mmgemini Posted April 8, 2008 Share Posted April 8, 2008 James. Yes again At least if you take a direct feed to the solenoid you know if it's the overdrive or the electronics. David. Funney thing but the overdrive engages quicker without the electronics fitted than with. mike Quote Link to comment Share on other sites More sharing options...
western Posted April 8, 2008 Share Posted April 8, 2008 could be worth removing the solenoid & powering it 'on the bench'so it opens/closes, it may be sticking & need a clean. Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted April 8, 2008 Share Posted April 8, 2008 It's a couple of decades since I was running the 1798cc MGB, but I seem to recall that the most common cause of OD malfunction, as mentioned in Club magazines, was an electrical fault, so that mirrors the experiences recounted by others in this thread. I also met someone whose OD problem was cured when the gearbox was topped up with oil. At that time, there was no electronic control, so I have no experience of that. Because the MGB didn't have a low ratio gearbox it was enough to limit the operation to 3rd and 4th, when the road speed, and thus gearbox output shaft speed, was sufficient to drive the pump fast enough to create the pressure required. To accomadate the increased torque the MGB V8 had OD only on 4th gear. The (MGB) OD manual I have does show test pressures, but to quote them here would be misleading. It's better for the information to be missing or accurate, rather than 'perhaps'. Cheers. Quote Link to comment Share on other sites More sharing options...
JST Posted April 12, 2008 Author Share Posted April 12, 2008 Well i thought it was sorted after the checks above and OD would engage at any speed above 30 as expected. But after a trip out yesterday and today its back to its old habits of surging and having to be above 55mph. It makes sense with the oil pump being an issue as you need the top end speed to get it to work. Also if you are going too slow ie >30 but < 55 and switch the OD on - nothing happens until you turn if off then it will surge IN then off again, is this becasue as the OD is turned off it closes the bypass valve and momentarily there is enough hydraulic pressure there to engage it. thoughts Quote Link to comment Share on other sites More sharing options...
western Posted April 12, 2008 Share Posted April 12, 2008 sounds like either the solenoid is playing up or a fault in the ECU box. Quote Link to comment Share on other sites More sharing options...
JST Posted April 12, 2008 Author Share Posted April 12, 2008 sounds like either the solenoid is playing up or a fault in the ECU box. ???? really I follow Daivds logic in that the pump etc needs to be working at a faster speed in order to get the system to engage. if it was the ECU then surely it wouldn't let the OD engage at all? Everything with it seems to work ie red light comes on if your less than 30mph and it disengages it if you drop below 20mph and light comes on (on the rare times it works properly), light doesn't come on when above 30 and switch pressed as you would expect. If its the solenoid how come it always then engages at 55mph? to me it sounds like it needs to be doing that speed to get the pump to push through sufficient fluid to get it to work (ie engage) Quote Link to comment Share on other sites More sharing options...
western Posted April 12, 2008 Share Posted April 12, 2008 maybe not then, so just ignore me Quote Link to comment Share on other sites More sharing options...
101sean Posted April 12, 2008 Share Posted April 12, 2008 Sound likes oil pump, solenoid valve or relief valve leaking past requiring high revs to overcome the internal spring pressure of the clutch. I haven't extracted them in my unit so can't say what the problem may be (needs a special spanner making up to do it). Quote Link to comment Share on other sites More sharing options...
JST Posted April 13, 2008 Author Share Posted April 13, 2008 Sean - do you think using a thicker oil would help or hinder? Quote Link to comment Share on other sites More sharing options...
Steve Hiatt Posted April 13, 2008 Share Posted April 13, 2008 The UK oil Gear Vendors recommend for the Laycock unit is castrol TAF-X, fully synthetic 75W-90 Quote Link to comment Share on other sites More sharing options...
101sean Posted April 13, 2008 Share Posted April 13, 2008 The UK oil Gear Vendors recommend for the Laycock unit is castrol TAF-X, fully synthetic 75W-90 That sounds a lot thicker than ATF but may be worth a try for diagnostics. Have a look here http://www.volvoclub.org.uk/faq/Transmissi...asicDiagnostics Also even better http://www.buckeyetriumphs.org/technical/jod/JOD1/JOD1.htm The set up on the Type J shown on the sites is the same as the Defender but without the modern electronics. Also recommends 80W90! Quote Link to comment Share on other sites More sharing options...
JST Posted April 14, 2008 Author Share Posted April 14, 2008 Cheers for the info and links, i will print them out and have a look through Quote Link to comment Share on other sites More sharing options...
JST Posted April 17, 2008 Author Share Posted April 17, 2008 OD is working like a dream today exactly as it should, and i havent don't anything to it yet! Now i am confused. Quote Link to comment Share on other sites More sharing options...
TJ101 Posted April 17, 2008 Share Posted April 17, 2008 Mmm, James,, Do you not think its time for a new one ,, Truck i mean What with funny O/Drive, and rear axle etc Quote Link to comment Share on other sites More sharing options...
JST Posted April 17, 2008 Author Share Posted April 17, 2008 nah road tax is too much i will run these into the ground (repeatedly probably) Quote Link to comment Share on other sites More sharing options...
western Posted April 17, 2008 Share Posted April 17, 2008 could have been a slightly sticking solenoid then or just dirty contacts. Quote Link to comment Share on other sites More sharing options...
JST Posted April 17, 2008 Author Share Posted April 17, 2008 i reckon its a partial blockage of the oil passage or similar, its currently dislodged when it goes back in the way i dont have enough oil Pressure unless over 55mph. contacts and solenoid were checked and cleaned as per your original suggestion. Quote Link to comment Share on other sites More sharing options...
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