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I have a 4 synchro A type o/d box in my TR2. Since starting to use the car again this spring, the o/d has been going in OK but then jumping out/in as I'm driving along.

I've checked and topped up the gearbox oil level, and the operating lever adjustment as I had problem with the latter last year.

I've now diagnosed it as an issue with the gear lever/selector position in that if I hold the lever back gently whilst in 4th, the O/D stays engaged perfectly (and it operates fine in 3rd without holding the gear lever), if I let the gear lever go whilst in 4th, O/D jumps in and out.

 

So I've worked out what the problem is, but I'm not sure about how to go about fixing it.

I don't really want to start by taking out the seats and harnesses (I have Revington bucket seats) and the tunnel first as it is a bit of a pain, so my question is this - is the problem likely to be the o/d switch in the top of the selector housing? Is there a simple adjustment I can make on the gear lever, or is there something else I can check?

Any other thoughts or advice would be most welcome.

Edited by Rod1883
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It sounds like a gearbox problem, not the overdrive which would drop out when not in gear!

I will take that back. It is probably a switch on the gearstick extention that is not making a good connection. Still not the overdrive though!

 

Cheers John

Edited by John390
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Hi Rod

 

I have the same problem and the gurus say it is the switch on to of the box that needs to be screwed in a bit. I have bought a new switch and next month out comes the seats and tunnel to do a proper job as we are off on a 3000 mile round trip to Stelvio in June and I don´t want any agro.

Years ago Don Elliot showed me his mod to the tunnel to get at the solenoid to replace it if necessary so I may make a second mod to get at those two switches, for as you say it´s a pain in the nuts to get the tunnel out every time.

Dave

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Dave / Rod

The issue definitely sounds like the springloaded ball in the switch isn't dropping far enough to close the circuit, unless the selector rod is pushed forward by pulling on the gear lever when in 4th.

 

Thinking about it logically (or trying to!)... screwing in the switch further will surely only make the problem worse? i.e. screwing the switch IN will mean the ball drops even LESS than before (relative to the switch), meaning it will be even more likely the o/d will not engage without pulling on the gear lever a bit.

 

Converseley, perhaps screwing the switch OUT a smidgin may solve the problem... but not too far otherwise it will allow o/d engagement when it shouldn't! Easily checked with a multi meter.

 

Either way - the tunnel needs to come off... and maybe the top cover of the gearbox, too... it might be as simple as a bit of dirt in the selector rod groove or on the ball of the switch...

 

Malcolm

PS - I suppose the problem could also lie with the selector rod... maybe it isn't being allowed to travel fully 'home'... but not familiar enough with this aspect to be able to suggest why this would happen or how to cure it.

Edited by bigmalcy
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Rod

 

If the overdrive limit switch is the same on the TR2 gearbox as in the TR5/6/saloon etc then this sounds like the cause.

The operating rod that connects the gearstick to the selector fork has a flat section on it that alows the spring loaded ball in the bottom of the limit switch to drop thereby making the electrical connection which then brings in the overdrive.

Holding the gearstick further back probably realigns this flat section with the switch and when you let it go the rod moves back (as the gearstick moves forward) and forces the ball up breaking the contact.

The bad news is that to adjust this you will have to remove the gearbox tunnel.

 

Hope this helps.

 

Cheers

 

Alan

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Malcolm

 

You seem to got there first. I didn't see your reply until I'd posted mine. I doubt you would be able to screw the limit switch in any further anyway. I think you can adjust the operating rod where it meets the bottom of the gearstick from memory. I have a spare box 2500S gearbox in my lock-up which I'll check tonight on my way home. I'm sure the TR2 box will have the same adjustment as my later box.

 

Alan

Edited by Alan Cochrane
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Rod,

 

You would not want to adjust the position of the operating rod as this could also affect gear selection.

 

On a TR2 and a 3A gearbox top in my garage there is no apparent adjustment at the base of the gear stick in any case.

 

Chances are that the ball on the 3/4 OD switch has worn a depression in the top of the Phospher Bronze selector thus holding the lever back allows the switch to close.

 

I am in the same boat as you, but my boat is also taking in water and a gearbox out job is the only cure ( no second gear)

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Paul... it's my understanding that the switch closes when the ball drops into the groove... thus any wearing of the selector rod by the ball would actually encourage the switch to close and the overdrive to stay engaged (wouldn't it?).

 

The problem appears to be that the ball isn't being allowed to drop far enough for the switch to close.

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That seems right to me.

I think that years of switching the large current taken by he OD solenoid has caused the contacts to recede a bit.

 

Been trying to imagine working on this switch without removing the tunnel etc.

Don't think this going to be possible.

