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Can this behavior be caused by old dirty fluid? Does this sound like a condition that a system flush could help?
I would assume that this condition is primarily caused by low fluid level, and then consequently air bubbles in the valve body and pistons. Given time, the air will work its way out of the system (usually within a few days at the most). However, I would strongly recommend a fluid flush if regular fluid changes have not been performed (4 quarts every 30,000 miles) or the transmission has been overheated or abused. You should notice a significant improvement in shifting with new transmission fluid.
Before changing the transmission fluid, you need to pull the transmission pan and clean out the sediment that is sitting in the bottom. The AW-70 transmission has a metal mesh filter screen which typically does not clog, but the worn clutch material does settle into the pan and collects on the pan magnets. (These magnets are undersized for the job and I advise adding another one or two before bolting the tranny pan back into place.) If you don't perform a pan cleaning, but flush the fluid anyways, the new fluid will start to look dark and dirty after about a week or two since the new ATF will start loosening up the sediment in the pan.
To remove the tranny pan, you will need a pair crescent wrenches with 12" handles (or longer) to loosen the dipstick tube. The rest is pretty simple, about 20 bolts holding the pan to the tranny. You don't need to replace the filter unless it looks visibly clogged or damaged, but you will need a new gasket for the transmission pan. You can order a complete kit (filter & pan gasket) from Napa for $20, or you can get just a pan gasket from Napa for $4 (they will have to order it and it takes about 3 days). The Napa pan gaskets are nice since they're made from rubber and can be reused if you have to take the pan off again soon. Budget yourself about 2 hours for a pan cleaning, and add another 3 if you're tackling the tailshaft bushing at the same time. You'll need to unbolt the transmission crossmember, tranny mount, and driveshaft to remove the tailshaft housing. Once the tailshaft housing is off, I'd advise a visit to a local machine shop and have them press out and install the tailshaft bushing for $10 if you don't have the tools at home.
One quick tip, when reassembling the tranny pan, put a dab of RTV on each of the bolt threads that hold the pan to the transmission. The transmission fluid, heat, and vibration can slowly loosen the pan bolts over time and a quick dab of RTV will hold them in place and prevent pan gasket leaks.
When flushing the transmission, disconnect one of the tranny cooler lines (that goes to the engine radiator) and flush out 2 quarts at a time. Buy aproximately 8 to 10 of the cheap $1 ATF quart bottles from your local AutoZone, etc, for your initial fush, and then flush in the quality ATF after that (about 5-8 quarts). Most people perfer to use Mobil 1 Synthetic since it does an excellent job in smooth shifting, reducing transmission heat, and clutch pack longevity.
God bless,
Fitz Fitzgerald.
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'87 Blue 240 Wagon, 258k miles.
'88 Black 780, PRV-6, 148k miles.
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