1969 Firebird TH400 Dipstick Fluid Fill
 

I need some help with how much transmission fluid to add. The transmission fluid was drained in order to change o rings and install the factory 1969 Firebird TH400 dipstick tube and dipstick that I acquired.

I placed a feeler gauge on the pan mating surface and marked the dipstick for reference. The reference mark is 1/8 of an inch below the ADD 1 PINT line.

If I use the stamped markings on the dipstick, the transmission fluid will be above the pan/transmission case mating surface.

What to do?

That's why you check the fluid with the engine running. With the engine off the fluid level could be anywhere. The longer the car sits with the engine off the higher the fluid level will get until all the fluid in the converter drains back as far as it can.

This is my understanding of when a th400 transmission is full. Since you marked the new dipstick that's your full mark. You need to get the fluid hot to take full measurement. Engine running , transmission in park.

For a TH400 transmission, the "full" mark on the dipstick is typically at the pan rail (the seam where the pan meets the transmission case) when the engine is running and hot in Park..

I should have been more specific with my question.

It was my intention to check fluid level after I had driven around to get to operating temperature.

I was asking whether it was okay to use the dipstick markings, or to use my mark since I know that it is at the top of the pan.

I honestly don't know where the level would be after the car is parked and the converter drains back into the transmission.

I have viewed a couple of YouTube videos where the hosts mention marking the dipstick an eighth inch above where the case and pan meet. The videos were instructional for using aftermarket dipsticks. Other videos stated at mating surface.

This dipstick I have didn't come with the dipstick tube; I bought it separately.

From my other posts, I was trying to get a measurement from an original 1st gen firebird equipped with a th400. The information that I received was the dipstick that I bought was the correct measurement of 26 and 5/8 inches.

My latest post is for keeping the correct level of fluid using the dipstick that I am using.

I think Chuckies76ta was able to understand my vague question.

Thank you both.

Use the new mark for full- that’s the whole point of checking aftermarket parts, they are often incorrect. This assumes the dipstick tube is fully seated in the case and the dipstick fully inserted.

You can zig-zag (or un zig-zag) the upper stick to tune the level to where your marker is.

Some steel is brittle and can snap if bent on a sharp edge.

Very Clever Expanding "Zig-Zag"
 

Thanks for the answers as to where the FULL line is located. Some said above the pan mating surface, and others said at the mating surface.

Once again, the idea to expand the tension kinks/bends is clever. My 1/8 inch difference would be solved without taking away from the functionality of the kinks/bends. I got a kick out of your idea.

I'm not so obsessed with the original markings being exactly where they're supposed to be. I can breath easy knowing I don't have to guess anymore or having to use the wrong dipstick with the bent tube.

A hair above or below the mating surface will not make a difference- look at the width of the cross hatch area indicating there is an “acceptable range.”