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Overdrive[200/90] posted by rick mordahl on
Friday, 7 July 2000, at 7:31 p.m.
Tried to get get the overdrive working on my sons newly aquired '85 240. Before I started messing with it, the main transmission worked great. After installing a new switch on gear lever the sytstem worked well enough to hear click of solonoid and activate light on dash. When we tried to use O.D on highway it would not engage, and car began to "freewheel" when coasting. That is, all braking effort normally provide by motor was gone and tach would drop to idle speed when foot was taken of off gas pedal. A change of transmission fluid revealed the round high pressure filter was full of gunk and partially collapsed. Replaced filter and reassembled but sorry to report car still "freewheels". It seems to do this when hot and work fine at start up. At times reverse gear does not engage with-out several attempts. Looks to me like I need to replace unit?? Any ideas appreciated!!
--Rick
Re: Overdrive[200/90] posted by Duane on
Saturday, 8 July 2000, at 8:31 a.m.
On this one Don is the closest if not right on the money.
First engagement allows pressure to build up and push past the small O-rings on the solenoids internal piston. After a while this fluid where it does not belong does not allow the piston to return to its "OFF" position keeping partial pressure in the OD.
This partial pressure keeps the sliding member "in between" its on and off positions, attempting to create OD but cannot because the sun gear is rotating and overrunning the Sprague clutch.
Since the sliding member has to be in contact with the output housing to create reverse, and it is not because the pressure is not being bled off, no reverse is possible as the Sprague clutch always freewheels in reverse.
One other possibility, since the filter was collapsed, some of that gunk could have gotten past the filter and created a sludge build up such that the sliding member cannot move freely. The fluid not being used to "hold" OD in gears 1 through 4 is dumped onto the output shaft of the trans right at the sliding point of the "cone clutch".
Recommendation: Remove the OD from the transmission, do not separate the housings but clean it thouroughly in a parts washer after removing the plugs at the bottom keeping the control valve parts in their proper sequence. Replace the actuatign piston seals since the OD is off and they can only be accessed with the OD off, then replace the unit.
Tip, loosen the solenoid with the OD on the vehicle. It can be real tight and the extra holding of the trans helps a lot.
If you need more advice or parts, better get to me quick, I'm leaving on a weeks vacation so will not be available during that time.
Duane
83-245 LH 2.0 M46 197xxx
85-245 LH 2.2 AW70 135xxx
Overland Park, Kansas
The OD Guru (Laycock only)