Well first of all I wanted to Congratulate you on your gear and especially the Trutrac install because I was such an *** before and never said anything...lol
The DTT has been on my mod list since day one.

Motive could have changed compounds within the metals of the gears but I just dont know???

The one thing most people arent aware of is that when doing a gear install, the crush collar needs to be set to check for proper check of the pinion depth. If this is incorrect by only a teeny bit, most shops are not going to tear things back apart to re-insert a diff. shim. They usualy role with the punch's so-ta-speak. No matter how much you play with the ring gear, you will never get correct alignment. Generally, a proper install requires 2 crush collars. One for setting things up and one for the final job, yet most shops use just one. That's fine as long as they get it right the first time which can happen. Usually, this is where the noise is originated from.
It's one thing I dreaded about the gear install I have done because that is the hardest part....dealing with the pinion gear.
Noise only happens for one reason...Improper alignment of the ring and pinion gears whether they are riding too high on the heel or riding too low on the toe. Both of those cause noise as well as improper backlash. If your truck dont slam(clunk) in drive or reverse then the backlash is correct.

Not to say some gears wont make noise, but it must be very faint. If it's very faint, i would debate on just leaving it be and working with the shop to have them agree to fix if anything werre to go wrong or it got worse after a few thousand miles.
Also, what type of gear oil did they use? Did they tell you about proper break-in procedure?
Drive the truck easy the frist few hundred miles ~300 is fine. Make sure the diff goes through a few complete hot/cold cycles. Like 4 or 5 and then you can begin to get on it.
Also, make sure you change your fluid after 500miles. You can go as long as 1,000miles, but make sure it gets changed.

 

There's a poll over on Dodge talk and it shows that quite a few guys w/ motives have some noise from 45-55 mph. As long as it's relatively quiet I think you're fine, if it changes or you hear a clunk or anything in the rear, then take it back to the shop.

 

i wonder why you have to change oil at 500 miles you don't do that on a new vehicle. should i go with synthetic on the gear oil. thanks for all the input

 

You can, since that is what dodge recommends but eaton says in the FAQ here http://www.eaton.com/EatonCom/Produc.../FAQ/index.htm dino oil for the truetrac. I'm running syn. w/ the DTT and I know of a few other guys as well so it's really up to you.

 

It's something that should be done but the manufacturer doesn't reccomend it because it's just another expense shoved onto the customer at such a soon interval. I did my first oil change at 1,000miles as well and then 2500 miles after that. now i am on a 5k interval using Synthetic.

DTT is not suppose to be ran with Synthetic as the Synthetic has different friction properties than dino oil and the gears need a certain amount to engage and run properly. Dino oil is what the manufacturer reccomends. You may be able to run with a Valvoline Synblend??? I'd call up and ask. Can't hurt.

I would do the change between 500-1000 miles. That is when the intial wear occurs. Then after that just do them at the reccomended intervals. I'd suggest 15kmi for normal/highway use and every 10kmi for towing/hauling.