C6 Fluid/Filter Change
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Senior User
Joined: Dec 2009
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C6 Fluid/Filter Change
Hello folks,
I'm new here........ and I recently purchased a 1986 F250 XLT Lariat, 6.9 IDI, 2wd with the C6 transmission and 126 000 kms.
I want to change the fluids and amoung the first things on the list is the transmission fluid and filter. I am just going to drop the pan to swap the filter and then refill as opposed to getting the tranny flushed. The biggest issue with this method (based on my understanding) is that there is such a large quantity of fluid that does not drain using this method (i.e in the cooler and the torque converter) The cooler is relitively easy to get most of the old fluid out (disconnect the lines going to it) but the torque converter my be another thing. Am I correct in my understanding that the torque converters on a C6 have a drain plug? If yes, can I access the drain plug without disconnecting/removing the tranny from the engine/vehicle?
Also, I seem to be finding conflicting info regarding the fluid specs. Some references say mercon and some dexron II...... some explicitly say NOT to use one or the other! SO, for a C6 in a 1986 F250, what is the proper A/T fluid?
Any input you's can provide would be very much appreciated!
Thanks a lot..... very happy to have found this forum already!
I'm new here........ and I recently purchased a 1986 F250 XLT Lariat, 6.9 IDI, 2wd with the C6 transmission and 126 000 kms.
I want to change the fluids and amoung the first things on the list is the transmission fluid and filter. I am just going to drop the pan to swap the filter and then refill as opposed to getting the tranny flushed. The biggest issue with this method (based on my understanding) is that there is such a large quantity of fluid that does not drain using this method (i.e in the cooler and the torque converter) The cooler is relitively easy to get most of the old fluid out (disconnect the lines going to it) but the torque converter my be another thing. Am I correct in my understanding that the torque converters on a C6 have a drain plug? If yes, can I access the drain plug without disconnecting/removing the tranny from the engine/vehicle?
Also, I seem to be finding conflicting info regarding the fluid specs. Some references say mercon and some dexron II...... some explicitly say NOT to use one or the other! SO, for a C6 in a 1986 F250, what is the proper A/T fluid?
Any input you's can provide would be very much appreciated!
Thanks a lot..... very happy to have found this forum already!
Post Fiend
Joined: Nov 2004
Posts: 5,638
Likes: 1
From: Manitoba
C6 uses Mercon/Dexron fluid....... not Mercon V
Total capacity......11.75 US Qts....11.2 Litres
Someone with a C6 will have to give advice re how you get to it....without removing the trans, but my schematic shows a drain plug.
Total capacity......11.75 US Qts....11.2 Litres
Someone with a C6 will have to give advice re how you get to it....without removing the trans, but my schematic shows a drain plug.
Lead Driver
Joined: Dec 2006
Posts: 6,496
Likes: 94
From: So. Jersey
The c-6 so called filter is only a screen. The torque converter DOES have a drain and it is on the front of the torque converter. It's located behind the dust shield and you will need to spin the engind over by hand to find it. It is in a recessed hole. A little mirror will help. Its a 7/16 socket and simply remove it and let the converter drain. Mark the converter with a paint marker so next time you can find it easier.
Just to be clear the plug is in a position just like the flex plate nuts, horizontal. It's not like the e4od drain where it's straight up from the bottom, vertical.
Dexron/merconIII , no merconV
Just to be clear the plug is in a position just like the flex plate nuts, horizontal. It's not like the e4od drain where it's straight up from the bottom, vertical.
Dexron/merconIII , no merconV
Thread Starter
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Senior User
Joined: Dec 2009
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thanks a lot guys..... Another type fluid that seems to come up a lot for the C6 is type F. I think that type F is for earlier models.....
I think I'll just stick with just plain Mercon..... that should be a safe bet, eh?
I think I'll just stick with just plain Mercon..... that should be a safe bet, eh?
Post Fiend
Joined: Jan 2005
Posts: 8,402
Likes: 10
Great info from everyone, especially 87CD about finding the torque drain. Never thought of the paint marker, will have to remember that one.
Type F was specified up to about 1978. If you look at the dipstick it may give the factory recommended fluid but I would think you will be OK with Mercron spec. fluid. You will need around 12-13qts for a complete fill.
Type F was specified up to about 1978. If you look at the dipstick it may give the factory recommended fluid but I would think you will be OK with Mercron spec. fluid. You will need around 12-13qts for a complete fill.
New User
Joined: Jun 2010
Posts: 3
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Great info in this site I had spent hours looking for the converter plug size and finally found it thank you 87crewdually a 7/16 socket will help me get this job done...Do I have to dissconect all the cooling lines to drain the oil in them?
Elder User
Joined: Apr 2002
Posts: 950
Likes: 2
From: West Bend
If you wish you can even get cans that you hook up to flush the cooler/lines out. Just make sure to follow the instructions on the can.
Nothing special to changing the C6 filter. Unfortunately they didn't come with drain bolts so it'll likely get messy dropping the pan. Loosen all the bolts up except 2 in the front and 2 in the back. Loosen the front bolts a few turns and remove the rear bolts half way, break the pan-to-case seal and let the fluid drain out best as possible. Then carefully loosen the front bolts a bit more and remove the rear bolts to drain more fluid out, then finally hold the pan up against the trans, remove the front bolts and then carefully lower the pan down to minimize oil spill.
Make sure you pull the pickup tube out from the old filter (note how it's placed in it) so you can put it in place of the new filter. I've seen people put their transmissions back together without the pickup tubes - makes for some interesting transmission issues.. The filter is just a matter of removing the bolts holding it in, removing it and reverse of removal.
Nothing special to changing the C6 filter. Unfortunately they didn't come with drain bolts so it'll likely get messy dropping the pan. Loosen all the bolts up except 2 in the front and 2 in the back. Loosen the front bolts a few turns and remove the rear bolts half way, break the pan-to-case seal and let the fluid drain out best as possible. Then carefully loosen the front bolts a bit more and remove the rear bolts to drain more fluid out, then finally hold the pan up against the trans, remove the front bolts and then carefully lower the pan down to minimize oil spill.
Make sure you pull the pickup tube out from the old filter (note how it's placed in it) so you can put it in place of the new filter. I've seen people put their transmissions back together without the pickup tubes - makes for some interesting transmission issues.. The filter is just a matter of removing the bolts holding it in, removing it and reverse of removal.
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Postmaster
Joined: Apr 2009
Posts: 4,086
Likes: 1
From: Malahat/Cowichan Valley
i just pay the 75 for a flush and fill, on these transmissions it is cheap. My mitsubishi galant from years back was about 110 lol. If you ever do drop the pan though, install a drain plug or replace the pan with an upgraded one that has the heat dispersing fins on it. makes future fluid changes a lot easier. Somewhere i remember reading about a guy that would jack his truck up on all fours(jackstands) and then put his truck in drive and drain out a couple quarts, then add, then repeat. not sure if it actually works to "flush" the system.
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From: Mi'kma'ki
Amazon.com: B&M 80250 Automatic Transmission Universal Drain Plug Kit: Automotive
don't use type F either Cruckie.
forget everything you've read and just listen to these guys about fluid type for your truck and you'll be alright.
don't use type F either Cruckie.
forget everything you've read and just listen to these guys about fluid type for your truck and you'll be alright.
Lead Driver
Joined: Dec 2006
Posts: 6,496
Likes: 94
From: So. Jersey
Thanks. I normally do disconnect the transmission cooler lines at the radiator and allow the coolers and lines to drain, usually while I'm draining the pan.
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