tranny fluid reads low when hot, high when cold. huh?
 

I'm trying to get my transmission fluid level just right after my indy waaay overfilled it on the last service (they had a brand new tech working on my car). It was reading about 3 inches too high on the dipstick and was foaming, showing bubbles, and not shifting right. So I'm now trying to get it back right on the money by draining a little, but there's a weird problem.

Ok, I've always thought that the transmission fluid level reads lower when cold then higher when it heats up and expands. However, I've been experiencing just the opposite. When stone cold, after sitting overnight, it reads right at the upper mark. Overfilled right? After all even the manual says it should read 12mm low when at shop temp. Problem is, after driving 20 minutes on the highway, parking on level ground, shifting throgh the gears, and waiting 5 minutes or so at idle, it reads low at an inch below the lower mark!

I've done this cycle all week just to double check myself, and it reads the same every time: at the higher mark when cold and an inch below the lower mark when hot. Am I going crazy or is there some explanation? I've never had a problem checking tranny fluid levels before and use the method as described above per the manual.

Car is a '92 300D 2.5 turbo, fluid is Dextron III ATF.

Thanks.

Engine running, trans in Park; fill betwen the marks when trans fluid is at 80C and disregard the rest.

If it continues to give problems check the dip stick part number and confrim it is the correct.

little known fact: at the stealer, they use their own diagnostic dipstick which is black and says something like MB Shop Only on it. just thought i'd throw that out there

Engine not running.

Engine running.


Use the "engine running" approach for all measurements and your data will be meaningful.

Might be drainback from the trans cooler or something.

Cold specs are approx and are cold-while-running. Do as Brian says, ignore the not-running reading.

Nice explanation. Levels should be read with engine running.

Hey thanks! I feel like I need to let go a good "Doh!" Yes, I was measuring cold with the engine NOT running. That's why I never ran into this before because until recently, I always thought you had to do it hot with the engine running. Then I started reading the manuals that talk about the cold reading and assumed it was with the engine NOT running, a la checking the oil. Too much information running through my brain. Should have just stuck with the old method then no confusion.

Ok, then my fluid is low and I will add some to bring it up to where it needs to be.

It was still waaay overfiulled by the shop at first, though, a good 3 inches above the full mark when hot, and bubbles galore. I can report that the bubbles are gone even now with the fluid level low by about a half a quart, btw.

Thanks again for making it clear the engine needs to be running when checking either hot or cold. Seems obvious now.:rolleyes:

Just a bit unclear here... I've taken two readings already, both while engine is running.

1.) Engine cold
2.) Engine @ 80C after ~1 mile drive.

I am way under the min mark when cold, and between the two marks @ 80C. Which is the correct reading?

If you can get your transmission fluid warmed up in one mile, you must be driving up a really steep hill!

When the motor has run 20 miles, check with engine running. The trans takes a while to get up to temp.

Thanks for clarifying! I was trying to go by what was posted in post #2.

Don't mean to hijack this thread, but on my 93 300d the trans dipstick takes two hands to force down the filler tube. Bought a new dipstick and it is no different. Is this normal? Thanks in advance.

You may have it oriented incorrectly. When you push it down the tube, the dip stick should be able to flex along the flat side.

Transmission Dipstick
 

'Can be a bit "Fiddly".
The "Handle" (and Lock) on the top of the Dipstick will swivel 360 degrees.
When you reach a "slightly difficult" spot during the insertion.try turning the
blade of the dipstick itself (Gently).It should ease on past the area.

Look down the Transmission Dipstick Tube itself...It Ain't no "Straight Shot".

All of my suggestions apply assuming "Someone" previously Has not Boogered
the dipstick by BENDING it.