Recently some of you commented on the possibility of the ZF automatic
transmission as fitted to the Range Rover having problems if the engine is
revved up in neutral or park after the transmission has been in gear.
Apparently fluid can fail to drain from the clutch packs when the
transmission is shifted into neutral, so that when the engine is revved
with the brake on, damage can occur to the clutch packs.
Comments were made about emission testing, which requires the engine to be
revved in neutral or park with the brake set, and the potential for
damaging a faulty ZF transmission by doing so. Some of you said you insist
that your Range Rover's engine be turned off and the transmission allowed
to sit for at least a minute to let the fluid drain off, after which the
engine can be started and revved up for the emissions test.
Not knowing squat about the innards of an automatic transmission, I wonder
if rather than turn off the engine for a minute or so, simply revving the
engine a bit after shifting the transmission into neutral with the brake
OFF would immediately indicate if there was a potential problem with the
fluid drain? After all, if the fluid has failed to drain properly and is
still in the clutch packs, reving the engine in neutral would cause the
vehicle to move, would it not? If it did move, then the procedure of shut
down, wait, and re-start would be the course to follow. If it didn't move
when the engine was revved in neutral, couldn't one assume the drain-down
function was working properly, and it was safe to rev the engine for the
test?
Like I said, I know nothing about automatic transmissions except how to
shift them, so perhaps my logic is full of holes. In this state (WA), you
operate your vehicle yourself for the emissions test, so it would be a
simple enough thing to do the neutral/brake off/rev-the-engine-to
see-if-the-vehicle-moves test. In states where you have to turn your
vehicle over to a tester to run through the process, it might be easier to
simply have them shut it down, wait, and restart rather than try to explain
some other process.
The earlier thread was the first I'd ever heard of the potential for a
drain-down problem in the ZF transmission (or any automatic transmission
for that matter). I'd be curious to know how common this failure really is.
________________________
C. Marin Faure
(original owner)
1973 Land Rover Series III-88
1991 Range Rover Vogue SE
Seattle, WA
marin.faure@boeing.com
faurecm@earthlink.net
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