oldbuffer Posted November 7, 2011 Share Posted November 7, 2011 I'm new to the world of Caterhams and have just purchased a new Supersport (140 Sigma) with limited slip diff. I have a knock coming from the transmission when there is any "slack" in it i.e. changing gear. It sounds just like a door knocker! Any advice please or is this a case of "They all do that Sir". Link to comment Share on other sites More sharing options...
Eugene Posted November 7, 2011 Share Posted November 7, 2011 Don't think it should do that... but I have a 'very' old 7, so am not up with the modern ones... However, it is not usual to have such noises from the drive-train. Can you locate it further? Gearbox, prop-shaft, rear axle, etc??? Link to comment Share on other sites More sharing options...
noet Posted November 7, 2011 Share Posted November 7, 2011 "The knock" you experience is probably coming from the diff and is caused by the backlash. What is backlash? When you turn the pinion on your differential it will turn a specific amount of space before it actually contacts the the ring gear to turn your axles. If you have too little backlash the pinion is jammed into the ring gear and this will produce a lot of friction and heat and will lock up your rear axle. It will not turn freely. If you have too much backlash the pinion and ring gear will be too far apart and this will allow the gears not to mess properly and with the force of your motor will chip and destroy the teeth of the gears. This will cause excessive whining and will eventually destroy your axle again. Link to comment Share on other sites More sharing options...
DJ. Posted November 7, 2011 Share Posted November 7, 2011 As it's a new car, I should take it back to Caterham to check it out. It could be backlash, or something moving in the drivetrain and hitting the chassis, or even a bolt that hasn't been torqued up. Duncan Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted November 7, 2011 Share Posted November 7, 2011 A local Sevener with a BMW LSD is getting his third diff fitted this week on a 7 month old car ! Link to comment Share on other sites More sharing options...
oldbuffer Posted November 7, 2011 Author Share Posted November 7, 2011 Quoting noet: "The knock" you experience is probably coming from the diff and is caused by the backlash. What is backlash? When you turn the pinion on your differential it will turn a specific amount of space before it actually contacts the the ring gear to turn your axles. If you have too little backlash the pinion is jammed into the ring gear and this will produce a lot of friction and heat and will lock up your rear axle. It will not turn freely. If you have too much backlash the pinion and ring gear will be too far apart and this will allow the gears not to mess properly and with the force of your motor will chip and destroy the teeth of the gears. This will cause excessive whining and will eventually destroy your axle again. Thank you all. The diff appears to me be the problem. I'll speak to After Sales and see what transpires. Link to comment Share on other sites More sharing options...
myothercarsa2cv Posted November 8, 2011 Share Posted November 8, 2011 Only 3 in 7 months? At least its an improvement... I had 4!!! Link to comment Share on other sites More sharing options...
Sheds Moderator Posted November 8, 2011 Share Posted November 8, 2011 It's a bit of a "they all do that Sir". Mine did it but it was ex race and had been diven a hard time. LSDs are noisier than open diffs (mine was anyway). The cure for me was to drive it im a very positive fashion - if you are accelerating, accelerate! Part throttle light load, say at low speed over poorly surfaced roads, was painful. Every bump had the diff clonking as there wasn't enough load to keep it at one end of the backlash. On good roads it was fine, just a clonk as you came off the gas and back on again when changing gear. Link to comment Share on other sites More sharing options...
noet Posted November 8, 2011 Share Posted November 8, 2011 When rebuilding the car I change from 6 speed manual to seqential gearbox. That made a difference. From the usual noise caused by normal backlash, - its now close to nothing in both upshift and downshift. Pinion and ring gear are nearly always engaged due to the quick gear shifts. Link to comment Share on other sites More sharing options...
coolbop Posted November 14, 2011 Share Posted November 14, 2011 Hi, My car is currently back in Dartford with the same problem. They are changing the diff today which will be it's third diff. I get a clonk whenever I come on or off the accelerator or when changing gear. I've not heard this noise on the two other cars I've driven although I think they were open diffs. The odd thing is, the noise appears to come from the nearside. Also, if I rock the car backwards and forwards with the handbrake on, I get a similar sound. I can't be sure it's the same sound but if it is, doesn't that eliminate the diff? Ian Link to comment Share on other sites More sharing options...
