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J type overdrive problem


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My J type overdrive started intermittently phasing in & out on the last spirited drive

 

followed me discovering that the gearbox was low on oil

 

in the absence of anything else I had topped it up with full mineral 20W-60 (not sure what had been in there previously) prior to the long (300km) drive

 

It started on RH corners then was doing it regularly in all circumstances

 

I thought it may be oil related so today emptied the gearbox & re filled with Penrite 80W-90 Gear Oil (which Penrite recommend)

 

doesnt seem to have made any real difference - when not under load it holds the overdrive gearing but under acceleration drops back Out of overdrive

 

any suggestions?

 

could it be the solenoid playing up & no relation to the oil?

 

advice welcome

 

Graeme

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Wiring/switch/earth issue perhaps Graeme, under load something not connecting properly?

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The selector forks move fore & aft a very small amount dependant on whether one is on drive or over-run. If a selector switch is not correctly adjusted for depth of insertion into the top cover, the small movement of the selector fork may be sufficient to cause the switch's contacts to open, thus disengaging the overdrive.

Ian Cornish

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Steve, Ian

 

Thanks for the replies

 

Took it on another Sunday drive today

 

Overdrive worked perfectly on flat motorway but on back roads which of course are bumpy was again intermittent

 

Leads me to electrical connections as my next check

 

Hopefully without needing to pull the tunnel Etc out

 

Many thanks

 

Graeme

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  • 2 months later...

Update

 

have removed gearbox tunnel cover & checked all connections, have ensured no chance of screws from gear l;ever surround are touching gearbox, angle drive (which was added prior to issue arising) is clear of any contact with chassis etc

 

Ive tried to eliminate a number of potential electrical issues & checked all connections and dont think it is a short circuit

 

is there anything in the gearbox/overdrive that would be affected by oil with extra zinc additive in it as the 20W-50 is extra zinc

 

I'm at a bit of a loss as I think if its not electrical it must be as a result of the oil top up

 

help /advice appreciated

 

Graeme

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Another thing that could be true is worn cut-out switches which cause a similar problem to Ian's suggestion, above. Bumpy road could potentially exacerbate this.

 

How about taking it for a drive down your bumpy roads while the tunnel is off and have a passenger watch for the lever moving causing the OD to go in and out?

 

This would indicate whether it's the electrics/switches that are the problem or, if the actuating lever (and therefore solenoid) stays "on", an oil or pump problem.

 

Cheers,

Tim

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Just replaced the column switch on my 74 '6' w/J-type. Intermittent problem, especially over bumpy road. Got worse after doing a service on teh gearbox and some other things (so, tunnel cover out). Anyway, upon removal, the column switch internals virtually came apart. New switch, no problemns. Not suggesting the column switch is your problem, but I'd focus on electricals....

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thanks guys

 

will check out the switch (but it is only 1 year old and was working perfectly), will also take tunnel off & drive it to see if anything is visible

 

yes Mal relay fitted

 

Graeme

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J Type - no visible mechanism.

You can check isolator switch cables & operation when the tunnel is off, Have had one of these fail before now that needed screwing in a touch further to complete the circuit.

Check the earth cable of the solenoid is intact & complete,

Check supply cable to solenoid is intact and complete.

 

Consider a direct connected cable to the solenoid through a switch from battery power that your passenger can operate when you run the car with the tunnel off - that should eliminate either the car electrical circuit fault or suggest an overdrive internal operation fault.

 

Consider dropping the filters out of the overdrive and cleaning them - they are behind the ribbed plate held on with 6 screws - item 47, You will probably need a gasket! see also 50, 55 here https://www.moss-europe.co.uk/shop-by-model/triumph/tr5-6/clutch-transmission-drivetrain/overdrives-components/j-type-overdrive-fittings-tr5-6.html

 

Cheers

Peter W

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Ah, thanks. Shows my lack of knowledge of those!

I'm with you Tim.

 

We once fitted a J type to brother's TR2 as it was higher ratio and had the 'special' pump inside. It was fitted to a Dolomite Sprint gearbox (all chosen from many for its cheapness as a NOS unit from the job lot clearance of parts when Abingdon Special Tuning closed) - required lots of fiddling and parts changing to get it to go in a TR2.

 

The stupid thing ended up too low in the chassis, the way we mounted it, and fouled its solenoid on the chassis and the casing on the exhaust. We found an A type not long after that and replaced the Sprint J type assy. The box and overdrive assy is still in our spares cave along with a CR Sprint box adapted for a TR. - all parts from a lot of racing aspirations/dreams.

Peter W

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I like the above suggestion...

"Consider a direct connected cable to the solenoid through a switch from battery power that your passenger can operate when you run the car with the tunnel off - that should eliminate either the car electrical circuit fault or suggest an overdrive internal operation fault."

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Consider a direct connected cable to the solenoid through a switch from battery power that your passenger can operate when you run the car with the tunnel off - that should eliminate either the car electrical circuit fault or suggest an overdrive internal operation fault.

 

Consider dropping the filters out of the overdrive and cleaning them - they are behind the ribbed plate held on with 6 screws - item 47, You will probably need a gasket! see also 50, 55 here https://www.moss-europe.co.uk/shop-by-model/triumph/tr5-6/clutch-transmission-drivetrain/overdrives-components/j-type-overdrive-fittings-tr5-6.html

 

Cheers

Peter W

 

Thanks Peter, good suggestions

 

Graeme

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