I bought mine with 91,000miles on it. All had been pulling a 5er. No problems so far. Lightly modded.

 

i love my DTT...don't get me wrong...but it shifts firm. Mine is set up to be nice around town but strong enough for race day. A buddy of mine has a DTT that jerks you a little when it shifts...just cause he wanted a good, firm shift. Believe it or not, firm shifts are better for the tranny as I am told.

Sticks are sooo nice cause you decide when and how hard you want to shift. My auto still shifts firm enough that people will comment on it....especially the females....but its not too bad.

For the money i put into my tranny, i could have had injectors and a CP3 upgrade

 

The reliability is Good with the 48re as long as you don't abuse it or mod the truck too much. The only issue I have is when starting off heavily loaded. The truck will rev up to 2300 rpms to get going. Shifts are fine and no other real quirks. I personally would like the TC to be tighter so I can roll on the throttle to get her going and not have to put my foot in it. Just my personal opinion though. Fluid flushes every 30,000 and filter changes every 60,000 and all should be good. To mod the 48re to pull heavy can get expensive. TC, VB, Billet input shaft/drum, flexplate. About 2800 dollars worth of parts.