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STS 2nd gear start with traction control off?


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Took my 97 STS for a spin last night to test the new brakes... at one stop light I switched the traction control off and I noticed it starts in 2nd gear, even if I pull the shifter into L1. What's up with that? Can I get around this in a simply way? I know why Cadillac wants it like that... but I don't like it!

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i don't know why you'd want to change that....feature comes in handy when the ice and snow falls...less spinning from a light in that stuff...any way WOT time...ya need traction control <grin>

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Scottshoe, it's like that so you don't blow up your differential. On most FWD cars (Cadillacs included), when you "spin the tires", it's usually one tire that spins. Since only one tire spins, and because of the action of the differential, that tire spins at TWICE the transmission output speed. So if you spin it wildly in first gear, the transmission output speed might equate to 40 mph road speed, and that's what your speedometer might read, but the one spinning tire is doing so at an equivalent of 80 mph!

Aside from the danger of blowing that tire and scraping your wheel wells and fender sheetmetal, the gears in that differential are spinning at WILDLY different rates, which can damage it (actually WELD the spider gears together). Here's some text from the old board from a Cadillac powertrain engineer:


Also, the second gear start is required on dry pavement to

protect the differential gears and drive axles. The motor has

enough torque that if you were to nail it in a patch of dirt or

puddle and then suddenly hit dry pavement the drive axles or

differential gears could be damaged by the sudden shock load.

Similar to the above, if one tire is on a very slick surface and

the other on a dry suface and you floored it the one tire spins

very rapidly...it actually spins twice the speedometer speed.

This is very hard on the differential gears and can fail them due

to the high RPM they are spinning...it can actually weld the

differential spiders to the shaft and break it. This is not

pretty. Traction control prevents this from occurring unless it

is turned off then the second gear start reduces the torque

lessening the likely hood of severe wheel spin.

Since you will accelerate the fastest with the traction on there

is never a reason to drive with the traction off

( ....OK...unless the traction control is acting up...) so we

never really felt the second gear start would be a

detriment....Except for the magazine writers testing 0-60. The

magazine guys just HAVE to turn traction control off... don't ask

me why... so...for the logic was changed several years ago to

allow first gear starts with traction off. To be honest I

forget which is the first year with first gear start with

traction off....maybe 99 or 2000....

Anyway, with first gear starts, traction off, there was special

computer logic developed for the PCM to protect the differential

and drive axles. It cuts engine power if it senses a wheel

spinning up or accelerating faster than it would on normal dry

pavement and it will cut engine power if it sees one front wheel

spinning much faster than another. It is called "differential

score protection"

One fo the advantages of a front wheel drive car is that the

traction control can be tuned to allow 5 to 10 % slippage which

will give you the best acceleration. That is why the Northstar

cars will squeel the tires on accel even with traction control.

It is OK to allow a little wheel spin as the front wheel drive

car does not try to "spin out" with tire slippage the way a rear

wheel drive car can. The RWD car cannot tolerate any wheel spin

in a turn as it instantly becomnes unstable. So, the traction

control systems on RWD cars are almost universally much more

aggressive and intrusive compared to front wheel drive cars.


In short, just leave traction control engaged. You will NOT get better performance with it turned off. If it engages, one of your tires is spinning anyway, and not accelerating your car. Cadillac did the 2nd gear lockout for a reason. If you try to override that for some reason (I can't think of a single one), do so knowing the risks! :)

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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