4x4 launch in a 98 12v?
 

I was just daydreaming about hitting the dragstrip and wondering about launch methods.

Transmission is a ATS with a billet input, Banks billet converter, and a billet flexplate....what are my limitations? I would like to do a boosted launch without tire spin or breakage. What PSI should I be aiming for, and 4x2 or 4x4?

If I launch in 4x4, should I try to shift it out, or run the whole track in 4wd?

Lock it in 4wd. I dont know how good the banks converter is, but im assuming its probably ok.

Since you have a billet input, then your output would be the weak link. You should be fine around 14-15psi though.

Leave it in 4wd the whole track.

Some guys try to switch out about of 4x4 about 1/2 track, they claim that although the hubs don't disengage, the transfer case does and they end up saving maybe a tenth and gain 1-2 mph.

I have read about guys hitting 115 mph in the 1/4 running 4x4 the whole way till they slow down and switch out before they turn off the track.

I have never read about parts failure one way or the other.

Jimmy Smith runs the whole 1/4 in 4wd. 9.5 seconds and 140+mph.

I switch out of 4x4 if i dont forget in the 98, i can feel it disengaging at about half way, and its quicker that way. not all 4x4s will disengage though.

i have a flexplate, billet input and TC, just like you, launching at 15 should be ok. i launch at 20 psi sometimes, and have broken 2 stock outputs

Thanks guys for the input.

Seems like 4x4 launch at 15 psi max should be pretty safe.

One more thought...I have a dana 70 rear end. Are any of you guys breaking those??

Let us know how many you get out of the shaft. I didn't get many before I snapped my first output.

So you are saying 15psi is too much??

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I agree with Mike D. I broke two (2) stock outputs in a 2002 Dodge CTD 24 valve I had.:( IMHO,...they can't take many drag race launches. I would save up for a billet output and get that thing in as soon as you can.
I launch my 96' Dodge CTD 12 valve in 4WD High and I leave it in 4WD all the way down the track. With the stock output I would keep that boost at around ten (10) pounds.

Good luck!

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John_P

It may take that much, it may not. I broke mine at around 15-18. I think they twist just a bit every time you launch until they break.

The billet shaft aren't cheap but it will save a bunch of aggravation for you and the buddy that tows you home.[coffee]

Agree with the 10 psi max for stock shafts still in the tranny.