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Without overdrive, the transmission enters a different shift pattern (uses more gas, offers more torque) and also adds in a touch more engine breaking to allow for more controlled stops. Never heard a suggestion for slippery surfaces myself until I gave the tape a listen. Never got a full explanation on gear selection in an automatic either as my family has always had manual.
Interesting. I didn't know it changed the shift points too. I guess later on they made it a separate tow haul switch. My manual doesn't say anything about using it on slick surfaces. Only this, which accelerates from a stop in 2nd gear:
"Low Traction Mode can assist in vehicle acceleration when road conditions are slippery. While the vehicle is at a stop, select the second gear range using Range Selection Mode. This will limit torque to the wheels after it detects wheel slip, preventing the tires from spinning. "
and
"Downshifting the transmission in slippery road conditions could result in skidding."
Last edited by mountainmanjoe; June 8th, 2019 at 3:29 PM.
Quite a few changes between the generations. Some following years got a CD in the manual as far I know. found the Camaro one in the bone yard and never got to listen to it.
There could be some electronics involved with newer vehicles. But 2nd gear start is an old feature of the 4L60 from before Stabilitrak. For example, the '99 Astro manual says:
"If you manually select SECOND (2), the transmission will drive in second gear. You may use this feature for reducing torque to the rear wheels when you are trying to start your vehicle from a stop on slippery road surfaces."
Another interesting thing I've noticed about GM transmissions. 2nd gear only will not roll backwards on a hill. There must be some kind of sprag clutch incorporated into it.
So I've been reading about DIY engine oil tests. There are various tests you can perform which will reveal some information about the condition of your oil, such as the "crackle" test for moisture content.
One of these is the blotter test. You can buy kits like this:
I'm pretty sure they are just dense paper though. So I dabbed some used engine oil on some card stock and let it soak in. Then I dipped an edge into some lacquer thinner and let it wick through the card to separate the sample. You can see a black stain where it left behind some contaminants.
This is oil with 10,000 km (192 engine hours). I went by the oil life indicator in the DIC. Obviously this is very amateurish, but it gives me a point of reference.
June 8th, 2019, 3:15 PM
