AdC Posted March 9, 2012 Share Posted March 9, 2012 Morning all! Bit of a beginner to all this, but I noticed yesterday a pronounced 'Clunk' when 'taking up the slack' after every gearchange / rolling off, then back on the throttle when in gear. It's definitely different to the first gear engagement "KER-LUNK!!!!!" (I'm happy with that - reminds me of my biking days) but I'm just wondering what the former could be. If anyone's had it (particularly bec / JW owners) I'd be interested to hear more about the issue / a possible fix. Thanks in advance! oh, the clunk appears to be coming from towards the rear of the drivetrain - somewhere below my left elbow. Edited by - AdC on 9 Mar 2012 08:29:34 Link to comment Share on other sites More sharing options...
Picon Biere Posted March 9, 2012 Share Posted March 9, 2012 Its possibly the slack being taken up between the crown wheel and pinion, half shafts and gear box and is down to the tolerances in the drive train. The more miles the car has done the more play there will be in the drive chain. Todd Link to comment Share on other sites More sharing options...
DSL Posted March 9, 2012 Share Posted March 9, 2012 Most likely source is going to be the inline reverse box back lash being taken up If this has just got worse all of a sudden then get it looked at before its goes tits up Get the car up on axle stands, go underneath & try to rotate by hand the opposite sides of the props to confirm its coming from there Link to comment Share on other sites More sharing options...
James_Russell Posted March 9, 2012 Share Posted March 9, 2012 Aren't the Fireblade cars Live Axle? If so, my money is on 'A'-frame bushes. They deteriorate quite quickly and when they are worn out you'll get exactly the symptoms you describe. They're about £4 and 15 minutes to replace. Edited by - James_Russell on 9 Mar 2012 10:13:39 Link to comment Share on other sites More sharing options...
northernmonkey Posted March 9, 2012 Share Posted March 9, 2012 A-Frame bushes - Mine leaks diff oil and rots them through - Last lot lasted 12 months - Gone for some non rubber ones this time and hope they last longer... 10 min job to replace! Link to comment Share on other sites More sharing options...
cskip Posted March 9, 2012 Share Posted March 9, 2012 The A frame bush would be my first thought. It could also be the bearings moving on the halfshaft, assuming that the are not shimmed. Link to comment Share on other sites More sharing options...
Area Representative Golf Juliet Tango Posted March 9, 2012 Area Representative Share Posted March 9, 2012 Like the last four posters, my initial thought was A frame bushes. I thought the Fireblades used Ital rear axles. Link to comment Share on other sites More sharing options...
James_Russell Posted March 9, 2012 Share Posted March 9, 2012 GJT- yep I think they're Ital Skip- the bearing float only really becomes apparent when cornering. Link to comment Share on other sites More sharing options...
Area Representative Nick Chan Posted March 9, 2012 Area Representative Share Posted March 9, 2012 Do you have a reverse box or electric reverse? If its an electric reverse, maybe check if there is a rubber doughnut/cush drive between the back of the gearbox and prop that's wearing out. Mine had to be replaced on the blackbird as one of the fixings had failed. Nick Edited by - Nick Chan on 9 Mar 2012 13:20:22 Link to comment Share on other sites More sharing options...
Blue-Lines Posted March 9, 2012 Share Posted March 9, 2012 As others have said, check the a-frame bush - although you might have a rose joint fitted in place of the bush? Check the reverser box mounts are all good and everything looks square. The chain in the reverser is a service item and a faff to change but there is a magnetic drain plug fitted so if you remove that and find a significant amount of swarf you need a new chain (£14 from nova). Check the rubber donut that the prop shaft attaches to the gearbox, I chewed mine up from tyre warming antics but gather it was one from a suspect batch and have had no problems since fitting a new one. Backlash on the CWP might be out, mine was, but only found that out when I was dropping the diff to fit a quaife atb in. Last but not least there is more driveline noise in a bec than a 'normal' seven Martyn Link to comment Share on other sites More sharing options...
