D Type OD Disengaging

[Darren Groves]

Vitesse 2L MK1 - Recently had a complete gearbox & overdrive rebuild by a reputable company in Norwich. Gearbox is absolutely fine and the OD engages well but when you disengage there is often a bit of a delay and it releases with a real bang. Now it did do this before it went in for a rebuild and I know the cone clutch was shot and needed replacing. I initially thought that  a GB mount or something in the drive train hadn't been tightened so have checked all this, all was fine.

So before I go back to the guys who rebuilt it, is there anything I should check?

Not my car btw, just involved in its recommissioning.

Darren

[JohnD]

The speed with which an O/drive engages is more to do with the build up of oil pressure inside it from the integral pump mechanism.  The pressure is very high, 540-560psi, and you need special equipment to measure it.  Your gearbox shop should be able to do it, indeed should have done it.

And the feeling of the bump is modulated by your driving while you do it.   Going up into O/drive needs a light lift on the  throttle, so allow to engine to slow more easily.  Going down,  out of O/drive needs slight pressure on the throttle to produce the opposite speeding up of the engine.  Get it right and changes in and out of O/drive can be almost imperceptible.

John

[Pete Lewis]

Od spares always good to talk to 

Heres some reading on disengagement 

http://www.odspares.com/phdi/p1.nsf/supppages/odspares?opendocument&part=3

[Darren Groves]

Thanks for replies.

I have an OD on my own car so get what your saying about getting the change right, but this disengagement is full on thump/bang through the car, far too aggressive for it to be just because I didn't get it right.

Will get back to the guys that rebuilt it.

Darren

 

[Pete Lewis]

If the tunnels off i would check the top valve , remove the cap screw and make sure the small spool valve inside has a clean hole through its centre,  watch you dont loose theball and spring  under the cap /plug 

Pete

[Darren Groves]

So spoke to the guys who rebuilt it, they say to drain out the EP90 oil and refill with 20/50 engine oil, EP90 is too heavy apparently. 

Any thoughts? 

Darren 

[Paul H]

5 minutes ago, Darren Groves said:

So spoke to the guys who rebuilt it, they say to drain out the EP90 oil and refill with 20/50 engine oil, EP90 is too heavy apparently. 

Any thoughts? 

Darren 

Hi Darren - I had my D Type OD professionally rebuilt for my Vitesse and running on EP90 

Paul 

[Waynebaby]

Darren,

I've heard it said that whilst the OD is OK to run with engine oil, the Triumph gearbox (an altogether less well engineered item) needs the EP oil (GL4 specification). I think the suggestion that the OD disengagement symptoms are the result of the EP90 oil is a red-herring. My OD runs fine with Comma EP80-90 GL4.

Wayne

 

 

[Pete Lewis]

yes the basic design spec by Laycock uses engine oils ,common in many gearboxes eg Rootes Group  but the poor old trumf gearbox will soon expire, there was agreement  to use    EP90  GL4 approved by  Laycock and Triumph

if it was not approved it would not be stipulated to use  EP90 in all the workshop manuals and service documents

ive run overdrives on it for 14 years with never a hint of drag or lazy engagement 

the next thought is  maybe find another repairer ,   they obviously dont  need design specs from the approved manuals 

have they used the specified pump relief valve setting, i would expect a too high a setting would induce hard changes 

you need to call dave twigger , he has all the answers

  Pete

 

 

[djn]

Hi,

I would be interested to hear how you get on with this. I have the same issue. The first time I select overdrive from cold, there is a slight delay in engaging. Fine after that but always releases with a fair thud. (spitfire 2500, d type OD)

[JohnD]

djn,

please see my contribution, on throttle control while changing in and out of overdrive, post 2.

John

[Colin Lindsay]

MY GT6 is running J-type and there's no real thump when engaging, just a slight gentle bump and a drop in the revs. Coming out of O/D is like changing down gears when you're driving fast, the engine and clutch have to cope with the increase in speed and there will be a reaction. As John says, your driving style will help dramatically. Get into the correct speed for the gear, and don't make the gears or O/D slow the car. My first car was a 5-speed and I'd learned to drive in a four speed, so the first time on the open road I went for 5th at about 70, didn't realise to bend the gearlever over to the right and got third instead. The engine nearly came out through the bonnet. It's the same effect with O/D - treat it gently and it'll last.

[Pete Lewis]

Then check the solenoid lever setting has its  holes in alignment and that the top spool valve has a nice clean very small hole down its centre

Seized solenoids due to rusty cores is a another possible

Oils and filters dont give any real troubles, but a wash of the gauze  filter is all part of a service.

Pressures are controlled by the relief valve one of the underside plugs,    just a spring and ball wirh shims to alter the load 

http://www.odspares.com/phdi/p1.nsf/supppages/odspares?opendocument&part=5

Dave twigger is awlays helpfull

[Nick Jones]

Viscosity wise EP90 and 20/50 are not that different (90 weight gear oil = 50 weight engine oil) so I don't buy that story.  Also, as already suggested above the Triumph box (especially behind a 6 pot) needs all the help it can get from lubricants.

You could try a 75/90 gear oil but I don't think the oil is the root of the problem.  I wonder if the OD had any attention at all or whether it was simply popped back on to the refurbed gearbox.....

Nick

[djn]

Hi again,

Found this on another forum. Hope I am aloud to paste items from elsewhere to here. "Paul" contacted "Overdrive Spares" and got this reply. 

 

Hi Paul

Ignore what it tells in the manuals it is not correct for every unit and would have only been correct when the overdrive was new 

The best way to explain it is thus 

with the operating valve /spring /ball/plug fitted 

if you take hold of the brass lever and push it towards the solenoid you will feel a light spring pressure 

if you rest your finger on the start of the spring pressure and energize the solenoid when set correctly the lever needs to jump 1.5 to 2mm towards the solenoid 

when the solenoid is not energized you should have some free play in the lever 

regards Dave.

 

Has anyone come across this info before. Will try this method of aligning the lever when I get a chance and will report back.

DJN

[Pete Lewis]

Ive said many times David is a good source and knows the quirks of these units 

Its correct, on D types  the sol plunger /armature does not move very much , certainly nothing like you would expect when you see the length of the thing,  its lever has to lift the valve or no oil pressure is transmitted to the operating pistons I have mostly found the hole align setting to be ok but wear and tear is very likely  with the top cap removed you can see the end of the valve to make sure its lifitng ok  and if the sol. doesnt reach the end switch you Very soon cook the coil in the sol.  If its stays on the 10-20 amp pull in current and doesnt get switched down to the holding coil of around 0.5amps

Pete