Flushing an automatic transmission.

You don't need the pump. You just disconnect one of the trans cooler lines (the output one from the trans) and run it into a container with an appropriate sized hose. Then run the vehicle until it's pumped out 4 qts, then refill the trans and repeat until the fluid runs clear.

On something as old as a J10, I would definitely want to drop the pan and clean out whatever may have accumulated in it, and also clean or replace the filter. In your case if you really want to do a full "flush" I would a) see if you can drain the torque convertor without dropping the trans (some older vehicles have a TC drain plug) and b) just do a standard filter service, then do it again after 1000 miles or so. That should change a decent amount of the fluid in the tranny.

If you're just doing this as PM I would leave it at that, if you are having problems I might do a third fluid change and also adjust the bands if possible at each change. When was the last time the fluid was changed? If it was more than 50K miles or so I would definitely do at least three maybe more changes as there is quite possibly some varnish buildup inside the trans - the additives in old ATF don't tend to last much longer than that.

BTW, nice truck - my great-grandfather had an old pre-AMC J10 that he kept in excellent shape (was really only driven on hunting trips, and occasionally my grandfather drove it to work to keep it limber) and I was disappointed when my grandfather decided to sell it when my great-grandfather passed on rather than keep it in the barn for me (well, I was maybe 10-11 years old) although my grandmother did later offer me his '70-something Chevy pickup (which I didn't take as I thought she might have needed the money at that point in time, and I couldn't afford to make pay her a decent price for it, not that she would have taken it...) woulda rather had the J10 though.

nate

That's definitely what I intended. It was running OK until the cold weather, now it's sulking and refusing to go into reverse. If you try it bucks and stalls the engine, as if a forward band isn't releasing. It will go into neutral and park though,

From the term 'power flush' I was hoping for something involving a few gallons of deisel as opposed to ATF. Like backflushing a radiator.

Unknown. I just got the thing. Dunno how much 'silver paint' I'm going to find at the bottom of the pan.

This could get expensive...

I've been happy with doing the cooler line flush after changing the filter even when the old fluid was very bad looking.

If the fluid starts looking dark or gunky within a few thousand miles, then just change the filter and flush it again.

ATF will do a better job of cleaning out crud than Diesel. ATF is actually fairly high detergent.

I doubt it. Worst case you will end up rebuilding the trans but I doubt it will come to that. If you still have symptoms after doing the above there are additives available that will help you eke a little more life out of it. Most tranny problems, unless the trans has been abused, come from varnish buildup which can be cleaned out and/or seals that have hardened, which if they're not too bad can be softened with the proper additive. If you DIY all it will cost you is a case or so of ATF.

good luck

nate

Just to present the radically grumpy side of the issue, I think you would be wasting time and money to try to build a power flush unit.

I think power flushing the transmission is without evidence of its worth in the first place, although it 'sounds good'.

Some here have suggested that it may also cause problems. Even more radical advice has suggested that changing the fluid at all may be counterproductive (I can't fathom up much support for this nasty concept, however).

Just change your fluid, with reasonable regularity.

If you install a drain plug in the pan, you can do it often and cheap.