Once in a while I'll see a car (high horsepower hotrod) that's got serious performance and horsepower "chirp" the rear wheels real quick when the driver shifts into gear.... either Drive or Reverse. I've always wondered why....

What parts of the drivetrain (engine, trans, stall convertor?) make this happen? Or is a combination? Is it because the engine is tuned to such a high idle RPM that the power is tranferred hard to the wheels? I've never noticed that they are idling super high or anything, just some serious power. Is it a transmission\stall convertor thing or just the raw power being tranferred through the drivetrain?
I want a car that I have to stand on the brakes when shifting to Drive!! graemlins/thumbsup.gif

My car chirps the tires in reverse or 1st gear when going into gear if the pavement isn't real sticky.

I think it has to do with a lot of things, converter, rear-end ratio, fluid pressures, etc. Lots of low-end torque helps too graemlins/thumbsup.gif

For what it's worth, my driveline consists of a Mike's full-race T400, 4500 stall converter, and 4.56 on a spool.

AH! The rear ratio.... I'd forgotten about that! That explains it if that's the reason it happens.

I've noticed it at some cruise ins. Seems like it's mainly cammed up big blocks or blown small blocks that do it. As mentioned the big torque and rear ratio contribute. The only chirp I can get is on the 1-2 shift at 6k, but I'll take it. smile.gif

graemlins/thumbsup.gif

When you put the car in to gear with an automatic you load the whole power train with torque. The brakes are supposed to prevent the car from moving. How ever the rear brakes don't apply that much stopping power so when the power comes the rear wheel will rotate slightly but the front brakes will keep the car still. You will also see the car make a jump when it gets preloaded with torque.

The same thing can happen in icy winterclimates, when you stand still at a stop light your rear wheels can be spinning but the car is standing still.

I think it is more because of low brake pressure to the rear wheels when standing still than anything else.

Pull the parkingbrake and it will not happen.

Jan

try lowering your IDLE and you will see this problem dissapear quickly.

Hell, even daily drivers lurch when put in gear, but I'm talking about seeing a WIDE slick or street tire literally spin on dry pavement.
That's gotta be some serious power. I was just curious as to the combination of things that cause it to happen. I hadn't taken into account the front\rear brake differentials either.
I want to duplicate it when the money tree blooms. :cool:

Thanks all...

Lowering idle is one thing, however due to the cams and intake combos, sometimes a nice 900rpm idle isn't in the cards. In my case, I can get an idle at about 1200rpm once the car is warm, however when the motor is cold, 1500+ is where it is. Even at 1200rpm the chirp is pretty much unavoidable, even with 15" wide meats.

Brake balancing to the rear wheels could cause this to be a cause in some cases, but usually it's just a heavy torque load combined with unforgiving drivetrains.

I agree... too high an idle.

I drove a 98 Grand Marquis yesterday that chirped the tires when i put it in reverse,So much for the high HP and torque therory.

I'm running a 30 over L-72 427 11:1, 4000 stall th400, 4:10 and idle at 1100 and have no problem with the tires chirping, maybe at 1500 you would but i always let my rings heat sync to the motor before going for a ride, which brings the idle back to normal. I'm sure I'm not pushing as much HP as you are with a blower but I'm still in the mid 600 range.
My father in law is running a 426 Hemi stroked to a 472 with a bds 8-71 blower pushing a true 1100 HP and doesn't have this problem either, it must just be in the setup. graemlins/thumbsup.gif

loose converter allows higher idle without making the trans "hit" so hard when putting in gear?