Quote:
Originally Posted by jbg
Just so I have this right I would disconnect a line going from the transmission to the radiator and place into a bucket.
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Yep. I forget whether the ZF feeds the fluid in at the bottom or the top cooler connection. I would unscrew the upper line connection and run hoses from both the cooler line and the cooler barb on the rad into your bucket -- that way whichever one it comes out of you will be covered. I guessed wrong once and it makes a big mess...
Transparent nylon hose is nice to use for this so you can see when flow starts and get a better read on the color of what is coming out. In the bucket it always looks dark even when it's clean.
Quote:
Originally Posted by jbg
Then start the car with the rear wheels raised and in gear.
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What 745 said, leave it in neutral, doesn't need to be in gear, just a good idea to have the rear wheels free to turn while it's idling in N. ZF autobox can burn itself up by partially applying the forward clutches when in neutral with wheels stopped if left to idle a long time that way (or worse, revved).
In WA State lots of ZF transmissions got blown up back in the day due to this syndrome during emissions testing, where an operator would have to hold ~2500 rpm in neutral for a few minutes. Legend is that many of those cars (Jags, BMW's etc in addition to Volvos) never drove out of the test station and the state had to buy a lot of transmission rebuilds, until they eventually made cars known to have ZF transmissions exempt from that part of the test!
Just idling rarely hurts them, but keeping wheels off the ground lets them spin if they want to, which saves the tranny from eating itself if it is trying to make friction.
Quote:
Originally Posted by jbg
At this point transmission fluid will start draining into the bucket, presumably a "dirty" color. As it drains I replace with fresh fluid via the dipstick hole?
Do I keep this up until the fluid exiting the transmission is a new/clean color?
How will I know how much fluid to add during the process?
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You can make a rough guess. Some people like to use some kind of graduated container (e.g. oil or coolant jug) so you can get a read on how much it is pushing out, or you can eyeball it. I usually run the engine for a minute or so, stop, add a quart or two in thru the dipstick tube, repeat, until the fluid is coming out the hose looking clean and new. Usually takes a few gallons to do the whole thing. As long as you don't overfill it during this process, once you're done and have everything buttoned back up you can check and top off the tranny fluid level in the normal way. You just want to try to pour in pretty much the same amount that is coming out, or maybe a little less, but not too much less. If you start seeing air bubbles or foam coming out the hose at any point while flushing it that means you let it get too low, shut it off and add more.
Usually you get a nice noticeable improvement in shift quality after doing this. I notice it especially in TC lockup engagement -- much smoother.
