reb78 Posted May 27, 2019 Share Posted May 27, 2019 Its a piston I think with an o ring. Definitely worth checking but I am not sure the OD needs oil pressure in its rest/off position. Quote Link to comment Share on other sites More sharing options...
western Posted May 27, 2019 Author Share Posted May 27, 2019 Piston & O ring are fine as is the relief valve parts. IIRC the 4 long springs move the brake cone from engaged to disengage position Haven't opened the unit up yet, been busy doing garden clearing work here at home Quote Link to comment Share on other sites More sharing options...
Snagger Posted May 27, 2019 Share Posted May 27, 2019 Which position did you say it's slipping in? Quote Link to comment Share on other sites More sharing options...
western Posted May 27, 2019 Author Share Posted May 27, 2019 Slipping in when disengaged giving me no drive & occasionally wouldn't transmit drive when engaging, it worked OK on the drive up to wiltshire a week or so ago Quote Link to comment Share on other sites More sharing options...
reb78 Posted May 27, 2019 Share Posted May 27, 2019 Its slipping at rest. If it wasnt it would be driveable. I am womdering if the cylinder the solenoid sits in is worn and letting pressure by when the OD is disengaged perhaps. Just enough to give enough pressure to pull the cone from the rest position. Quote Link to comment Share on other sites More sharing options...
western Posted May 27, 2019 Author Share Posted May 27, 2019 I haven't removed the solenoid yet, I'll pop it off tomorrow morning & take some photo's I have my old solenoid & a spare. Quote Link to comment Share on other sites More sharing options...
reb78 Posted May 27, 2019 Share Posted May 27, 2019 (edited) IIRC - Neil tried new seals and then a new solenoid on that unit. Thats why I am wondering about the bore it sits in. Edited May 27, 2019 by reb78 1 Quote Link to comment Share on other sites More sharing options...
western Posted May 27, 2019 Author Share Posted May 27, 2019 I can compare the bore with my original unit in morning Quote Link to comment Share on other sites More sharing options...
V8 Freak Posted May 28, 2019 Share Posted May 28, 2019 I've pretty much replaced all but the case itself at one point... Rich is right, the oil pressure isn't used when not in Overdrive mode as far as I can work out... Therefore, the springs are important to keep the pressure on the brake cone and give you normal drive. When the solenoid is activated, it pumps oil to move the brake cone to lock the internals and force the drive through the three planetary gears. It should just be clamping pressure from the springs needed for normal drive. So unless oil pressure is getting by the solenoid and acting against the spring pressure, it "should work". Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 28, 2019 Share Posted May 28, 2019 That's my basic understanding of these work too, the springs do the had work when disengaged. Only gleaned from my Domite days when I was younger. Quote Link to comment Share on other sites More sharing options...
western Posted May 28, 2019 Author Share Posted May 28, 2019 Thats as I thought to, Cheers for the extra info, pretty sure we can cure it. Quote Link to comment Share on other sites More sharing options...
V8 Freak Posted May 28, 2019 Share Posted May 28, 2019 Although already under pressure when fitting the nuts to the spring retainers, it may be worth trying spacers / washers under the nuts to add a little more spring pressure and see if it make the difference you are looking for? Quote Link to comment Share on other sites More sharing options...
western Posted May 28, 2019 Author Share Posted May 28, 2019 Tried to remove the soleniod but I haven't got a spanner thin enough or the correct size [26mm] to fit between the casing & solly body, so it'll have to wait. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 28, 2019 Share Posted May 28, 2019 Domite should have been Dolomite, sigh. 1 Quote Link to comment Share on other sites More sharing options...
Snagger Posted May 28, 2019 Share Posted May 28, 2019 9 hours ago, V8 Freak said: Rich is right, the oil pressure isn't used when not in Overdrive mode as far as I can work out... Therefore, the springs are important to keep the pressure on the brake cone and give you normal drive. When the solenoid is activated, it pumps oil to move the brake cone to lock the internals and force the drive through the three planetary gears. It should just be clamping pressure from the springs needed for normal drive. So unless oil pressure is getting by the solenoid and acting against the spring pressure, it "should work". That makes sense - it would be a fail-safe to leave the car operable if there was an electrical or pump failure. I'd be surprised if enough oil could get pas a small leak on the o-ring to do this. Does it go into a sealed actuator? In that case, a small leak would retain pressure and I can see how a gradual slackening on the clutch pack would occur. I would have been looking for a problem with the clutch pack linings or the spring pressures, but I'm no engineer and have never used, let alone rebuilt, one of the these. Quote Link to comment Share on other sites More sharing options...
reb78 Posted May 28, 2019 Share Posted May 28, 2019 I agree but the clutch pack and springs are new on that unit ^^^^^. Quote Link to comment Share on other sites More sharing options...
western Posted May 28, 2019 Author Share Posted May 28, 2019 I have a boroscope thing which I can have a look inside at the spring. Quote Link to comment Share on other sites More sharing options...
Snagger Posted May 29, 2019 Share Posted May 29, 2019 9 hours ago, reb78 said: I agree but the clutch pack and springs are new on that unit ^^^^^. "New" doesn't guarantee "good", as we know from certain brands (and unbrands). Even genuine stuff sometimes has flaws, though less common, and there is the possibility of wrong spec replacement parts, given how long the overdrive was in production - a different suffix unit might have subtly different components. There's no way to tell without close examination of the parts, but I wouldn't rule them out. Quote Link to comment Share on other sites More sharing options...
Snagger Posted May 29, 2019 Share Posted May 29, 2019 8 hours ago, western said: I have a boroscope thing which I can have a look inside at the spring. That'll reveal if it's broken, but will give no information on the pressure it's applying, especially as temperature increases. Ideally, it needs testing of its stiffness. Quote Link to comment Share on other sites More sharing options...
soutie Posted May 29, 2019 Share Posted May 29, 2019 Have you had a look at the J type overdrive write up here to see if that explains what is going on? https://www.buckeyetriumphs.org/gearbox Quote Link to comment Share on other sites More sharing options...
western Posted May 29, 2019 Author Share Posted May 29, 2019 Boroscope exam this morning didn't show much, all 4 springs look intact but I think further dismantling will be needed at the weekend, I'll have a read of the link, cheers all for the suggestions/advice so far Quote Link to comment Share on other sites More sharing options...
western Posted June 2, 2019 Author Share Posted June 2, 2019 Managed to get some time to open up this overdrive, it's quite clean inside, the 4 springs are the same length as the 4 from my previous unit, haven't found any broken parts, the friction material is intact on both sides, the inner & outer brake ring faces look fine, only thing I'm not sure of the brake rings & cone friction faces were all coated inPAS fliud is that correct ? took these photo's & a short video, only thing I can think of is the 2 piston seals the 4 springs may need changing, can get those from Devon4x4. Quote Link to comment Share on other sites More sharing options...
western Posted June 2, 2019 Author Share Posted June 2, 2019 Quote Link to comment Share on other sites More sharing options...
reb78 Posted June 2, 2019 Share Posted June 2, 2019 The whole lot runs bathed in ATF Ralph so thats normal. 1 Quote Link to comment Share on other sites More sharing options...
western Posted June 2, 2019 Author Share Posted June 2, 2019 Thanks for confirming, one less thing to worry about, it wasn't 100% sure, the video should be watchable now. VID_20190602_154742.mp4 Quote Link to comment Share on other sites More sharing options...
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