Overdrive slow to disengage

Hi Folks
BJ8 has been running really well this summer and trying to drive her as she was designed fairly hard but with consideration for age. (Mine that is). The overdrive though is still a bit of a mystery to me more to the correct operation than the theory of operation, Engaging seems easy as they say treat it as fifth gear, disengagement seems a bit more vague sometimes it appears to lock in and all though I down shift to first it still remains in overdrive and I have to turn the ignition off and restart as the reverse lock is engaged. I am going to check the continuity of the 1-2 switch any other suggestions would be appreciated.
kr
Rob

Hi Rob, the only way for the overdrive to remain engaged electrically in all gears is if the gearbox overdrive switch is stuck closed. Easy to visualize the problem being intermittent too as with any sitting after use it eventually would spring back to normally open position with gear shifter in any position other than 3rd or 4th. Switch is under $8 from Moss. dm

I had the problem of the OD refusing to disengage. It turned out that the clutch was very worn. I had to stop, put the car in reverse to disengage it.

Thanks for the replies I am sure you are right it must be stuck in electrically, don't think it's the clutch because it's engaged it would lock against going into reverse. I will check the switch circuit.

Probably obvious but are you blipping the throttle to activate the overdrive throttle switch?

Yes on the up shift it is a bit vague coming out
of O/D maybe I am not blipping hard enough to
dissengage.

Hi All,

Maybe I am misunderstanding Derek's comment so to clarify (in my own mind), as I understand the OD will activate without a blip but requires raising the RPMs to deactivate.

What oil are you using in your OD?

A while back I changed from 30W non-detergent to Redline MTL and filled the unit to the mark on the dip stick. All went well until it would not shift out of OD. Upon my return to the garage, I checked the fluid level and found it was a little low but also found no evidence of leaks on first look. Since my OD and transmission are original and have given me no problems, I decided to pull the transmission cover and, on closer investigation and removal of the solenoid cover, found the synthetic oil lacked past the blocking "O" ring into the compartment housing the solenoid and locked it up the piston. After cleaning, allowing the Synthetic fluid to settle just below the seal, and checking the adjustment of the solenoid (with the button below the piston), I closed up the unit and it has been operating perfectly for the past 10 years.

By the way, make sure the button under the solenoid piston is in place as it is needed to keep the piston from traveling too far and out of the effective magnetic range of solenoid. The button is needed to keep the piston from extending too far and as a buffer for the piston. If the button is badly deteriorated, activation/deactivation inconsistency could be experienced and, if totally lost with the piston extending beyond the limits of the solinoid, I would expect more severe deactivation conditions to be encountered.

Hope this helps,
Ray(64BJ8P1)

Hi Everyone
The oil I am using is millers classic 20-50 and I have probed a bit further with the electrics the continuity of the dash switch is ok and with ignition on engine not running in third and forth gear select overdrive and the reassuring click is heard, now again turning the ignition on flipping the overdrive switch on then back to normal (with no throttle) then on again no click which is as it should be still engaged, however I then select normal and depress the throttle hard, I think l hear a click but I am sure it still remains in overdrive as the reverse lock is activated, the only way I can select reverse is by tuning the ignition off. Could it be the throttle switch is faulty although I can hear it activate or possibly the gearshift switch ?

On the overdrive relay, disconnect the throttle switch from terminals C2 and W1 and install a jumper between C2 and W1. That takes the throttle switch out of the circuit. If the OD now works correctly (push in the clutch when disengaging), your problem is in the throttle switch. It could be mis-adjusted.

Also, 20W-50 is a bit thick for a normal OD. That would make it slow, but it should still operate.

Thanks John but won't the jumper lead between C2 and W1 keep the overdrive engaged?

Had similar problem. It was binding in compartment where solenoid plunger engages operating mechanism. See RAC68 post above for cause. Bad button appeared to allow too much over travel and jamming when solenoid was energized. You can check when it's stuck in O/D by pulling down lever on right side of tranny.

4tecdog said:

Thanks John but won't the jumper lead between C2 and W1 keep the overdrive engaged?

Click to expand...

