Reading the transmission dipstick

6716

Well-Known Member
Ok, so the fluid level is between the dots, but on the "back" side of the stick there is fluid several inches up the stick. The other side of the stick is dry above the dots.

I know I overfilled it previously and I just pumped a little out but now I am not sure I trust myself reading the level.
 

aaserv

Well-Known Member
Are you on a level surface? Ive always heard, keyword= heard, that you should read both sides and go with the highest mark... Still overfilling a stock transmission shouldnt be a big problem anyway ....again from what Ive heard. Im certainly no transmission expert..
 
OP
6716

6716

Well-Known Member
I have been checking on reasonably level surfaces. On the side where it shows up really high it is kind of "streaky" ... it's not thick across the whole stick like it is between the dots.

It's probably ok. Maybe. I guess.

What is the downside to overfilling? I know that I ended up having excess fluid coming out the dipstick tube at first, so there is fluid loss and mess. But what does it do to the transmission I wonder.
 

budwich

Well-Known Member
you are "reading" the stick wrong. The level of a liquid is shown on both sides and will agree with the physics of liquids. The higher "liquid mark" on one side, is caused by liquid coming of the wall of the fill tube. Over filling a tranny is not a good idea because it can cause issues like frothing and potential seal leaks (my reads).
 

Reprise

Lifetime VIP Supporter
^^^ x2. Air (from frothing) doesn't lubricate parts. Seals can blow out from overpressure.

Also, as a 'just in case' reminder, the trans fluid level is only accurate when checked with the engine running (and trans at op temp). If you're checking with the engine off, that is not a correct measurement.

There is one thing measuring with the engine off is good for, and that's to check if the pump is working (the fluid should measure lower, after the engine is started). Otherwise, measure with trans hot and engine running. If it's anywhere between the dots or in the crosshatch area, depending on your dipstick, it's acceptable. The space between the dots is (generally) about 1 US qt, so if it's close to the bottom / minimum mark, it's OK to put 1 qt in, in that case. Slightly over the top mark is fine (e.g.; it doesn't have to be 'perfect', exactly at the top mark).

However, if you find yourself actually needing to add fluid, there's a leak somewhere, as the trans is a considered a sealed system, unlike the engine (no combustion cycle). Best to find the leak.

If not in the pan area, the next most common area for leaks is the rear seal, and it'll generally be a slow leak; the tailpiece area or the front of the driveshaft (on/ near the u-joint, just in back of the yoke) will show a dark discoloration or even wetness.) That area will also attract / retain dirt, so the area may look greasy, as well.

If the trans is significantly overfilled, there's a vent up top at the rear, with a hose leading from it. Excess will flow out of that hose. But it's still not advisable to overfill to that point.

If the trans pan has a drain plug, it's a simple matter to drain the fluid, get a 1 qt bottle, and use it to transfer the fluid back into the trans (5 total, on a 4L60e). That way, you know how much is in it.

A fluid level check afterward gives you a baseline to work from. If you need to, take a pic with your phone (I haven't done this, but it's an option, if you think you might not recall where the level was at, previously)

If you have a few oz. left after transferring the fluid back in, it would be OK to re-add it back in. (Note: I'm talking up to half a quart, maximum. More than that, and I'd put it in bottle(s) and use for potential top-offs.)
 

NJTB

Silver Supporter
Same thing happens to me, but I've found if you let the car sit for a while both sides of the stick will be the same.
When changing the fluid, (car is cold) fill it up to the bottom of the dipstick and drive it around the block a few times. Take a reading and add as necessary.
As other posters have said, overfilling is not good. I don't think a quarter inch overfull will hurt, but between the lines is best.
 

Mooseman

Moderator
If one side of the stick is lower than the other, I use the lower side. As mentioned, the higher side is likely from the tube or it crept up on that side. If you want to be safe, have the higher side at the highest point in the crosshatch or hole and the lower one should be within the acceptable level just below.
 

TequilaWarrior

Well-Known Member
In addition to the transmission needing to be "at temp" and the engine runnning, I've always placed the transmission into every gear before reading fluid level. I usually put it in Reverse, then 1st, 2nd, Drive, Neutral and Park. Then check the fluid. I don't know if that changes anything. Also, as @Mooseman stated, use the lower reading, not the upper reading. The stick wouldn't be "dry" if there were fluid up to that level. The lowest "wet" level IS the level.
 

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