Grind/Clunk when selecting reverse gear - 6 speed gearbox

[Ant2]

420S 2020, but with a 6 speed gear box. Push down for reverse

When the car is cold it always does a loud clunk/grind once it's selecting  reverse, sounds like changing gear with no clutch  (I reverse it out of the garage), so is noticable/annoying. It does select fine.

Clutch is fully depressed, car is not moving and just started. It does not usually occur once car has been running for a while (wondering if it's just because the other gears have been selected first). I tested it after a run today 5 times, as I wondered - back and forth and no noisee. The next thing I was going to try was just going to first, or a series of gears before first selecting first to see if it helps.

No issue ever in any other gear and gears feel very smooth.

 

It has been like this since I bought it, I remember hearing it on the test drive. I didn't think about it at the time,  as as there is a hell a lot of noise coming from a variety of places

Is this something I should worry about or is it normal - as it does have 5 months warranty remaining?

Edited April 19 by Ant2

[7_Malc]

I don’t think there is a synchro on the reverse gear, so I always select another gear while stationary, and then slide it smoothly in to reverse. Into ‘first’ , keep the clutch in, then into reverse.

[Ant2]

28 minutes ago, 7_Malc said:

I don’t think there is a synchro on the reverse gear, so I always select another gear while stationary, and then slide it smoothly in to reverse. Into ‘first’ , keep the clutch in, then into reverse.

So this would appear to be normal on this gear box ? I'll try just that and see. thanks

[PlastererPete]

Always had this intermittently on my 2005 CSR with a 6speed box. I found the same as 7_Malc. Select first then reverse. Its usually after a drive and reversing on the drive. Sometimes just waiting a few seconds in neutral works aswell, but thats not applicable to your situation. 

[ECR]

Sounds like the clutch is dragging a little

[Ant2]

1 hour ago, ECR said:

Sounds like the clutch is dragging a little

Would you get the garage to do something about it?

[ECR]

If cable operated try adjusting the cable. If hydraulic bleed the clutch…

[Ant2]

20 minutes ago, ECR said:

If cable operated try adjusting the cable. If hydraulic bleed the clutch…

It had the clutch fluid replaced 300miles ago (when I bought it) as part of 24 month service. It also did it before the service

[ECR]

Ok then I wouldn’t worry too much about it. As has been said there’s no synchro on reverse it’s just a simple cog.Nothing to break really

[Ant2]

Okay, thanks.

I'll continue to select 1st gear before putting it in to reverse, which seems to prevent it.

 

 

[ScottR400D]

It’s normal, not a gearbox issue and not a clutch problem. 
As said no synchro on reverse so the teeth will grind. Starting in the garage cold, depress the clutch then start it’ll engage cleanly because both shafts are stopped. Start in neutral, go into a forward gear, move,  then come out of gear and straight into reverse, griiiiind. 
Again as said in such a case go in and out of first while stopped then out of first into reverse. Contrary to what PP thought waiting a few seconds with clutch depressed then going into reverse does work. 

[Geoff Brown]

17 hours ago, Ant2 said:

So this would appear to be normal on this gear box ? I'll try just that and see. thanks

Not 'normal' at all. My 11 year old six speed does nothing of the sort. Could be a slightly dragging clutch ? More noticeable when cold & selecting reverse.

[Ant2]

25 minutes ago, Geoff Brown said:

Not 'normal' at all. My 11 year old six speed does nothing of the sort. Could be a slightly dragging clutch ? More noticeable when cold & selecting reverse.

Same hot or cold. If I put it in first before reverse then it never clunk's.

[ScottR400D]

27 minutes ago, Geoff Brown said:

Not 'normal' at all. My 11 year old six speed does nothing of the sort. Could be a slightly dragging clutch ? More noticeable when cold & selecting reverse.

Entirely normal with a non synchro box. Explain the mechanism the stops it.if it’s not if it wer a dragging clutch starting with clutch depressed would help but it does of course. 

[aerobod - near CYYC]

I agree with Peter on this, entirely normal based on not just the Caterham, but any non-synchro gear in a car gearbox. If the input shaft is still spinning due to just having moved the car forward, a grind is possible. It also can vary with oil temperature and viscocity which can affect when the shaft stops spinning.

[SteliosV]

I have this too - putting it into first prior to engaging reverse helps, but if going back and forth between first and reverse (e.g. when manoeuvring) the clunking manifests itself again after around the third engagement of reverse.

[Ant2]

4 hours ago, SteliosV said:

I have this too - putting it into first prior to engaging reverse helps, but if going back and forth between first and reverse (e.g. when manoeuvring) the clunking manifests itself again after around the third engagement of reverse.

Thanks for the feedback.

Commentw would now suggest this is 'normal' in that some suffer with this issue in varying amounts due to lack of synchro,  putting it in first each time is not too much of a pain to help guide it in and there's nothing that can be 'done' to eliminate such an issue.

Perhaps some cars have the shaft spin a bit more than others and hence why it's more noticeable 

[ScottR400D]

7 hours ago, SteliosV said:

I have this too - putting it into first prior to engaging reverse helps, but if going back and forth between first and reverse (e.g. when manoeuvring) the clunking manifests itself again after around the third engagement of reverse.

What clunking? We’re talking about gear chatter and that shouldn’t change other than maybe a tiniest bit as it warms. 
If there's a clunk beginning it’ll be the diff warming up.