I own a 1991 volvo 240 dl and when car is cold
The automatic transmission fitted on these models could be the AW-70, AW-70L or AW-72. The three transmissions are very similar. They are conventional in design though they are clutch-type (no brake bands) and very sturdy.
The automatic transmission is a complex unit, but if not abused, is reliable and long-lasting. Troubleshooting these units is fairly complex, so the home mechanic should be concerned with one thing to start: oil level and condition. Begin by having the idle line pressure tested when warm (it tends to drop as the oil warms up). If the level is low, ensure no leaks are present and top it off as needed (do not overfill - fill when the transmission is hot - if overfilled, this can damage the transmission as well as cause hot oil to be ejected from the fill hole) and test drive it again. Ensure to follow procedures when topping up automatic transmission oil, and ensure it is of the correct type. If the oil level is OK and line pressure is not then replacement of the oil and screen along with cleaning of the magnets should be done. The magnets are there to trap metal contaminants before they can damage the transmission.
The oil should be flushed out, filter changed and magnets cleaned at least every 80,000 miles. Have this done first to see if the problem goes away. If it persists, then the clutch pack for that gear or the valve body is suspect. If the oil is new and proper drain and flush procedures have been followed, it's possible that the check ball in the valve body is sticking once warm. What I have done with these is drop out that valve body and clean it thoroughly, provided scrupulous cleanliness is observed. While cleaning it, replace the check balls and associated springs. If this checks out OK after the maintenance, then it's possible the pistons, accumulators or clutch packs have probably worn out.
If by this point, the transmission still doesn't function normally, then replacement is the only fix. No DIY repair is recommended and may be exchanged in part exchange for a new or rebuilt unit.
1991 Volvo 240
on Dec 22, 2014