Healey Overdrive Upgrade with Larger Piston & Stiffer Springs Pros/Cons?

[mwagon]

Might be an existing thread on this, but wasn't able to find one. There's existing info on the web & a few of the euro Healey parts sources sell a larger 1 3/4" dia. Accumulator Piston & stiffer springs to upgrade the Overdrive to a fast street or Works level of operation. It sounds like the Accumulator Housing isn't used when you step up to the 1 3/4" dia piston. The only change I've read so far is the overdrive shifts quicker & maybe can handle more torque for the modified engines. My thought is the Accumulator Housing gives a replaceable wear surface for the Steel Accumulator pistons.
I'm in the process of rebuilding an overdrive, that needs a new Accumulator Housing & piston & wanted to get feedback on the plus/minus's of the larger piston & stiffer spring's. My Healey won't be driven to the limit

Link on Overdrive problems & Upgrading info
https://www.ntahc.org/techtips/OVERDRIVE1.html

 

[Bob_Spidell]

Have heard--note: hearsay only--that the 'uprated' accumulator and springs gives a quicker, but more emphatic shift. IOW, the O/D engages with a jerk instead of smoothly. Have two thoughts on this: I've never felt that a delay of a second or two to engage O/D is an issue, at least for normal street driving and, if there was an advantage to this 'uprating' it would have been used on our cars given that it doesn't seem like it would cost much (but who knows with BMC bean-counters). I drive my BJ8 hundreds, and occasionally thousands of miles from home and my greatest concern has always been to minimize stress on the drivetrain.

 

[57_BN4]

I asked this same question a couple of years ago and was advised that it made the OD vicious and quite unpleasant for road use. The standard setup in good condition with the modifications/suggestions in the Buckeye Triumph rebuild pages give a shift approximately equal to a modern automatic in sport mode, i.e. a shove forward but no tyre squealing. The delay is about equal to a moderately fast shift of a modern manual trans, i.e. flick the switch, back off throttle and right back on again in od with no delay.

Andy.

 

[TimK]

I raced an MGB with the 3rd/4th switch disabled. I had a shift knob with the OD on/off switch in it. I was able to use OD in all gears, but only used it on 2nd, 3rd, 4th. One cold morning I went out on the track to practice and engaged 2nd OD while the gear oil was cold and thick. The shift to OD was so hard that it snapped the layshaft of the transmission. I would avoid anything that made the shift to OD more aggressive for normal street use.

 

[Keoke]

I'm in the process of rebuilding an overdrive, that needs a new Accumulator Housing & piston & wanted to get feedback on the plus/minus's of the larger piston & stiffer spring's. My Healey won't be driven to the limit:


Best way I know to ruin a good transmission. Listen to what TimK had to say--

 

[bob hughes]

The upgrade can be vicious as stated above, but for anyone bent on going through with it, why not dip the clutch as you pull the switch.? As you would changing gears normally.

A better upgrade would be to get some one to alter the gearing to give you a higher gear hence better MPG. Not sure what it entails but I understand that it can be done.



Bob

 

[DerekJ]

I have a competition overdrive on my car. It snaps in and out much quicker and is essential for any kind of competition work. Two points I would add though. I drive my car on the road all the time and I would not say that the operation of the overdrive is vicious, just faster. There is probably not much point in changing for general road use, plus the effects are much more effective when the throttle switch is dispensed with and the switch is direct and on the gear lever.

 

[Randy Forbes]

Not sure how rare the Laycock overdrive was on Triumph TR3/TR4s__I have successfully avoided close contact with the Marque__but they were supplied with the larger piston and spring. I saved just such a set from a salvage xmsn, and will likely use it when I next pull my overdrive for servicing or repair.

TR3 accumulator spring compared the the Healey's:

Sometimes, you just have to make your own determination on a controversial subject.

 

[John Turney]

The upgrade can be vicious as stated above, but for anyone bent on going through with it, why not dip the clutch as you pull the switch.? As you would changing gears normally.

...

Bob

That's what I do. If your transmission leaks like mine does, I use VR-1 50wt oil to slow the leakage. It also softens the OD change.

 

[CanberraBJ8]

I also dip the clutch when actuating the OD and deactuating (is that a word?). But if the higher spec spring is to speed up the OD's actuation surely dipping the clutch would cancel that out? My standard OD is fast enough to keep up with my clutch dipping....???

 

[Keoke]

The upgrade can be vicious as stated above, but for anyone bent on going through with it, why not dip the clutch as you pull the switch.? As you would changing gears normally.

Yes you can do this to relieve shock on the tranny.
All of my Volvos have the Bang/Bang overdrive and require using the clutch when engaging.
But my Healey just glides in or out like a passing gear-

 

[Bob_Spidell]

I never 'dip' the clutch when engaging--don't see a need as the gears are in constant mesh and O/D works so smoothly--but do slip it just a tad on disengaging. My O/D has 185K miles on it and still works flawlessly; the only problems have been with the electricals (dash switch and relay). IMO the Laycock O/D is an elegant piece of engineering and design.

 

[bob hughes]

Bob

I do not dip the clutch when going into overdrive either, it was just a suggestion of how to over come the sudden engagement, and yes, perhaps vicious was a bit of a harsh word to use ( no pun intended)



Bob