AdC Posted March 10, 2012 Author Share Posted March 10, 2012 Thank you for all the replies - I'm not an engineer so all the pointers are really appreciated... Picon Bierre - if I had to guess, the Crown Gear & Pinion is exactly where it feels like it's coming from. If I was to convert the Ital axle to LSD, I'm assuming they'd be replaced in the conversion? I didn't get a chance to look between the reverser box to the diff, but the Bailey Morris propshaft between gearbox and reverser box does have a few degrees of play in it (i.e. you can turn it a few degrees before it makes mechanical contact). Btw - the rubber donuts on the shaft seem in good order Blue-lines) Everyone who said 'A' Frame bushes - fingers crossed this is the problem - a cheap easy fix! When you say "'A' Frame bushes" are all three to be replaced or is it just the one under the differential? And if so, where's the best place to source them? Thanks. However, I believe JW Fireblades have 'rose jointed suspension', so maybe it's not the answer (sorry if it sounds dumb - I'm up country for the weekend so can't look at it until Monday to confirm). Nick Chan - it's the mechanical reverser as described here. I'm wondering if I could get by without reverse altogether? Thanks again everyone - any more suggestions gratefully received Edited by - AdC on 10 Mar 2012 15:03:58 Link to comment Share on other sites More sharing options...
Andrew Walker Posted March 10, 2012 Share Posted March 10, 2012 AdC - I don't think that the JW FireBlades had 'rose-jointed' A frames - certainly not as standard. The rear dampers were generally 'rose-jointed'. Link to comment Share on other sites More sharing options...
AdC Posted March 10, 2012 Author Share Posted March 10, 2012 Hi Andy - thanks - my confusion! Okay, 'A' frame bushes to start, then. What happened to your car? You kindly spent a lot of time furnishing me with details of it when selling - sadly I moved, ended up with no garage and so the idea was put on the backburner. Still look back and think I should have found a way... Adam Link to comment Share on other sites More sharing options...
James_Russell Posted March 10, 2012 Share Posted March 10, 2012 AdC- in answer to your question, the 'A'-frame bushes we all mean are the ones under the diff. The ones where the frame meets the chassis never seem to wear. The bush is actually a pair of top hat bushes, one inserted from each side. They are on Caterham's online store and Redline will also have them. Alternatively take your old ones to a motor factors and order twenty of the blighters- they don't 'alf get through 'em. Link to comment Share on other sites More sharing options...
AdC Posted March 11, 2012 Author Share Posted March 11, 2012 Thanks James. I looked on the Caterham website and came up with these. Can anyone confirm these are the rear ''A frame bushes I need? If there is an alternative, longer lasting varient I'd appreciate a nudge in the right direction. Thanks again. Link to comment Share on other sites More sharing options...
Andrew Walker Posted March 11, 2012 Share Posted March 11, 2012 Hi Adam, yes my C-FB was sold in 2007, and the chap who bought it has still got it - he regularly has it on trackdays. I do miss it as they are great cars to drive. I would give Redline a call to get some bushes. I believe some people go for the longer lasting 'neoprene' (?) bushes - but I'm not convinced that they are that much better in this application. Link to comment Share on other sites More sharing options...
James_Russell Posted March 11, 2012 Share Posted March 11, 2012 AdC- those are the correct bushes, and longer lasting Polyurethane alternatives are available. I have very little experience of those though. Link to comment Share on other sites More sharing options...
blade_runner Posted March 11, 2012 Share Posted March 11, 2012 As DSL said if it's got a Nova reverser box then its a 'dog' engagement on the straight through shaft, couple that with a dog box in the blade engine and a clonk will be heard coming off and on throttle its a case of TADT. Link to comment Share on other sites More sharing options...
AdC Posted March 11, 2012 Author Share Posted March 11, 2012 Thanks again all. I'll change the A frame bushes but I've a feeling the clunk may well be 'shaft-y'. Shame if it is 'TADT' Blade Runner, as it does feel 'wrong'... Link to comment Share on other sites More sharing options...
