1. Don't use the automatic kickdown to choose a lower gear when climbing.
Shift down manually. This will maintain higher pressure on the clutches in
the transmission. Manny (the foremost TH425 expert) doesn't install
kickdown switches in his rebuilds.

2. Don't try to make real power at low RPMs, particularly below 2000.
Choose a lower gear. As Dick Paterson says to justify this recommendation,
the oil pump is only moving at half the speed of the engine.

3. Therefore, if the grade is so steep that you can't maintain RPMs in the
power band (2400 to 3600 RPMs, or thereabouts), slow down, manually
downshift, and keep the engine in the power band.

4. At low speeds and while accelerating, the transmission will do the right
thing.

5. From a stop, the stall slip of the torque converter will do what needs
to be done.

6. The GMC isn't a race car.

Rick "we have to be the drivetrain control computer" Denney

On Mon, Dec 18, 2017 at 11:25 PM Vadim Jitkov
wrote:

>
>
> Here is a follow up question (let me know if I need to start a new thread
> for this):
> from the point of view of transmission, what is the best way to tackle
> hills on the road? In the area where I live, we have significant grades on
> nearly all our roads. We've got multiple grades of 3-4% in any direction
> we get going and some very steep grades of 6-7%. I've read that its best to
> slow down and downshift to "S" gear for tackling the grades. Should this
> be done on all climbs or just on those very hard 6-7% grades? What about
> driving in town (again lots of hills, but driving at 25-35 MPH)?
>

> --
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
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