Rear end service

[Jackmchome]

Just finished my first tow on the 2007 3500 D/max. 300 miles with a 15K fifth wheel. I will make the same trip next February. Do I change the oil in the rearend now, or wait till February?

[DmaxMaverick]

If you are not planning on any towing until February, I don't see anything wrong with waiting until just before then. If your future towing will be mostly the 15K 5'er, I do suggest using 75-140 lube. Just be sure you use either the GM lube ($$), or a compatible full synthetic.

[WILLYD-MAX]

Amsoil sells 75/140 severe gear for a reasonable price. If you are changing the fluid yourself it takes 3qts. and 12oz. that puts it right at 5/8 in below fill hole. A good way to check the fliud level is to stick the short end of an allen wrench in the hole and hold it level with the short end down then remove and measure the level. I think I learned that from someone on the diesel page , works good for me.