vulcan bomber Posted September 27, 2019 Share Posted September 27, 2019 On 9/26/2019 at 6:13 PM, western said: I was a bit worried on the pull away from home, but got drive instantly, glad it's working & hoping it'll make long drive a bit quieter, may go for a longer run tomorrow to get it nicely warmed up, sticking with the standard sump plate at the moment, hopefully Mr VB is sorting out a spacer or bigger sump to increase the fluid capacity, I don't really want to remove the transfer box big sump for the M. O. overdrive sump to go on. Still need some bolts to match as the supplied ones don't match the gkn threads I'm working on it slowly Ralph, along with a mountain of other stuff. Bolts are 1/4 UNF just so you know. Quote Link to comment Share on other sites More sharing options...
western Posted September 27, 2019 Author Share Posted September 27, 2019 Thanks for the bolt info, look forward to seeing the result of the increased fluid capacity. Quote Link to comment Share on other sites More sharing options...
western Posted September 29, 2019 Author Share Posted September 29, 2019 Had a day out yesterday with some local LR friends, Overdrive behaved very well, could happily cruise at 65 + on A30, seems to be working correctly. 1 Quote Link to comment Share on other sites More sharing options...
western Posted October 11, 2019 Author Share Posted October 11, 2019 completed about 270 miles since the OD was refitted, occasionally it slips disengaged when cold but don't understand why as the 4 new springs should be keeping it in the disengaged position, it can & has left me with no or very little drive at traffic lights or moving of from junctions/turning onto another road. when engaging/disengaging it does those operations fine & is working Ok when engaged so far without slipping. Quote Link to comment Share on other sites More sharing options...
reb78 Posted October 11, 2019 Share Posted October 11, 2019 (edited) I think pressure is getting by the solenoid when at rest Ralph. I would be tempted to try the back section of your old OD on the rest of this one from Neil. It must be pressurising when it shouldnt be. I dont think it is the solenoid as that one on it was new. Edited October 11, 2019 by reb78 Quote Link to comment Share on other sites More sharing options...
western Posted October 11, 2019 Author Share Posted October 11, 2019 I'll swap one of my solenoids on to it & see what happens, I cannot undo the 3 caps on the rear part of my original unit so cannot access the circular filter to clean it & the fluid galleries The insides of the fitted unit were all spotless clean for the rebuild as we're the 2 filters, new seals on pistons as well. Quote Link to comment Share on other sites More sharing options...
reb78 Posted October 12, 2019 Share Posted October 12, 2019 (edited) My theory is a small amount of wear in the channel that the solenoid sits in and so the seals on the solenoid cant work properly and let oil pass through when it it is not supposed to be engaged which is causing the cone to move at rest but not engage either way. Do you have a tool for those caps? It might be worth us making something up but they must come undone. Edited October 12, 2019 by reb78 1 Quote Link to comment Share on other sites More sharing options...
western Posted October 12, 2019 Author Share Posted October 12, 2019 I managed to undo the caps in the OD I bought from V8 freak, used an adjustable angle grinder disc change spanner with 2 pegs on it, but it's not the right size pegs, can't undo my original unit with it, the caps are very tight, May try to obtain some new seals if possible for the solenoids. Quote Link to comment Share on other sites More sharing options...
V8 Freak Posted October 12, 2019 Share Posted October 12, 2019 That was a new solenoid from the OD refurb company up T'north... Such a freekin annoying OD.. Why can't it just work with all them parts new in it ! 1 Quote Link to comment Share on other sites More sharing options...
western Posted October 12, 2019 Author Share Posted October 12, 2019 I'm thinking the same, even more after its super clean inside & new seals on the pistons. Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted October 13, 2019 Share Posted October 13, 2019 Tools for getting them caps undone is on my list as well chaps. 1 Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted October 13, 2019 Share Posted October 13, 2019 I suppose it is possible there is a hairline crack in the casing ? 1 Quote Link to comment Share on other sites More sharing options...
lo-fi Posted October 13, 2019 Share Posted October 13, 2019 Have you checked that the valve bores are true, round and parallel too? 1 Quote Link to comment Share on other sites More sharing options...
western Posted October 13, 2019 Author Share Posted October 13, 2019 The 2 bores for the pistons looked fine similar the the bores in my original unit, the only thing that touch the bore sides is the O ring seals which are new, the pistons are not pressurised in the disengaged position. The is no oversize pistons or seals for them, It works OK when engaged & the piston have pressure. Quote Link to comment Share on other sites More sharing options...
