I have the open dif (3.21) and want to add an LSD. The guy at the shop is a hard core dodge guy. He said the stock unit is junk, the auburn is better but the cones wear out (I think he said at ~ 40K miles). He is a big fan of the Tru Trac. I asked him about the reliability of the Tru Track and he said the old ones would break but the new ones are really good. He runs them in the front and back with 35s on his '08 QC. His truck has been featured in some off road magazines. One drawback is the price of the Tru Trac ($580)
He can get me factory gears for $365, labor is $395, install kit is $120, optional axle bearings and seals $46 and gear oil is $23. Comes out to $1134 Parts + $395 Labor + $110.57 for tax = $1639.57.

I know it's expensive and he can get me cheaper gears and the auburn and skip the axle bearings and reduce it by about $300.

The last issue is the gear ratio since I'm going from the 3.21 to either the 3.55 or the 3.92. I tow a lightweight 3500# trailer and the 3.21s do fine so I'm inclined to go to the 3.55. I'm just torn by the decision since I really like the 3.21 highway manners and I feel the 3.92 may be overkill for me.

Just looking for some encouragement and some real life experience with the Tru Trac.

 

Auburn clutches are rated for 100k miles. I had one in my 2nd Gen that had 68k miles on it when I sold the truck, still performed like new. I wanted to try the DTT in my 3rd Gen, but at the time Detroit was having a real problem with them grenading, especially with tires over 33", so I went with the Auburn again. Haven't heard of the DTT having issues in a few years now, so I'd say your "gear guy" is right with his assessment. I do know that at one time, running a DTT with tires over 33" voided their warranty. Dunno if it's still the case.

People rarely complain about either brand. Although most "track" guys use the Auburn as the clutches grab a bit faster than the technology in the DTT. However the DTT has a slightly higher bias ratio than the Auburn "Performance Series". Most off-road guys opt for the DTT.

You really can't go wrong with either...

Is a shop in my area, is right next door to where KRC Performance used to be. Great reputation. They charge $600 per axle for gears, install kit, fluids & labor. If installing a LSD at the same time, they don't charge any additional labor, just the cost of the LSD unit. Price also includes a 500 mile "after break-in" check and fluid change.

IMO, if you are thinking 3.55s, I'd stay with the 3.21s and just have him put in the LSD, I highly doubt you'll notice the difference going from 3.21 to 3.55. I dunno how the newer Hemi with MDS reacts to gearing, but the non-MDS Hemi has a "sweet spot" right between 2000-2200 rpm and actually gets better fuel economy than cruising at say 1600 rpms. Hence why most of us went to 4.56 gears, especially with 33" or larger tires...

 

Hammer, good input, you're right about the labor - once they open it up there's no real savings on labor so going for the gear change isn't really a money issue. I'm running the stock 31" tires and thinking about the next set being a little more aggressive and going with a 33"s. If I stay with the 3.21 that basically eliminates the 33"s and if I go bigger than 33, then I need a lift. From what I've read here, there are some issues with the leveling kits and lifts. I've owned several GM LSDs and they were worn out before the truck was. Since my truck is a 2WD, a good LSD makes a world of difference for me especially if it doesn't loose effectiveness. The sweet spot for the 4 Gen is around 1800 RPM for MPGs but for power it's around 22-2300. What I see for me is a stock truck with 33s that will go just about anywhere and good highway manners, that's why I thought the 3.55s with 33" tires would be better. After a couple of beers though, the 3.92s are back in play - it's only gas money