Passing Gear Ques.

[David]

New to this group I see we have some highly experienced experts offering
advice. I'm looking to purchase a Saturn in the very near future,
because of the 35~38mpg rating these cars have established. Over the
past 3 weeks or so I have test driven 4 or 5 Saturns ranging in years
from 1999 to 2002, all of them SL2's, all automatics w/ overdrive. One
thing I found in common with all of the Saturns I've driven is what
seems to be a down-shifting flaw. At speeds around 45 or 50 mph, when
you step down on the gas (to hit "passing gear"), the transmission
doesn't down-shift to the next ratio, say 4th to 3rd, or 3rd to 2nd. It
seems to drop aaaaLL the way back to first gear, causing the engine to
"rev" to a very uncomfortable 5~6,000 rpm. This can't be good for the
engine! My question is,..is this a malfunction? or is this normal
operation? Is it a mal-adjusted passing gear linkage?, or a glitch in
the computerized shift program? Do all of the Saturns downshift this
harshly?..it's odd that all of the one's I've test-driven behaved the
same. I would like to add that my wife's car, a 2001 Chevy S10 2.2 litre
4cyl. w/ 4spd overdrive automatic, also downshifts in the same manner,
all the way down to 1rst, no matter how lightly you press the
accelerator. Is this simply the way GM designed the shift pattern for
all its' 4 cyl. automatics?...a design flaw?...or just something out of
adjustment? Any input will be greatly appreciated. Hope to hear from you
soon.

 

[Steve]

New to this group I see we have some highly experienced experts offering
advice. I'm looking to purchase a Saturn in the very near future,
because of the 35~38mpg rating these cars have established.
<snip>

Hi, David,
Can't answer your main question but thought I should let you know that
AFAIK you will not get anywhere near 35 + MPG in a 1999 SL automatic. I have
a 1999 manual and get a bit over 40 during warm weather and 35 - 38 in cold
weather, doing about 2/3 highway and 1/3 "city" driving.
Good luck!

 

[David]

Nobody out there can share their thoughts on this subject? Surely you're
not all driving manual tranny's?

 

[RK Henry]

...One
thing I found in common with all of the Saturns I've driven is what
seems to be a down-shifting flaw. At speeds around 45 or 50 mph, when
you step down on the gas (to hit "passing gear"), the transmission
doesn't down-shift to the next ratio, say 4th to 3rd, or 3rd to 2nd. It
seems to drop aaaaLL the way back to first gear, causing the engine to
"rev" to a very uncomfortable 5~6,000 rpm. This can't be good for the
engine!

I don't think it's actually shifting all the way to 1st gear but is
probably is going to 2nd, depending on how hard you've hit the gas.

This is a fairly common design feature these days. It's designed to
work that way. In the ancient times, cars equipped with
large-displacement V-8s could pull away from a standstill in high gear
and burn rubber at the traffic light, putting on a great show. For
spectacular displays of torque, there's no substitute for cubic
inches.

But look at how cars are designed today, with the focus on fuel
economy: four valves per cylinder to allow it to breathe efficiently
at high speed, overhead cams that minimize valve float at high speed,
and a tachometer with a redline at 6500 rpm or more. These powertrains
are designed to produce their torque at high speed with the help of a
trasmission that keeps the revs up. What's the point of those all
those extra valves in the cylinder if the engine is going to loaf
along at just above idle speed? These engines were built to rev.
They'd probably hate being lugged in high gear.

I notice that my mother's Northstar Cadillac works this way too,
though the Northstar is a lot quieter than my Saturn when it does it.

Don't worry about the breaking the engine, the computer will protect
it from overreving.

RK Henry

 

[Laz]

Don't worry about the breaking the engine, the computer will protect
it from overreving.

really ? seriously ? usually things break when they are over-revved. I've
always driven to avoid this jump in revs in my saturn

Laz

 

[RK Henry]

really ? seriously ? usually things break when they are over-revved. I've
always driven to avoid this jump in revs in my saturn

According to what I've read in the service manual, if revs get too
high the computer will regulate engine speed by selectively shutting
down injectors.

RK Henry

 

[blah blah]

According to what I've read in the service manual, if revs get too
high the computer will regulate engine speed by selectively shutting
down injectors.

RK Henry

This came about around the time of OBD II for a majority of cars so you
dont want to paint everything with the same broad brush. While in gear a
healthy Twincam wouldnt have a problem running all the way out to
7000rpm. It just tends to create undo wear...

 

[Philip Nasadowski]

This came about around the time of OBD II for a majority of cars so you
dont want to paint everything with the same broad brush. While in gear a
healthy Twincam wouldnt have a problem running all the way out to
7000rpm. It just tends to create undo wear...

IIRC, there's a fuel cutoff at 7500? 4000ish if not moving. I don't
know if 4000 is a good launch RPM or not for Saturns but I wouldn't put
it past GM's engineers to have picked that number for that reason...

My '93 does this. IIRC, the cutoff isn't an EPA thing but more related
to turndown ratios of the injectors and preventing the possibility of
going 'oops too lean' at high RPM because the injectors hit 100% duty
cycle.