lo-fi Posted October 13, 2019 Share Posted October 13, 2019 I was just thinking that as you've changed everything else, the housing is looking like it might be worthy of scrutiny. If I understand operation correctly, springs hold the cone clutch disengaged, then to engage it there's a solenoid that passes oil from the pump via a filter to those two pistons, forcing the cone into engagement, which transmits drive via the epicyclic gears? What I can't figure out is what locks input to output when the cone clutch is disengaged? You mentioned a brake ring in the first post, but I can't see how that's actuated and assume that's something to do with it? Quote Link to comment Share on other sites More sharing options...
reb78 Posted October 13, 2019 Share Posted October 13, 2019 The brake ring is static. The cone clutch has two sides covered with friction material. In one position the clutch is held static against the brake ring and in the other it sits against the driving gear. The oil pressure moves the pistons out, as you say, and that moved the clutch and therefore engages/disengages drive. I think it is the rear housing too. But my gut feeling is it is the bore that the solenoid sits in. Quote Link to comment Share on other sites More sharing options...
lo-fi Posted October 13, 2019 Share Posted October 13, 2019 Ah, thanks. In which case I'd bet on that too. Maybe a hairline crack as Bowie suggests, a little porosity right in the wrong place, or even a machining error. I can't see what else could cause loss of drive, all other things being equal. There must be a pressure relief valve from the pump? Is oil pressure needed for anything other than actuation? I'm thinking take the entire hydraulic circuit out of the equation by removing the relief valve spring or outer pump gear (if practical). If it drives fine, you know there's no mechanical fault and the circuit is pressurising when it shouldn't. Quote Link to comment Share on other sites More sharing options...
western Posted October 13, 2019 Author Share Posted October 13, 2019 Managed to fully strip & clean the rear part of the OD casing from my original unit, the piston bores look OK, as does the reciprocating pump parts & relief valve bores & associated parts, the solenoid bore looks OK & all the spare sollys x 3 work when powered up. need to get some new seals for the 2 pistons, a new large filter & seal, Some photos Quote Link to comment Share on other sites More sharing options...
landroversforever Posted October 13, 2019 Share Posted October 13, 2019 If you’re considering the possibility of cracks in the housing/bores, it’s probably worth having or doing some NDT like dye-pen testing. I assume it something you’d have access to at work Ralph? For those not in the know, with dye-pen (dye penetrant) you douse it in a dye which can wick into tiny imperfections. The object is then cleaned and sprayed with a developer which is like a chalky substance and you can then see the dye soak out of any imperfections. Quote Link to comment Share on other sites More sharing options...
western Posted October 13, 2019 Author Share Posted October 13, 2019 Pretty sure neither unit have any cracks in the piston or solenoid bores, going to get my original rear body part to a working state & swap it with the currently fitted rear body. then see how it behaves if that doesn't cure the disengaged slipping, I'll most likely remove it & go back to normal transfer box set up. Quote Link to comment Share on other sites More sharing options...
Snagger Posted October 13, 2019 Share Posted October 13, 2019 I would expect the unit to fail safe to disengaged, so any oil pressure problem, including leaks, would not cause disengaged slipping. It still seems like a brake pack preload problem, either the springs to short, brake pack too thin or something in the casing or on the shafts that is worn and allowing too much endfloat. Quote Link to comment Share on other sites More sharing options...
reb78 Posted October 13, 2019 Share Posted October 13, 2019 34 minutes ago, Snagger said: I would expect the unit to fail safe to disengaged, so any oil pressure problem, including leaks, would not cause disengaged slipping. It still seems like a brake pack preload problem, either the springs to short, brake pack too thin or something in the casing or on the shafts that is worn and allowing too much endfloat. You would think, but I dont think thats the case. The clutch is new and thicker than the one that came off, this is the third (?) set of springs tried on it. Quote Link to comment Share on other sites More sharing options...
western Posted October 13, 2019 Author Share Posted October 13, 2019 I've ordered a new circular filter & gasket & a gasket seal kit from https://www.overdrive-repairs.co.uk/ as I'm not happy the existing filter is clean enough in my original unit & new piston seals from devon4x4 .lets see what happens once the rebuilt rear case from my original OD is fitted to the in use OD. Quote Link to comment Share on other sites More sharing options...
Snagger Posted October 13, 2019 Share Posted October 13, 2019 1 hour ago, reb78 said: You would think, but I dont think thats the case. The clutch is new and thicker than the one that came off, this is the third (?) set of springs tried on it. I know, but they’ll be pattern springs and it’s also why I suggested a worn bearing seat. Quote Link to comment Share on other sites More sharing options...
western Posted October 13, 2019 Author Share Posted October 13, 2019 Don't know where devon4x4 have the springs made, but they look exactly like my original OD springs in diameter/length/wire diameter, the cone clutch bearing in each unit is in ATF all the time the vehicle is running so it can't run dry & they feel good when rotated by hand with no unwanted play. Quote Link to comment Share on other sites More sharing options...
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