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BigMalcy,

 

You have put an element of doubt in my mind so I have just measured an OD switch on the bench. The switch closes when the ball is pressed into the body of the switch not vice versa. This is consistent with setting up by inserting a card spacer between the switch and the gbox top, so that the ball does not protude too far into the box.

 

My OD switch is from a TR3a, not sure if switches on the later cars work in a different way as the Moss reference numbers are different.

 

Paul

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Paul

That is strange! I have the distinct recollection that the selector rods have grooves in them which (I surmised) were positioned such that the balls in the switches would drop into the grooves when in 3rd or 4th gear, thereby closing the switch, completing the circuit and operating the overdrive relay... but what you are saying blows all of that out of the water... so now I'm completely confussed!

 

Edit: and now having read this I'm even more confussed!

http://www.buckeyetriumphs.org/technical/Gearbox/GearboxCover/GearboxCover.htm

Looking forward to being re-educated...

Edited by bigmalcy
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Thanks everyone for the comments and advice.

My gearbox was rebuilt only 15 months ago so I would hope it isn't worn in any way, but it does seem that there is something awry in the selector and switch area.

Following up on Malcolm's link, and looking further around that site I found this:

http://www.buckeyetriumphs.org/technical/Gearbox/ODSwitches/ODSwitches.htm

 

(The link wouldn't paste so I've typed it in - if it doesn't work follow Malcolms link above and then click on the Buckeye Triumph logo, then scroll down to "Adding OD Isolator Switches to Gearbox top cover" under the TR50 and TR6 Gearbox heading).

 

Two thirds of the way down it shows a good picture of the selector forks and how they lift the ball in the switch to make the contact for the o/d.

This suggests that mine must be slightly in the wrong place for 4th, although why it has worked fine for a year I don't know.

There is a comment at the bottom of the article that says how little tolerance there is with the selector raised sections in relation to the indents in the selector shaft, but I must admit I'm not sure I really understand this bit.

The other thing that is slightly odd with my gearbox is the gear lever itself - mine doesn't have the recess with a little spring and ball in the bottom of the lever, so just maybe this is contributing as it isn't there to push/hold the gear lever back whilst in 4th?

 

I'm tempted to try to take the switch out and put back in with one less washer to see if that allows the switch to operate, from memory of the area I might just be able to achieve this without removing the tunnel - the danger is that it will protrude too much into the top cover area I suppose.

 

Any further thoughts welcomed.

Rod

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Rod et al

Humble apologies for doing my best to lead us all up the garden path... but thank you, too, for shining a light on this and re-educating me! In particular, apologies to Dave Larnder who I think may have given you the correct answer in post #3 before I went and hijacked it :)

 

Still reckon the tunnel has to come off, though!

 

Let us know how you get on with it...

 

Malcolm

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Malcolm et al.

Thanks for all your suggestions although some seem contrary. I intend to follow the instructions in the manuals about setting up of the distance washers to get the right height of the ball.

Early next month ( after our club run out on 26thApril,) it´s out with the lot and in with a new switch (cheap enough) to try to eliminate sticky switches like I have just experienced and cured with the brake light switch by replacement , again cheap enough when balanced against the labour and agro of having to do it.

What I did intimate in my first message is that a cut out and cover plate over both those switches will mean that if the trouble re-occures at least I won´t have to take the tunnel out (Hooray!) as I have done for solenoid replacement thanks to Don Elliott for that tip.

 

Dave

 

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Malcolm - don't apologise, it's the discussion and input of all that gets built up and ultimately takes us to the correct end point, hopefully.

 

I think I might see if I can get a gear lever with the spring and ball arrangement in the base just to see if this holds the selector in position better than mine without these parts, before I start taking the car apart again.

Does anyone have one they would be willing to sell to me - ideally the short stubby sidescreen car gear lever including ball and spring?

 

Rod

Edited by Rod1883
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Rod, I don't think the ball and spring will make a difference. It shouldn't alter the selector rod positioning in 4th gear. I reckon if you set the inhibitor switch up as per the book you'll have more success.

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I wouldnt bother to waste your time trying a gear lever with the anti rattle spring, they are only there to prevent the lever chattering, and in many cases the springs have broken anyway so they do virtually nothing.

 

If you could feed some thin steel or aluminium between the gearbox top and the tunnel as protection it may be possible to drill an access hole with a hole saw to get at the OD switch , you would need to be very careful though to avoid any damage.

 

Best of luck.

Edited by Paul Down
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Oh take the seats out pull the carpet and the cover, you'd have it done while discussing options,

there is not nearly enough room under the tunnel to do anything properly with these switches.

 

Set them correctly as per the book, prove you've cured the problem, and then drill the tunnel,

find big grommets that fit, so you can address anything in the future, (Or cover with two layers of duct tape, laid at 90 degrees')

and go and enjoy your TR!

 

John.

Edited by john
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