Gearbox crunching in 2nd
Discussion
Hi there. I've had my Supersport R for a year now - I built it last summer and completed the running in process in late spring this year. Ever since I've been able to use full revs, Ive found the gearbox crunches when changing from 1st to 2nd if the revs are over 4,500rpm.
I assumed that the clutch needed adjusted or bled, so tried this a few times to no avail. I changed the gearbox oil too just in case (PitA).
Eventually, with the 12 month warranty due to expire, I booked it in with Caterham (using Revolutions in Perth) to have them look at it. Unfortunately due to a series of unfortunate circumstances between the dealer and the factory, they ended up having the car for 2 1/2 months getting the gearbox out, sent down to Road and Race for repair, then back to Revolutions for fitting.
Complete nightmare missing out on the whole summer (and 2 booked track days and a proposed road trip with mates), but I was just glad to get the car back. When I picked it up, I was advised to keep the revs low on the drive home to let the box bed in.
I did a couple of hundred miles like this and all seemed fine, but when I first tried revving it above 4,500rpm again (with engine/fluids up to temp), crunch. Not good.
I've dropped it back to Revolutions again to have the box removed and sent down south, but have asked for a proper gearbox swap now.
I took a short (poor quality) video clip to demonstrate the issue. Holding the revs steady at about 4,500-4,750rpm in first, then changing slowly into second. It happens every single time.
http://youtu.be/UBfqQsK0pdQ
Has anyone else experienced this? Its the 5-speed Type-9 box. Brand new in July 2013.
cheers
Scott
I assumed that the clutch needed adjusted or bled, so tried this a few times to no avail. I changed the gearbox oil too just in case (PitA).
Eventually, with the 12 month warranty due to expire, I booked it in with Caterham (using Revolutions in Perth) to have them look at it. Unfortunately due to a series of unfortunate circumstances between the dealer and the factory, they ended up having the car for 2 1/2 months getting the gearbox out, sent down to Road and Race for repair, then back to Revolutions for fitting.
Complete nightmare missing out on the whole summer (and 2 booked track days and a proposed road trip with mates), but I was just glad to get the car back. When I picked it up, I was advised to keep the revs low on the drive home to let the box bed in.
I did a couple of hundred miles like this and all seemed fine, but when I first tried revving it above 4,500rpm again (with engine/fluids up to temp), crunch. Not good.
I've dropped it back to Revolutions again to have the box removed and sent down south, but have asked for a proper gearbox swap now.
I took a short (poor quality) video clip to demonstrate the issue. Holding the revs steady at about 4,500-4,750rpm in first, then changing slowly into second. It happens every single time.
http://youtu.be/UBfqQsK0pdQ
Has anyone else experienced this? Its the 5-speed Type-9 box. Brand new in July 2013.
cheers
Scott
OK, I don't think that is the gearbox, and if it has been to Road and Race, then it will now be OK. But whatever it is it doesn't sound right. I'd put my money on something making contact with the chassis - maybe even just the exhaust. Also, I'd of checked at the clutch plate when the gearbox was out.
I'm sure it'll be a case of kicking yourself when you work out what it is !
Edit: it you want a second opinion, I'm not too far away.
I'm sure it'll be a case of kicking yourself when you work out what it is !
Edit: it you want a second opinion, I'm not too far away.
Edited by DCL on Monday 3rd November 12:35
Edited by DCL on Monday 3rd November 12:38
It definitely feels internal to the gearbox - theres resistance to the shift as it crunches. I've checked engine mounts and exhaust clearances and they all look fine. It's only ever 1st to 2nd (plus reverse every now and then).
Thanks for the offer of help but the car is back up at the dealer in Perth now for tests and strip down. Much appreciated though - I'm a big fan of your R400 (500+) threads!
Thanks for the offer of help but the car is back up at the dealer in Perth now for tests and strip down. Much appreciated though - I'm a big fan of your R400 (500+) threads!
The noise you are hearing is the synchros. Theya re nhot able to work becuuse the clutch is not disengaging properly.
Its unliklely to be the release bearing itself, but could be the mechanism whihc trows the release bearing in and out.
For the 1st to 2nd change you have the biggest ration gap, so teh synchos have to work hardest. If their operation is impeaded you'll hear it going 1st to 2nd.
So what happens if you try to macth the revs before selecting neutral - no crunch right?
I'd adjust the cable so you are sure the clutch is fully engaged. Do it on a slope using 1st as a handbrake, then add some extra pull on the breaing in, to be sure its fully disengaged. If its not that, its likely to the the clutch arm bent/flexing or a bad slave or master cylinder.
Its unliklely to be the release bearing itself, but could be the mechanism whihc trows the release bearing in and out.
For the 1st to 2nd change you have the biggest ration gap, so teh synchos have to work hardest. If their operation is impeaded you'll hear it going 1st to 2nd.
So what happens if you try to macth the revs before selecting neutral - no crunch right?
I'd adjust the cable so you are sure the clutch is fully engaged. Do it on a slope using 1st as a handbrake, then add some extra pull on the breaing in, to be sure its fully disengaged. If its not that, its likely to the the clutch arm bent/flexing or a bad slave or master cylinder.
Edited by IBDAET on Saturday 15th November 23:03
It's hydraulic clutch on this car!
If it is the synchro gears that are crunching (and I'm not convinced they are) then the sychro cones are not working well enough to overcome the force applied to them. Either the clutch is dragging, or simply the inertia force at this RPM are too large for them.
But this could be compounded by the force applied to the gear lever being too small, or a bit timid. The Synchro cone need a bit of pressure to allow them to do their work - the six does respond well to sharp positive use. That's not saying it needs to be like that - just that this synchro cone could need to do some work to settle in a bit more (wear, or run-in a bit more) and become more effective.
I'm sure there are many owners out there that have had crunchy new boxes that seem to get better with use (but maybe not this bad).
If it is the synchro gears that are crunching (and I'm not convinced they are) then the sychro cones are not working well enough to overcome the force applied to them. Either the clutch is dragging, or simply the inertia force at this RPM are too large for them.
But this could be compounded by the force applied to the gear lever being too small, or a bit timid. The Synchro cone need a bit of pressure to allow them to do their work - the six does respond well to sharp positive use. That's not saying it needs to be like that - just that this synchro cone could need to do some work to settle in a bit more (wear, or run-in a bit more) and become more effective.
I'm sure there are many owners out there that have had crunchy new boxes that seem to get better with use (but maybe not this bad).
Edited by DCL on Sunday 16th November 11:44
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