trans/diff fluid change ?'s

[mercurygm88]

So being that god only knows when the last time my trans fluid was changed was im going to do it tonight. So far im figuring ill need about 12-13 quarts of mercon v and a filter and pan gasket. Now after I get the pan off and drained whats the procedure for draining the torque converter, and what is the proper method for refilling an empty aod? Also while im at it should I change the differential fluid or just check the level? If I change it what particular type of fluid should I use? I dont know much at all about differential fluids.

[Kestas]

I have the same transmission. I heard there's a drain for the torque converter. I never bothered with it. I use what's called the "cooler liner method" of changing the fluid every 30K.

Transmission Fluid Exchange

For those interested, here's the fluid change method I use on all my cars that don't have a torque converter drain:

1. Pull the transmission dipstick (located near the firewall in most cars). Fresh fluid is translucent and cherry red. Some darkening is normal, but if it is reddish brown or mustard color and smells like burnt varnish, it is worn out.

2. Make sure the fluid is warm.

3. For pans that don't have drain plugs, remove all pan bolts except for the corners. Remove the bolt from the lowest corner, then loosen the other corner bolts a turn or two. Carefully pry the pan to break the gasket seal at the lowest corner. Drain mostly from this corner. With good technique you can avoid or at least minimize the red bath.

4. Remove pan. Inspect the pan before cleaning. A small amount of fine grey clutch dust is normal. However, if you find metal shavings, there has been transmission damage. Remove all old gasket material. Clean the pan and magnet with solvent and wipe dry so there is no harmful residue. Shop air can be used to clean the magnet. Hammer back any pan damage from previous overtightening.

5. (Optional) Drill hole in pan at low point and install a drain kit available from most auto supply houses. Make sure the kit protruding inside the pan doesn't interfere with anything on the transmission.

6. Replace filter. If it’s a metal screen filter, it can likely be cleaned and reused.

7. Position gasket on pan. Some gaskets have four holes slightly smaller than the rest to allow four bolts through the pan and through these smaller holes to hold the four bolts and gasket in place.

8. Hand tighten pan bolts in a criss-cross pattern. After that, use a torque wrench to tighten bolts to proper ft-lbs as per manufacturer.

9. Refill the transmission using only the amount shown as “refill capacity” in the owners manual (or an equal amount that was drained), using the type of fluid specified for the vehicle.

10. You now have replaced the trans fluid and filter according to manufacturer’s requirements. Fluid is changed in the pan only.

You can stop here and go to Step 17 if you just wanted a regular drop-the-pan fluid change. For a complete exchange of the fluid (including transmission body and torquer converter) continue with the next steps.

11. Obtain the total system capacity of the vehicle from the manufacturer. Have this amount - plus a bit more - of fluid readily available.

12. Disconnect the oil cooler line from the transmission cooler. Tickle the ignition to find the flow direction. Direct the stream of fluid toward a receptacle. It is better to use a clear length of hose with a shoplight laying next to it so you can see when all the old fluid has left the system.

13. Start the engine, let it idle to pump out old trans fluid until you start seeing air bubbles.

14. Stop the engine. Refill transmission through fill tube with fresh fluid - same amount as pumped out (usually about 2-3 quarts). After the first iteration, it helps to shift the transmission through the detents, pausing at each one, to get the old fluid out of the circuits.

15. When either the fluid color brightens or the total capacity has been replaced, shut the engine off and re-attach the oil cooler line. All trans fluid has now been changed.

16. Button everything back up. Clean up the mess.

17. Recheck the fluid level. With the car on level ground, set the parking brake and the transmission in “Park” or “Neutral.” Let the engine idle for a few minutes. Shift the transmission through all detents, pausing momentarily at each position, before returning the lever to “Park” or “Neutral.” Check the fluid level again and check for leaks. Refill fluid so it is slightly undercharged. This way it can be properly checked and topped off after a long drive.

If you don't know the history of the differential fluid, go ahead and change that out also. I'm not sure what is specified (80W-90?), but Mobil 1 75W-90 synthetic should work well for your car. Make sure any fluid you use is GL-5 and meets viscosity requirements.

[Piece-it pete]

X2 on the diff fluid. I suggest gravel drive or yard - used gear oil is nasty.

Pete

[GM_Guy]

Makes little difference if you go 75-90 or 80-90, but I'd definately recommend using a synthetic if for no other reason than it doesn't smell like a nasty outhouse when it comes time to pop the cover off on your next oil change, or when you need to r&r the axle seals. I've got Amsoil 75-90 in mine.

Alex.

[sly]

synthetic with friction modifier still smells seriously like ass... just not as bad as dino oil.

how I found out... (see attached)

[zoomie]

mercon v is good stuff, its what i put in my trans when i installed it. and x2 on the smell its naaasty!

[nfldfordltd]

synthetic with friction modifier still smells seriously like ass... just not as bad as dino oil.

+1 on the stench of friction modifier. I use the occasional bottle of that in my AOD to help rough 1-2 shifts and it smells like tom cat piss X1000...

[zoomie]

oh and do your best to not get gear oil on your clothes i got some on a shirt one time and the smell never completely went away, even after 6 yrs.....

[BerniniCaCO3]

hahahaha.
Yeah, when I did my diff oil, at 109,000 miles (no pretensions that it had ever been done before), MY GOD.
But when I did my sister's limited slip at 84,000 miles, oddly, it did not smell? Maybe it was so thick with clutch material, that it was no longer volatile, no longer gave off vapors you could smell.

There's a 10mm bolt on the front (where the studs meet the flywheel) of the torque converter, as a drain plug. But yeah, loosening a cooler line ought to pump it all out anyway.
That's exactly what we do for volvos at the dealership, too.