Transmission filter change and fluid flush

[LiftedAWDAstro]

I decided I needed to flush all the fluid out of the tranny rather than just change the filter and the 6 - 8 quarts in the pan. Here is how it's done:

First thing is to jack the van up and support on jack stands. I had the front end up for the front gear swap so it was already supported. Here is a pic from when we worked on Dunedog's van. These jack stands are rated at 6 ton each.



You then need a large catch pan for the fluid as well as a 13mm socket, 6" extension and a ratchet and/or air ratchet. Remove most of the bolts holding the pan on leaving 3 or 4 bolts tight. Start loosening the bolts on one side about 1/2 way. Then loosen slightly the bolts on the opposite side. The pan might start dropping and you WILL have fluid all over the place. Try to catch most of it. Once the fluid is mostly drained, drop the pan the rest of the way. I hold it up tight with one hand and remove the bolts with the other. I then drop it down trying to keep it level. You may have to shift it to the passenger side to clear the shift cable mount bracket. Once it's out, you will see the guts with a filter covering them. The filter comes straight down with a light twisting motion.



Where the filter came out of will be the seal. It looks like this:





It fits in here:





Run your finger in there and feel if it is smooth. If it is smooth and still soft, no need to replace it. At this time I let the tranny drip off for a while. Now is a great time to clean the pan and check for debris.

Here is what it'll look like on the bench after dumping most of the fluid out.





Here is the magnet. You will see some fine material on it but there should be no chunks. I have a few chunks but they are from the rust that was on the rag I threw in the pan. The fluid is dark but does not smell burnt. I did a filter change last year, about 18k miles ago.



At this point, you can clean it all up.

[LiftedAWDAstro]

Now, lets discuss the difference in the pans. You may have a standard or a deep pan. This is very important to know as the filter kit is specific. I used NAPA filter kits and they include a rubber gasket.

Here are the 2 pans. Deep on the right. The one on the left is from the old SPB and is standard height.



You can see the height difference here:





Deep pan is not smooth on the bottom:





Standard pan is smooth:



Now that the tranny has dripped off for about 20 minutes or so, climb back under with the new filter after applying some fresh tranny fluid on the neck so it slides in the seal easily. Insert the new filter using a slight twisting motion and light force. It'll pop right in and should be tight. If it is loose or falls out, replace the seal.



Now you can place the new gasket on the pan and hold it in place with a few bolts and install it on the tranny. Once all the bolts are started run them up snug using a criss-cross pattern. Finally, tighten to 10 foot-pounds or 120 inch-pounds. If you don't have a torque wrench, just make them snug. The case is aluminum and you can strip the threads out. I go around and check them twice to make sure I didn't miss one. Wipe everything down and then it's time to place the van back on the ground so you can add fluid.

[LiftedAWDAstro]

Now find the tranny dipstick and fit a funnel. Add 6 quarts of fluid at this time. If you have a standard pan, only add 5 quarts.

Now we'll get prepared to do the flush. Remove the grill so you have access to the aux cooler. If you don't have an aux cooler, that should be done now! If not, you'll have to pull the top cooler line from the radiator and place a hose on the rad fitting and over the rad support. It would be a pain so install an aux cooler and do it that way!

Here you will see my aux cooler. The return line is the upper one.



Remove the aux cooler hose that goes to the return line to the tranny. Add a short length of hose to the aux cooler where you pulled the line off of. You also need a catch pan (same one I used for the filter change job) and something to set it on to get it near the cooler unless you run the hose to the ground.



Now is time you start flushing. Roll the drivers window down and reach through starting your van. You'll get fluid pumping out one of the lines.



Run until you pump about 2 or 3 quarts out. Shut the van off. Re-fill with 2 or 3 quarts. You don't want to run it dry. Keep doing this until the fluid being pumped out is clean. It took me 15 quarts to complete this task. Once all the fluid is clean, install the hose back onto the aux cooler and start the van, checking for leaks. You can at this time run the gear selector through the gear to make sure fluid is pumped all around. Leaving the van running, check the fluid level. It should be around the cold mark on the dipstick. If it is good, take it for a drive to warm it up. Once you get back, check it again and add if needed. If you have too much fluid, you can pull the aux cooler hose again to flush some out. I then installed the grill and signal lights. Make sure you button everything up, clean your tools and wipe all the spilled fluid and you are done!

