Yet another 4HP22 trans fluid change question

[youngbimmer]

I’ve never done a trans fluid change on any car, 735 will be my first. What is the process to drain/fill to change trans fluid? Is it like engine oil? Drive car to warm up the fluid, park, jack, remove trans drain plug, replace plug, fill through trans dipstick hole? Is there danger in overfilling? Is it safe to use full synthetic ATF without knowing what is already in the trans? Should pan be dropped to replace filter? I don’t know if fluid has ever been done in this car’s 32 years. It’s at 109K miles, don’t know if it is safe or not.

[shogun]

yes, 4HP22/24 is quite easy, same like engine oil change as you describe it. Filling thru dipstick hole.

4HP22/24 with dipstick and filling from top thru dipstick pipe: 1988 E32 owners manual states on page 63: automatic transmission, checking oil level: the car must be standing on a level surface with the transmission at operating temperature 80 degree Celsius. Allow the engine to idle with the selector lever at P or N. Pull out the dipstick, wipe it with a non-fluffy cloth and push it back to measure the oil level. It must be between the two notch marks.
The quantity of oil represented by the space between the two marks on the dipstick is approx. 0.3 liter when the transmission is at operating temperature. If necessary, add fresh ATF at the oil level check pipe.
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First fill up w/o engine running, when you have filled up enough that you can see it on the dipstick, start the engine and slowly switch thru the gears and then select again P or N, let engine run and fill up to correct level at operating temperature.
We always use synthetic ATF for the 4HP22/24. ATF pan has to be dropped to replace filter and pan gasket. Just pay attention to the ATF filter, there are filters for the 4HP22 with long neck and short neck, the older 4HP22 for example on the E30 have a more shallow ATF pan and there the short neck version is used, when the ATF pan is bigger, then the long neck version is used. The long neck version goes deeper into the ATF pan. Normally 4HP22 in the E32 have the long neck filter. from built date 03/1988,
For models with production date through 2/1988 short neck. here you can see the differences in length of the suction neck/pipe, I use the Meistersatz (made in Taiwan) kits from autohausaz. https://www.autohausaz.com/catalog/c...kit?s=d&page=1

[CamE32]

I’ve never done a trans fluid change on any car, 735 will be my first. What is the process to drain/fill to change trans fluid? Is it like engine oil? Drive car to warm up the fluid, park, jack, remove trans drain plug, replace plug, fill through trans dipstick hole? Is there danger in overfilling? Is it safe to use full synthetic ATF without knowing what is already in the trans? Should pan be dropped to replace filter? I don’t know if fluid has ever been done in this car’s 32 years. It’s at 109K miles, don’t know if it is safe or not.

Drain the fluid into a container and take note (make a mark or something) of the exact amount of fluid that came out. Clean it out and fill the container with exactly the same amount of new ATF, then pour down the dipstick tube.

I've had good luck with good old mobil 1 synthetic ATF. Within the next 2 weeks I plan to finally drop the valve body and clean the solenoids. I've done no less than 5 fluid changes (+ the filter the last time) and it's still not perfect, but I think that's because my car sat for so long. The old ATF filter had a solid film of black gunk, even after all the fluid changes! From what I've read the only way to restore like-new shifting is by dropping the valve body and cleaning each solenoid with brake parts cleaner. That's my plan anyways...

Hindsight is 20/20 - If I could do it all again, I would've dropped the pan and did a thorough cleaning before my first test drive.

[TheStigg]

At 109k miles, you're probably fairly safe. To be cautious, I would start with a couple 2 quart partial drain and fills and drive it 50 miles +/- between changes. As mentioned, fill with the same amount of new as what was drained. Verify the level with the car warmed up and parked and running on a level surface and cycle the trans with your foot on the brake thru all gears and check to see if it's close to the full mark. A few ounces either way won't matter. Once you've done a few, then go to a few 4 quart drain and fills, again, spaced approx. 50 miles apart. After that, drop the pan and clean it and the magnets and replace the filter. If you have an older 32-bit computer, I wrote a simple Qbasic code to calculate the percentage of new fluid vs. how many quarts it takes to get there. I am partial to Amsoil ATF for the ZF4hp22 trans. Do the 1st couple drain and fills with any cheap Dexron you can find at Walmart, then transition to Amsoil for subsequent changes. Your transmission will thank you.

The theory about "high mileage" transmission failures I have read has to do with the aggressive cleaning nature of new ATF. Hypothetically, over time, dirt and crud will embed itself in the clutch friction material and fresh detergent ATF goes a bit overboard trying to clean everything, to the point of loosening and dissolving the clutch friction material and adhesives, leading to failure. 100k miles is at the tipping point where one might be better off leaving it alone if the trans fluid has never been changed before, so by going easy on it by only introducing a small amount of new fluid at a time, lessens the "shock factor" of dumping a lot of new fluid at once into an old trans. Here's the program. If I recall, it takes approx. 24 quarts of new fluid via partial drain and fills, to end up with the equivalent of say 98% new fluid.

http://www.nmia.com/~dgnrg/page_12.htm

Edit: Check the fluid level with the engine running with the trans in either park or neutral.