Problem: Overdrive Going On and Off

[Whiskey Whistle]

Hello there,

I recently experienced a phenomenon while driving with the overdrive engaged, it suddenly disengages for a split second then reengages. When it happens, the engine revs up to match the speed for a moment, and then back down when the OD reengages. I noticed it has happened at around 47-53mph, and going uphill--maybe 8% grade or more. It hasn't happen at 55mph+ at any grade, or on flat ground at all.

Anyone have experience with this? I searched the forums for a while with no luck, but if someone remembers seeing this come up before, please help me find it.

Thanks!
Whiskey

 

[alpine_64]

If you haven't changed fluids or anything lately ( and if you did and they are correct) so no new potential items.... if the overdrive slips ..

Check the oil level in the OD not just the gearbox. If low it can slip.

Check the solenoid and the relay are ok.

If it gets worse and the oil level is fine... Could be the overdrive cones clutch faces... But I'd go with low oil or electrical hopefully.

 

[Alpine Addict]

I have this happen and found the contacts in the relay were dirty. Cleaned then and all was good!!

 

[bulldurham]

While we are on OD units , I have a question. Is there any problems swapping a apparently '62 OD into a full syncro transmission?

 

[alpine_64]

While we are on OD units , I have a question. Is there any problems swapping a apparently '62 OD into a full syncro transmission?

Depends what you mean by swap .... The adaptor plate and OD will bolt right up...but you need a full synchro overdrive mainshaft to make it work.... Hens teeth.

The OD mainshaft is longer to go into both units... But they are not interchangeable between od and non OD.

You can cut the end off the non synchro OD mainshaft and have it spliced and welded onto the full synchro main shaft by a very competent machine shop....

 

[albeam]

hi Whisky Whistle,

i experienced your problem some years ago and i did find the answer on the Forum. if you lift your carpet over your gearbox tunnel you will have an inspection cover just in front of your gear lever. it is held down with about 4 or 6 fastners. When you lift the plate it will expose the top cover assembly of your gearbox. if you look to the front of the assembly on the top right is a nut/plunger like a reversing switch (my car is right hand drive) with wiring atttached from memory. you can access the nut with a shifter. unclip the wiring and wind nut out. On mine was a series of shims. i do not know if they were original or not but i removed one shim and put it back together. the plunger would now go all the way home and overdrive stayed in contact. i am not saying that this is the answer to your problem, but if it is, you have a very cheap and easy fix.

Albeam

 

[beamdream]

Step 1 - check the oil level.

 

[alpine_64]

s a nut/plunger like a reversing switch (my car is right hand drive) with wiring atttached from memory. you can access the nut with a shifter. unclip the wiring and wind nut out. On mine was a series of shims. i do not know if they were original or not but i removed one shim and put it back together. the plunger would now go all the way home and overdrive stayed in contact. i am not saying that this is the answer to your problem, but if it is, you have a very cheap and easy fix.

Albeam

The shifter switch.. forgot that one.. yes... They did shim them as required.. if the detent on the swicth has weakened that could cause it to have issues engaging.

 

[bulldurham]

Depends what you mean by swap .... The adaptor plate and OD will bolt right up...but you need a full synchro overdrive mainshaft to make it work.... Hens teeth.

The OD mainshaft is longer to go into both units... But they are not interchangeable between od and non OD.

You can cut the end off the non synchro OD mainshaft and have it spliced and welded onto the full synchro main shaft by a very competent machine shop....

Was suspicious of something like that; thanks you for responding.

 

[Tom H]

I've worked on these ODs a LOT. I assume this is an SV and SV OD. Almost surely the problem is the OD relay and NOT the switch on the shims on the OD lock-out switch on the tranny. In your description you indicated that the OD would cut out and then reengage- I assume this re-engage happens without you reactivating the OD switch. That tells me it's NOT the lock out switch. If it were the lock out switch, the OD relay would turn off and would only re-engage if you re-actuated the column switch.

