Overdrive Oil Pressure

[RickPA]

Hi all. I've run into an unexpected issue. My overdrive in the BJ8 started not to engage after about 20 minutes of driving. Since the unit was supposably rebuilt a few years back and had been working fine, I suspected the solenoid and, indeed, it could be part of the problem. But I also put a pressure gage on the control valve and found oil pressure to be ~455 psi.

This is new to me and I'd like some advice on:
1. Is this a pressure that can cause my issue? and
2. What can I do to fix it?

I know there's a lot of resources about this, but I haven't found anything that says what pressure is the minimum needed to function.

Thanks.

 

[Bob_Spidell]

I don't have my literature handy, but IIRC 455psi is acceptable. I'd suspect the electrics: flaky dash switch, relay and/or solenoid; I've had issues with all of them at one time or another. Is the issue regular or sporadic?

 

[RickPA]

Thanks, Bob. It's constant although it was rare initially. I'm running straight 30wt oil, as I always have for decades with no problems; always a crisp engagement/disengagement. It only started happening after a restoration. I don't know what they did to the OD although I was told damage had been found.

My first thought was also the electrics. I've have a new solenoid to install but it will be the third one in 5 years. I did, however, manage to to get OD to work by manually pushing the operating lever while driving. That makes me think there's something wrong with the pull-up circuit of the solenoid as the lever snapped right into place when I moved it and the OD started working.

Seeing a low oil pressure freaked me out!. Thanks for the reply

 

[AUSMHLY]

Hi Rick. OD pressure for a BJ8 should be 400-450 lbs/in. 455 should be fine.
Are you using non detergent 30w? When was the last time it was replaced?
I'd look into the solenoid lever. Maybe it's not in the correct place and needs adjustment.

 

[roscoe]

If the problem is repeatable and you are brave and careful enough to drive with the tunnel cover off, you could watch the pressure when the OD cuts out. Bob is correct, 455 psi is absolutely enough if it maintains it. I've done it driving and also while on jack stands. The latter is scarier to me eventhough jack stand failure is unlikley.

When it cuts out, if you pull over and shut the engine off but turn the ignition on, you should be able to get the solenoid to audibly click when you shift from 2nd or neutral to 3rd or 4th. If it does but the OD is still not engaging when you drive you have eliminated the solenoid circuit. You may also be able to see the solenoid actuate or fail to do so while you drive and you can certainly check for that while in the driveway with the engine off. While parked, wiggle some wires and see if you can get the solenoid to go in and out due to a poor or broken connection with the ignition and OD on and in 3rd or 4th gear. There is a lot of info on this site about your symptoms and some causes.

 

[Bob_Spidell]

... I did, however, manage to to get OD to work by manually pushing the operating lever while driving. That makes me think there's something wrong with the pull-up circuit of the solenoid as the lever snapped right into place when I moved it and the OD started working...

That pretty much convicts the solenoid. If the O/D engages consistently it's probably the 'maintain' circuit, which gets the most time in use hence heat which can degrade the circuit. Three in five years is excessive, but I've heard there are low-quality solenoids in the wild; I bought a good one from a well-regarded supplier who bought a quantity of known pedigree and sold them for a while. I carried it as a spare--though I don't know how I'd adjust it on the road--until I installed it a couple years ago at overhaul (even though the one I had, probably original, was still functioning).

Of lesser likelihood is the 3-4 switch, possibly just an adjustment issue.

Flaky dash switch: O/D will not activate consistently ('jiggling' sometimes works).

Flaky relay: O/D can activate but disengage at random times (fixable with a points file).

 

[RickPA]

Thanks guys. At this point I guess I'll throw in another solenoid, reset the linkage and see how it goes. Having to replace the same part so often made me think that maybe it was something else. I also think I'll try leaving the gauge on while driving to see if the pressure drops after 20 minutes or so. I'd hate to do it but maybe a heavier oil is the easy bodge.

Appreciate the comforting responses

 

[roscoe]

Do not eliminate intermittant wire open, either bad wire terminal or creaky old wire that opens intermittantly while driving. Engage the solenoid with jumper wires and let it sit for a while before you scrap it.

 

[Healey Nut]

Happy reading