BJ8 Overdrive issue

Hello All,

Drove my car to be in a 4th of July parade yesterday and had some overdrive/reverse gear issues. I came out of overdrive exiting the freeway and the RPM's came unusually way up just below redline when I put the OD switch in normal. After that the car seemed normal as I went thru all of the gears. Upon trying to reverse the car it almost seemed like there was a "braking" feeling as the car rolled backwards. I immediately stopped as I remembered never to back your car up with the switch in OD (but it was firmly in Normal)!
Driving on the freeway heading home I flipped back into what seemed like normal OD and it worked. After that the OD switch seemed dead, no effect of any kind. Again, the car seemed to pull nicely thru all the gears at an RPM that would indicate the OD was off or at least failed in the off position! I tried reverse gear and it still drags a bit so I stopped!
Question...Did my OD system fail in the"on" position and if so how do I get it out of OD with the switch now dead? Maybe the plunger is still in? Also, could it be causing my reverse gear issue? Finally, when these systems fail is it usually the solenoid( which could be very old) or throttle switch( also old) that needs replacing? There is plenty of fluid in the system and my gearbox and clutch had service just a few years ago. Car rolls freely in neutral both forward and back. With key turned on and shift lever in 3rd or 4th gear there is still a clicking noise in the gearbox when I put the switch in OD and back to Normal.

If my understanding is correct, the OD cannot stay engaged without over 400 psi of oil (hydraulic) pressure. It would require some unfathomable failure of the springs that have to be overcome by hydraulic pressure to engage the OD and failure of the shifter switch that disengages the solenoid when shifted out of the 3rd/4th gear side of the shift pattern as well as continued power to the solenoid after the OD switch is turned to normal and the throttle switch is engaged by depressing the throttle about 1/3rd of its travel. My guess is the OD is not engaged and further trouble shooting is required.

Without taking much apart, with the car at rest, go under the car on the passenger side. Reach for the operating lever ( opposite side from the solenoid ). See how it moves, if at all. Pushing it forward, you should feel some spring resistance. The lever should want to return when you let go. If this operation seems stiff, or stuck one way, you can then check the operating valve. This requires some interior removal. I have experienced bent operating valves.
Good luck,
Bob

At one time my OD was stuck "On." The only way to get it out of OD was to flip the switch to "Off" and put it in reverse. It would pop out of OD immediately. It was described to me that the OD clutch was worn so much that the pistons would slide too far.

John Turney said:

At one time my OD was stuck "On." The only way to get it out of OD was to flip the switch to "Off" and put it in reverse. It would pop out of OD immediately. It was described to me that the OD clutch was worn so much that the pistons would slide too far.

Click to expand...

Could be, but would be the outer part of the cone clutch (the side that engages the brake ring). I've found slipping the clutch just a little when engaging or disengaging OD makes things smoother, and I believe it saves wear on the cone clutch as it allows it to engage without being under load.

I would suggest that you start checking the electrics since that is the easiest. This is the order of sequence I have found useful.
1. Ignition on but do not start engine. Gear in neutral.
2. Switch OD on. No sound should be heard.
3. Press gear lever to the right. The solenoid should engage with a loud click. Wiggle leaver to right and left
There should be a loud click everytime it is moved to the right.
4. Ignition still on, engine off, put gear in third or fourth. Engage OD. Switch back to off. No sound should be heard. Press accelerator. A less audible click should be heard showing that OD solenoid disengages.
5. OD on, gear in third or fourth. OD should engage. Press accelerator. If OD disengages the OD relay is the likely culprit (solenoid is powered thru accelerator switch instead).
5. If these test fail, check switch , OD relay and accelerator switch and look closely at wiring.
6. If above does not indicate any problem, run a wire from battery to cockpit. Disconnect white wire from OD relay going down to OD solenoid and connect a wire to it, which is also routed to cockpit. Drive the car in third or fourth and connect wires to each other - OD should engage and remain engaged with gear in third and fourth until wires are disconnected.
7. Measure current by connecting an ampmeter between the two cables to the cockpit. It should show around 1 amp when engaged. If much more (around 20 amps) or much less the OD solenoid is the likely culprit.
8. If none of these tests indicate a problem it is most likely not an electrical issue.

Thank you for all of the thoughtful replies! I will try the electric trouble shooting as outlined by Novamonte. Ultimately though this project is probably beyond my scope of ability. Will be taking the car to Mark at Britsports here in Seattle. He does a great job and his specialty is gearbox and paint work!

If you have a Pertronix ignition review the thread - ‘Left my ignition on for 5 hours’ for what you should do when you are testing with the ignition key on with the engine not running.

Yes, be careful with leaving the ignition on. That also applies to cars with points as you can fry the coil if the ignition is on for a longer period and the engine is not running, if the points are closed. The tests should just take a minute, but if you leave the ignition in for longer disconnect the low voltage connections to the coil or put a piece of paper between the points.

Yes, the OD can still be engaged, with no hydraulic pressure. When I disassembled my OD, the cone was wedged in tight, had to press it apart. The DPO had put hypoid gear oil, 90wt in the box, instead of 30wt oil so I presumed it produced too much pressure, wedging the cone in. Even though the cylinder walls were severely scored. I simply rebuilt the piston/cylinder and put the right oil in and it is still working today.

good luck with your investigations,

Jerry Rude
BJ8

Lotuswins said:

Yes, the OD can still be engaged, with no hydraulic pressure. When I disassembled my OD, the cone was wedged in tight, had to press it apart. The DPO had put hypoid gear oil, 90wt in the box, instead of 30wt oil so I presumed it produced too much pressure, wedging the cone in. Even though the cylinder walls were severely scored. I simply rebuilt the piston/cylinder and put the right oil in and it is still working today.

good luck with your investigations,

Jerry Rude
BJ8

Click to expand...

I'm not an OD expert, but I doubt the gear oil caused the problem. 90W gear oil is roughly equivalent in viscosity to 50W engine oil--using a different standard--and some owners run 20W-50 oil in the gearbox/OD without any problems (I did for years before switching to synthetic). See:

http://www.doolittleoil.com/faq/viscosity-sae-iso-or-agma

The oil pump is driven directly off the gearbox and is capable of creating extreme pressure--400PSI and above--and theoretically could create enough pressure to break something. It's regulated by the accumulator, which has a small return hole which is exposed after the heavy piston spring is pushed back far enough. Gear oil is not recommended for our gearboxes as it can erode brass components--like the shifting forks--but I understand it is recommended for similar gearboxes so who knows.