd change at 50k (looked same as first). About the same accumulation on the magnet. Replaced with Mobil 1 75w90 Synthetic both times.

Rear Axle - 1st change at 10k. It was dark and looked like it needed changed. More sludge on magnet than front. 2nd change at 50k (looked same as first). About the same accumulation on the magnet. Replaced with Mobil 1 75w90 Synthetic both times.

 

I'm envious....I wish I could run 80W90 conventional year round. It just gets too darn cold where I live.
As for the conventional vs syn issue in our diffs, I feel that if it's good enough for rigs, its good enough for me.

 

I'm going to run conventional March through November....75w90 the rest. Delo 80W90 ESI.

 

I live around Edmonton too and have always run synthetic 75w90 year round in all 5 of my CTD's over the years with no issues.

 

Yes, I changed the differential fluid at 20,000 miles & put in Mobil 1. The original axle fluid looked good, as did the Mobil 1 after 95K miles. The tranny fluid looked good being changed for the first time at 115K miles.

 

Wow you guys like living dangerously. When I got my truck at 55k miles, I changed EVERY single fluid. T-case and diffs will be done every 20k atleast. Couldn't imagine leaving T-case fluid for that long, especially considering how cheap it is to replace.

 

I tend to agree. I even use a pump and pull out my power steering fluid and replace it as well. I normally change all my fluids every 20K miles but have considered going up to 25K for next time.

The only fluid still original in my truck is the brake fluid at 115K.

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