[photo_van]

Nice easy way to flush! I've always had a hard time getting that filter seal out, any tricks?

[LiftedAWDAstro]

I don't know of any tricks. That is why I recommended leaving it in as long as it is soft and smooth and not nicked.

[MountainManJoe]

This is a really good topic. It should be a sticky.

I'll consolidate some of my old postings here for completeness...

To remove the notorious transmission filter gasket, I sharpened the end of an old toothbrush into a chisel shape. Plastic won't harm the soft aluminum valve body. With a hammer, I drove the tip between the gasket and the housing until the gasket was deformed enough to grab with needle-nose pliers and it came right out.

The following is my own method of removing old transmission fluid. It circulates the entire system the way it would under normal operation, and delivers fresh fluid to the pump, torque converter, cooler(s), lines, rotating parts (gears, shafts, clutches etc) and valve body. This method does a good job, but requires a lot of fluid. To be any more thorough, the torque converter would have to be drained, and the transmission would have to go through all the gears while in motion, several times etc.

Keep in mind that you will never get all the old stuff out, and you don't need to. I talked to several transmission mechanics who say that under normal circumstances, doing a pan and filter service at the manufacturer recommended interval is all that's needed, (48,000km IIRC) and I agree. Those fancy machines they hock at quick-lube places were meant to flush your wallet. Only do a full flush if the transmission has had heavy use, or was not serviced in a very long time.

Under normal driving conditions, the ATF fluid is very durable. It mainly functions as a hydraulic fluid to transmit power through the torque converter and pressure through the valve body which is the brain of the transmission that actuates all the shifting mechanisms. It also cools, lubricates, and transports debris to the filter. Unlike engine oil, It is not exposed to combustion contaminates. Doing a pan service will replenish the oil additives that the transmission needs.

Anyway, onto the flush. Start with the pan and filter out per Lifted's instructions.

Materials:
- 8 feet of clear vinyl tubing - 3/4" to 7/8" outer diameter. 1/8" thick.
- 1 large funnel - Bottom opening roughly 3/4" OD.
- 6L Dexron III ATF for OEM system. More for additional coolers.
- Large tray underneath transmission to catch the draining ATF

1. Thread one end of the tube into the funnel and jam the other end into the filter gasket (which you have already installed). You can double flare the end of vinyl tube with a bit of heat to make it fit snugly. It gets slippery once oiled.

2. Hang up the funnel with a bungee cord.

3. Fill up the funnel all the way and let the fluid settle to prime the pump so it doesn't run dry.

4. Start the engine. The pump will begin to quickly suck the fluid from the funnel, and a torrent of ATF will gush out the bottom of the tranny and into your pan.

5. Keep pouring fresh fluid into the funnel; It will disappear as fast as you can pour. When that transmission starts to make a slurping sound, shut the engine off.

According to my calculations, 6L should push out all the old stuff and send some extra through. Some old fluid will remain hanging in the TC and other parts but dont be concerned.

Reassemble per Lifted's instructions. I topped it off with another 5L (5 quarts) of fluid.

[MountainManJoe]

These are both factory GM 4L60E pans, just from different year vans. I'm not sure which.

Shallow pan (2 1/4")

Deep pan (76.6mm).
(Notice the extra 'step')

pan- deep (76.6mm).jpg (35.35 KiB) Viewed 35909 times

and here is the gasket (same shape for both pans)

[MountainManJoe]

Filter+gasket kit: approx $18
The pan gasket is rubber. The holes are smaller than the bolts to facilitate installation.

