jmarsa

iTrader: (1)

Building a autocross/track car...

If during the course of competition your car spins with a manual trans if you disengage the clutch you can prevent the engine from reversing right? What about an auto? Is there a mechanism built in the trans to prevent this? Can the torque converter spins backwards? Can it "grip" in reverse rotation and cause the engine harm?

--JMarsa

12secSS

iTrader: (30)

An automatic uses fluid coupling, so there is no direct attachment from the engine to the transmission. The vehicle will continue to roll backwards if it is in a forward gear. Haven't you ever been on a steep hill with an auto, at a stop light? It will roll backwards if you are not on the brakes. This is because the output shaft now has more leaverage against the converter than the engine does. Causing the turbine fins (input/engine side) in side of the converter to spin slower than the impeller fins (output/trans side). The angled turbine fins toss fluid to the angled impeller fins to turn them. If the impeller spins faster than the turbine, you have effectively no engine/trans coupling. Nothing bad will happen, just hit the brakes when you spin out and hold it until you stop moving. Then proceed again. Unless the track is situated on steep inclines, you have nothing to worry about. I have Auto-Xed my A4 many times and never had a problem.

jmarsa

iTrader: (1)

Thanks for the reply George. It makes sense. I was thinking of those spins in the middle of the apex situations where there is alot of momentum and the car rolls backwards for a car length or two. It also helps for getting out of the way!

--JMarsa