Coming out of the waterbox "squeak"
 

I've read here that it is very hard on an automatic transmission to let this happen. My question is it the same harm when doing the 1-2 upshift?

WaterBOX

I raced weekly from 86 to 2011 and always did the 1-2 shift burnout and never hurt a thing doing that.Every car I see does the squeak at the end of your burnout when the tires grip.

As everything in this hobby …”your mileage will vary”

I’ve personally, blown 3 sprag elements.

If you run a th400 transmission, I suggest a first gear only burn out in the water box IF you run a standard valve body.

If you race infrequently and really don’t care about consistent heat to the tires, carry on with your 1/2/3 burnouts….you may or may not experience an issue

For a loooong time now, I ONLY do third gear water box burnouts. After the burnout, I no longer dry hop the tires for affect…..no need….no squeak ..no sprag issues. Still racing as of 9.10.22

My radial slicks squeaked when they hooked way more than bias slicks. DOT radials also squeak more.

Open your door slightly or use your side mirror and glance back when you drive thru the water. I like to "blip" the throttle in the water then roll to where it's just coming out of it. Set the line-lock and start your burnout. Once the tires are heated up release the line lock and allow the car to move forward. You know at this point that the tires are going to clean off the water and stick pretty hard so ease back off the throttle so you aren't shocking the piss out of the drive train when this happens. Let the vehicle roll forward, stage the car and make your run. You will learn to time things out so you are cleaning off the tires effectively then minimize the "hit" when they finally grab.....

https://www.youtube.com/watch?v=6zVdoLR-VzM

Cool, thanks guys. A related question, now driving on the street with street radials and stock TH400 does a chirp from 1st to 2nd cause any particular harm to the trans?

You should always do one spin on the water , move up to dry put it in the highest gear possible and then spin. Spinning in the water just throws water up on to the wheel wheels to drip down onto the tires .

The reason for not shifting is it destroys the sprag. If your spragless your good to go.

Also you never want to move forward and CHIRP the tires as it wipes off all the hot rubber. Just let off and let the wheels spin to a
Stop then move forward.
Even I don’t always do this to the letter but it is the proper way to do a Burn out .

Hadn’t read through the posts but cliffs explanation sounds correct as long as your not moving forward under hard power but more rolling out of it

Just cause everyone does it doesn’t make it right. Chirping the tires out of the burnout will clear the grip off the tires more then not doing it. Ask any tire manufacturer.

How can you be spragless if the direct drum contains the sprag.? I thought that is what everyone is referring too.
Intermediate sprag being roller on the 1-2 up-shift.