The problem is almost likely in the OD relay. That relay is unusual and a troublemaker and hard to find replacements for. It has TWO contacts inside. One contact applies power to the relay coil to hold it in the ON position. The other contact applies the power to the solenoid on the tranny that engages the gears inside the OD. The 2 contacts are actuated by the same coil and that coil has just enough power to close both contacts. It's not unusual that the contact holding (latching) the relay ON will stay closed, but the other contact, that carries the heavy current to the solenoid, will open, un-powering the solenoid, and disengaging the OD. These contacts are each on the end of a 1-1/2 inch springy "blade". and it does not take much vibration or bump, to break the contact momentarily.

The other likely cause could be a bad solenoid. It too has an electrical contact inside itself that can go bad.

See the diagram on Page 5 here:

https://sunbeamalpine.org/wp-content/uploads/2017/10/8-Overdrive-and-Gear-Box-E.pdf

The best way to test to determine if it's the OD relay or the solenoid is to wire up a simple test circuit. One LED (like from a Christmas tree set) a 1000 ohm or so resistor. connect the positive end of the LED wire to terminal C1 (where the Yellow -Purple wire connects and connect the other end of the LED with another wire -to ground. Place the LED where you can see it while driving. Test it out in your driveway. When you engage the OD, you will see the LED light up. Take it on the road and when the OD cuts out look at the LED. If the light is ON even though the OD is not working the problem is the Solenoid. If the light goes OFF when the OD cuts out, the problem is the OD relay.

If it's the relay I can tell you a couple solutions. If it's the Solenoid, get a new one and install it.

Tom

 

[Whiskey Whistle]

I've worked on these ODs a LOT. I assume this is an SV and SV OD. Almost surely the problem is the OD relay and NOT the switch on the shims on the OD lock-out switch on the tranny. In your description you indicated that the OD would cut out and then reengage- I assume this re-engage happens without you reactivating the OD switch. That tells me it's NOT the lock out switch. If it were the lock out switch, the OD relay would turn off and would only re-engage if you re-actuated the column switch.

The problem is almost likely in the OD relay. That relay is unusual and a troublemaker and hard to find replacements for. It has TWO contacts inside. One contact applies power to the relay coil to hold it in the ON position. The other contact applies the power to the solenoid on the tranny that engages the gears inside the OD. The 2 contacts are actuated by the same coil and that coil has just enough power to close both contacts. It's not unusual that the contact holding (latching) the relay ON will stay closed, but the other contact, that carries the heavy current to the solenoid, will open, un-powering the solenoid, and disengaging the OD. These contacts are each on the end of a 1-1/2 inch springy "blade". and it does not take much vibration or bump, to break the contact momentarily.

The other likely cause could be a bad solenoid. It too has an electrical contact inside itself that can go bad.

See the diagram on Page 5 here:

https://sunbeamalpine.org/wp-content/uploads/2017/10/8-Overdrive-and-Gear-Box-E.pdf

The best way to test to determine if it's the OD relay or the solenoid is to wire up a simple test circuit. One LED (like from a Christmas tree set) a 1000 ohm or so resistor. connect the positive end of the LED wire to terminal C1 (where the Yellow -Purple wire connects and connect the other end of the LED with another wire -to ground. Place the LED where you can see it while driving. Test it out in your driveway. When you engage the OD, you will see the LED light up. Take it on the road and when the OD cuts out look at the LED. If the light is ON even though the OD is not working the problem is the Solenoid. If the light goes OFF when the OD cuts out, the problem is the OD relay.

If it's the relay I can tell you a couple solutions. If it's the Solenoid, get a new one and install it.

Tom

Well explained, thank you. I'll give it a try when I have time to hook up a bulb, and then I'll try to induce the problem again. That could be the tricky part since it wasn't a consistent.

 

[bkasl]

There is also an internal filter on the side of the OD box that I always check when changing or adding the 30wt non detergent oil, this could also cause intermittent cutting out if dirty