Area Representative Nick Chan Posted March 11, 2012 Area Representative Share Posted March 11, 2012 Quoting AdC: Nick Chan - it's the mechanical reverser as described here. I'm wondering if I could get by without reverse altogether? Hi, you can get by without a reverse but I believe it can restrict certain events that you may wish to enter as some organisers will refuse cars that cannot reverse if the spin off the track. For road use, no reverse isn't a problem as the cars are so light. I tend to reverse mine by hand 9 times out of 10. I was more thinking of a possible problem if you have an electric reverse like mine and the way the front prop is slightly angled towards the gearbox putting a load on the rubber doughnut. Apparently speaking to Nova, having their reverse box aligns the props correctly, eliminating the issue. Nick Link to comment Share on other sites More sharing options...
AdC Posted March 18, 2012 Author Share Posted March 18, 2012 Well, it's not the 'A' Frame bushes - shame. The removed ones appeared in decent condition but I changed them anyway. A trip out to Loomies today and the clunk's still there. Luckily, I managed to leave my Mechanical Sympathy Hat at home, so it was still a good laugh. It's due an MOT and a service next month so I'll ask James Whiting what he thinks. Oh, and in going to Halfords for a second 19mm spanner I now find myself with 149 other new tools as well. Every cloud and all that... :-) Edited by - AdC on 18 Mar 2012 15:33:34 Link to comment Share on other sites More sharing options...
blade_runner Posted March 18, 2012 Share Posted March 18, 2012 its prob just the Dogs in the gearbox and the reverser box, with a little bit of backlash in the CW&P thrown in for good measure. Link to comment Share on other sites More sharing options...
AdC Posted March 19, 2012 Author Share Posted March 19, 2012 It does feel like backlash in the CWP, Blade-runner. Do you know if this is something that's easily fixed? If you read this, Blue-lines would you comment on how ftting your LSD helped? Was it the LSD per se or would a simple swap to a new / fixed non LSD diff help (assuming the problem is a worn CWP). Any other comment on how LSD changed your driving experience also appreciated. Ta'. Edited by - AdC on 19 Mar 2012 07:57:49 Link to comment Share on other sites More sharing options...
Blue-Lines Posted March 19, 2012 Share Posted March 19, 2012 Adam, fitting the LSD did not help per se but when the diff was out to have it fitted, and subsequently rebuilt, the crown wheel and pinion backlash was set up with tighter tolerances than previously. When bumbling around on part throttle I still get a "clang" sound if I come on or off the throttle relatively abruptly, and this is as others have said the dog cut gears and two sliding propshafts winding up. Driving style plays a part and with some finesse you can smoothen out things out no end. Other than that perhaps some sound deadening in the transmission tunnel and/or a torque resiliant tube propshaft in the rear would help? I have done neither of these as my car is mainly used on the track, or for spirited road drives where the ear plugs are in and all you can hear is induction roar and the banshee wail from the exhaust The ATB diff just means I can do donuts and that I have one less excuse for being off the pace in sprints and hillclimbs 😬. In practice the car feels much more progressive on the limit and quicker coming out of the corners. I chose an ATB diff over a true LSD as plate diffs can themselves be noisy and a bit clunky when pootling. Hope this information helps? Sounds like you need another Fireblade pilot to determine it is a TADT’s or not! Edited by - Blue-Lines on 19 Mar 2012 19:25:59 Link to comment Share on other sites More sharing options...
AdC Posted March 19, 2012 Author Share Posted March 19, 2012 Thanks for your views Blue-lines. I can't see myself going down the sound deadening route - good or bad I'd rather hear it, and, as you say, the induction and exhaust noise soon take my mind off it. It really is addictive, this car - "Just one more trip past 10,000 rpm, just one more bootful on the next roundabout...". I'll discuss tightening up the backlash in the CWP / installing an LSD when I get it serviced / MOT'd next month. I like the idea of donuts! Thanks again, all. Edited by - AdC on 19 Mar 2012 21:08:37 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now