SpitFireSIX Posted March 28, 2023 Report Share Posted March 28, 2023 Hi, My TR6 OD gearbox has been fine. Tonight returning from work I found 4th OD did not function. 2nd & 3rd OD work fine. Thought it must be a 4th OD switch problem. I can only see a 3/4 gear single switch in all diagrams. Any ideas? Cheers, Iain. Quote Link to post Share on other sites
Motorsport Mickey Posted March 28, 2023 Report Share Posted March 28, 2023 Maybe a pressure problem when the oil gets hot and more viscous, have you tried it from cold when it may work immediately ? Mick Richards Quote Link to post Share on other sites
RobH Posted March 28, 2023 Report Share Posted March 28, 2023 3rd and 4th use the same switch but use different parts of the selector rod to operate it. Perhaps the switch position adjustment is just 'on the edge' and 4th doesn't quite make it any more ? It's fairly easy to check that electrically without dismantling anything. Quote Link to post Share on other sites
Mike C Posted March 28, 2023 Report Share Posted March 28, 2023 Can yo hear a click when you engage the O/D in fourth with the engine not running , ignition on. Quote Link to post Share on other sites
Tom Chatterley- Cox Posted March 29, 2023 Report Share Posted March 29, 2023 Definitely sounds like the top of the selector fork is worn in 4th. There should be 2 paper/fibre washers underneath the corresponding inhibitor switch on top of the gearbox. If you remove one, it should be enough to start working in 4th again, but you need to make sure the circuit does stay open when in neutral else the OD could be operated in reverse. Quote Link to post Share on other sites
SpitFireSIX Posted March 30, 2023 Author Report Share Posted March 30, 2023 Hi all & thanks, Yesterday fourth OD started working again. Today coming home from work lost all OD’s. Then when able to try the lower gears third started to work perfectly but the fourth never worked. Two OD is no more. Temperature range has no effect on whether the OD works or not. Oil is a quite wide VI 75W90 GL5 for manual transmissions. I have never been able to hear it "click". In the olden days, I would have put the radio on LW to test. I need to fit a quick/simple way of measuring current to the solenoid while driving to see if it’s electrical. I will measure the load current and fit a series resistor that drops two volts to light an LED. I doubt a 2-volt drop will impact solenoid operation as my ignition circuit is around 14 volts. Thanks, Iain. Quote Link to post Share on other sites
Paulfc Posted March 30, 2023 Report Share Posted March 30, 2023 Please excuse my ignorance, but I thought the J-type only operated on 3rd and 4th. Have I got this wrong? Quote Link to post Share on other sites
SpitFireSIX Posted March 30, 2023 Author Report Share Posted March 30, 2023 (edited) 14 minutes ago, Paulfc said: Please excuse my ignorance, but I thought the J-type only operated on 3rd and 4th. Have I got this wrong? Interesting as I only have two switches & one is reverse because reverse lights work. Maybe it would operate in 1st? Never tried or been aware that it was. Cheers, Iain. Edited March 30, 2023 by SpitFireSIX speeling Quote Link to post Share on other sites
elclem1 Posted March 30, 2023 Report Share Posted March 30, 2023 Interesting thread, So you have two switches and one is reverse therefore the other must be 3/4 OD therefore no second as per standard J type box. If it is working occasionally then i suspect wiring or sticky switch if the reverse switch is working swap them over and see what happens.? Quote Link to post Share on other sites
RobH Posted March 30, 2023 Report Share Posted March 30, 2023 (edited) 32 minutes ago, Paulfc said: I thought the J-type only operated on 3rd and 4th. Have I got this wrong? It is possible - but not generally advised on a J type - to fit another interlock switch in the unused boss, to allow use in second gear also as is standard with the (stronger) A type. If yours had OD in second Iain but without that switch fitted, there is likely a problem with the interlocking which is very dangerous for the health of your overdrive were it to engage in 1st or worse, in reverse . Edited March 30, 2023 by RobH Quote Link to post Share on other sites
SpitFireSIX Posted March 30, 2023 Author Report Share Posted March 30, 2023 Hi, my gearbox. the second switch is on side you cannot see. It works on second as I use it. Reverse always works fine with OD switch "ON". Cheers, Iain. Quote Link to post Share on other sites
RobH Posted March 30, 2023 Report Share Posted March 30, 2023 The switch on the side of the remote is the reversing switch as you say. That single inhibit switch on the top should only allow OD in 3rd and 4th I think. Quote Link to post Share on other sites
Tim D. Posted March 30, 2023 Report Share Posted March 30, 2023 3 hours ago, SpitFireSIX said: Hi all & thanks, Yesterday fourth OD started working again. Today coming home from work lost all OD’s. Then when able to try the lower gears third started to work perfectly but the fourth never worked. Two OD is no more. Temperature range has no effect on whether the OD works or not. Oil is a quite wide VI 75W90 GL5 for manual transmissions. I have never been able to hear it "click". In the olden days, I would have put the radio on LW to test. I need to fit a quick/simple way of measuring current to the solenoid while driving to see if it’s electrical. I will measure the load current and fit a series resistor that drops two volts to light an LED. I doubt a 2-volt drop will impact solenoid operation as my ignition circuit is around 14 volts. Thanks, Iain. I suspect if you have been using GL5 spec oil you may be in trouble. These gearboxes are designed for GL4. GL5 has a habit of attacking the yellow metal components of the box. May not be related to your OD issue but i would drain, wash out and refil with GL4 asap. Quote Link to post Share on other sites
