Transmission temperature sensor

[kchurch05]

Hey all-
I recently posted a question about my 93 Impreza not shifting into
(what I thought was) overdrive (and was corrected - really the torque
converter lockup kicking in), and got a lot of helpful responses.
Anyway, I took the car to the Subaru dealer because I was convinced
the temperature sensor was faulty, since it was taking a good 15-20
minutes for the torque converter to lock up and put me at max fuel
efficiency "cruising speed." I know that this occurrence is common in
cold weather, but I vividly remember this happening when it was 60+
degrees out - still took at least 20 minutes to make that "shift."
Also, if I remember correctly, it's only designed to do this until the
transmission reaches 20 deg. Celsius? That's not exactly hot, and
those days where it's way above 20 C it still refuses to lock right
away.

I just heard back from the dealer, who charged me a gracious $94 to
plug in the computer and tell me absolutely nothing was wrong with the
sensor. He then recommended I flush the transmission in case there was
any gunk stuck on the sensor. I wisely called up my regular mechanic,
who advised me not to. The transmission fluid is synthetic.

Anyway, I'm now pretty bummed because my car is still not behaving
quite normally and I'm getting incredibly crappy gas mileage. Not sure
if this is safe (tell me if it isn't), but is there a way to
disconnect the transmission fluid temperature sensor? Voodoo?
Something? In reality, I'm driving 55-60 mph on the highway at 3000
rpm - that can't be too good for a tranny. I feel like I've covered
all the bases, but it's still driving me nuts! My fuel economy is
getting worse and worse. Any ideas?

Thanks!

-Kendall

 

[Edward Hayes]

My 4EAT only drops ~250 rpm at lockup. That makes my think something
else is causing a decrease in you're mileage.

 

[David]

I'm driving 55-60 mph on the highway at 3000
rpm - that can't be too good for a tranny.

Sounds like 4th gear, close to 1:1.

 

[kchurch05]

As long as I'm not going to blow up my tranny, that's cool.

When I spoke to my mechanic before bringing it into the dealer, he
mentioned it might be a solenoid (sp?) issue, hence my bringing it to
the dealer (as mechanic does not do transmissions).

This may sound dumb, but does letting the car warm up/idling for about
5-10 minutes actually have any effect on the transmission fluid temp?
The last time I did this it locked up much more quickly, maybe a few
miles earlier than when I let it sit for 2 minutes every day while I
run back into the house to grab my lunch/keys/coat/whatever I've
forgotten already. (Sub-20 temps = grumpy car.) Makes me think that
it may use less gas by idling for a longer time than running it in 4th
at highways speeds for that much longer.

-Kendall

 

[kchurch05]

Meant to add this in my other reply... the tach definitely drops about
400-500 rpm when it locks - I always cheer when it does.