8 replies to this topic

[cbpldc]

Okay, I've seen several references to the OD relay, but I have no idea where it is. When I press the button on my shifter, the arrow comes on, and it seems to do nothing but light up this light. I'm running at nearly 4k RPM at 75-80 mph. Killing my fuel economy.

Can someone point me the right direction?

THanks,
Chris

[cbpldc]

Okay, I've located the relay, but it doesn't seem to be the problem. The light turns on and off and the relay clicks nicely. So, it appears to be a failed OD solenoid. I'm going to attempt to remove and install, clean and blow it out, put RTV on the orings and reinsert. This sound like a good plan? If so, it possible to find out exactly what I'm looking for?

[Three Fat Tigers]

Odds are the OD solenoid is toast, where the wire coil part of the electromagnet has suffered an internal breakdown.

Normally, in a quiet neighborhood, you can lean way over down toward the sill, or lie down under the driver's side of the car, and hear the solenoid on the trans clicking while you/someone operate the OD button (ignition on, engine not running). Otherwise you should be able to put your hand on it and feel the solenoid clicking while it is operated. If you hear/feel nothing, disconnect the electrical connector and test for power reaching that point, best to use an incandescent test lamp (like a brake lamp) that draws some power to verify enough amperage is reaching the connector; or pull the solenoid off and bench test it, touch the wire to the positive cable on the battery and touch the case of the solenoid to a ground point; again it should click. No power at the connector would indicate the relay where in rare cases the relay can burn out a contact or suffer a failed solder joint while still allowing the dash light to operate normally; simple to pop the cover off the relay and have a look; although a bruned relay contact failure is usally caused by a defective solenoid or the wiring to the solenoid shorting to ground.

Odds are attempts at cleaning out the solenoid will do nothing for it, but you might try some carb cleaner, then bench test it. Should the solenoid need to be replaced, it can be expensive new, same part is used on all 240/740/940 with similar transmission; going with a used part can be hit or miss as this is a common failure.

You can also take the defective solenoid and cut a channel between the holes, this would allow the OD to stay available, it will still downshift out of OD when you give it throttle, you just won't have the option to manually turn it off. Use a drill bit and drill in the holes at an angle to cut over into the groove (mounting it in a vise helps), the idea is to create a fluid path between the holes, the metal is very soft so it's quick and easy to do (note this might actually work without the drilling if you just reintall minus the center o-ring, though I've never personally tried it that way). Reinstall minus the center o-ring, RTV sealant on the large o-ring should be sufficient, you can cut the wire off the solenoid as it won't be needed. To access: jack up the entire driver's side of the car, clean the area around the solenoid first with brake/carb cleaner +rags to minimize dirt contamination, remove the two bolts (12mm, flex head gearwrench works best) be ready for some fluid leaking out, but it shouldn't be too much. If the outer larger o-ring is too old it may be rock hard, but it will still work with some RTV if not broken. It's an odd size so finding an exact replacement without a trip to the dealer might be difficult, you can take a larger diameter o-ring and cut out a section where the remainder joined together will complete the correct size, then glue the ends together with super glue; this plus RTV should work fine.


For reference:
Driver's side: http://www.threefatt...reOutSide2c.jpg
Solenoid: http://www.threefatt...Dsolenoid-1.jpg
Modify: http://www.threefatt...olvo/ODmod1.jpg
As on the 240: http://www.threefatt.../ODsolenoid.htm

FCPGroton likely has the best price on a new one:
http://www.fcpgroton...category_id/208

[cbpldc]

Dude. Fantastic write up. Thank you. I'll do that and report back.

Chris

[Tyler T5R]

If that doesn't work get the overdrive bypass kit from ipdusa.com. Worked perfectly on my 740.

[Three Fat Tigers]

Tyler T5R, on 12 February 2012 - 02:14 PM, said:

If that doesn't work get the overdrive bypass kit from ipdusa.com. Worked perfectly on my 740.

IPD's bypass kit does the exact same thing that my aforesaid DIY modification does, which means that if my suggestion does not work, IPD's kit will not help you either.

IPD's kit costs over $47.50 delivered; not too far from FCP's price for a new solenoid. My DIY suggestion above costs you nothing if you have a drill, a drill bit and 60 seconds of time to spare; around here it's pretty easy to buy a drill and bits for less than that.

[cbpldc]

I'd rather maintain the functionality of the button in case I need to gear down for any reason. So, I ordered a solenoid and will be doing the work soon.

THat being said, this car shifts much nicer than my 94 na 940 wagon. The na car will hold a gear longer than you think it should and then it kind of squirts you quickly into the next gear. Its enough that most people who drive it think the transmission is bad, but its shown no other symptoms. Is this how they're supposed to shift and my Turbo car is lazy? It reminds me of an old Mercedes transmission.

Thanks,
Chris

[cbpldc]

So, chasing the wiring from the solenoid I found that it is a little yellow wire that comes up into the cabin and and plugs into a black plug under the fuse box. Which is totally different from the solenoid I got from FCPgroton which is a pin that pushes into a round receptacle.

Should I just cut the end off and splice or do I need to try another option.


Chris

[Three Fat Tigers]

Not sure, the last two 940 tranmissions I pulled (both '94) used the bullet connector under the car just like the 240 photo I posted above.