Input Shaft Seal Leaking on the Forward Rear Differential

[Rawze]

What are you calling a "rear auxiliary transmission"? - Is it the differential lock?, do you have a set of 2-speed rears?, just curious there. Maybe a picture or 2 would help.

337k miles is still fairly new in its lifespan. It would be very unusual to replace one that early except under perhaps abuse, or perhaps an oil leak that no one bothered to spot. Even so, at every oil change, I have the level of my rears and tranny inspected on my own truck. Most oil change places do it as a courtesy.

Like HHow55 pointed out, they act up and make noise when starting to fail.

If someone suspects a rear diff to be going bad, then is has to be pulled out and inspected. Any damage or excessive wear can be seen easily, backlash of the gears can be measured for proper clearance, and pictures can be taken of it. Eaton-Dana has repair and service manuals all over their website to download for free on how to inspect it and measure it for excessive wear or replacement. -- I would demand the measurements of backlash so that you can compare them to the manual + pictures + a visual inspection of any damage before approving a replacement, warranty or not.

I am not playing around with "opinions" and such, especially when there is good correct information out there provided by the manufacturer.

You keep taking that truck to the "stealershit" and you are only going to continue to be brioke and ger ripped off. Even under warranty, they do not pay you for all the lose big $$$ in down-time while you wait for days to "get into the bay" only for some jerk-off to charge you for "environmental fees " and all sorts of other jack-legged crap that is only designed to drain your wallet through highway robbery. -- screw that, I will buy a set of tools and find out what is wrong for myself.

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Last but not least by any stretch,.. if you have to replace a rear --- It is the perfect opportunity to re-gear the truck for a better profit margin... Get rid of the tall gears and go with something more reasonable like 3.79's or something so that the expense becomes an investment with a return through higher profits and slower driving speed.