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Proper Engagement of Overdrive

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Bob_Spidell

Bob_Spidell

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Having just rebuilt my BJ8's OD and with a newfound understanding of their practical workings, I started thinking about how to dis/engage the OD so as to preserve the cone ('sliding') clutch, which are not available from the usual suspects (all I could find was a rebuilt one from DWR, requiring lots of dosh and return of a core). Like most of us, I used to just hit the switch, either while cruising but usually while accelerating, but with the understanding of the clutch and brake ring wear points I started looking for the 'right way' (although my clutch and brake ring were still in apparent good condition after almost 200K miles). I have found two experts and, surprise surprise, they have differing recommendations:

1) https://www.quantumechanics.com/

2) https://www.britsportofseattle.com/2010/05/how-to-drive-your-laycock-overdrive-eqipped-car/

Since the rebuild, I've been engaging it per #2; #1 differs in that it doesn't call for pushing in the clutch. This works well because with an upgraded accumulator the OD engages all but instantly, so by the time I put the clutch pedal in, throw the switch and let the pedal out I am in overdrive (but I don't get the satisfying rush of engaging 'warp speed'). Using this method means the OD clutch is fully engaged before the load is (re-) applied, so would presumably preserve the lining on the sliding (cone) clutch (but would also somewhat increase wear on the engine clutch). OTOH, I've driven this car for almost 200K miles by just throwing the switch under WOT, and it's still got, I'd guess, at least another 100K on it. It looks like the OD is a robust unit--electricals notwithstanding--that could tolerate ham-fistedness like mine, but what is your take on 'best practices?'
 
I have never used the clutch to engage or disengage the overdrive on numerous Healeys and Triumphs I have had with the O/D transmission over the years. I have also never had a mechanical failure with one (though many electrical issues). I suppose the cone clutches can wear out, and I suppose there is no harm in hitting the clutch pedal would prevent a little wear, but in my opinion also takes some of the "magic" out of it. I think John Esposito's recommendations are more than adequate unless your goal is to have some sort of hypermiler Healey like that guy with the Volvo P1800.
 
Engagement; no clutch, come off throttle at about 40 mph, flip switch, feather in throttle. Disengage switch after down shifting to 3rd, come off throttle at 35 to 40 mph, blip throttle to deactivate solenoid, feather throttle back in. In both cases it feels like a normal gear shift. Makes sense to me and avoids any additional wear on the big clutch.
 
I have also never used the clutch when engaging or disengaging and I don't believe it was the idea to do so. The throttle switch is the built in protection for the system so that the overdrive is only disengaged when the throttle is open and the revs increasing. I no longer have a throttle switch but always make a point of using the throttle just before switching out of o/d.
 
I don't use the clutch with the overdrive, and I don't think it was originally designed to use the clutch. Interesting idea, though, to use the main clutch and save wear on the overdrive clutch.

I suppose the real question is: when will someone start manufacturing replacements for the overdrive clutch (and other overdrive parts)?

Keith
 
A BJ8 Overdrive does not require the use of the clutch.

Older Healeys and other car systems DID.
 
DerekJ said:
I have also never used the clutch when engaging or disengaging and I don't believe it was the idea to do so. The throttle switch is the built in protection for the system so that the overdrive is only disengaged when the throttle is open and the revs increasing. I no longer have a throttle switch but always make a point of using the throttle just before switching out of o/d.
Click to expand...

I agree with Derek here in that I don't believe the idea was to need to use the foot pedal clutch, But...
I too do not have a throttle switch and always ensured that I would blip the throttle just as I was turning the OD off. This was fun and contributed to a robust driving style. It must be old age, I got tired of that. The conscious effort to always pick the right time/speed/circumstances to come out of OD while blipping the throttle ended up that at times I would either be sitting at a stop sign or traffic light and still in OD or even then forgetting to turn the dash switch off and resulting in driving away and realizing that I was in OD after I upshifted into 3rd. This scenario is what started me to use the clutch to come out of OD because it allowed that I could come out of OD at anytime and created a habit of just shifting as if I had all gears up and down from 1st to 5th.
 
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