Overdrive engagement time

I have a question for those of you running an A-type O.D.
How long does it take yours to shift up, or down, after flipping the switch?

Mine:

Engaging overdrive: Flip switch, 1-1/2 - 2 seconds, engage.

Disengaging: Flip switch. If my foot's on the gas, engine speed immediately goes up, but if my foot isn't on the gas, it seems to "freewheel" for about a second and then grab.

Proper operation, or problem?

My two A-types each shift differently. One kicks in almost immediately, while the other has a bit of a delay. Under heavy acceleration, both take a little longer.

Keep the oil level topped up and continue to enjoy it.

Sounds like a problem to me, though probably not enough to bother tearing the unit down. Shifting both directions should be practically instantaneous.

For slow engagement, I'd start by looking at the 'drop' of the solenoid. IOW how far it drops down from the engaged position, which is set by a stop under the plunger. Early units actually had an adjustment for it, but later ones used a rubber plug that is frequently missing. Mine has been modified to have the adjustment. If the drop is too far, it can actually lead to burning up the solenoid.

Also worth checking how far the ball in the operating valve actually moves. It's becoming quite common to find units that are worn enough that the "setting lever" is no longer accurate, and measuring ball movement is the only way to accurately set them. Some people like to reduce the ball movement to slow down engagement, but I prefer not to.

For slow disengagement, I'd start by pulling the operating valve out and checking the little hole near the base of the stem for swarf. If it gets clogged completely, the OD may hang in overdrive or between OD and direct; either of which can damage the unit.

Thanks guys! Good info.

If you are flicking into overdrive, let up on the gas pedal for a microsecond after flicking the switch. It should engage right after that witout slipping. Don't use the clutch when shifting into or out of overdrive. When clicking out of overdrive, keep you foot on the gas and just click the switch. It sould disengage immediately.

Hi,

I was told by my shop to always use the clutch when shifting in or out of OD. Is that not necessary?

Thanks.
1962 TR-3B

Vaark01 said:

I was told by my shop to always use the clutch when shifting in or out of OD. Is that not necessary?

Click to expand...

That's a long-running debate, with no clear answer, IMO. There are a couple of places where it's mentioned in the literature that the OD can be shifted under full power (implying no clutch), but there is little doubt that it places extra strain on the unit. So I'd say it comes down to personal style : if you are going for maximum preservation then always use the clutch.

Personally, I use the clutch for 'casual' upshifts, mostly because shifting the OD at part throttle makes things bang around unpleasantly. But I also do the occasional full-throttle shift ... which oddly enough winds up being much smoother as the torque from the engine causes the OD clutch to slip for just the instant needed to perform a smooth shift. And I never use the clutch to downshift, unless I would otherwise (eg coasting to a stop sign).

The OD clutches are similar to the main clutch in design (composition friction material running against a steel face). Although they do have less area, the taper and the oil bath seem to more than make up for it. They almost never wear out unless some other failure causes slipping or dragging.

Randall --
When I engage OD, I kind of feather the gas pedal, letting the RPMS down easy. It takes over a second to engage.
When I disengage OD, (downshift) the RPMS go up right away, if I keep my foot on the gas. If I take my foot off the gas when downshifting, RPMS will actually drop first -- it "freewheels" -- and then jerk up when the the thing catches after about a second. Needless to say, I'm not making a habit of doing it that way.

For the time being, I think I'll live with it. Maybe in Spring I'll take a look at the operating valve.

I do it like Moseso above, a off the gas going on, a little gas going out, helps the motor match the car speed for smooth engagement.

I have used the O/D a lot on my cars that had it, never a mechanical problem--I think they are happier if you use them then let them sit, funner too.

TS 1 LO was the first TR2 build in the production series and it had an "A" type overdrive. These cars were designed and built for pleasure, but also for the race and rally types. Ken Richardson who got all the kinks out of these sidescreen cars also rallied them in many of the top European rallies of the time. As an engineer, he would not have wanted the drivers to use the clutch in a competition as this would cause them lose speed and/or time.

Using the clutch, or letting up on the gas pedal, before shifting into overdrive very often causes a loud clunk and IMO, this clunk does more damage that I could have done to the "A" type overdrive I have in my 1958 TR3A. That's the way I ordered it and back then, 50 years ago, that's how everyone was shifting their overdrive. No clutch = no clunk.

Hard to argue with the original owner! But in my case, I've now started to use the clutch. I really only engage od in 4th anyway on the highway, and by using the clutch it behaves very much like a regular 5 speed transmission and is very smooth. Dropping out of overdrive, though, I don't mess with the clutch.

Randy

Randy,
Some time when you are feeling adventurous and accelerating briskly, try flipping the OD switch when the tach gets to about 4500 rpm in 2nd gear, without letting off the throttle. If your OD is healthy, I think you'll be pleased at what happens.

TR3driver said:

Randy,
Some time when you are feeling adventurous and accelerating briskly, try flipping the OD switch when the tach gets to about 4500 rpm in 2nd gear, without letting off the throttle. If your OD is healthy, I think you'll be pleased at what happens.

Click to expand...

oh boy, i can hardly wait......

Thanks to everyone for your responses. I will continue using the clutch engaging OD, but not taking it out. I really only engage OD when cruising in 4th gear anyway.

I am not comfortable when shifting into OD without the clutch as I get a slight clunk and shake from doing that. That may be normal, but I don't want to ruin anything.

Paul