Clutch parts for fitting a Triumph Overdrive gearbox onto a 1970 Triumph Herald 1200

[Pete Lewis]

J type does not need a relay in its feed to the solenoid but the feed must go via the inhibitor switch so it must only work in 3r/4th  

the inhibitor switch is the one you circled its operated by a cam on the end of the selector rod  inside .

so ignition feed to the operating switch ( on column or gear knob) then to the inhibitor and then on to the remaining terminal on the solenoid

as there has been a few J types with solenoid problems i would unscrew the sol and give it a shake, it should give a nice rattle 

if its sticking  remove the small 10mm circlip in the end and shake the internal piston valve out give it all a squirt and clean and reassemble

because when its on the car its not an easy task 

while its off   its simple 

[Colin Lindsay]

1 hour ago, jagnut66 said:

Though I am now left wondering what the electrical spade connections circled in my second picture, located on the top of the box are for, I take it they are nothing to do with the overdrive unit?

Best wishes,

Mike.

You need to control the overdrive so that it only comes on when in 3rd or 4th, so this switch is an inhibitor and activated by the gearbox levers when the 3rd or 4th gear is selected, and not in any other gear, especially reverse. That's a very simple screw-in switch and worth replacing as they do wear.

Think of the electrical circuit as a straight line. Power comes in (from the battery but via the ignition circuit, or wherever you take the power from. You don't need a relay.)

It will run straight from the input to the overdrive solenoid, which it activates, then to earth. However you need to control it, so that it's not on all the time, and this is in two places - the inhibitor switch, and the control switch, either gearstick or column mounted. Input runs to the control switch, and is connected via bullet or spade connectors. In one side, out the other. Then it runs to the inhibitor switch on top of the gearbox. Two spade connectors, one in, one out - the out goes to the solenoid, through that and then to earth. It's just one long cable broken into four parts - power to switch to inhibitor to solenoid to earth. You have to join the breaks in two places - switch and inhibitor - before it will work, in order to have 3rd and 4th gears as well as 3rd and 4th overdrive. It's a really simple circuit.

 

[jagnut66]

4 hours ago, Pete Lewis said:

J type does not need a relay in its feed to the solenoid but the feed must go via the inhibitor switch so it must only work in 3r/4th  

the inhibitor switch is the one you circled its operated by a cam on the end of the selector rod  inside .

so ignition feed to the operating switch ( on column or gear knob) then to the inhibitor and then on to the remaining terminal on the solenoid

as there has been a few J types with solenoid problems i would unscrew the sol and give it a shake, it should give a nice rattle 

if its sticking  remove the small 10mm circlip in the end and shake the internal piston valve out give it all a squirt and clean and reassemble

because when its on the car its not an easy task 

while its off   its simple 

 

3 hours ago, Colin Lindsay said:

You need to control the overdrive so that it only comes on when in 3rd or 4th, so this switch is an inhibitor and activated by the gearbox levers when the 3rd or 4th gear is selected, and not in any other gear, especially reverse. That's a very simple screw-in switch and worth replacing as they do wear.

Think of the electrical circuit as a straight line. Power comes in (from the battery but via the ignition circuit, or wherever you take the power from. You don't need a relay.)

It will run straight from the input to the overdrive solenoid, which it activates, then to earth. However you need to control it, so that it's not on all the time, and this is in two places - the inhibitor switch, and the control switch, either gearstick or column mounted. Input runs to the control switch, and is connected via bullet or spade connectors. In one side, out the other. Then it runs to the inhibitor switch on top of the gearbox. Two spade connectors, one in, one out - the out goes to the solenoid, through that and then to earth. It's just one long cable broken into four parts - power to switch to inhibitor to solenoid to earth. You have to join the breaks in two places - switch and inhibitor - before it will work, in order to have 3rd and 4th gears as well as 3rd and 4th overdrive. It's a really simple circuit.

Thanks to both of you for this valuable information.

I think I will follow Pete's instructions and give the solenoid a service whilst it's off the car.

And Colin's advice about replacing the inhibitor switch, I've already found one on eBay, I take it this is the right one?

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I will also need to replace the speedo cable but which one do I use? One from a Vitesse (as below)?

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Best wishes,

Mike.

[jagnut66]

4 hours ago, Josef said:

No, the part that the cover you’ve indicated is bolted to is what I mean. The selector mechanism is fitted to the top cover and pokes down to engage with the shift hubs inside the gearbox. The only thing you need to watch out for is getting the selector forks from the top cover engaged to the shift hubs when you reassemble, but it’s pretty impossible to get this wrong as there’s no space for anything to be in the wrong place. And yes taking the top cover off will require a new gasket to be fitted. 

