bstark Posted August 22, 2003 Share Posted August 22, 2003 And surprisingly, it wasn't from any of the passengers, who seemed to really enjoy themselves On the way back from the exceptionally hot BHGP trackday a couple of weeks ago, the car started making a whining noise (loud enough to be annoying, but not drowning out other noises) at around 60mph - but only if on a very light throttle, or slightly backing off. As soon as any load was applied - either accelerating or decelerating, the noise went away. I used the car for the first time since the trackday last weekend, and the noise is still there, but it seems to be engine speed related rather than road speed related (3rd and 4th gears, between around 2500rpm - 3000rpm, and only when on an extremely light throttle / backed off the throttle very lightly - again if any load is applied the noise goes). I can't tell for sure which direction the noise is coming from - gut feeling is behind (passenger certainly thought so), but it appeared to be louder to me than the passenger and its hard to tell. My first thoughts were that I'd cooked the axle, but as it also happens at same revs in a different gear I don't know now. Is it some sort of carb noise? Any ideas? Bob Stark Supersprinter Link to comment Share on other sites More sharing options...
j_thombs Posted August 22, 2003 Share Posted August 22, 2003 I have exactly the same thing after a trackday at Donington. It went back to CC and was a no fault found/they all do that sir. The noise is still there 2500 miles later but the car does not seem to have any performance/handling differences. Any possible suggestions as to what it is would still be interesting though I also wondered if it was carb related e.g a resonance of some kind ? Out of interest is it a live axle car ? Jon Beaulieu no31 My Caterham Pics Edited by - j_thombs on 22 Aug 2003 10:32:14 Link to comment Share on other sites More sharing options...
Robster Posted August 22, 2003 Share Posted August 22, 2003 Sounds like diff has suffered oil surge, this causes the case hardening on the gear teeth to wear and means that the gears don't mesh proplerly....most likely in a live axle car. Caterham 'they all do that' is just not true, diffs only whine when they are worn and the teeth are not meshing correctly. Worn bearings in the diff are possible, in which case a rebuild would save the CWP, although both of mine that did this, the crownwheel was worn, in which case carry on using, you have nothing to lose. Link to comment Share on other sites More sharing options...
bstark Posted August 22, 2003 Author Share Posted August 22, 2003 Sorry - I forgot to mention the spec! 1700 xflow Supersprint with Ital Live Axle. The axle itself was very recently rebuilt with a new bearing and healfshaft by Redline. If it is the axle, how come it is engine speed related and not road speed? Bob Stark Supersprinter Edited by - bstark on 22 Aug 2003 11:23:05 Link to comment Share on other sites More sharing options...
MikeW Posted August 22, 2003 Share Posted August 22, 2003 Agree with Robster that it sound like the diff. I wouldn't worry until you start getting a lot of vibration through the car and it is really noisy. Have you checked the oil level in the diff? MikeW 1600 VX Black/Ali Race No 134 Membership No 6582 Link to comment Share on other sites More sharing options...
bstark Posted August 22, 2003 Author Share Posted August 22, 2003 Not yet - but I am thinking that changing the oil completely would be a good idea if I have cooked it. Still doesn't explain (to me, anyway) why it seems to be engine speed and not road speed related... Bob Stark Supersprinter Link to comment Share on other sites More sharing options...
Bedazzled Posted August 22, 2003 Share Posted August 22, 2003 Hmm, sounds like it might be the diff (but I'm no expert!). Mine made a howling noise when on the over-run between 40-60 and I recently had it replaced under warrenty. It had the same basic symptoms that you're describing and made a slightly different sound depending on which gear was selected. The new one's much better, but they all do seem to whine a little bit at certain speeds, I think it just depends how bad the noise is as to whether it's faulty / worn. By the way what tyres are you using? I used to have a live-axle classic and I was advised by CC not to use very sticky tyres on track-days etc as it would put strain on the diff / half-shafts and wear them out more quickly... Link to comment Share on other sites More sharing options...
bstark Posted August 22, 2003 Author Share Posted August 22, 2003 They're sticky-ish Yokohama O21Rs - but it was a very hot day, and I had a passenger each time out. Bob Stark Supersprinter Link to comment Share on other sites More sharing options...
Robster Posted August 22, 2003 Share Posted August 22, 2003 I have found that it seems to be oil surge that kills these diffs, not power. Sticky tyres will not wear half shafts..they just create more Gs and more surge. They really should all be baffled if you are using on a track and pour loads of extra oil into them. Not sure why the diff is engine speed related...except that driving along engine speed correlates exactly to CWP speed in each gear (unless you have cooked the clutch as well!). New CWP sets are like rocking horse dung to find..or they are in 3.9 spec...has anyone found where they can be bought?? My feeling is that the halfshafts should never get enough torque to snap or do much damage to the diff through straight torque as the car is so light, the wheels will spin first. Oil surge is the weakest link in this chain. Link to comment Share on other sites More sharing options...
millsn Posted August 23, 2003 Share Posted August 23, 2003 Sounds like the wife to me. Cover her in oil and apologise before going on another track day. If there's anything more important than the car being trackworthy, it's ensuring that the wife is more so! Nigel Mills - 2.0 Zetec carbs Link to comment Share on other sites More sharing options...
bstark Posted August 26, 2003 Author Share Posted August 26, 2003 😬 I had considered that possibility, but it also happens without the other half being inside . She was also one of the passengers on the day - so perhaps its her fault Bob Stark Supersprinter Link to comment Share on other sites More sharing options...
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