Originally Posted By: 63CadillacBill
What's the correct type and weight lube for the rear differential in my 2004 Dodge Ram 1500. This is a 9.25 sure-grip with 3.55 ratio. The reason I ask is that I've heard the 9.25 is a problem child (design defect). My '96 Ram had the same rear and despite using Mobil One it still smoked the bearings at about 75K. I don't want to go through that again. BTW - The factory fill was changed at 10K when they repaired a bad pinion seal, now she's got 20K. Any comments and/or ideas?
I actually had an 04 1500 w/ 3.55's myself. The correct lube as stated is a synthetic 75W-140. No limited slip(LS) additive needed unless you have the LS differential which you don't w/ 3.55's.
The issue with the 9.25 Ram rear axles was with the LS models. There is a little retaining clip( may be 2 - can't recall ) that comes loose and trashes the gears( only needed for assembly - many pull cover and remove them as they are not needed once everything is assembled and in place ).
The standard rear axles are bullet proof and only fail due to water getting in, low fluid, or lack of proper maintenance. Use the correct fluid and change it every 2 years/30K and you will be fine.
Run a quality 75W-140 synthetic gear oil and you are good to go. I have had excellent success using Royal Purple MaxGear. Worked great in my 04 and I will swap to it in my 08 at 10K.