Volvo AW7X Valve Body Rebuild Index Page
Aisin-Warner AW-7X Valve Body Service in a Volvo 7XX-940 Car: Page 1
All information written by Brad Wightman and used by his kind permission. For information on rebuilding the entire transmission including clutch packs and drive elements, see the FAQ file Auto Transmission Rebuild.
The valve body in the Aisin Warner 71L automatic transmission is a very complex piece of kit. Servicing this unit is not a job to be taken lightly. Go about it the wrong way and you could end up with costly repairs. Go about it the right way and the job is relatively simple albeit a bit challenging if it's your first time. Before even considering servicing the valve body there are some considerations: The Volvo Automatic Transmission service manual (TP 31642/1) is an absolute necessity. DON'T attempt this job without this manual. At a minimum, have the following parts on hand: Valve body gasket kit (5 gaskets), 5.5mm check balls (Volvo part number 1377746), transmission fluid, filter and filter gaskets (2), fluid pan gasket. See pics below.
It's a good idea to have a plate to hold the accumulator pistons in place in the transmission as you take the valve body out. I've heard of people getting by without one but I felt it was better not to risk having the pistons drop out onto the floor. I made one from a scrap piece of 1mm thick steel plate. Three holes are drilled in the plate corresponding to the pan bolt holes and it is held in place using the pan bolts. See pic below. The arrow points to the correct holes. I had to redrill them because I was slightly off with my measurements, so ignore the bottom holes.
Accumulator piston holding tool
If you are planning to do a full valve body service, allow a whole weekend. This is NOT a job you will do in an afternoon so plan it for a time when you won't need the car for a couple of days. It is possible to replace just the check ball and put everything backtogether in a day but while you're in there you might as well do a thorough job.
Also have plenty of rags to mop up the fluid off the floor. You WILL lose quite a lot.