Changing transmission fluid -- how?

[ssybert]

I've got a 1996 3500 and am planning on changing transmission fluid this weekend. I bought the truck used and am quite sure after having driven it for about 5k miles, the previous owner did little no no maintainence on it. I picked up a new transmission filter and some fluid a week or so ago and tried to do it last weekend without any success. First off, there's no drainplug on the pan. Ok, most vehicles dont have one. There is also no drain plug on the torque converter. I've never done a transmission oil change but am ready to try it.

What I need to know is how do I get all the fluid out of the system including the torque converter? I know I can drop the pan, but that's only going to yield about 5 quarts right? How about the fluid everywhere else?

Lastly, how many quarts do I need TOTAL? I bought 15 but I suspect I'm going to need more for the torque converter as well?

Thanks,
Scott.

[MTTwister]

I'm preparing to do this too.

1. There is a 2WD tranny pan with a drain plug - part number 8685921 which I finally found after Gm did a nation wide search last week. Now at $45. The only reason I was hell bent on this was to put a tranny temp probe in the drain hole.

2. To complete flush the transmission - read this:
http://www.amsoil.com/faqs/faq8.htm

Per Greg at lubrication specialists, expect to use 17Quarts.
Per the GM parts counter guy - he believes that the GM techs use about 12 Qts.

Refill the tranny pan, note number of Qts used, subtract that from 17 to give remainder, Mark the drain bucket ( accurately) so that you know when your about to pump out the last couple of QTs so you can shut it down in time. Evidently it doesn't pump out That Fast.

Hopefully it starts to run clean before the full 17 Qts are dumped in, but I got 5 gal of Tranny fluid just in case!

It's Gonna be messy, I'm sure.

(pre-edit Whoa, just hit the Tab key and 'flooded' the server with Add Reply strokes. Sorry about that!)

[markrinker]

I used to do my own tranny fluid changes, but now take it to have them use the machine which gets all the fluid out, torque converter and all. For all the mess and then still ending up with a mix of old and new fluid, the price is worth it to me.

[Craig M]

Read the Amsoil method of pouring new fluid in while drining old. In a prior posting of this problem one reader just let the old fluid out via the pump, untill it was completely out of fluid. His comment was that under no load condition this was ok. Not all agreeded with his statement as I recall, but some did.

[GMCHORSHAM]

Sorry to butt in guys, :confused:
However I was interested in reading the thread attachment for Amsoil, If doing a complete fluid replacement.
Not sure if I missed something or just being critical?? :confused:
Quote; 11. Step2.
Disconnect the oil cooler line from the oil cooler. As you may not know which is the pressure side and which is the return side, have both directed so the stream of fluid will be directed toward a receptacle.
End Quote.
Surely if you wish to drain all fluid, you would need to determine pressure side and return side.
After this determination, re-attach pressure side and drain via return side.
My point here is that you cannot have both lines unattached and drain all fluid. If you leave both lines unattached from the oil cooler this in effect, is by-passing the oil cooler.
IMHO, you need to determine the flow direction, so that you can drain all fluids by disconnecting from the end of the flow cycle,
"so to speak". In this case would't this be the return line after the oil cooler. So in effect you are using the transmission pump to effect the drain flow.
I could be wrong, I read this point a few times and could not make Head-nor-Tail of the reasoning.
Have Fun, Safely.
Rod.

[MTTwister]

And - So wouldn't the pressure side be where the Trans line enters the Radiator? Then I would assume ( Haven't been under there yet) the a line comes from the Rad to the cooler, and the return line goes to the Tranny. Unless they're parallel versus series, this "should" be obvious.

Caveat - haven't been on my back under there yet - but it's coming. Input appreciated.

[autocrosser]

For years on cars I have disconnected the lines comming from the transmission to the readiator, I then blow air into the radiator cooler line opening to push the rest of the flud out and let the engine idle while the fluid was pumped out of the disconnected line. As soon as I see bubbles I shut it down. I would then put a little fresh fluid in it and repeat the process to push out the rest of the old fluid. I have done this on a number of vehicles when I felt that a complete change was needed and never had a problem. I am 62 years old so you can guess by that how many vehicles I have done this with. and I don't get rid of vehicles very often so I drive them awhile.

Some folks might not agree with this but it has worked fine for me for many years.

[sturgeon-phish]

When I changed mine I put a piece of tygon tubing over the transmissions line to the radiator, other end in a 5 gal bucket, started the truck, and added fluid as it pumped out fluid through the tube. When the color of the fluid changed from dark red to bright red, shut off the truck. Disconnected tubing and re-attached the trans line to the cooler, checked level, drove a bit checked level. NO mess. When I had my pan off, I added a drain plug for next time!

[lupey6.5]

fluid changes don't help old filters. that is why there is no drain hole in the pan. most of these should have reusable pan gaskets anyway that only need a good wipe down to be used again, provided they aren't damaged. if you take the tranny mount bolts out of the cross member, jack the tranny up and put 2 2x4 wood blocks between the mount and cross member, this will provide more than enough clearance to drop the pan and do it right. mine still shifts like new at 240,000 mi. with org. trans and torque converter. it just feels better to do it right. my $.02

[damork]

I agree the filter needs to be replaced, but I also think the pan needs a drain plug to help reduce spilling ATF all over the garage floor.

