Retroanaconda Posted February 1, 2015 Share Posted February 1, 2015 Hi gents. My Series III has a noisy gearbox, sounds like a rumbling bearing to me but thought is ask the collective before dropping it out. I filmed a video going though the gearbox with the transfer box in neutral to show the noise in action. It's clearly audible above the engine tickover (which is fairly loud due to non-existing soundproofing): Any thoughts? Quote Link to comment Share on other sites More sharing options...
Boydie Posted February 2, 2015 Share Posted February 2, 2015 Well if its a derivative of the R380 then the only bearing subjected to any serious turning motion during idle is the front input shaft bearing. The output shaft being on the same plane as the input shaft (the input fits inside the output) is stationary, so it cannot be the output shaft bearing and the idler shaft will also be stationary as no gear has been selected so it cannot be the two idler shaft bearings. The only other bearing is located in the splitter plate and that again carries the output shaft supporting the union of the two shafts, ergo I think you have a worn input shaft bearing or a cactus clutch race bearing. Quote Link to comment Share on other sites More sharing options...
ejparrott Posted February 2, 2015 Share Posted February 2, 2015 Pre-dates the R380 by some considerable time. It's not layshaft bearings, one of my old boxes threw the layshaft bearings and that was silent in top and top/OD. You're looking at either the tail end bearing or the input bearing, if it is a bearing Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted February 2, 2015 Share Posted February 2, 2015 Gearbox, I can't help with, but I bet you now wished you had lubricated that clutch pedal! :-) Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted February 2, 2015 Author Share Posted February 2, 2015 Thanks gents. I suspect input bearing is a good candidate. When I dip the clutch with the box in neutral you can hear whatever is rumbling coast to a stop, and in theory that has to be the input shaft as it'll be the only thing moving when the engine is idling. I'll obtain a good second hand box and swap it in, then I can strip this one down at my leisure and see what the problem is. Clutch pedal definitely needs some oil on it! Quote Link to comment Share on other sites More sharing options...
Snagger Posted February 2, 2015 Share Posted February 2, 2015 I think it's the transfer box output shaft gear. Mine has always done that, when new from LR years ago, after its extensive rebuilt in 2004 and still after I installed lower low range gears a few years ago. It's either that or my hand brake chattering, and it sounds much like that noise and also increases with gear, smooth in first but chattering more the higher the gear selected but quietening down when the revs increase. The big sliding gear on that shaft s very loose on the splines and wobbles around quite a bit when not under load and not turning fast enough to be subject to gyroscopic forces. Phil will probably know what it is. Quote Link to comment Share on other sites More sharing options...
Serious Series Posted February 2, 2015 Share Posted February 2, 2015 When at idle the layshaft is also turning as it is permanently coupled to input shaft , thus other gears on mainshaft are also turning just not coupled to drive it. Been going to cut an old box open for ages so that I can make innards viewable for a video showing what turns when ! Quote Link to comment Share on other sites More sharing options...
ejparrott Posted February 2, 2015 Share Posted February 2, 2015 Mine made no noise unless you were in 1, 2 or 3rd, when in fourth there was no load on it so it made no noise. Quote Link to comment Share on other sites More sharing options...
xychix Posted February 5, 2015 Share Posted February 5, 2015 Thanks gents. I suspect input bearing is a good candidate. When I dip the clutch with the box in neutral you can hear whatever is rumbling coast to a stop, and in theory that has to be the input shaft as it'll be the only thing moving when the engine is idling. I'll obtain a good second hand box and swap it in, then I can strip this one down at my leisure and see what the problem is. Clutch pedal definitely needs some oil on it! if its the input bearing I'd expect the problem in gear AND in neutral with a depressed clutch. Quote Link to comment Share on other sites More sharing options...
Snagger Posted February 5, 2015 Share Posted February 5, 2015 There will be a light chatter at idle because of the backlash in all the gears - apart from reverse, they're all permanently meshed and they all turn, even in neutral, if the clutch is engaged (no pressure on the pedal). That is not a sign of a bad primary pinion bearing. If the chatter dies way as the revs are raised, then that'll prove the above - a bad bearing won't quieten down. If like me you have a noise when driving in 1st,2nd and 3rd but not in 4th, then you have lay shaft bearing issues. That is far more likely because these bearings are smaller and, being lower down, are more prone to swarf ingestion. Unless you have run the box dry, then primary pinion and main shaft rear bearing wear is unlikely, though not impossible, and you'd have problems elsewhere too anyway. Quote Link to comment Share on other sites More sharing options...
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