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Overdrive only works when cold


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Hi - Just bought a 1500 which had a recon gearbox and o/drive fitted 1000 miles ago. Problem is - the o/d only works when cold. When the box is cold the o/d works great. As it warms up, the changes seem to slow down until it finally sticks in the 'out' position. Have changed the oil, which was on the low side, but problem still persists. Anyone have any ideas.

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Could be

- solenoid overheating and becoming inneffective once hot.
- oil rings on the solenoid not sealing properly once the oil has warmed up (and perhaps thinned a bit).  New o-rings from Rimmers are thicker than those that come as standard on the solenoid and work well.
- low oil level might have this effect
- the other unusual cause of this type of symptom I've come across was one of the little roll pins which hold the solenoid body onto the solenoid valve having dropped out. This was allowing the body to move when the solenoid was switched on and prevented the valve sealing properly.  

Those are the cheap and easy things - beyond this it gets trickier
- faulty pressure relief valve
- faulty oil pump in OD unit

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Had a thought anorak - what oil did you put in?

I found 'proper' EP90 a bit harsh when I put my recon unit in at the end of 2008 & ended up running for a few thousand miles on EP75/80 - the OD operated perfectly.  Not sure what the science behind that is but maybe worth a try as an experiment.

I've heard it said that EP90 is intended for top ups only and that EP75/80 should be fine otherwise - but again I don't know if that is fact.

I now use Halfords EP80/90 GL4 when I change the oil.


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Update: Just checked the invoices I got when I bought the car and it wasn't a recon unit as such but was described as 'reconditioned where necessary'. The owner was charged £310.00 just for parts! This was in June 2004 and the car then stood in the garage for 6yrs. It did 200 miles this September when it was MOT'd and then I bought it in December. When I drained the oil it was short by about 1 litre. I filled it with EP80W/90 GL4. I used about 1.75 litres although I did spill a bit! When I bought it the gearstick switch was broken so the overdrive wasn't working. I replaced the switch and drove for a test and still it didn't work, although I could now hear the solenoid clicking. I was out in her a couple of days later and the o/d suddenly worked. It then started this problem of stopping working, with the o/d out, once the car had warmed up. I have been on some long runs and it definately won't work again until the engine and gearbox have cooled down. When it is hot and the o/d has stopped working, it is still possible to hear the solenoid clicking. I have checked this by stopping the engine, turning on the ignition, putting into 4th and flicking the switch. Given the fact that she was left standing for 6 years, I tend to think of sticking valves but you would think that it would be worse when cold although if it is a new part could it be expanding and sticking when it gets hot?

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  • 1 month later...

Just an update for anyone with a similar problem now or in the future. I removed the o/d on the basis it could be a serious problem. Took the cover of the bottom to find the magnetic strip was chock-a-block with sediment. Cleaned this off. Then took the larger Pressure filter plug out. The oil that came out was filthy. The filter was 75% blocked. I think what was happening was this. When the car was stood the sediment on the filter fell to the bottom of the casing thus leaving a small area of the filter clear. When first run this allowed the o/d to work for a couple of times. As the oil became agitated and the sediment became mixed in the oil again and was sucked up against the filter eventually blocking it completely. No oil pressure - no o/d! Then when the car was left to cool, the sediment once again fell from the filter into the bottom of the casing thus allowing the o/d to work again the next time it was run. I cleaned the filter, replaced some O rings and the non-return valve and now she works perfectly. The sad thing is that the PO paid £1200 for a recon g/box and o/d. I guess it just proves that there are some cowboy outfits around.

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BrendanD wrote:
Just a thought... I had this problem on my GT6.
It turned out to be a frayed gearstick cable that made contact when cold and not when hot !
Maybe the cable got more flexible when heated up?

Same happend to me as above :-/

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always a good read


or talk to


worrying where all the debris has worn from , but I guess the reputed repair was a myth

the problem of oil is the laycock OD  is designed to use engine oil , the triumph gearbox is definitley not.
as the oil is common to both units you cant mix it , so to enable gearbox survival you have to use EP oils
and never any addatives unless you want OD clutch slip .

EP 80/90 GL4 is a good available compromise  to gearbox life and speedy OD operation
for the gearox Triumph specified  staright EP90 GL4 which is still available     eg TSSC shop and some factors


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