My 85 240 5 speed is not consistently shifting into OD when I engage the button
on the gear shift. I assume it's a solenoid or such as it seems I had a mechanic replace it 10 years ago. Do you think that is the problem or could it be something else? How difficult is it to replace (I replaced an OD unit on my 92 240 automatic)? The mechanic wants to charge $300 and if I can do it reasonbly easy I will. Thanks

What occurs as you attempt OD mode?

Dash light comes on and stay on when the OD doesn't work? If it does, the 4th gear switch, wires in the shifter and relay are all OK. For those of you who wonder how I know this from afar, the dash light is wired together with the wire to the solenoid on the OD at the relay socket.

Dash light goes out. Most probable cause is the 4th gear switch on the tranny. Test by pulling the shifter further back and to the right to see if you get dash light. Or if sitting still, with dash light on, wiggle shifter to see if light goes out. Ignition on, engine off, in 4th gear allows all potential electrical connections necessary for OD mode with out speeding down the road doing testing.

Since this only seems to occur as you push the button and the OD does not drop out on its own, the connections at the solenoid may be tight but maybe not clean enough to allow free movement of electrons. ALso check ground wire.

As for your original question. You have done it once except the unit you had was internally damaged beyond repair using what was there.

The biggest problem you will face since this OD works sometimes is getting it back on. Remember how the pistons are inserted, with the trough toward the bars so you can grab the bump in the middle and pull them out, and get the bars down tight you will be fine. Watch the pump parts if you take that plug off, which if you have had problems with reassembly before I suggest just leave the pump system alone.

This also applies to a used unit from a salvage yard. The largest amount of effort in "rebuilding" an OD is getting it off the tranny. If your OD does not make noise, a reseal kit is all that is necessary.

Duane

There is also a switch on the gearbox that senses when you are in fourth gear and enables the overdrive to be engaged. These switches can wear and even though you are in fourth gear sometimes they will not complete the circuit needed to engage overdrive.

There is some good reading in the FAQ's on the Laycock overdrive unit.

Randy

When you want overdrive and push the button, what happens?

If you are in 4th gear, you should go into overdrive and the green light come on.

If you get the light but not the engage, and are in 4th, best to check electrical. The switch on the tranny that is closed in 4th can go bad. Also, the solenoid can go bad, too.

You can check them using a voltmeter. Locate the connector for wires going to under the car via the shifter box. It should be under the carpet at the lower right corner of the control panel. Sometimes you can get at it by removing the kick panel on the right side of the central control panel. Pull carpet a bit.

Set up the car so it should be in overdrive. 4th gear, green arrow on. Push the button several times and listen (helper under the car??) If the solenoid clicks, the under car wiring is OK. If it doesn't click, find the red wire at that connector, ground it. If you can hear the solenoid engage, the 4th gear switch is no good

If that gives no clues, see if you can re-solder the relay. Check the archives or FAQs, there should be good info. The relay is wired such that the light can work just fine but the o/d only work whenever or never. If that doesn't work, invest the $$ in a new relay.

Good Luck,

Bob

:>)

Also the switch on the gearlever, or the connections to it, or the wires at the bottom where they flex as you change gear.
The simple starting point is just to wire a temporary power lead direct to the solenoid from the battery -does it click reliably on/off?
Then try the same thing, but with a temporary switch inside. Try driving around and operating the O/D. If everything works properly then, you know the fault must be exyernal to the unit itself.
DON'T leave the O/D engaged in lower gear, and especially NEVER in reverse.

Also try changing the gearbox oil, clean out the overdrive filters, and refil overfull by tilting the car.

it could just be the OD relay...at its age though it could be the seals. i've done that job, while not particularly hard its and undertaking. and the OD didn't work when i put it back together either. there were broken pieces inside of it...i can't remember exactly what. i know the metal bars the pistons engauge against were bent all out of shape (which i tried to fix). it would try to engauge, then slip real bad. the mechanic is probably thinking its something electrical (which is easy) and looks to make a quick $300.