Sheds Moderator Posted November 14, 2011 Share Posted November 14, 2011 If the handbrake is on and it knocks, it isn't the diff. The diff is stationary when the brakes are on, it has to be. Diff noise is when you have it in gear and either driving it with the engine or turning a road wheel back and forth makes it knock. Link to comment Share on other sites More sharing options...
oldbuffer Posted November 14, 2011 Author Share Posted November 14, 2011 Quoting coolbop: Hi, My car is currently back in Dartford with the same problem. They are changing the diff today which will be it's third diff. I get a clonk whenever I come on or off the accelerator or when changing gear. I've not heard this noise on the two other cars I've driven although I think they were open diffs. The odd thing is, the noise appears to come from the nearside. Also, if I rock the car backwards and forwards with the handbrake on, I get a similar sound. I can't be sure it's the same sound but if it is, doesn't that eliminate the diff? Ian My clonking isn't as bad as it was or should I say it doesn't clonk as much. Driving it more positively has made a difference but it's still not acceptable. There is obviously a problem with the LSD's - reading others experiences. I have now clocked up 600 + miles and hope to reach the 1000 miles this week and hopefully get it in for it's first service v. soon (before the salt is on the roads). Hopefully it will be resolved on the service?? Link to comment Share on other sites More sharing options...
charlie_pank Posted November 14, 2011 Share Posted November 14, 2011 If you get it rocking back and forth with the handbrake on, it isn't the diff. Perhaps it's your rear brake pads moving around in the calipers? Link to comment Share on other sites More sharing options...
coolbop Posted November 14, 2011 Share Posted November 14, 2011 Quoting charlie_pank: If you get it rocking back and forth with the handbrake on, it isn't the diff. Perhaps it's your rear brake pads moving around in the calipers? I was thinking along those lines - except if that was the case, you wouldn't expect it to make the noise when on and off the throttle when driving? My original diff was the BMW diff with sintered plates. This made a horrific noise - whenever pulling away or going round a corner you would get a series of knocks - loud enough to make people on the street turn and look. When I first drove it away from Caterham I went round the first roundabout and took it straight back because I though the back axle was about to fall off. Now it's been changed for for a carbon plated diff it doesn't do that any more, it's the same noise, just it only happens as I go on and off the throttle. Link to comment Share on other sites More sharing options...
charlie_pank Posted November 15, 2011 Share Posted November 15, 2011 2 separate problems? Link to comment Share on other sites More sharing options...
coolbop Posted November 15, 2011 Share Posted November 15, 2011 Yep, could well be. In fact the handbrake thing isn't a problem - I just thought if it was the same noise, it couldn't be coming from the diff. But I think now it's probably a red herring and it is probably diff noise. Ian Link to comment Share on other sites More sharing options...
Michael G Posted November 15, 2011 Share Posted November 15, 2011 My experience is similar to that of Coolbop's. The clonks - more like bangs - from my original LSD were real head-turners. My replacement carbon plated diff is very much quieter; knocks when changing gear and when going on or off the throttle. I understand that this is as good as it is gets. Whilst the noise is now reduced to nuisance level rather than being a problem, I have to say that had I known when speccing my car that an LSD was going to commit me to listening to this knocking for the next x years, then I almost certainly would have gone for an open diff instead. Link to comment Share on other sites More sharing options...
2slo Posted November 15, 2011 Share Posted November 15, 2011 My replacement carbon lsd has become quieter in the 1000 or so miles since it replaced the original very noisy one which was fitted to the new car. As mentioned above, Caterham know some diffs have problems and, from my experience, sorted it out straight away. Link to comment Share on other sites More sharing options...
coolbop Posted November 16, 2011 Share Posted November 16, 2011 Well, I got my car back from Caterham yesterday and unfortunately it's much the same. Caterham have described it as a tapping noise, and it does sometimes make this noise, but it also often makes a loud knock or clonk, particularly when changing gear. I'm coming to the same conclusion as MichaelG - I'd rather have an open diff than put up with that noise. Link to comment Share on other sites More sharing options...
6speedmanual Posted November 16, 2011 Share Posted November 16, 2011 Coolbop Have you checked the torque on the A frame bush fixing below the de Dion tube? If that is loose it will knock as it reacts the braking and driving forces. Peter Link to comment Share on other sites More sharing options...
coolbop Posted November 16, 2011 Share Posted November 16, 2011 Hi Peter, I haven't although I would have hoped that CC would have eliminated something like that? Would that bush had to have been removed and replaced/retorqued when they replaced the diff? Link to comment Share on other sites More sharing options...
charlie_pank Posted November 16, 2011 Share Posted November 16, 2011 Have you done enough accel/brake/coasting/downhill/uphill/stationary/in-gear/in-neutral tests to be sure that it's the diff? Link to comment Share on other sites More sharing options...
6speedmanual Posted November 16, 2011 Share Posted November 16, 2011 Coolbop Not necessarily. the diff can be extracted through the A-frame. A mechanic instructed to "change the diff" will do that. May not check anything else. Dead easy to check. Just need two scockets 3/4" to check if it's tight. (3/4" and 19mm will also do if they are in one socket set). If it is found to be loose (or not really tight), I suggest taking the nut off altogether, apply loctite, reinstalling and re-torque to correct figure. Peter Link to comment Share on other sites More sharing options...
coolbop Posted November 16, 2011 Share Posted November 16, 2011 Hi Peter, I checked that bolt and it's well tight. I also watched it while rocking the car back and forth on the handbrake and it doesn't move. In fact the noise seems to be coming from the calipers so it's probably the sound of the pads moving around so that was probably a red herring! Thanks Ian Link to comment Share on other sites More sharing options...
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