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To Clutch or Not to Clutch

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Randy Forbes

Randy Forbes

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I never used the clutch. It might help to let up on the throttle when going into overdrive and adding a little throttle when coming out of it. Experience will dictate how much modulation is required.

As far as overdrive and reverse are concerned, one of the mechanical components of the overdrive is called a uni-directional clutch (ONE WAY). It didn't get that name for nothing!
 
Using the clutch is a matter of personal preference. Whichever you are most comfortable with. The factory did not recommend using the clutch & many people simply just shift the OD which was designed to be used this way. If you wish to treat the car a little more gently, don't upshift or downshift under full throttle. If really cautious, use the clutch.

Good advice on the reverse gear situation. In theory, the safety interlocks provided in the OD control will prevent any mishaps even if the selector is left in OD. Sometimes these switches don't work correctly or have been changed so it is safer to make sure the OD switch is off before using reverse.
D
 
Excuse me if I am jumping in (should I start a new thread?) My BN2 kicks in to overdrive with no problem. But when I switch it off, many times it will not disengage. It will if I swtich off the ignition - which I only did as an experiment.
It will sometimes disengage if I "goose" the throttle. But only sometimes.

Thanks for any thoughts.
Bruce
 
I have a BJ8 Phase I also (Oct 1963). I use the cluch when I'm going out of OD. I hate that jurky feeling and I think it cannot be good on a 40 year old drive train. But in is very smooth.
 
It is possible that Bruce's complaint & TH's jerky feeling are both caused by the throttle switch (switch on the firewall that is connected to the throttle linkage) being defective or out of adjustment. The switch should only allow a shift to direct when the throttle is open a bit - even if the dash control is off. I could email a small jpg which shows the OD circuit & how it works if anyone is interested.
D
 
I have a 64 BJ8 Phase 1 with overdrive. Question is whether is better to depress the clutch when engaging and/or disengaging the O/D? The only advise I received from the previous owner is to never put the car in reverse with the O/D engaged.

Thanks.
 
The best way to shift into overdrive is to reduce engine RPM. The OD clutch tends to wear excessively if we accelerate under power during the shift process. There's no need to use the clutch pedal at all. Accelerate to approximately 45-50 MPH and turn on the overdrive switch. As the overdrive engages, lightly feather the throttle to keep the road speed the same as the engine RPM’s are reduced. This method minimizes stress to the overdrive.

Also, it stresses the OD clutch to shift into overdrive at low speeds. Avoid shifting out of OD at very high speeds because this may cause the engine to over rev when the OD is disengaged.

To shift out of OD, perform the reverse of the above process. Turn the overdrive switch off. As the OD disengages step lightly on the throttle to maintain the same road speed, and increase engine RPM until the overdrive is fully engaged.

The key is to reduce wear on the unidirectional OD clutch during shifting.
 
In the next to last paragraph, last sentence, I should have said ". . . fully DISengaged." Not engaged.

Sorry.
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Dave Russell:
The switch should only allow a shift to direct when the throttle is open a bit - even if the dash control is off. I could email a small jpg which shows the OD circuit & how it works if anyone is interested.
D<hr></blockquote>


Dave - I also emailed you.

Not sure what you mean by "only allow a shift to direct". Does this mean as an example, if one has their foot completely off the throttle pedal that the OD switch when turned on will not shift, but then would as soon as the pedal is pushed down?

Regardless I will check that switch. I assume it is a mechanical hookup to the throttle system.
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Bruce Bowker:

Does this mean as an example, if one has their foot completely off the throttle pedal that the OD switch when turned on will not shift, but then would as soon as the pedal is pushed down?
I assume it is a mechanical hookup to the throttle system.<hr></blockquote>
It means that if the foot is off the pedal when the car is in OD, it will not shift to direct (out of OD) when the OD switch is turned off, until the throttle pedal is depressed.

It will shift into OD when the switch is turned on, without regard to pedal position.

Yes - It is a mechanical hookup.
D
 
Mark,
What you say is probaly true for the "J" type OD's found in some Triumphs & Jags. The "A" type OD as used in the Healeys is much more robust, has quicker, more positive shifting & generally does not need the "kid gloves" treatment that the "J" type does.
D
 
Thanks, Dave, you're probably right. By employing the OD shifting techniques I described, we can minimize wear and tear on any OD box. It's not the most fun way to drive a sports car, but it may save us some money in the long run!

The instructions I provided above are similar to those provided on the Quantummechanics website, a professional OD gearbox restorer.
 
Again,
The much weaker type "J" OD & it's associated slower shifting & lower operating pressures may preclude shifting into OD at low road speeds. Not the case with the AH type "A" OD.
D
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by vagt6:
This general method of "feathering" the throttle is simply a general guide to follow if we want to minimize wear and tear to the OD.
It's perfectly logical, actually. Powershifting into or out of OD is far more stressful to the box than lightly feathering the throttle as indicated.
<hr></blockquote>
Hi Mark,
I thought that is what I said in my original post. Maybe there is a great distinction in "feathering"?

"If you wish to treat the car a little more gently, don't upshift or downshift under full throttle. If really cautious, use the clutch."
D
 
Thanks for the insight, Dave. I agree with you in an indirect way on this.

I double checked the Quantumechanics site, it refers to ANY overdrive unit. And, John Esposito's instructions, as I paraphrase above, don't "preclude" (i.e., it's not totally necessary to do it this way) anything. This general method of "feathering" the throttle is simply a general guide to follow if we want to minimize wear and tear to the OD.

It's perfectly logical, actually. Powershifting into or out of OD is far more stressful to the box than lightly feathering the throttle as indicated.

Thanks for the suggestions, Dave and everyone, it's good to get other opinions on these subjects.
 
Hey! I tried that this morning and it shifted out of over-drive smooth as can be. All this time I've been waaring out the clutch for no reason. When I had my foor off the acceleraton and down-shifted, it always jerked to decelerate. Wow, a hole new world! Thanks all. I learn so much from this forum.
 
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