Measuring the transmission fluid level (727)

system11

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So here's my problem - I checked the transmission fluid last week and I was seeing a bead of oil just on the twisted end of the dipstick. This was after warming the car up, shifting through the gears a few times and leaving it idling in neutral.

I took this to mean the level was low - so I bought some semi synth Dexron III equivalent to play it safe, and today I put in just over a pint of fluid. Problem: I still get the exact same 'reading' on the dipstick.

Higher up the stick I'm seeing a sliver of lubricant just on the right side of the back of the dipstick, front stays totally dry. It may just pick this up from the fluid ending up in the dipstick tube each time I remove it to check, however the fluid is so easy to run that I'm not sure if the level was ok and I've overfilled it, or it's lower than I thought.

Are there any tricks to doing a better check? The metal dipstick seems next to useless. I started to wonder if a very long pipe cleaner would work or something. I'm trying to avoid jacking the car up and emptying the transmission & refilling with the right amount as it's not going to be doing many miles for the winter and next year I'll be getting the transmission rooster comb changed anyway.
 
Put the car in Neutral as the pump is disengaged in park (Be sure to block the wheels). Have the car on level ground when checking the fluid level. ATF 4 is a better choice for fluid.

Dave
 
Yeah I did that - level & warmed up, and in neutral. Can't tell if the oil is genuinely still low after adding a pint, or if its just running down the dipstick faster than I can pull it out.
 
Check in neutral. The fluid is splashing on the dipstick from the fluid dumping in at the left rear from the cooler return. Type F fluid is a better choice (old school friction modifiers), 4, 3 are all backwards compatible or so they say.
 
Yeah I did that - level & warmed up, and in neutral. Can't tell if the oil is genuinely still low after adding a pint, or if its just running down the dipstick faster than I can pull it out.

A 1/2 quart doesn't move the needle (level) very much. It sounds like you're low to me. My comment from experience on dipstick accuracy is that when the level reads low, the trans doesn't act right, be it shifts or stall-speed. When the level is correct, it's fine, all other things being equal.
 
Ignore the sliver on the back of the dipstick. It's just residue from when you added trans oil. The level on the front of the dipstick shows the true fluid level. The dipstick is not useless. You need to add trans oil.
 
Thanks, they must not have filled it properly when it was rebuilt & fitted in that case - there's nowhere for the fluid to have actually gone, that whole transmission case is clean enough to eat food on.
 
Be sure to get it real hot, not just warm. This will affect the reading significantly. Warm will show low, it may be up to level once it gets really hot.
 
One other consideration. You might have the engine "warmed", but the temp of the trans fluid probably is not. Circulating the trans fluid through the lines and cooler in the radiator tank will take time for the fluid to get to operating temp just by doing that. Best way is to drive the car for about 10 miles to get ALL of the fluids' temps normalized at "operating temperature".

For reference, the oil will be warmed by the engine coolant. When it gets back to the trans, it'll need to warm the trans case, valve body, and clutches. Then it makes another circuit to the radiator. Getting the trans "guts and case" to operating temp will take a good bit of time, just letting the engine run and not driving the car.

On the GM THM dipsticks, there's usually a little dimple near the end of the dipstick, below the "ADD" line. That's the level the fluid should be at 0 degrees F temperature. As the fluid warms, it'll expand to or just above the "ADD" line.

In adding fluid, consider the size of the trans oil pan and then how much you need to raise the level. 1/2 pint increments is a good choice, but might take a while. Aim for just at the "ADD" line. Let it all settle out when the engine is stopped. Then later on, go out and start the car and do the fluid check to see where it is. If the fluid is at or near the "ADD" line, drive it for a good bit, town, highway, freeway, for about 30 minutes. Then when you get back to a level section of ground, apply the parking brake firmly and do the trans fluid level check. Then adjust according from there. Near but not over the "FULL" mark will be good. Worry about how much oil is on the flat section of the dipstick, not what's on the side of it. DO be sure to fully seat the dipstick cap on the top of the dipstick tube, for good measure.

Once you get the fluid level stabilized and gain some confidence in checking it, it should be fine.

Just some thoughts,
CBODY67
 
No no no no no no!.
You check the fluid while it is Drive!!!
I will argue to the death on this.

In a prior thread, you mentioned that you came "to FL to die". Be careful! We're not ready for that to happen YET!

CBODY67
 
Last edited:
No no no no no no!.
You check the fluid while it is Drive!!!
I will argue to the death on this.

I've never heard of that technique before. Are you cereal? If so, where did you learn of it and what is the advantage? It's stamped right into the dipstick to check when hot and in neutral.
 
I respectfully submit my evidence...

DSC03190.JPG
DSC03191.JPG
 
My mentor taught me that way when I was 16.
Old timer transmission rebuilders who remember 727's have told me the same.
They beat it into me.
I have the scars.
You guys do it your way.
 
My mentor taught me that way when I was 16.
Old timer transmission rebuilders who remember 727's have told me the same.
They beat it into me.
I have the scars.
You guys do it your way.

Im not saying you are wrong Stan...Im only saying that's what the FSM told me.
Super Mario.gif


:lol:
 
My mentor taught me that way when I was 16.
Old timer transmission rebuilders who remember 727's have told me the same.
They beat it into me.
I have the scars.
You guys do it your way.

If you carefully check it in "D", rather than "N", then the fluid level would be lower as the various valve body passages would have pressurized oil in them, as would the various "apply" accumulator and friction item actuators. Not sure how much that might be, quantity-wise, but it could make a difference. But the level in "N" would sure be higher than with the lines charged in "D", I suspect.

Just some thoughts,
CBODY67
 
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