Do I really have to change both differential fluids at 15k?? The truck has 12k on it now, only about 1500 of that is towing a 5k lb boat. I was looking at "schedule a" and you don't have to change the diff. fluid til 100k. So I was planning on changing them at 30k just to be safe.

 

I couldnt tell you for sure but I dont know anyone personally that ever has or ever will change the diff fluid. I did change mine at about 20k but I dont know that I will ever do it again.

I do think it is a good habit to have as I am sure it is good for the truck but I know people that have put 150k+ on front and rear ends with no oil change and no probs, same goes for manual trannies too, but I will change mine out sooner or later anyway.

the above statement is just my opinion and nothin more

 

I'd would have changed it at about 1k to get the OEM crap out - that stuff is the worst junk I've ever seen. I went 24k on my last truck (97 CTD) with RP 85w140, not much towing and the analysis was great. I changed every 12k when towing a lot even tho the reports said it was OK to run. It's not worth the chance! Craig

 

I change mine as per the severe duty schedule "B", and have no regrets. I will extend the interval to 30k on diffs after the 7/70 warantee is up. I just changed the diffs a week ago, and with 43k on the clock, there are still machining marks on the ring gears. Thats with Amsoil 75-90 in them every 15k, since 15k. I am a BIG fan of preventive maintenance.

 

as cheap and easy as it is to change both diff fluids, I can't think of any good reason not to change it, but that's just me. I probably change fluids too much, but if my truck craps the bed, I know it won't be a result of poor maintenance on my part.

 

Cheap? At 80 bucks a change, it doesn't take THAT many changes with expensive synth gear oil to buy you a whole new set of gears! I did mine the other night, had valvoline 75w-90 in for about 22K, and there wasn't even enough wear material to cover the end of the magnet hardly. I switched to 75w-140 Amsoil Severe Gear and it is staying in til 100K. (Which will be 62K miles in service) Maybe I will be proven wrong, but I would wager any sum of money that when I drop that fluid at 100K that those gears will look great, and this truck is almost exclusively hooked to a trailer.

 

Those who have 4wd will want to get the front changed no more than 20k. It is worth it and very easy to do yourself. Should take more than 15 minutes without power tools.

 

It is always a good idea to change the diff oil at or around the first 5k miles of the trucks life just to get all of the break-in slivers of metal out of the mix, then go to a normal schedule as per your driving habits or needs, I do mine every 30k if it needs it or not.
Chip

 

I strongly support Chips recommendations !!

 

you should if your launching that boat.Just to check for water contanmination . I have never had water in mine after a boating season. But it should checked

 

That's my line of thinking. Waited until 30k, the used fluid looked great. Shoulda' left it in there. Was really easy to do though.

Of course if I was launching a boat I'd do it yearly.

And it's not cheap if you use the full synthetic stuff like you're supposed to!