[Healeys] Transmission / Overdrive or Clutch slippage

Michael Salter michaelsalter at gmail.com
Thu May 20 21:14:18 MDT 2021

Hi Rafael,
Bob and Roland have both given very good advice but I  feel a little more
diagnosis may help.
With the gearbox tunnel loose get the car hot enough that the reverse drive
problem is established.
Then remove the tunnel and then manually operate the overdrive valve by
pulling up on the lever on the side of the overdrive opposite the solenoid
several times.
Now remove the plug above the overdrive operating valve. Be careful as
there may be some residual pressure. Lift out the spring spring guide and
ball (use a magnet) then pull out the operating valve. This will ensure
that there is no oil pressure in the unit.
Now try reverse.
If the problem persists then the issue is mechanical and the suggestions
that others have made should be followed.


On Thu., May 20, 2021, 5:46 p.m. Rafael Abugattas via Healeys, <
healeys at autox.team.net> wrote:

> Hi all,
> Last year I requested your help regarding a strange overdrive or slippage
> problem I have in my 1962 Tricarb BT7.
> I received very valuable comments and suggestions but sadly the problem
> persists: Overdrive would not activate under any circumstances and when the
> engine / transmission is warm and we engage reverse, the engine revs but
> the car won´t move.
> There is slippage somewhere in the transmission / clutch or overdrive.
> When the car is cold, reverse engages without any issues. This only happens
> in reverse gear after the car has been driven a few miles and the engine
> and transmission are warm. Forward gears engage all the time without any
> issues.
> The car has been recently restored. Before the restoration the overdrive
> was operational. Now it’s not.
> The transmission and overdrive have been taken apart and assembled twice
> looking for something visually wrong. Everything seemed to be OK.
> The clutch and plate were also removed for inspection. The clutch was
> recently redone, adjusted and tested.
> A friend suggested we should verify the oil pressure on the overdrive. On
> this link you will find a couple of videos of a test we have recently done
> with a manometer installed on the overdrive to check the oil pressure at
> different RPM´s.
> https://www.dropbox.com/sh/t5p8kqz6v6yduyt/AADizyVMyBKPozy284B-udA4a?dl=0
> The pressure on 3rd and 4th gears goes up to 400 psi and drops as it goes
> to lower gears. At idle is between 150 to 200 psi
> In forward gears the car runs fine; the problem that we need to solve is
> that the overdrive would not activate(even though it is connected and
> everything seems visually OK) and the slippage we have when engaging
> reverse (the car won´t move) when the engine / transmission is warm.
> We are located in Lima – Peru and as you may imagine, there are not many
> experts in this particular area of expertise.
> Any thoughts or suggestions from you collective knowledge and wisdom on
> how to proceed will be much appreciated.
> Thanks in advance!
> Rafael
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