Mongo

I have read numerous FAQs and added about a quart and a half of Dexron VI to my reservoir when the transmission was cold (engine running of course). I have had the car idling for about 5 minutes and ran it through the gears P, R, N, D for 10-15 seconds in each. The transmission fluid level still is slightly above the 20-30C line, which is the very bottom line of the reservoir.

FAQs say that this is what the fluid level will be when the transmission is cold after startup and the torque converter is filled. My car has always had an issue of the TC draining back into the reservoir and overflowing the bottle. My wife has gone so far as to leave a Maxipad on my car's windshield as a joke which has contributed to cheering me up in the morning on the way to work.

Questions are:

- Despite the engine idling for about 5 minutes and running it through the gears, should the ATF level be higher for the amount of time indicated?

- Did I add too much if the level is slightly higher than 20-30C if the first question is answered that the fluid is still cold?

- Is Five Minutes enough time for fluid to 'warm up'?


I heard some sounds of frothing noises prior to discovering that the damn bottle was empty and probably was that way for about a month. The car isn't driven much so I'm worried about any damage that could have been done, or if I caught it in time.

kombatrok

If the trans had enough fluid that it was still shifting normally then I really doubt it was low enough to cause any kind of damage.

5 min with the car sitting idling won't have warmed the transmission fluid up much at all.

Schocki

Checking the ATF level on a cold tranny does not really work well. Drive the car until everything is fully warmed up and check.
The difference between "Min" and "Max" when warm is only about 200 ml. Adding one and a half quarts to just "top it off" sounds a lot to me.
This is exactly how I overfilled my GTS automatic when I did my first fluid change in 2004.
Yes, the reservoir will be full and there is always fluid draining back. If the lid is tight and the ventilation hose on top ok it will stay dry under your car. If the TC has a serious draining issue you won't be able to drive your car until it is full with ATF again (takes a couple of seconds).

davek9

As far as the leaking goes, did you replace the cap seal and make sure the vent pipe is secure as that is where it leaks when it backs up.

Mongo

Cap and seal are only a few years old. I'm aware that excess fluid may overflow if the car sits for too long, which is what this one does. It was a good 2 months before driving it hence the loss of ATF. This car has always had this problem, even after a new reservoir bottle (two new ones actually) and caps. Pan was sealed real tight after its filter change in 2008.

I read somewhere in an article that the fluid level is more accurate when the transmission is cold, versus checking when hot.

Schocki

ATF level should be checked warm.

Since you changed the parts in question already, I would assume that the problem is somewhere else. Did you check the area around the B2 cover already and also the little pressure port at the bottom right of B2?
That is exactly where mine leaked...

Mongo

Sorry, do you happen to have a picture of these areas for reference?

Schocki

Si claro hombre

Here is the link to my tutorial on how to repair reverse in our 722.3 automatics. It also talks about B2 cover O-ring replacement.
https://rennlist.com/forums/928-foru...ement-diy.html

Mongo

Perfect! Thanks! I will look when I get home.

I also found this from the WSM:

*Check ATF Level

Also check appearance and odor of ATF.
Burnt friction linings cause a burnt odor.
Contaminated oil could cause failure in valve
body.

In this case transmission must be removed
and repaired or replaced. ATF lines and
cooler must also be flushed.

ATF level check is carried out at engine idle
speed, parking brake applied and selector
lever at "N". Car must be on level surface.

Let engine run at idle speed 1 to 2 minutes
before checking fluid level, so that torque
converter will be full.

ATF level can be checked on a cold or warm
transmission. However, the level will
be more accuate on a cold transmission
(20 to 30 degree C/ 68 to 86 F ATF tempeture)
than on a warm transmission (80 C/ 176 F)
ATF temperature). ATF temperature of
80C/176F can only be estimated.

This information came from 38-102 of the WSM.

dr bob

That instruction applies to 'normal' transmissions that don't have issues with torque converter housing draining internally.

Also-- if the trans really was a quart and a half low, you'd notice when you tried to drive it.

It takes a while to get everything filled again inside, and requires some actual cycles through all the gears before you get anything close to an accurate level reading. And... the car needs to be perfectly level for a valid reading.

My opinion -- I have more trust in the readings at normal temp, mostly because that what the temps are almost always at when I'm driving it. Just my opinion of course. *** See disclaimer below ***

Mongo

I really want to know what is causing my TC issue of constantly overflowing the damn reservoir. I did notice that when the torque tube was replaced by my mechanic back in '02 that the transmission was NOT the original. In fact it had that yellow paint marker on top of it saying "87 928 AT" telling me that the previous owner probably dropped in a wrecking yard one in this car, maybe even with the torque converter too due to a failure of something.

I'll be driving it around tomorrow anyway so that will allow me to check the level. Since the car has a single exhaust running on the left side of the car now, I won't be getting anymore burns checking the fluid levels.

I remember a long while back when I had some serious leaking issues due to the ATF lines running from the transmission to the radiator were leaking profusely caused the car not to move in any gear when selected. Now that was a low fluid symptom! Scary too..

Schocki

Just looked at my GTS owners manual. It clearly states to check the ATF level when warm, on a level ground, engine at idle and either in "P" or "N".
Never heard about the cold is more accurate method.

BTW the MB guys with a 722.3 check their automatics like mentioned in the 928 owners manual too...

Mrmerlin

Andy if your adding that much fluid then it must be leaking.
so you will find a puddle on the ground,
or oil being sprayed on the underside of the chassis ,
OR the coolant reservoir will have oil in it.

Check the fluid after you have driven the car 5 miles UNLESS after starting,
you dont see fluid in the tank,
then add till the fluid level stays constant with the engine running.

Fluid drainback is part of how this system operates,
there isnt much you can do to stop it except swap out the 4 speed auto for a 5 or 6 speed manual.

Schocki

Fluid drainback is part of the system, correct. But if the tranny has good seals all around and is not overfilled, it should stay dry. Even if it sits for a longer time (like winter storage).

Mongo

After adding those 1 1/2 quarts I noticed the transmission is shifting significantly smoother this morning. It must have been low. I did scrunch down to check the level, but it was cold at the time of course after about 2 minutes of idle. The fluid level was above the 20-30c 'Cold' mark ever so slightly again. I will check it on my lunch after a 10 minute drive.