It should disengage when you flip the dash switch. I actually don't have a throttle switch on mine and that's how it's wired. The throttle switch and dash switch are in parallel, so once the relay is closed by the dash switch, the throttle switch holds it in place until it opens.

John, just to clarify your comment for the the original poster. If the overdrive switch is wired correctly then the overdrive will NOT disengage if you only use the dash switch. You must depress the throttle, so that there is load when the overdrive disengages to avoid damage to the overdrive. The throttle switch on my car has also been removed so the overdrive now disengages immediately when the dash switch is operated, however I always make sure to depress the throttle just before switching out.

Thanks for your comments guys I understand the principle of having the various switches to prevent overload when disengaging I think now my problem is that the solenoid is slow to engage and disengage, Under driving conditions I assume overdrive should be immediate once the switch is activated mine is not even though I depress the clutch and lower engine revs. It can be a bit vague and engage a few seconds later. Also the click I hear when I turn the ignition on engine not running and activate the O/D switch with no throttle is only the relay and not the solenoid (I assume as it is a click not a clunk as I would expect) I will get down to some resistance checks over the weekend and have a look at the clearances.

It depends on what you mean by slow. A competition overdrive is very quick to engage and disengage but a normal overdrive is slower. Disengaging the clutch won't affect the performance of the overdrive. Not clear why you would be 'lowering' the engine revs.

I share Derek's understanding and confusion. At this point I would remove the vertical console and transmission cover to have a close look at the solenoid, its wiring, and adjustment to validate that all is clean, adjusted properly, and functioning correctly. A short drive with all exposed will also validate condition and operation.

Following this task and also checking the throttle switch adjustment along with all other components involved, I would change the trans fluid from 20W50 to straight 30W non-detergent (as recommended in the manual) or even Red Line MTL synthetic to allow for quicker hydraulic OD response. Keep in mind that, as Derek described prior, it is important to increase RPMs (reduce load) when disengaging and I have retained the use of a throttle switch in my car to allow this to happen without thought.

Based upon your comments, it is difficult to appreciate your expectations for OD switching or the effective speed your unit is actually switching at. Keep in mind that we are dealing with hydraulics and, depending upon the condition of your unit (and the thickness of its oil), a buildup will be needed to engage. Although I would not expect a number of seconds to engage, I also would not expect it to be instantaneous. As mentioned, clean all electrical connections, adjust the throttle switch and solenoid lever and change the oil to a lower viscosity fluid.

Enjoy your Healey,
Ray(64BJ8P1)

Thanks All
Cleaned all contacts and adjusted throttle switch and all working as it should, a short delay on engaging but I can live with that down shifting and kick down is instant, I did not change to 30 grade left the muligrade in as recommend in the Haynes manual as I have no leaks now I did not want to upset the apple cart! Now on to the next issue dim lights relay or not to relay.

Install the relays. Give your headlight switch a break.

If I want to defeat the throttle switch, it only takes a couple seconds to put both wire connectors under the same screw.

There's a little trick about drilling a slightly larger bleed hole on the actuating plunger. It's not like a night and day difference. but might help with a slow to disengage overdrive.

4tecdog said:

Thanks All
Cleaned all contacts and adjusted throttle switch and all working as it should, a short delay on engaging but I can live with that down shifting and kick down is instant, I did not change to 30 grade left the muligrade in as recommend in the Haynes manual as I have no leaks now I did not want to upset the apple cart! Now on to the next issue dim lights relay or not to relay.

Click to expand...

I just replaced the overdrive solenoid and got the OD working after 12 years. It now kicks INTO OD very quickly, but is very sluggish to kick OUT of overdrive. What did you say the trick was to get it to kick OUT of OD? How "quickly" should it come out of OD once you flip the dash switch off and touch the throttle? The solenoid is switching instantly, but the overdrive "slips?" badly for a few seconds on the way out of overdrive. If I give it gas, it continues to slip badly and won't go in or out of overdrive. I have found that giving it a few seconds to eventually come out of OD works the best.

Running 30WT non-det and the oil level is full on the gearbox dipstick.

Chris
BJ8