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BJ8 Overdrive Stays Engaged

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Bob_Spidell said:
Then you should only use oil manufactured in the 60s; IIRC Reid has some stashed away somewhere ;)
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Yes, here's a glimpse of some of it, and note it's not for sale:

Castrol cans.jpg
 
Bob_Spidell said:
Here's an experiment to get more info. Note I haven't done this myself--at least not lately--so if anyone sees a flaw in my logic pipe up:

Get on a straight, traffic-free piece of road. Get into 4th/overdrive in the normal way at about 50-60MPH. Put in the clutch, put the gearbox in neutral, flip the O/D dash switch to 'Normal' (off) then rev the engine. This should isolate all the electricals from the O/D. Then put the gearbox back into fourth and let the clutch out gently (give it a little gas if necessary); if you're still in O/D as evidenced by engine RPM vs. speed the problem isn't in the electricals (it isn't likely, but not impossible that the solenoid is stuck in the on/up position). If you're still in O/D the problem is in the O/D itself: either the operating valve is stuck open or, as John suggested, the O/D cone clutch is embedded too far into the brake ring (that's all I can think of, anyway).

Have you tried fresh fluid? If the operating valve is sticking it might free it up. How many miles on your car? Has its fluid been changed regularly (20K miles or so for dino fluid; synthetic can go longer). I pulled my O/D at 205K miles and the cone clutch lining was still serviceable.
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My OD stopped working, I filled it with 20/50 racing oil with Zinc. It started working again. It drops out of O/D sometimes by itself and yesterday on the way home from our Grand Strand British Car Club meeting in Myrtle Beach it stopped working again. Not sure why this happens.
 
A flakey dash switch can cause your symptoms; esp. if it occurs when accelerating. The throttle switch, assuming it's set correctly, will keep the O/D engaged after the dash switch is set to normal until the gas pedal is pushed a bit. Easy enough potential fix.

I don't think zinc has any benefit to the gearbox or O/D (but likely won't cause any problems). Gear oils use sulfur compounds for 'extreme pressure' additives (it's why they smell bad).
 
Bob_Spidell said:
A flakey dash switch can cause your symptoms; esp. if it occurs when accelerating. The throttle switch, assuming it's set correctly, will keep the O/D engaged after the dash switch is set to normal until the gas pedal is pushed a bit. Easy enough potential fix.

I don't think zinc has any benefit to the gearbox or O/D (but likely won't cause any problems). Gear oils use sulfur compounds for 'extreme pressure' additives (it's why they smell bad).
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When the OD is working, if I flip the switch to normal, it kicks down immediately, gas pedal or not. How do I adjust the throttle switch? Thank you.
 
Someone might chime in here with a more exact answer but here’s the jist of it. The throttle switch is a holding circuit to hold the relay and as a result the OD engaged when you turn off the dash switch. This is to hold the OD engaged until you apply some throttle. With throttle applied this avoids a harsh shift out of OD. The book says something like at a quarter throttle the od should disengage. So just adjust the linkage between the throttle linkage and the throttle switch so that it doesn’t open the throttle switch until the gas pedal is depressed some. You can use a continuity meter to tell when the throttle switch opens. You have to remove the wires to do so. I avoided all this by just plain removing my throttle switch. Who needs it. I shift my od while using the clutch. Nice smooth engagement and it’s just like shifting into a fifth gear.
 
craigshealey3000 said:
My OD stopped working, I filled it with 20/50 racing oil with Zinc. It started working again. It drops out of O/D sometimes by itself and yesterday on the way home from our Grand Strand British Car Club meeting in Myrtle Beach it stopped working again. Not sure why this happens.
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What oil were you using before the 20/50? If you were using SAE 30 engine oil, you may have low OD oil pressure, from a worn pump non-return valve or accumulator.
 
craigshealey3000 said:
When the OD is working, if I flip the switch to normal, it kicks down immediately, gas pedal or not. How do I adjust the throttle switch? Thank you.
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Vette called it; I think the shop manual specifies a 5/16" drill bit under the throttle lever, but you can adjust 'to taste.' Here's some info from 'The Man:'

Throttle switch adjustment : Healeys List Archive : The Austin-Healey Experience

This read-only message was archived from a public mail list. Mail From: "Don Anglesey" <(email redacted)> I have adjusted the throttle switch according to the manual but have been unable to keep power to the overdrive once the switch has been tu
www.ahexp.com www.ahexp.com

The switch can be a "poor man's kickdown." When following a slow vehicle with only a little throttle, you can throw the switch then when you punch it to pass the O/D will disengage, effectively a passing downshift.
 
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I’ve been running straight 30w in my trans and OD for years.
 
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