auto box racing start

texpis · Post by **texpis** » Thu Jul 19, 2007 7:48 pm

Hi all says it in the title realy just wondering what is the best way to do a racing start. I have a Bowler Tomcat with range rover ZF autobox. Can I rev it in neutral and slam in to gear or will this destroy the box?

Mick

ihatesissycars · Post by **ihatesissycars** » Thu Jul 19, 2007 8:03 pm

You need a trans brake for that don't you?

You put it in gear, engage the brake which locks the box up then rev the engine to the point where the torque converter is really biting but the brake is holding the the car stationary and when the lights change you release the brake and all hell breaks loose!

Slamming an auto box in gear whilst revving it would bugger it up surely?

texpis · Post by **texpis** » Thu Jul 19, 2007 8:28 pm

Thanks for the reply I haven’t tried slamming it in gear from neutral thought it may not be good for the box. I have been left foot on the brakes and revving similar to what you suggest. Just thought if any one would have a better idea they would be on here.

Mick

4x4x383 · Post by **4x4x383** » Fri Jul 20, 2007 6:39 am

Without a transbrake, which is only really used for drag racing or similar, keeping your footbrake on with a few revs is the best bet.

This has the advantage of taking up all the slack in the drivetrain so you are much less likely to break something.

ChrisJC · Post by **ChrisJC** » Fri Jul 20, 2007 7:16 am

Holding the car on the footbrake and flooring the throttle is a standard test in the Land Rover manual to check the torque convertor stall speed.

However it does say only do it for 2-3 secs max! Things will get very hot very quickly.

Chris.

Eliot · Post by **Eliot** » Fri Jul 20, 2007 7:32 am

def dont slam it into gear.
As others have said, foot on the brake - give it some gas. Will need some practice to avoid bogging it.
Drag racers change to the torque convert to increase the 'stall' point. So they can launch at higer RPM. But on a 4x4 (like me) - the last thing you want is a high stall convertor - as the fluid will get very hot when going slowly.

mgbv8 · Post by **mgbv8** » Fri Jul 20, 2007 7:51 pm

As said before, dont stuff it into gear at high revs. I left foot the brake and hold the revs at 3000 on mine. I know my coverter has a 2800-3000rpm stall speed so thats what I go by.
Transbrake is the way to go for hard launches, but that brings its own set of problems with the drivetrain.
Do you know the stall speed of your converter?
You can experiment once you know this.

texpis · Post by **texpis** » Sat Jul 21, 2007 10:48 am

Hi Thanks for the replies guys. I dont know the stall speed but I believe Range Rover auto boxes stall at 2K I will have a play

When I was experimenting before I did notice it bog down thats why I asked the question what causes that?

Mick

ozrover · Post by **ozrover** » Sat Jul 21, 2007 12:42 pm

DONT REV THE ZF IN NEAUTRAL AT ALL!!!! If you do a quick websearch,you will find heaps on how a design fault with the hp22 and hp24 boxes allows fluid to bypass in neautral and park which partially engages the clutch packs causing them to heat up and burn out.Even emisions testing in the US causes this on BMW's,volvo's RR's ect.It is the weak link with this box.For the type of use you are talkin about .better off with a TF727 or a chev t350,t400 or beefed t700.
Regards Doug

x.l.r.8 · Post by **x.l.r.8** » Sat Jul 21, 2007 1:58 pm

In addition, jack the rear up of the car and run it through the gears, or drive it around to warm up the trans fluid, cold oil in an auto does nothing for the bands, it slips more and is far less consistant. And on the strip consistancy is the name of the game. Many racers get frustrated when dialing the car in the 60ft because they have not preped the car the same each time. Reving with the car in gear and your foot on the brake will cook the trans in a very short period.