when do you need a built trans

[sonicblue04]

how far can you go with mods before you need a built trans. what kind of power can the stock hold up to.

[L8 APEX]

I have seen mild slippage over 440. The early 2001 J1 code trannies break over 420. It is a balance of time and luck. The harder it shifts the sooner it will break stock parts.

[Mark #2]

Mine has been good for over 500Hp for 2 years now.

[Silver_2000]

On my 2000 I went thru a bunch of transmissions - I think the tune has a lot to do with it since I was only pushing 410 HP or so on my 2000

[WA 2 FST]

The harder it shifts the sooner it will break stock parts.

See, and this is what I don't fully understand. Theoretically, the trans needs to shift very _quick_ in order to avoid slippage which causes overheating, burnt fluid and burnt clutches in the trans.

This is then seemingly contrasted with a _hard_ shift that is tougher on parts (I would think the input/output shaft would be most effected here).

So exactly how do we get a _quick_ shift that is not _too hard_?

[L8 APEX]

The weakest link is the stock intermediate sprag it has 34 elements the HD version has 45 elements. It is a mechanical one way clutch. It free wheels in 1st gear and when you apply 2nd it engages and starts spinning its drum in the opposite direction that it was turning in first. That is a very high shock action.
You want to keep the line pressure down on stock sprags as they can fail at the hard apply of 2nd gear under high load.

[Sixpipes]

I've managed to hold on to my stock transmission for 90K+ miles and I think one of the reasons is I never had a chip burned with an increase in line pressure. I've only had a shift kit under normal stock shifting pressures. My truck has been 400+ rwhp for a long time and although I haven't raced it a lot recently, it still works very well. I have recently replaced the rearend and I'm sure the tranny is going to go in the not too distant future, but I have been very pleased with my stock 99 drivetrain. :cool:

[sonicblue04]

I just got a built motor with cnc ported heads and stage 2 cams. I am planning on a kb later on that is why i ask. i thank everyone for the response.