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AH 3000 activating the overdrive

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davidb

davidb

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Was just reading the posts on "Overdrive Issue", and it brought to mind another question that a buddy of mine and myself have differences of opinion about.

What's the procedure when taking your car out of overdrive? Usually I depress the clutch and then flip the OD switch back to normal. My buddy just flips the switch back to normal without depressing the clutch, but this tends to "jar" the transmission, in my view. Or does it matter?

Any thoughts?

Thanks

D.
 
The throttle switch is supposed to reduce the jarring by requiring the throttle be opened about 1/3rd before allowing the OD to shift out of OD.
 
Tim is correct. The overdrive should not disengage unless the throttle is open, and this prevents it disengaging while decelerating and jarring the drivetrain. In fact, if you just depress the clutch and flip the OD switch off, the overdrive should not disengage until you begin accelerating. When I flip the OD switch to off, I often don't have the throttle open enough to allow it to disengage. I have to momentarily depress the accelerator to cause it to disengage. I'm pretty sure this is how it's supposed to work.
 
davidb said:
What's the procedure when taking your car out of overdrive? Usually I depress the clutch and then flip the OD switch back to normal. My buddy just flips the switch back to normal without depressing the clutch, but this tends to "jar" the transmission, in my view. Or does it matter?Any thoughts?
Click to expand...

I've always done it 'your' way, unless, for some reason, I wanted to wait until the next time I hit the throttle for the OD to disengage.

On the flip side, read on one of the rebuilder's site that you shouldn't do what I've always done, which is to engage the OD while accelerating; i.e. you should only engage the OD after you've reached your cruising speed. Apparently, not doing it that way puts more wear-and-tear on the cone clutch, but when you've just got to get around an RV on a mountain road, the 'boost' comes in handy.
 
I believe Tim and Keith have it right. But the main point is to not come out of OD when decelerating. I do not have a throttle switch on mine and for many years I would just blip the throttle when I pushed the dash switch to off. But since my most recent restoration, (3 years ago) I have decided to use the clutch each time I engage or disengage the OD. Without a throttle switch is acts just like shifting into or out of a 5th gear. It is very smooth in and out.
 
Tim is correct.,Yep.:encouragement::iagree:
 
My thanks to all for your considered comments and taking the time to reply. As usual, BCF comes thru.

D.
 
Interesting post I have always been a little concerned about the correct way of using the overdrive, Is it correct to say the best way is to select is when cruising and not accelerating, because I find it is not always immediate this way, To disengage I flick the switch with the clutch in and blip the throttle. Again not always immediate.
How feasible is it on a long journey to stay in overdrive all the time and let shifting gear do the selecting and just disengage when manovering? Anyone got an A-Z on overdrives.
 
My experience with OD goes back to 1968 when I bought a '66 MGB and went SCCA racing with it in 1969-70. I got a shift knob with a switch in it and disconnected the reverse lockout wire so that I could use OD in 2nd gear. I had a very high performance engine. Using OD in 2nd, 3rd and 4th, gave me an effective close-ratio gear selection. I engaged OD in each gear under full acceleration and disengaged under full decel with no problems over the course of 2 drivers schools, 4 regional races and 9 national races. The only problem occurred when I went out to practice on a very cold morning and after slowly coming out of the pits in 2nd gear and not accelerating, I shifted into 2nd OD. There was a bang and then no drive -- the lay shaft (?) had broken. (The transmission oil was very cold and the shift into OD was extremely quick).

With my Austin Healey, I make sure the oil is warm enough and then activate OD with the dash switch allowing it to go in and out while driving normally on the street never using the clutch. My OD works as it should after I overhauled the accumulator (which had accumulated a lot of sludge resulting in the OD coming out of "gear" while cruising) and tapped with a small hammer to fully seat the small ball bearing that allows the accumulated oil pressure to activate the OD.
 
Performance driving aside, because I've never done it, for normal driving I wait until I'm going 40 mph + or - in 3rd or 4th, come off the accelerator and flip the switch and then resume with enough pedal to engage the OD. No clutch. This has always seemed very smooth to me and feels the same as shifting gears. To disengage I wait for the same 40 mph, come off the gas and flip the switch and resume with enough acceleration to disengage. I don't care which gear I'm in, just the speed.
I went through several overdrive issues when I built up the car and I ain't gettin' any younger (it's been working flawlessly) so maybe if I baby it a bit it'll last until they pry the drivers license from my fingers (and hide the keys). Of course sometimes it is easier to just come to a stop at a light etc. and flip the switch, blip the throttle at a stop to disengage. This saves having it re-engage as you accelerate into 3rd gear resulting in a less than smooth change.
 
Is the advice then if coming to a stop or having to change down from third it is kinder on the drive train to flick the switch to disengage overdrive then engage when reaching 40ish in third or top. Sorry I am still a bit slow on the uptake of the correct operation of the Healey overdrive. I remember my dads old Bristol three push buttons and a kick down simples !
 
It is set up to be pretty fool proof. Just flick the switch. The relays and junk will protect the system. The owner's manual (for the BJ8 at least) just says to flip the switch to activate the OD. The only other instruction is to not disengage the OD if you are going faster than top speed in direct drive. Nothing about dipping the clutch.
 
I might not have been clear in my description in my last sentence. If you leave overdrive on, it will come out of overdrive when you downshift to 2nd. If you come to a stop and still have the switch in overdrive on position, 2nd gear is normal but you will not be in third when you upshift, you will be in 3rd with the OD engaged and to me it feels like you are lugging a bit. So even though you can leave overdrive on when you come to a stop and then drive away and it probably does no harm, I prefer turning OD off and then back on every time I downshift to 2nd ( usually because I'm going to stop).
 
Thanks Roscoe that makes sense, I assume shifting from 2nd to 3rd with the overdrive switch still on the overdrive will quickly engage with acceleration, and it will stay in 3rd until the accelerator switch activates, Does this put stress on the overdrive?
 
Perhaps a bit but it depends on how hard you are accelerating.
 
Beats me but I'd guess that since the OD has a clutch, eventhough it is separate from the engine clutch and operates automatically when the OD is on, that some may think clutch = clutch pedal. That plus depressing the clutch and releasing it as you wish potentially eases the stress on the gb if you are ham footed with the accelerator.
 
roscoe said:
" depressing the clutch and releasing it as you wish potentially eases the stress on the gb .
Click to expand...

Also, with No Throttle Switch, when using the "Clutch Pedal" you will never give the drive train a hard jolt while manually shifting out of OD while decelerating. Just clutch it like you would any other 5 speed.
 
I've always tapped the clutch and blipped the throttle coming out of OD, because it makes the 'downshift' almost undetectable if you do it just right. But, I only got 125K miles on my clutch, so maybe it's not a good idea.
 
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