I've been lurking a while, I have a question for the oil gurus. I recently bought a '93 Dodge pickup with the Cummins and a Getrag 5 speed. The manual recommends 5W-30 motor oil and says you never have to change it. Not surprisingly, these transmissions have a reputation for failed input shaft bearings. Many people advise overfilling the trans by half a quart to alleviate this problem. I believe this masks the actual problem, which is that normal 5W-30 motor oil can't handle the shearing action of the gears and thickens over time, causing poor lubrication splash/flow. I think the lube needs to be changed more often than never (well, duh). What oil do you guys think I should use, and how long do you think it should be left in? Please explain your reasoning when you answer, even if your reason is "That's what I sell." Thanks in advance for any info.