robgeev Posted May 17, 2007 Report Share Posted May 17, 2007 A type overdrive, fine when on shortish journeys, but after a good run tendency to drop out. Any ideas? Rob. Quote Link to post Share on other sites
Rhodri Posted May 17, 2007 Report Share Posted May 17, 2007 If it is not electrical then I would guess that the pump is not holding its pressure, either it is worn or the ball valve is worn. This can be checked with a pressure guage. If you are using 30 weight oil then a heavier oil may help by not thinning so much. If you are using a detergent oil then perhaps it is foaming when hot and can not hold pressure. An oil change is the easiest thing to do- trust the level is up to the mark? Quote Link to post Share on other sites
robgeev Posted May 17, 2007 Author Report Share Posted May 17, 2007 New EP90, I assume gear oil is unlikely to foam? Cheers. Rob. Quote Link to post Share on other sites
Phil Kirk Posted May 17, 2007 Report Share Posted May 17, 2007 Rob, I have heard good reports of Overdrive Repair Services, they are based in Sheffield. I have not used them but maybe worth a call. Good Luck Phil Quote Link to post Share on other sites
Richard Crawley Posted May 17, 2007 Report Share Posted May 17, 2007 New problem since you changed to oil or old problem you tried to cure by changing the oil? Quote Link to post Share on other sites
robgeev Posted May 17, 2007 Author Report Share Posted May 17, 2007 Old problem I was hoping had gone away, short runs, no worries (20 miles or so),long runs-annoying drop out. Oil was changed whilst we serviced the car hoping it was an oil quality problem. How about synthetic ATF? It's all we use in Land Rovers now, any thoughts? Rob. Quote Link to post Share on other sites
Richard Crawley Posted May 17, 2007 Report Share Posted May 17, 2007 As Rhodri has already pointed out, it seems you may have a problem with pressure loss when the oil reaches operating temperature. I assume you’ve checked the solenoid operation & adjustment? Also check the operation & adjustment of the actuating valve & re-seat the ball; if that doesn’t work then it could be problems with the pump or even the oil galleries blocked with sludge. I assume you drained the gear box oil at the same time & thoroughly cleaned the filter in the bottom of the O/drive unit? Before it’s resto, my A type would drop in & out to the point of being unusable, particularly on a light or trailing throttle. There was no quick & easy cure & the muck that came out when I stripped it had to be seen to be believed + the pump piston, rings & bore were totally knackered. Although it may give some temporary relief, I don’t think changing the type of oil you use is the answer as you may do more harm than good & I certainly would not use synthetics. I still only use EP 90 as originally recommended (but make sure it’s GL4 spec. & not more the modern cocktails!) & both the box & O/D are perfect now. If doing the above doesn’t cure it, I think you may have to resign yourself to removing the unit for a thorough overhaul. Quote Link to post Share on other sites
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