Mike C Posted March 30, 2023 Report Share Posted March 30, 2023 3 hours ago, Paulfc said: Please excuse my ignorance, but I thought the J-type only operated on 3rd and 4th. Have I got this wrong? +1. My understanding is that the J type could not withstand the torque levels in 1st or 2nd. Note the wiring is worth checking- a previous owner had wired my A type O/D to engage in all gears, which included reverse. Quote Link to post Share on other sites
elclem1 Posted March 31, 2023 Report Share Posted March 31, 2023 The switch on the side is reverse and the one on top is 3/4th so if you say it works in second then its difficult to see how it can with no switch to operate the overdrive.. Have you checked the operation of the solenoid switch? Quote Link to post Share on other sites
Chris59 Posted March 31, 2023 Report Share Posted March 31, 2023 Imho, it's not an electrical problem, but more something wrong, as suggested before, in this (Dolomite Sprint ?) gearbox. Quote Link to post Share on other sites
DRD Posted March 31, 2023 Report Share Posted March 31, 2023 15 hours ago, Tim D. said: I suspect if you have been using GL5 spec oil you may be in trouble. These gearboxes are designed for GL4. GL5 has a habit of attacking the yellow metal components of the box. May not be related to your OD issue but i would drain, wash out and refil with GL4 asap. That's what I was thinking! Quote Link to post Share on other sites
SpitFireSIX Posted April 2, 2023 Author Report Share Posted April 2, 2023 Hi, Removed the OD enable switch; Switch opens and closes properly. When in circuit No current flows thru switch in any gear. Reverse light works fine. I have ignition voltage on one wire to OD switch measured with high Z meter. I have an open circuit. Sad its not the switch. "The thing about GL5 oils attacking yellow metals is based on out of date information." Cheers, Iain. Quote Link to post Share on other sites
RobH Posted April 2, 2023 Report Share Posted April 2, 2023 When tracing power on a car Iain, it is a good idea to use to use a low-impedance device like a small 12v bulb with wire leads. A high impedance meter can fool you into thinking that voltage is present, when in fact it is coming through a poor connection which cannot supply any significant current. Quote Link to post Share on other sites
SpitFireSIX Posted April 2, 2023 Author Report Share Posted April 2, 2023 12 minutes ago, RobH said: When tracing power on a car Iain, it is a good idea to use to use a low-impedance device like a small 12v bulb with wire leads. A high impedance meter can fool you into thinking that voltage is present, when in fact it is coming through a poor connection which cannot supply any significant current. Advantage of the then cheap 2kOhm/Volt meters of yesteryear. Quote Link to post Share on other sites
astontr6 Posted April 3, 2023 Report Share Posted April 3, 2023 On 3/30/2023 at 7:14 PM, Paulfc said: Please excuse my ignorance, but I thought the J-type only operated on 3rd and 4th. Have I got this wrong? J types can be made to work on 2nd as I have done! My car is a very early type CR. BL were using up the previous gear box extensions by punting in a blanking plug on the 2 gear O/D threading. I removed the blanking plug screwed in another switch plus a bit of wiring and hay presto O/D on second. Very useful in London traffic. Bruce. Quote Link to post Share on other sites
RobH Posted April 3, 2023 Report Share Posted April 3, 2023 This slight thread drift is getting away from the interesting fact that Iain apparently has OD on second even though the necessary interlock switch is not even fitted. That puzzles me and I can only suggest that if it is not electrical, the solenoid might be sticking ? Quote Link to post Share on other sites
astontr6 Posted April 3, 2023 Report Share Posted April 3, 2023 On 3/30/2023 at 10:40 PM, Mike C said: +1. My understanding is that the J type could not withstand the torque levels in 1st or 2nd. Note the wiring is worth checking- a previous owner had wired my A type O/D to engage in all gears, which included reverse. I think that you would have trouble convincing Volvo GKN's biggest customer for O/Ds, that the J type O/D could not take the torque levels that the A type could? It was Volvo who wanted to ditch the A type as they did not like the wham bam engagement of the A type and BL did not like the warranty claims for the diff mounts so they deleted O/D on 2nd when they introduced the J type. Bruce. Quote Link to post Share on other sites
elclem1 Posted April 4, 2023 Report Share Posted April 4, 2023 If the solenoid is sticking then it could be as suggested do to type of oil among other things. or perhaps the filter/strainer needs a good clean! Quote Link to post Share on other sites
TonyC Posted April 4, 2023 Report Share Posted April 4, 2023 Connect a wire to the solenoid positive (the opposite connector to that going to earth) and run the cable into the cabin. Connect a 12 volt lamp to this cable and run the other side of the lamp to earth. Drive the car and select overdrive function in 3rd and 4th ie J type OD. If the light operates when engaging OD then the circuit is fine and the problem lies at the solenoid (unlikley if light operates in third and not in fourth) or beyond. This is a relatively easy op monitor, allows you to 'see' what's happening as you drive the car and may just help you id other 'silly' issues before you start pulling switches and adjusting op levers. We found a rogue bullet connector adjacent to the steering column as cause for a similar problem on a pals 6. Hope it helps. Good luck. TonyC Quote Link to post Share on other sites
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