Transmision fluid change

Could anyone tell me how to change out all the fluid in an automatic transmision? The '94 Merc. Sable I posted about before, is still in good shape, and if a fluid transfer helps it, great; if not then I am only out the time and expense of the fluid. I am wondering if this is something I can do under the shade tree.

 

How many miles on the tranny? Does the fluid look clear? Does the fluid have a burned odor? Is the tranny shifting properly?

If the fluid is clear, maybe a little darker than fresh, no burned smell, and still shifts okay, I would leave it alone. I suspect that you have in excess of 100K miles on a 14 year old car and I would just drive it until the tranny fails. At that time you can decide on a rebuild or replacement vehicle.

 

you can, but it'll require using extra fluid and a couple 5 gallon buckets. your transmission hold about 12 quarts...maybe a bit more. when you drop the oil pan to change the filter, you only get about 6 quarts out that way. to get at the rest of the fluid, disconnect the oil cooler line at the radiator and put it in a bucket, then start the engine and let idle. pump out a couple quarts and then shut it off and add a couple quarts, then repeat as many times as you want.

so, drop the pan, clean it and replace the filter (if you find metal, especially iron or steel {use a magnet} in the pan...don't waste your money on exchanging fluid, it's toast). you can even cut your old filter open and examine inside the filter, lots of crap gets trapped here.

if thats all good, then do the flush described above.

PS...don't expect a miracle, there are many, many places for small particles to hide esp the valve body and all the flushing in the world will not get them out and free up stuck valves. stuck valves are a result of ground up components in the trans...disassembly and cleaning is the only way to repair properly...this is worst case scenario but given the history of that trans and your description, I think the odds are against flushing solving the problem. good luck...

 

Carguyinva is correct. It's called the cooler line method. Here's the same thing Carguyinva mentioned, except in excruciating detail. I use this method 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 probably 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 oil 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).

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.

 

well, without getting into disassembling half of your lines, here's a simple way(recommended by mitsubishi owner manual, done many times)
1. you need to find out total volume of fluid in your trannie. TOTAL, not refill. refills are usually around 4 quarts, but it might vary some. my galant had 12 quarts total volume.
2. purchase as many quarts as you need to replace total volume.
3. get a sizeable drain pan, mine is 5 gallons, and ramps
4. i am keeping my fingers crossed that you have drain plug, as many fords don't, then you are either hosed or have to go through hassle of lifting engine and removing fluid pan and draining fluid off the edge. that's why they charge $400 to change fluid on some makes. (mazda 626, eg. per dealership, powertrain needs to be removed to change fluid)
5. get on ramps, drain your fluid. let's assume that drain volume is 4 quarts. drain, reinstall drain plug, refill trannie with 4 quarts.
6. drive for about 15 miles, drain again, refill, drive 15 miles again.
do so untill you have entire volume replaced.
as a result, it takes about an hour to do. at the same time, you have your trannie naturally flushed, as fluid pump creates high pressure and fluid flushes all kinds of crap out. you did not have to mess with disconnecting fluid lines, which can always end up in leaks/ripped lines. you can add a can of transtune, which is seafoam product designed to clean trannie's guts, about a week before flushing, as you can drive on it.
if you are planning on replacing filter/gasket(some cars do not have fluid pan gasket, just silicone sealant), do so before the last refill. after you drained the fluid, remove fluid pan, and replace filter. i have learned to remove filter 1st, THEN go buy a new one, as you can match those. oh many times did i have pan dropped just to find that filter or gasket don't match. so take fluid pan/filter with you to parts store.
if you need to replace gasket, avoid cork/rubber composite ones, they have tendency to crack on corner holes. find black rubber one, the best.
be very gentle tightening the bolts. very. tighten in criss-cross manner, and never overtorque them, or you'll rip the gasket. done many times, learned my lesson.