changing transmission filter (91)

I am about to change the transmission filter. As far as I can see there is no drain plug? Any hints or is this all very straightforward? Can you reuse the gasket?

I don't think there's a drain plug. I think you have to just drop the pan. I'm not sure how to change the filter, but i would not use the old gasket again. Go with a new one!

Don't know if a 91 park avenue has the reusiable gasket but my 95 does if its a rubber gasket u should reuse it. With the filter u have to pull on it. It's a pretty straight foward job. Just make sure u have a pig container and some newspapper the job can get messy.

remove all the bolts on 3 sides of the pan, then loosen the remaining bolts enough while holding the pan that you can loosen them by hand then place a container under the oppisite side that your holding and slowly let it down. it will pour out. after it stops pouring out remove the rest of the bolts and pour the remaing fluid out.

take some paper towels or old rags and clean the inside of the pan out to get rid of the crap that settles to the bottom DO NOT REMOVE THE MAGNET! it is very important to catch pieces of metal. usually it is a 2x2 square thing glued to the bottom.

take your new filter out of the box and compare it to the one on your tranny still. remove the old one and make sure the seal comes out with it. take the new seal and push it where the old one came out. if it doesnt go in very far or is hard to push in lightly tap it with a rubber mallet or block of wood with a hammer. take the new filter and put it in so the little tube on top goes into the seal. you may have to wiggle it to get it in and make sure its all the way in.

take a scrapper and get the old gasket off the transmission pan. take a small amount of grease (very thin layer) and rub it arpund the lip of the pan then place the gasket over it. this will help hold it in place while you line the pan up with the holes.

put the pan back on and hand tighten some bolts to get hold it up there. finish putting the bolts it and tighten them down.

pour about 4-5 quarts of tranny fluid in wait a few mins and check the level with the car off. when it shows up on the stick (little below the full mark) you can start the car and finish topping it off. check the pan for leaks and tighten bolts near the leak as needed.

take the car for a ride then check the fluid level again.



hope this helps. i also think the bolts are 10mm.

Thanks all. The reason I'm asking about the gasket, the dealer wanted around $80-90 for a new one, which seemed an awful lot for an oil pan gasket so I didn't get it.

I have no idea what kind of gasket it is. I am used to MB oil pan gaskets, a simple square rubber gasket which you get for free with the filter while you really don't need it.

Thanks all. The reason I'm asking about the gasket, the dealer wanted around $80-90 for a new one, which seemed an awful lot for an oil pan gasket so I didn't get it.

I have no idea what kind of gasket it is. I am used to MB oil pan gaskets, a simple square rubber gasket which you get for free with the filter while you really don't need it.


The replacement gaskets are included with some of the transmission filters in the aftermarket. And I assume they are available separately at different auto parts stores if you don't get one with the filter. You may be able to reuse the one on the car.

The 91 gasket is not reusable as the newer ones are.

That is good to know - I almost took off the oil pan without having a new gasket. I see they are priced between $3-$35 (ACdelco), what is the difference?

That is good to know - I almost took off the oil pan without having a new gasket. I see they are priced between $3-$35 (ACdelco), what is the difference?

I reused the gasket on my 93 IIRC. The cheapest ones may be a little less resilient to adjust to uneven shapes of the pan surface. They probably all work work if you don't reuse the one on your car. IF it's the original, it needs replaced. If it's already been replaced it might be reusa-ble.

I changed the transmission filter, but the fluid came out black ! :uhoh:
After loading it with new fluid, I drove it for a couple of minutes and checked the fluid on the dipstick. It was very dark, so I drained it again (the filter too) and refilled. Now after about 40 miles the fluid is light brown which concerns me.

How much fluid remains in the transmission when you remove the oil pan?

I understand there is no torque converter which can be drained seperately?

You only drain a little less than half of the fluid when u do a pan drop. If the fluid was black it would end up being brown when u put the fresh fluid in. Mine was dark brown when I did a pan drop and turned light brown when I did the fluid change. The thing I noticed most was the diffrence in smell. Once I put the new fluid in I noticed a big diffrence in the smell of the fluid. So i'm assumming the additive package got used up. Transmission still shifts the same since I got it so. I don't think you have anything to worry about.

Thanks, well that makes sense. I did not know only half of the fluid could be drained. Even after 2 fluid changes there will still be 25% of black fluid.

Strange, I received an email notification from a reply in this thread from imidazol but it doesn't show up here.
Anyway he wrote that the fresh fluid will dissolve old deposits in the transmission, which will clog up valves and such. :uhoh:

I don't drive the car that much, maybe 100 of 200 miles a month. Any recommandations what I can do to prevent transmission failure?

Strange, I received an email notification from a reply in this thread from imidazol but it doesn't show up here.
Anyway he wrote that the fresh fluid will dissolve old deposits in the transmission, which will clog up valves and such. :uhoh:

I don't drive the car that much, maybe 100 of 200 miles a month. Any recommandations what I can do to prevent transmission failure?

I had posted but didn't realize several new posts were in between the beginning and the end. You had already filled, run, drained and refilled. I deleted the original post.

My point was suggesting to drive the car some between further drains to allow the new additives in the fresh fluid to dissolve some of the deposits that may be on the inside and on working parts of the transmission. I'd take the car on longer drives that get the transmission fluid up to normal temperature and help the additives in the new fluid do their job.


I'd go another 5000 to 10000 miles and drain again. If I found a lot of new scum on the bottom of the pan, I'd change the filter at that time; if not, I'd keep the old filter till the next drain.