First time doing ATF change myself - any tips? - UPDATE


Well, I got 'er done today. The change went well, but it was a long messy job. Definitely would be easier on a hoist!

A couple questions…there were some metal specks in the old oil, in the pan…also one spot with some hardened metal and gunk…and the little magnet was covered with a fine grey substance (really pulverized metal?) and metal filings…how bad is that for a tranny on an 85 Olds Cutlass with 220k kms (136k miles)?

Also, is it ok for the fluid level to be a little bit over the max line on the dipstick or is it important that I siphon some fluid out? I was adding a bit at a time but it snuck up on me…

And finally…can a new filter/fluid help with gear changes? I don’t know if I imagined it, but on my test drive, doing 50mph, I stomped on the gas pedal, and the downshift and subsequent upshift after reaching about 75mph seemed a lot smoother. The tranny has always shifted pretty smoothly but that combo has been a bit rough previously.

Thanks again, and to those who offered tips in the original post.



I forgot to mention, this is a THM 200C tranny, 3 speed. And yes, I did clean out the pan till it was spotless and dry. :slight_smile:


At that age and mileage you’re probably going to see a little debris in the pan and on the magnet. I would not worry about until you have to scrape it out by the spoonful!

Running it a bit over won’t hurt anything. I’ve been routinely overfilling my transmissions and engines for 40 years with no problems. (Usually about 1/2 or 2/3 of a quart. I look at it as a small insurance policy.)

Yes, fresh fluid and new filter can help the shifting. I can always tell when my Lincoln needs it because around the 35k mile mark on the fluid it may develop a very, very subtle shudder in the converter at times. A fluid change always cures it.


Thats just normal clutch wear, you see that in all automatic transmissions. If you change the fluid every 25 to 30k miles as some do here, you won’t notice it as much.


Thanks for the peace of mind OK! As much time it took and how messy it was, it still gave me a warm fuzzy feeling inside…especially since it’s been out for a few drives now and no leaks. :slight_smile:

Thanks keith, too…I will be doing this on my vehicles from now on on a regular basis.


Transmission fluid expands with heat and over filling will cause the oil to foam and damage the transmission. The dipstick and experience are all that you have regarding overfilling. If ever the transmission breaks loose (engine races/no power)on a forced downshift it is likely overfilled. It may be easy to disconnect one of the cooling lines at the radiator and start the engine for a few seconds to dump a pint or two if yours is overfilled. I have a 700R4 that is particularly touchy while my Jeep A40 is not so picky regarding over filling. I prefer to be on the low side, though.


It doesn’t seem to be “breaking loose” in any situation, including forced downshifts…It’s really only about a centimeter or two over the max line, I doubt it’d be a pint even. So, I think it’s fine?


So far, what you found was normal. Sometimes, the shifting will be different right after you change the fluid, but may go back to normal tomorrow. Keep checking the fluid level for the next two days.