Differential Oil Change Interval ??

[wilnis]

Hi-I need to be educated. I have a Dodge diesel 3/4 ton p/u with 49,000miles. I tow a #12,000 gooseneck 2000miles/year, and a #6000 bumper pull 6-7000 miles/year, and the rest are chores.
I changed the differentials at 1000 miles, got the usual nasty junk out and put Mobil synthetic 75-90 in the front and synthetic 75-140 in the rear. I did changes at 15,000 and 30,000 miles with MoleKule's gear oil at the same weights and the 45,000 front with MoleKule's oil and rear with Amsoil severe gear oil, sames weights as above. At these changes, the oil came out almost as clear as when I put it in.
My questions-Am I and others who obsessively follow the owner's manual severe schedule for these changes really doing the equivalent of 3000 mile engine oil changes with synthetic oil or are these differentials really worked so hard that this is necessary? Big rigs seem to run forever on minimal changes with synthetic oil, and I don't begrudge the expense or time to do them but wonder if it is necessary or if I'm wasting resourses like I use to with 3000 mile engine oil changes?
Please advise. Thanks-Bill

 

[salesrep]

Yes.

 

[bmwtechguy]

If you are changing diff oils at 15k miles with synthetic such as Severe Gear, you are probably changing at least twice as often as needed. I think the Dodge rec. severe interval of 15k miles is with regular gear oil. With Severe Gear or one of the others you used, I would probably go even longer, especially with open diffs. Are these diffs open or posi-type units?

 

[wilnis]

Mark-Thanks for your succinct answer, your experience is appreciated.
BMWtechguy-the front is open, the rear is positraction. The owners manual is specific about 15,000 intervals, and synthetic oil requirements.
Bill

 

[pickled]

Double the factory recommendation with the severe gear...it will hack it. Big rigs run 5 gallons of long life gear lubricants...the volume certainly helps.

 

[PT1]

Do a change at 15k and get a used oil analysis. Then you won't be guessing. My bet is the Amsoil will go 30k.

 

[Harley Anderson]

Well Amsoil Severe gear application guide says 50k severe, 100k on normal service. I did my first change at 15k, then 40k on the rear and 50k on the front. Wish I had done a used oil analysis, but the fluid was so clean, I felt it was worthless. If I could change anything I would of done a change at like 2k, one at 30k, and then 50k intervals.

 

[SubLGT]

Originally Posted By: PT1
Do a change at 15k and get a used oil analysis. Then you won't be guessing...........


I agree with PT1.

 

[D-Roc]

I don't use Amsoil Sever gear, but I'm sure not going 15000K...tha's way too early. Amsoil SG I would run what Amsoil says to run...For me, I'm probably going every two years with what I have in my Diffs...(right now Pennzoil (75W90). Every year is unecessary.

 

[mikeinaustin]

personally, i would change it every 30k.