C6 Service

[mp470]

The fluid is pretty low and completely black. Pan leaks slowly, gasket is definitely shot. I've heard these are robust transmissions but I have no idea about the history of maintenance, probably little to none. I've got everything for the service, just thought I'd throw it out there to see how it might react to new fluid (slippage, hard shifts etc.). This will just be a pan drop, not a flush. It still shifts quite well unless it gets down to freezing, then it won't go out of 1st until after a few circles around the block.

Slightly related note, the transmission mount is so worn it's basically just metal on metal. Best practices for replacement...undo the nuts, jack up on the pan with a block? Or is it much more complicated?

[Gary Lewis]

Changing the fluid, filter, and gasket isn't too bad - with the exception of the draining part. From the factory there's no drain plug so you have to guess which corner is low, loosen the pan bolts, and pry that corner down to get as much out as you can. And then drop the pan. Be prepared for a big mess.

Don't forget that the torque converter holds as much fluid as the tranny itself. So you really need to drain it as well. There's a little pipe plug that drains it, and you need to pull the inspection cover and rotate the engine until that is at the bottom. Pull that to drain it, then put it back and it'll be filled when you fill the tranny.

The pans are somewhat flimsy and over-torquing the bolts dents them, so check the pan to see if it is dented and, if so, use a small ball pein hammer to work the dents out. And when you put the pan back don't over torque it. I like to use a good layer of RTV on the gasket, put the pan on, snug up the bolts by hand, and let it sit over night for the RTV to cure. Then torque it to specs, fill it, drive it, and check the level as it'll be a bit low. But if you put RTV on and try to torque it down then the gasket will squirt out the sides due to the slipperyness of the RTV and you'll have a leak.

On the mount, I'd put the jack under the tail housing or transfer case rather than the pan. As said, those pans aren't the most robust so I don't like to jack on them. But, if you put a piece of wood about the size of the pan between it and the jack that will spread the load and it'll be fine.

[Bruno2]

Changing the fluid, filter, and gasket isn't too bad - with the exception of the draining part. From the factory there's no drain plug so you have to guess which corner is low, loosen the pan bolts, and pry that corner down to get as much out as you can. And then drop the pan. Be prepared for a big mess.

Don't forget that the torque converter holds as much fluid as the tranny itself. So you really need to drain it as well. There's a little pipe plug that drains it, and you need to pull the inspection cover and rotate the engine until that is at the bottom. Pull that to drain it, then put it back and it'll be filled when you fill the tranny.

The pans are somewhat flimsy and over-torquing the bolts dents them, so check the pan to see if it is dented and, if so, use a small ball pein hammer to work the dents out. And when you put the pan back don't over torque it. I like to use a good layer of RTV on the gasket, put the pan on, snug up the bolts by hand, and let it sit over night for the RTV to cure. Then torque it to specs, fill it, drive it, and check the level as it'll be a bit low. But if you put RTV on and try to torque it down then the gasket will squirt out the sides due to the slipperyness of the RTV and you'll have a leak.

On the mount, I'd put the jack under the tail housing or transfer case rather than the pan. As said, those pans aren't the most robust so I don't like to jack on them. But, if you put a piece of wood about the size of the pan between it and the jack that will spread the load and it'll be fine.

If you are changing fluid it probably wouldn't be a bad idea to add a filter on the return line. New fluid with fresh strong detergent breaks loose stuff in the radiator and cooler.

[JMUBullnose]

Interesting! I was just contemplating rebuilding the AOD this winter on my Ford. Good winter project as I don't use the truck much during that time.

[mp470]

Well the service is done, somewhat. Being a weeknight, didn't have enough time, so didn't drain the TC. The fill was messier than the drain, that tube holds the funnel too horizontally and it fell a couple of times, sending fluid everywhere. Drained about 4.5L out of it so it was definitely low. The black stuff I saw on the dipstick was just the fine metal particles at the bottom of the pan. The fluid itself wasn't too terrible, although dark.

Thanks all.

[Gary Lewis]

Well the service is done, somewhat. Being a weeknight, didn't have enough time, so didn't drain the TC. The fill was messier than the drain, that tube holds the funnel too horizontally and it fell a couple of times, sending fluid everywhere. Drained about 4.5L out of it so it was definitely low. The black stuff I saw on the dipstick was just the fine metal particles at the bottom of the pan. The fluid itself wasn't too terrible, although dark.

Thanks all.

Did it change the shifting?

[mp470]

Did it change the shifting?

I haven't driven it yet, it still needs more fluid. It got a bit too dark out to finish last night.

[Ken Blythen]

I haven't driven it yet, it still needs more fluid. It got a bit too dark out to finish last night.

Given the condition of the fluid , I would REALLY recommend draining the converter; it can still be done if the engine hasn't been started.

You can also disconnect the cooler lines & gently push the fluid out of the pipes & cooler with compressed air (just light pressure).

The whole refill is about 12 quarts, so there is still a lot of contaminated oil in there, mainly in the converter.

[Gary Lewis]

Given the condition of the fluid , I would REALLY recommend draining the converter; it can still be done if the engine hasn't been started.

You can also disconnect the cooler lines & gently push the fluid out of the pipes & cooler with compressed air (just light pressure).

The whole refill is about 12 quarts, so there is still a lot of contaminated oil in there, mainly in the converter.

Excellent point, Ken. Just turn the engine slowly with a 15/16" socket on the crankshaft bolt until the drain plug is at the bottom, pull it to drain the converter, and then refill things when the plug is back in.

[mp470]

Given the condition of the fluid , I would REALLY recommend draining the converter; it can still be done if the engine hasn't been started.

You can also disconnect the cooler lines & gently push the fluid out of the pipes & cooler with compressed air (just light pressure).

The whole refill is about 12 quarts, so there is still a lot of contaminated oil in there, mainly in the converter.

I had already started the engine at that point for the hot check, will do it next time.

Took it out for a highway cruise, runs like a clock as usual, shifts perfectly. It's incredible that this 33-year old vehicle has perfectly working cruise control.

Only complaint is the low oil pressure at hot idle but not much to be done about that, will throw some Rislone in it and hope for the best. Crankcase pressure is high, blow-by to the airbox and out the PCV valve hose etc. I wish I had the time, money and place to really dedicate to rebuilding the engine, body etc. For now, it's just a camping truck for 1-2 seasons of the year.