Roberto Posted March 10, 2020 Report Share Posted March 10, 2020 In my TR250 there's an Overdrive Laycock de Normanville "J" type. When the overdrive was manually engaged and disengaged all worked well. Some months ago I stopped the car with the overdrive engaged but when I started again the fuse on the + circuit broke down and since then I wasn't able to repair the overdrive system. I replaced the whole electrical system (wires), the fasten, the solenoid valve, the inhibitor switch and naturally the gear compatibile oil. Can anyone of you help me to try to solve this issue? Thanks for any suggestion and best regards from Italy Roberto Quote Link to post Share on other sites
tr graham Posted March 11, 2020 Report Share Posted March 11, 2020 Roberto to clarify a bit more does the solenoid pull in and out , But nothing happens internally with the Gearbox that will determine whether it is the box and overdrive itself or an electrical problem ,if you are unsure run a live fire down to the solenoid from the battery and watch and listen. caio graham Quote Link to post Share on other sites
Waldi Posted March 11, 2020 Report Share Posted March 11, 2020 Hi Roberto, welcome to the forum. What is exactly your problem? Blown fuses, no sound, something else? The better the description, the preciser the answers. Cheers, Waldi Quote Link to post Share on other sites
Roberto Posted March 11, 2020 Author Report Share Posted March 11, 2020 Dear Waldi the overdrive works perfectly if I engage or disengage it manually. If indeed I just reduce speed, downscaling the gear, without disengaging it manually it blows the fuse. No sound at all. All electrical components have been replaced but the problem persists. Best regards en goeie avond! Roberto Quote Link to post Share on other sites
RogerH Posted March 11, 2020 Report Share Posted March 11, 2020 (edited) Hi Roberto, when you reduce speed whilst still in OD the engine/gearbox will twist due to the torque coming off. Still could indicate that a wire is shorting to the GB casing etc. You say you have replaced all the electrics but have you replaced the loom? Roger Edited March 11, 2020 by RogerH Quote Link to post Share on other sites
RobH Posted March 11, 2020 Report Share Posted March 11, 2020 The terminals on the J type solenoid can be quite close to the chassis - perhaps gearbox movement on a down-shift is causing it to touch? Quote Link to post Share on other sites
Waldi Posted March 11, 2020 Report Share Posted March 11, 2020 Hi Roberto, Looks indeed like an electrical problem. Which in fact is better than a OD internal problem;) There is a reverse light switch too on the GB which is live; have you maybe switched wiring? Just a thought. Waldi Quote Link to post Share on other sites
Aldpilot Posted March 12, 2020 Report Share Posted March 12, 2020 +1 for trying the inhibitor switch. I had an intermittent problem for over a year and once I bit the bullet and took the gbox tunnel out and swapped the reversing light switch and the o/drive inhibitor (they are the same, with both attached to the gbox under the tunnel) the problem was found. A new switch for under a tenner sorted it and I have had no problems for 2 years now (that’s done it). Mike Quote Link to post Share on other sites
ntc Posted March 12, 2020 Report Share Posted March 12, 2020 Test supply with a headlight bulb if bright ok if not it will be a electrical fault, do not presume your solenoid is ok even if new. Quote Link to post Share on other sites
Roberto Posted March 15, 2020 Author Report Share Posted March 15, 2020 On 11 marzo 2020 at 3:32 PM, tr graham said: Roberto to clarify a bit more does the solenoid pull in and out , But nothing happens internally with the Gearbox that will determine whether it is the box and overdrive itself or an electrical problem ,if you are unsure run a live fire down to the solenoid from the battery and watch and listen. caio graham Dear Graham thanks for you contribution. As soon as we are out of the quarantine I will check what you suggest me. I'll let you know the result. Unfortunately my TR is by now by my technician in the neighbouring municipality and we are not allowed to travel anywhere best regard ciao Quote Link to post Share on other sites
Roberto Posted March 15, 2020 Author Report Share Posted March 15, 2020 On 3/11/2020 at 3:32 PM, tr graham said: Roberto to clarify a bit more does the solenoid pull in and out , But nothing happens internally with the Gearbox that will determine whether it is the box and overdrive itself or an electrical problem ,if you are unsure run a live fire down to the solenoid from the battery and watch and listen. caio graham On 3/11/2020 at 9:56 PM, RogerH said: Hi Roberto, when you reduce speed whilst still in OD the engine/gearbox will twist due to the torque coming off. Still could indicate that a wire is shorting to the GB casing etc. You say you have replaced all the electrics but have you replaced the loom? Roger Hi Roger, could you please specify me a bit more what do you mean by replacing the loom? thanks so much and kind regards Roberto Quote Link to post Share on other sites
Roberto Posted March 15, 2020 Author Report Share Posted March 15, 2020 On 3/11/2020 at 10:32 PM, RobH said: The terminals on the J type solenoid can be quite close to the chassis - perhaps gearbox movement on a down-shift is causing it to touch? Hi Rob, I'll check this. Thanks and best regards Roberto Quote Link to post Share on other sites
Roberto Posted March 15, 2020 Author Report Share Posted March 15, 2020 On 3/12/2020 at 11:48 AM, Aldpilot said: +1 for trying the inhibitor switch. I had an intermittent problem for over a year and once I bit the bullet and took the gbox tunnel out and swapped the reversing light switch and the o/drive inhibitor (they are the same, with both attached to the gbox under the tunnel) the problem was found. A new switch for under a tenner sorted it and I have had no problems for 2 years now (that’s done it). Mike Hi Mike I actually replaced both the switches but had no results. I will change them again and see what happens. Best regards Roberto Quote Link to post Share on other sites
Roberto Posted March 15, 2020 Author Report Share Posted March 15, 2020 On 3/12/2020 at 2:06 PM, ntc said: Test supply with a headlight bulb if bright ok if not it will be a electrical fault, do not presume your solenoid is ok even if new. Thanks I'll follow your suggestion. best regards Roberto Quote Link to post Share on other sites
RogerH Posted March 15, 2020 Report Share Posted March 15, 2020 Hi Roberto, there is a small wiring lom that joins the GB to the main loom. Is this in good condition. Roger Quote Link to post Share on other sites
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