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Dec 21, 2017 12:49:22 GMT
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Greetings all, Further to my post a couple of months ago, where my RRC is eating gear selector linkage bushes, I contacted Dave at Ashcrofts, who has suggested that the box is overheating, softening the nylon of the bush, and allowing the gearchange action to mash it up. He's suggested putting a temp strip on the side of the box to see what temperature its running at, not easy since the box is no longer in the car, and changing RRC boxes is a job that I like to avoid at all costs, since its the most difficult one on the car! Anybody got any thoughts on what would cause a box to overheat? It doesn't do offroading, the driver (me) doesn't smash it from gear to gear, it doesn't usually go above 60mph, andf although I tow with it a fair bit, thats pretty gentle normally too. My best guess ATM is that theres a blockage in the internal filter which is preventing a good oil flow, but I would expect this to manifest itself as bearings/selectors failing, not just a nylon bush, and its not easy to check because Land Rover in their wisdom put the filter in the bottom of the casing which means you have to dismantle the whole box to get at it! Anybody any thoughts?  |
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alecf
Part of things
Posts: 424 
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Dec 21, 2017 13:04:15 GMT
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plenty of folk race using the r380 without oil coolers and ive not heard of one overheating, even after some serious abuse.
I would say its an oil flow issue and needs a strip down.
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Dec 22, 2017 11:33:14 GMT
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Yeah, but I still don't see why its only the bush thats failing, I should have said I've replaced three in 18 months and they've all failed to the degree shown in the pic, the last one managed six weeks!
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moglite
Part of things
Posts: 815
Club RR Member Number: 144
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Dec 22, 2017 12:54:29 GMT
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Have you got a sump-guard ?
It has been known for those to upset the air-flow under the vehicle and therefore overheating the grearbox.
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1967 Morris Oxford Traveller
1979 Toyota LandCruiser BJ40
1993 Daimler Double Six
2007 Volvo XC70 2.4D
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Darkspeed
Club Retro Rides Member
Posts: 4,885
Club RR Member Number: 39
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Dec 22, 2017 13:12:18 GMT
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Have a look at the oil pump and make sure that the filter and the gears are in good condition - The death of the earlier LT77's in the RWD configuration was accelerated by little bits of metal embedding into the fibre gears rounding all the teeth off and losing oil flow. Also the flow paths were formed by a couple of bushes and if these wear the oil flow is also reduced. Cant say its the same on the later and the 380 as there were plenty of upgrades but worth a look.
When its together if you have an mechanical electrical type oil gauge a nice trick is to have a drain plug drilled for a 2nd temp sensor and then fit a switch on the dash to swap between engine and gearbox oil temps. You could use the high level plug as well as this will still give the bulk temp and leave the magnet on the drain.
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Last Edit: Dec 23, 2017 17:08:37 GMT by Darkspeed: To change mechanical gauge to electrical - brain and fingers obviously non synchro !
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Dec 23, 2017 15:54:48 GMT
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No sump guard fitted, Looks like its stripdown time then, what fun!
Do like the idea of the temp sender Darkspeed
Thanks all for your advice,
'Yuletide felicitations'
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Dec 27, 2017 16:29:55 GMT
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Like that 2nd temp sensor idea.
If it's definitely an overheating issue then I agree with what's already been said. But are you sure you're replacing the bush correctly, and with a Genuine item rather than aftermarket (if you can get them non-Genuine... I don't know)? I had that bush replaced with a Genuine one on my old Discovery's R380 at about 165k miles and it transformed the gearchange. Stayed perfect for the remaining two years I was driving it.
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1968 Land Rover Series IIA 109in
1992 Fiat Panda Sky
(Previously)
2000 Alfa Romeo 145 Cloverleaf
1998 Land Rover Discovery 300Tdi
1976 Land Rover Series III diesel
1978 Land Rover Series III petrol (in bits)
2003 Ford Transit SWB
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Dec 27, 2017 17:48:01 GMT
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its had genuine, Bearmach and sh*tpart (because I couldn't get anything else at the time, and needed it fixed like yesterday).
Only thing I had noticed when I took the box out is that there appears to be a small gap between the bellhousing and the box itself, so I guess the bellhousing isn't completely 'home', so I don't know if its a resonance setting up which is causing the failure?
Replacing the bush itself isn't a difficult job, it can be done without removing the box, and its not really possible to get it wrong.
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Dec 27, 2017 17:49:11 GMT
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BTW anybody know what temp the box should actually be running at, so I can work out what really is 'overheating?'
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Darkspeed
Club Retro Rides Member
Posts: 4,885
Club RR Member Number: 39
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Dec 27, 2017 21:06:27 GMT
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The oil temp is the only thing that needs to be worried about - same with the engine - because as soon as the temp gets above the bulk oil temp that the lubricant starts to break down thats when the problems start. 120C is a typical maximum and 95 is about a norm.
When my mate did the two oil sensor trick in his rally car he thought the gearbox sensor was broken as in one switch position the gauge was not reading. The oil temp sensor that was working was reading quite steady at 95 and was at around the engine water temp. Quite a shock when he realised that the engine oil sensor did not have an earth on it and it was the gearbox temp he was watching all along. He thought the gearbox would be at 50/60C not at 90-100C.
If its getting above 120C then its overheating - which is why those engine temp tell tale strips are popular.
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