soontobered84

Besides the obvious reason of AT fluid all over the floor of your garage, is there any good reason not to overfill the AT?
It wouldn't appear to cause the same issues as overfilling the crankcase with oil.

Lizard928

the real question is why are you asking

928drvr86.5

You will over-pressure the supply line to the transmission cooler and a leak will most likely occur at the hardline-hose transition between the torque tube and passenger side frame rail. Or, that is at least what happened when I overfilled mine years ago.

soontobered84

Just stupidly curious

Ed Hughes

said the curiously stupid fellow.

Mrmerlin

if your tanks clean then you should have no problem seeing the correct level, with the engine running in park

soontobered84

Ed,
you need to fix your avatar. The white car is now in the Northern climes wondering why it's not being driven.

ROG100

John,
Get down from the tree house with the young ladies and get under your car and check the ATF level the way it should be checked.
Roger

soontobered84

No really guys. The treehouse was a lot of fun....oh....I mean I filled it up properly. I really was just wondering. And by the way, those young ladies were of age.

soontobered84

Ben, Why would overfilling the reservoir increase the pressure in the system? It just seems that the pump will have a maximum pressure regardless of the volume of the reservoir. I'm not saying you are wrong or trying to start an argument of any sort. I just have always heard " Don't overfill" but fail to understand how it would be bad for the tranny.

What if you put a larger reservoir in place of the stock one? That shouldn't damage the tranny, which in effect, is what you'd be doing by overfilling.

I know it sounds silly, but I just want to know.

PorKen

IMHO, the pressure of pumping oil through the 20+ feet of small diameter pipe/hose, combined with banjo fittings at the transmission is a contributing factor in flexplate creep. (Even at the stock fill level.)

My old '86's flexplate stopped creeping when I put in a rear cooler, and straight through fittings. I have yet to convert my new '86, and it's flexplate moves the regular 3-4mm after a short time.

Note that the four speed has a thermo-valve inside that delays shifting when the oil is cold, which is annoying if you install just an air/oil cooler, I found. This time I'm going to use a thermostat, along with a cooler with an integrated fan.

Ed Hughes

Yes you are.

SeanR

So, John,

Did you, or did you not follow the WSM on the proper way to fill a transmission?

I could have talked you through it instead of 10 phone calls to others and a post here.

Mongo

Mine is overfilled. It used to leak a lot after the car was shut off. Now it doesn't leak much, but when I get the ATF hot, it will come out of the cap, compromising the seal. The wind also picks it up and mists it onto my exhaust pipes causing this lovely caked on crust...

My transmission service is coming up soon, so I'm going to synthetic and making sure the fluid level is correct so it will never happen again.

Ed Hughes

Actually, the AT is the least of John's problems. Sean's driveway is evidence of what too much oil (apparently, as the engine was REJECTING it!) does....