Thanks for the confirmation Josef.

Best wishes,

Mike.

[Clive]

You would indeed be wise to replace the black earth wire. 

I have had 2 fail (both times were very inconvenient and no previpus warning) they looked OK but had fractured inside the insulation. And took some faffing to find the fault.

Has anybody mentioned cleaning the OD filters prior to fitting? Well worth doing as simple while the box is out. 

[johny]

Another thing Mike, did the gearbox come with an angle drive for the speedo cable? This is a little gear unit that screws onto the output at the end of the gearbox and allows the speedo cable to run in the right direction towards the dash under the gearbox cover. They can be damaged inside so should be checked for smooth running...

[DanMi]

I believe that the electrical connectors you have circled is the overdrive inhibitor switch, this allows the overdrive to only work in 3rd and 4th gear and should be wired in series with the overdrive switch.

[Clive]

There is one other thing I can see may be an issue. Gearstick. 

Do you have an overdrive gearstick for the bix with the knob/switch? If not, do you have a gearstick for it at all? Your herald gearstick is totally different. 

[68vitesse]

If not mentioned the speedo gear might need changing to match your car.

Regards

Paul.

 

 

 

[Pete Lewis]

luckily there are a number of speedo pinions available for j types if you need to change the Turns per mile  of your speedo 

fitting a washer (any washer that fits inside ) the angle drive is most important

even places like rimmer state no washer  ..no warranty 

finding a single rail od gear stick is a bit of a sherlock job 

a column or dash mounted is a lot less hassle if thats a idea that suits 

Pete

 

[johny]

I think Rimmers may have changed their advice concerning the washer now cos this is what they say (see drop down box to right of the photo):

[Josef]

So an overdrive MG Midget 1500 needs an extra washer but an overdrive Spitfire 1500 doesn’t!? Seems very odd differentiating that way given (nearly?) all the bits involved will be common across all marques.

[johny]

Dont think the Midget was ever offered with OD was it?

[Pete Lewis]

most angle drives fail due to the primer drive gets pre loaded 

any 7/16 di washer will work steel copper or fibre  doesnt matter but do fit one or an expensive angle drive with die quickly as many have found 

if you dial up angle drives on rimmers you get all thats available and the one you need says   add the washer  

the fact it says not on a 1500 triumph is not to be considered golden advice   the BL tech note says it all   thats the bible 

just depends who interprets it 

Pete

Pete

[johny]

Never had a problem without on any of mine but hey ho cant do any harm to stick a washer in....

[Pete Lewis]

are we talking angle drives ???

I tend to agree on a 13/60 OD fitting we used a hole saw on the tunnel and fitted the orig cable to run direct run the cable under the carpet 

the std cables  quite long enough

  it also doenst help if the knurled thumb wheel nut is attacked with mole grips and gorilla fingers Ha 

Pete

[Josef]

21 minutes ago, johny said:

Dont think the Midget was ever offered with OD was it?

I don’t know. My point was all the overdrives are made by Laycock, all the angle drives, instruments etc are / were made by Smiths. So BMC vs Triumph needing different treatment seems daft!

[johny]

There could easily have been difference between the units supplied to each surely and this seems to be what Rimmers indicate by specifically saying a washer is not required on Triumphs....

[NonMember]

23 minutes ago, johny said:

Never had a problem without on any of mine but hey ho cant do any harm to stick a washer in....

Neither have I.

17 minutes ago, Pete Lewis said:

are we talking angle drives ???

Yes. All three of mine currently have J-type overdrives with angle drive adapters, none have needed washers. Two of them have been that way for thirty years.

[Pete Lewis]

it may just be the J type has more clearance to prevent preloading ???

Pete

[johny]

yes or maybe there were some rogue angle drives back in the day and later their design was corrected so then it was no longer a problem? Rimmers certainly still seem to want to cover themselves when suppying their angle drives for use on non Triumph BMC cars fitted with either D or J type overdrives....  

[Pete Lewis]

 for the cost of a simple washer vs the potential cost of a failed angle drive   theres no contest.

Pete

 

[johny]

of course, I was just trying to do my usual role of myth buster😁

[Pete Lewis]

well we wont make fortune out of selling washers  ha !

Pete

[jagnut66]

12 hours ago, clive said:

Do you have an overdrive gearstick for the bix with the knob/switch? If not, do you have a gearstick for it at all? Your herald gearstick is totally different. 

I had a gearstick adapted for me, to retain a more 'standard' look inside the car, the overdrive will be operated by a (Vitesse?) column stalk.

Best wishes,

Mike.