Crunch from 3rd to 4th

[Benjam]

At a track day yesterday and the car developed a bad crunch when changing from 3rd to 4th regardless of revs and even when slowing the shift speed right down. Tried to bleed the clutch but that made no difference. Car is a 2011 Academy (Roadsport) with a standard Sigma engine and 5-speed Type 9 gearbox.

My novice assessment is a knackered synchro but any additional thoughts please? Is this a common issue with the Type 9 and if so, what is the likely cause?

Thanks
Ben

[BigCol]

I was at the Dartford factory last week picking my car up after its 1000 mile service and to discuss my gearbox that I thought was faulty. I keep crashing changes from 1st to 2nd and often it takes more effort than I think it should to get into 1st and reverse.

I went out on a drive accompanied by a technician who said "we see this sort of problem more often with race cars and the 3rd to 4th change"

So, whilst this post offers nothing by way of diagnosis or help with a fix of your problem, it is an issue known by the factory - so no doubt they could advise... and maybe give you an "in" to discuss a discounted fix by them if it is really that common.

[greengreenwood7]

sounds likely that its the baulk ring, had a similar\ thing after a track day - 5 spd type 9. Mine was also graunching on 4th to 5th - perhaps slightly less so.
I was told by BGH and others that a Type 9 doesnt like swift changes and that eventually thats the way the damage is manifested.....no doubt others will have an opinion.

anyway, if it is that - i whipped my box over to Phil at Road/Race at Sevenoaks and later the same day twas sorted.......

[TeflonT]

Type9 5spd synchro rings do not last well with aggressive changes, particularly at high revs (7k+). Normally 4th/5th and 3rd/5th fails. NOt seen it on 1st 2nd ever.

Phil at R&RT is the man...

[Benjam]

Thanks very much guys. Interesting comment about the 3rd/5th Synchro. Could block changes from 5th to 3rd without any heel-toeing (ie. lots of engine braking) be a likely cause?

Cheers
Ben

[Benjam]

Ps. Will call Caterham, Road/Race and BGT on Monday... Thanks.

[TeflonT]

Benjam said:

Thanks very much guys. Interesting comment about the 3rd/5th Synchro. Could block changes from 5th to 3rd without any heel-toeing (ie. lots of engine braking) be a likely cause?

Cheers
Ben

Very likley. Bigger gap in ratios puts stress on the synchro rings causing them to crack where the blocker bars locate.