drag racers-when is it time to upgrade the carrier?

i would be more worried about the t-5 than the axles or carrier, they are cheaper to replace than a trans IMO.. depending on how you drive all of those components should be replaced if you are using full slicks and going to be launching the thing really hard..i have a g force t-5 in my car and i have no worries about that breaking for a long time.

I would never rebuild the stock rear, with stock parts. Not that the factory stuff is bad, but having it done twice sucks.
I also would never do a full rear rebuild myself, too many back yard mechanics screw them up and destroy hundreds in parts.

Get some 31 spline axles and an eaton center section. I run an auburn, which has been good to me for 10 years, but here and there i see some complaints about it.
If you want discs, now is the time for that too.

What does the NHRA rule book say?? thats when. Now that being said lol, I ran 31 spline axles for years with a Ford diff. that I had the clutches stacked in and the fiber ground off the clutch plate so they would not wear out and they didnt they would just brake the ears off it got to the point where I was rebuilding the rear 1 to 2 times a year depended on how much I drove the car (this is a auto car) the thing about it they would brake at the worst time like in the semi rounds at the track a few times and I would lose the race due to wheel spin. So I moved up to a mini spool that lasted 1 year broke it to then I move to a full spool and 33 splines it don't brake any more and I love it, peace of mind you know. it is really not to bad on the street, just real tight parking lots I would do it again and again and not think twice. this was when I reached the high 10s with 1.50 60 fts before I went to the 33 spline set up. The 33 spline set up as been bullet proof gone much faster but it should be also. But I also have a customer that runs high 10s with stock stuff and a lincoln locker (you know welded up rear) but it is also a auto car.