I swapped my non-drain plug pan for the drain plug version then added a temp sensor port for my trans temp gauge by using a weld in 1/8 female pipe bung (got it from an Autometer kit).

For flushing, I pull the return line from the RH side of the trans and route it to a white bucket - this captures all the OLD fluid being pumped through the converter and cooler. I keep refilling until the dark stuff turns bright red in the bucket.

[JohnC]

At the risk of repeating what has been said, here's how I do it. First, remove the line going into the top of the radiator. This is the feed from the trans to the cooler (4L80E, others DO vary!) Stick a piece of 3/8" hose on the line and put it into a 5 gallon bucket. Run the engine at idle until the fluid stops coming out into the bucket. This pulls most of the fluid out of the cooler into the pan and pumps it up into the converter. Next, drop the pan, which is now nearly empty and easy to handle, and change the filter. Clean the pan, put it back and add in 7 quarts of new fluid. Run the engine at idle again until the fluid stops coming out. Now the clean fluid is up in the converter and nearly all the old fluid is in the bucket. You may refill the pan and run a little more into the bucket, but it's hard to control at this point and the rewards are negligable. Anyhow, refill the pan, reconnect the upper cooler line and check the level per the owner's manual. It's easy, no mess, and you'll get 99% of the old fluid out and not waste more than a quart or 2 of the new stuff.

[MTTwister]

JohnC - Thanks for details on how you do it - Seems like the least likely to screw up which line is which - I'm going with your process.

Question - how hard is it to pull the tranny pan? Some mentioned jacking up the rear of the tranny to get clearance. Noticed shifter partially in the 'way'. Never pulled a pan myself, so I'm looking for any hints and suprises to dodge in the process. Thanks!

[JohnC]

When I pulled the pan on my '95 4x4 it was pretty easy. IIRC, I couldn't quite get a stright extension and socket on to the rear-most bolts, but that was the only problem. Didn't have to jack anything or remove any cross members.

[Dezman125]

Hi
If you are going to go through all the work to change the filter,and all fluid,then for afew dollars more you should get a can of cooler cleen.Most transmission shops will have it.You hook it up to your lines and it is presurized.The stuff i use is biodegadable.It cleens deposits out of your cooler,helping it flow better,and getting rid of miss.particals.
Very important if changing out a bad trany
My .02 worth

[GMCHORSHAM]

MTTwister & JohnC,
Head-nor-Tail has been determined.
Thanks JohnC, I agree with MTTwister, that your method is the way to go (The Plan).It makes good sense and helps to reduce the loss of New fluid during the process. smile.gif
Have Fun Safely.
Rod.

[lupey6.5]

filters do need replacing but has anyone else seen these aftermarket drain plug kits? i would have to do some research to find them now but it is available. you remove the pan drill a hole and install.

[Phil Holmen]

I have added the drain plug kit where you drill a hole and thread the bolt in and install the nut on the other side. Works great but will still leave a small amount of fluid in the pan, minor compared to before. It will also accept my temp sensor. BONUS smile.gif smile.gif

[MTTwister]

Phil - Can you give us a 'contact' for the aftermarket drain plug kit? I have a feeling that the temp probe doesn't fit with the OEM drain plug on the 2WD pan - It's probably Metric. What's up with that, anyway? Thanks.

Speaking of what were they thinking - Why the H... did they use a Trox head bolt and metric nut for the transfer case shield? Gimme a break!

EDIT - From an AskJeeves Search:

I bought a drain plug kit from PepBoys for $3 for my 95 Tahoe and put it in.
Be REAL REAL careful about where you locate it so it doesn't hit something on the valve body when installed. I found a small area that was very open to locate mine.
Also, I strongly recommend using some auto sealant between the washers on the inside & outside of the through-plug to make a gasket. It will prevent seepage, which I had after installing the kit without sealant.

** and -
Go to the local hardware store and get a washer head hex bolt 1" long, 3/8" or 1/2" NF thread, a matching nut, a nylon washer which will go on the outside of the pan under the head of the bolt, and a tube of epoxy glue. Transmission fluid has no effect on dried epoxy. The rest is self-evident. There is a flat on the pan where the drain plug goes. Be sure to clean the pan with alcohol so that the epoxy will hold the nut to the inside of the pan. When you glue it up on the bench, tighten the bolt only a little more than finger tight to hold the nut in place as it dries. You do not want to squeeze all the epoxy out. Also, put a little grease on the threads of the bolt so that it won't allow any epoxy to stick to the bolt. Allow drying per the label; shining a shop light on it will speed the process.
Total = $5 or so.

** and
I just bought a kit from the auto supply for the next time my Sub's pan/filter is worked on. It's double nuted so it won't work lose and you can do the epoxy thing to the inside nut. The bolt is about a 1/4-20 that plugs the hole through the two nuts (one nut is really a bolt with a taped hole through the length).
Motormite brand (div of R&B inc, PO Box 1800 Colmar, PA 18915-1800), part number 65241 (UP code 3749565241). $2.99 at the local NAPA auto supply, but have seen it at Kragen's, WalMart, Target "

One of these ought to do it - Now, Just need my temp probe to check threads.

[ 04-01-2004, 02:48 PM: Message edited by: MTTwister ]