Originally Posted By: rslifkin
With the trans in park, the output side of the converter is spinning freely (trans is in neutral with the park pawl engaged to lock the output). In drive, the converter is being forced to slip more, as the output is locked at 0 rpm. It does make more heat in drive because of that.
Thank you. I was confused by the replies to my comment, but then came to accept that they did not know/forgot how a torque converter works.
Originally Posted By: doitmyself
Some people are shifting into park while others are shifting into neutral. Does this make a difference?
If a person shifts their transmission 5 extra times per day trying to reduce wear: 5 x 365 days = 1865 more shifts x 5 years = 9,125 more shifts. Is there extra component wear from these 9,125 extra shifts that negate the "savings" vs. just sitting in gear with brakes on??
The component wear would be roughly the same as repeated 1-2 shifts, which many fleet vehicles can make hundreds of times a day...
HEAT is what kills ATF and automatic transmissions, not shifting usually.
Also consider that a shift like 1-2 deals with a much larger RPM differential between gear ratios vs an 800rpm to 0rpm N-to-drive engagement. The 1-2 shift also takes longer, meaning more slippage on that clutchpack.
So the 1-2 clutch pack sees much more engagement each day, and it's shifts are slipped more/modulated longer than a quick (often rolling) engagement of the forward clutch.
I'm a convert; I used to be about just leaving in it gear, but eventually realised using fuel to further stress the transmission truly makes no sense.