The OD in my '82 with M46 tranny only works when the oil is cold. When the car warms up, the OD disengages. I know this is due to bad O-rings and resulting insufficient hydraulic pressure to keep the OD engaged, and I plan to replace the OD with a good used unit when time permits. I noticed that my Triumph TR6, which also uses the Laycock J-type OD unit, uses 90W gear lube in the tranny and OD instead of ATF as recommended by Volvo. Is it OK to use the 90W in my Volvo tranny and OD? I'm sure the OD would then work all or most of the time because the thicker gear lube would "hold" hydraulic pressure better than the thin ATF. But would this destroy anything?
TIA for any help!
Colin

Well I had a slightly different problem on my 82 240 M46. The OD would work when it was warm but took forever when the temperature was down in the 30's or 40's. I finally traced the problem with some help from this board to the OD switch. I checked the switch and found it worked(but not right away when cold). I just replaced the switch today and the OD will work as soon as the car goes into 4th gear.

My point here is to make sure what the true problem is. I have had problems with the ground wire near the solenoid break and had to make sure that connections are good on the solenoid. When was the last time you change the fluid in the transmission? Are you sure you don't have a problem with the OD relay?

Do not under any circumstances put the heavy oil in the transmission.

There is no substitute for proper mechanicals...

Do NOT use normal 90W in your tranny.....I have used Amsoil synthetic 75W-90 and it worked fine, and it shouldn't destroy anything, but still now use and advise to use what Volvo recommends: Type F, albeit, synthetic in the form of Amsoil Supershift.