[Healeys] OD Good news Bad news

[WILLIAM B LAWRENCE]

The accumulator in the overdrives installed in Austin Healeys have a reduced bore size to moderate the force of the shift into OD. The bore sleeve or liner has rubber o-rings that seal the pressure in the accumulator bore. These o-rings deteriorate with time, heat, and use and then they allow oil to leak past the accumulator piston thus reducing the pressure that can be developed.

To replace them you need to remove the side plate that holds the accumulator in place, place a dowel in the piston to hold it in place and pressurize the OD from the actuator port valve thus forcing the sleeve out so the o-rings can be replaced.

Bill Lawrence
BN1 #554
________________________________
From: Healeys <healeys-bounces at autox.team.net> on behalf of Bob Spidell <bspidell at comcast.net>
Sent: Saturday, June 29, 2019 3:40 PM
To: healeys at autox.team.net
Subject: Re: [Healeys] OD Good news Bad news


Either the pump, actuating pistons or the accumulator.  My guess would be the accumulator; mine still worked at 200K miles, but the cylinder was scored a little from the metal rings on the piston.  The actuating pistons have rubber O-rings that wear so may not provide enough pressure to override the heavy springs that keep the OD a 'single shaft' when the it's not operating.  I believe the accumulator and pump can be replaced in situ, but I've not done it.  Or some combination of the three.  If you end up replacing the accumulator I recommend the DWM 'uprated' one if you like crisp activation.

Check: 1) pressure at the actuating valve port (should be over 400psi at speed, but I think it'll work as low as 350--not sure), 2) that the actuating shaft rises the correct distance--I believe it's 1/32"--when activated.  If you have good pressure that rules out the pump.  If you got the DWM accumulator, and it wasn't the problem, at least you'll have a crisper OD when after you tear into it to replace the O-rings.

I'm not surprised it disengages quickly; all the hydraulics are there to override the 8 heavy springs; the springs shouldn't fail (it's recommended to replace them if you do a complete rebuild, though I'm not convinced it's entirely necessary unless the OD was slipping when engaged; I think it's a 'might as well while it's on the bench' thing).

Bob

ps.  My stock accumulator still worked normally, and I kept it; if you want it I'll let it go for shipping cost.


On 6/29/2019 7:20 AM, Warren wrote:

Recently had the OD quit working. First time in 52 yrs. Luck? Removed tunnel and checked electrics and switches and solenoid seemed to work. Some hesitancy with solenoid at first. Replaced solenoid and interrupter switch as these were original parts and with close to 200K on the car thought it prudent to do so. Tranny oil topped off regularly and drained and cleanout of screen and magnets every two years. Using Redline MT90 for many years. Before that used ND 30wt.



Now I got it to go into OD. Every time. The good news. But it takes a loooong time. Many seconds. Just flip the switch at speed and “eventually” it slowly slides into OD. Not crisp and instant like before. The bad news. It disengages normally as before. Flip, depress clutch slightly, blip accelerator.



I’ve researched the archives as much as possible on all the forums but am hesitant to proceed without forum\list wisdom.



WD     67 BJ8








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