ive been avoiding cops at high speed by downshifting on auto. couple of my friends told me that it would ruin my transmission. would it ruin my trans?

 

You mean by using the sport shift feature? I hope not because I do so in the off ramp to my place every time... 80 to 25 mph in less than 10 secs (also using the brakes a bit)! After the posted-20-mph-turn, I put the gear to Drive and on I go.

 

If you're using the SS and it doesn't over rev, you should be fine. However, instead of downshifting, try using the brakes next time. They are much more effective at slowing you down.

 

Using brakes is a lot more cost effective and does a better job slowing you down than the tranny (be it MT or AT).

 

you will not ruin your transmission. using your brakes with engine braking is the safest way to slow down your car.

 

I do this too every now and then. Is it bad? I was always taught that it's more economical to slow down a 5spd car using the transmission and downshifting rather than applying brakes, b/c energy is lost when you hit the brakes. Is that true? Also isn't downshifting supposed to be better for gas mileage?

 

It's not any more economical - especially if you blow your tranny downshifting. Energy is lost no matter what you do to slow down. The only time this applies is on a hybrid car that uses the motor part of an IMA system to recharge the batteries.

Downshifting does not save gas. It gets you in the proper gear/power band the next time you need to accelerate.

 

I think so, too. Yet I always keep the RPMs under 4500.

 

Engine breaking is a useful tool, especially in bad weather. On downhills in slippery conditions engine breaking can give you better control when decelerating. You're still better off using the brakes as your primary way to stop/slow down, that's what they're there for.

 

I down shift all the time, I live in the foothills...
I lightly used the brakes in the hills.. coasting down hill , while in lower gears, and down shifting when needed...this is the norm for me.

No issues yet...6500 miles on it.

 

Do both downshift and break all the time. As long as the RPM is not too high, it should be ok.

 

I think the reason he's not using his breaks is because the "cops" he's been avoiding would see the brake lights. The police often take the break lights as an admission of guilt. . . if you weren't speeding why'd you slow down. . .

 

Downshifting is fine for it. Keep it under 10mph when you go into first. That is the main concern (1st gear).
But why put it back in auto after downshifting? Keep it in SS =)

 

The AT-SS will prevent downshifts into a gear that overrevs the engine. The gear indicator just blinks a few times.