I am about to change the fluid andfilter in my '89 with 69K miles. I was just going to drop the pan and replace the filter then refill with the Mobil 1 synthetic trans fluid, but I thought of a few things?

Isn't there more fluid in the converter and other areas that won't get changed?

If so will mixing the synthetic with the other be a bad idea.

Is the synthetic a good idea with a 69K mile transmission?

Thanks for any feedback.

Mike

 

Yep you will still have some fluid in the converter. Mobil one says there fluid mixes with conventional fluid without problems. I have changed all my vehicles to Mobil1 some with very high milage and have had no problems. I have seen a 10 to 15 degree drop in temps with the synthetic. There has been some problems with people doing a complete trans flush on a neglected Transmission and had failure afterwards

 

:cheers: Mike

First, synthetic is fine, I did mine the first time at 73,000 miles!

You are right though, you need to get all the fluid out, about 13 quarts. That's true wether you switch to synthetic or not.

Look in tech tips, there are lots of posts on this.

Basically, you drop the pan and replace the filter, then you disconnect the two cooling lines at the RAD.

Keep the tranny full of fluid at all times and let the tranyy pump it out.

Like I said, search the tech tips for the complete story :D

:seeya

 

Pan removal: 10 pints Total transmission capacity: 23 pints So you see you are not even getting half of the fluid this way. The only way to get a complete fluid change is either a rebuild, or a power flush at one of the service stations who have the power flushing equipment. Been there, done that, three times in the past 18 months.

 

I just did mine today on the vette.........here's a way to change all the fluid without disassembly: You need 10 -12 quarts of ATF (I got 10 since the Mobil 1 stuff is expensive and 10 will completely flush the entire trans), a new filter (don't get aftermarket ones...I looked at NAPA an they are not as good as genuine GM and the price is the same) and your tools.
First disconnect the upper ATF cooler line from the radiator. This one feeds the cooler in the radiator. Now push a 5/16 rubber hose over the end of the line. Just leave the fitting in the radiator open. Nothing will come out. Route the hose into a 10 quart bucket. I have one that has quart and liter markings on the side(really helpful!!!). Once you somehow fastened the hose to the bucket or have a friend hold it, start the car and let it idle......ATF will flow fast and nocely out of the hose until the ATF starts sputtering and spitting out of the hose. It will come out with a little force, but not too bad. This wayI got about 7 quarts out of the tranny within about a minute.
Next, you take the tranny oil pan off.......guess what, it is almost empty and no ATF will spill all over..NICE !!
Replace your filter and clean the pan out. WARNING!! If you decide to change the filter seal in the transmission housing it is difficult !!! If your sela looks good, leave it alone and just pop the new filter in it. If you deceide to take it out, here is the only way you can do it at home: The seals is composite metal and rubber. Take a hammer and a small flat screwdriver and try to catch the outer metal ring in the tranny with the srecdriver, hammering it to the middle until the seal collapses and you can get a hold of it with needle nose pliers. There is NO WAY you can pull the filter seal by trying to hook soemthing behind it and pulling on it. TRUST me !! I spend an hour before calling the Chevy dealer and they told me. You just need to try to catch the rim of the sela with the blade of the screwdriver and hammer/bend it inwards. After you did that it will come right out. Be careful not to damage the case bore!! It is aluminum and easily done. Now tap the new seal in with a scoket as a driver. Oil well before doing this! and pop the new filter in. Get the trans pan bolted back up to the tranny and fill the tranny from the top with 7 quarts of you choice ATF.
Now, do not hook the cooler line back up, leave it in the bucket (quart marks are REALLY helpful for this and accurate enough) and start your engine and let the motor pump another 3 quarts into the bucket. You'll see the old oil coming out first and then -voila- fresh ATF. Stop the engine and put the remaining three quarts in the tranny and your done.


[Modified by Alex D, 3:24 PM 3/31/2003]