Wix item numbers
Shallow pan kit: 58904
Deep pan kit: 58847

Filter comparison

Shallow:

Deep:
(Notice it has standoffs on the bottom. It prevents the filter from being sucked against the pan and blocking the intake. This was a problem in the past.)

[Wiley]

Any tips on getting the pan off and on, like pulling off one side first, its pretty tight and i remember struggling to finally get it both off and on. Im sure its just keep wiggling it around but if you have any tips i do for a filter change.

I used timelessbeings method last year and it worked great, though inlove the simplicity of lifteds method

[astrozam]

Any tips on getting the pan off and on, like pulling off one side first, its pretty tight and i remember struggling to finally get it both off and on. Im sure its just keep wiggling it around but if you have any tips i do for a filter change.

I used timelessbeings method last year and it worked great, though inlove the simplicity of lifteds method

Start in 1 corner and work back along both sides, this will drop the pan in the corner and help with draining the fluid.

[Wiley]

Sorry, i should have specified i meant after i drained the majority of the oil and removed all bolts, theres a pipe or something that gets in the way, lots of twisting and trying different angles before i get it, 10 or 20 min if i recall. Probably tighter due to awd Just wondering, maybe it will go better this time

[Wiley]

I hate bumping instead of editing, sorry.

So the shift cable mount bracket is what is ALWAYS in my way. After trying every angle again for 5 minutes, I just grabbed a pair of pliers and bent it over the few mm I needed, then it worked like a charm.

I did discover some not great, but not quite deal breaking news. One bolt head broke off while removing with no exposed part of the bolt left, and two others are stripped internally so just spin instead of tightening to proper torque. I torqued them last time, so I think they were damaged from the mentioned banging on speed bumps, as they are all in the same corner. Its ok for now, just need to decide if I should have someone fix them properly, or just swap out the tranny for 4x4 which would be a better fix if you ask me. Waiting to decide on how long I plan on keeping the van.

The point of my rambling, if you have trouble getting the pan off it appears to be ok to bend the mount slightly for clearance.

[pharside]

Excellent post guys. Thank you for the info and flushing tips.

[Bret Schmerker]

Sorry to bump an old topic, but thanks for the detail photos. My down-as-of-16-September-2018 1997 Safari SLE's gearbox is coming due for an overhaul and I see a LOT of things that could use major upgrade. R Performance Transmission and Driveline Specialties (Oakley, CA, USA) can do the flush procedure described here on the bench in order to get as much junk out of the clutch packs and gears as possible prior to the actual teardown; I've a plan for blueprinting the gearbox to 2011 Camaro 4L65-E standard and ideally retrofitting dual external filters and a Mag-Hytec® two-piece finned aluminum deep pan with drain plug. (The cooler-line spin-on is the easy one, as it catches the junk upstream of the coolers; but I'd like a second, "full-flow" spin-on in line between the main pump and the valve body, àu Allison 1000.)

[Mmusicman]

This flush idea is excellent!!! It allows the transmission to flush the fluid "naturally"... using it's own pump, to pump out the old fluid exactly as it pumps fluid when it's running normally. There is no shock or danger to the system, just freshly infused fluid!

But I think I have a much easier "variation" of the same method.. that will accomplish two things nicely.

1) Pump the old fluid out first! Do this BEFORE you drop the pan! (using same method pumping from disconnected hose at radiator into a bucket). Note: fluid pumps from bottom up. Pump ONLY until you start getting air, then shut down immediately (better to have someone at the key while you watch). You will get most of what's in the pan, but not all. The BIG plus is that you can now drop the pan with ZERO mess!

Empty and clean the pan, change the filter, put the pan back on.

2) Now fill the trans with new fluid (through dipstick).. and continue the flush. You will still be pumping only fresh fluid at this point, but it will be coming from the cleaned pan, being fed via the dispstick. Continue feeding and pumping until fluid pumping out is red.

SIMPLE! NO MESS! DONE!

This uses the same great method as the original idea, without the hassles, extra hoses, and mess.

Cheers!

See my flush here: https://www.astrosafari.com/viewtopic.php?f=70&t=135177