Re: [A/S] Tranny lock-up kit and exhaust brake

[Jim Dunmyer <jdunmyer@xxxxxxxxxxx>]

Spencer,
 When you install an exhaust brake, its purpose is to make that Diesel
slow down more under a "no throttle" condition than it would otherwise.
This is to get better engine braking when going downhill.

However, when you lift your foot from the accelerator pedal, the torque
convertor unlocks, causing a near free-wheel condition. That negates the
effect of the exhaust brake. Well, actually, it doesn't completely
free-wheel, the torque converter is still passing torque from the
driveshaft to the engine, causing severe heating of the transmission
fluid on a long downhill.

If you can force the torque convertor clutch to remain locked until the
truck is going very slowly, you'll get much better engine braking and
lower transmission temperatures to boot.

BTW: there was a thread here a few days ago about the necessity of a
cooldown period for your Diesel truck. I saw a web site with a chart of
cooldown times, based on what was going on just before you want to shut
it down. Times varied from 'none' if you were just driving around to as
long as 5 minutes if you just pulled into a rest area after a long
upgrade with your trailer behind. They apparently even sell an
auto-shutoff device that allows you to turn the key off and walk away
while it monitors exhaust temperature and shuts the engine off when the
temperature falls below 300 degrees. 

The problem isn't that the engine is overheated, but the turbocharger
can be very hot if you've been pulling hard. Shutting it down stops the
oil flow and thus the cooling to the turbo, causing the oil in the
bearing to cook. Allowing a cooldown period eliminates that.

                                               <<Jim>>