Crunching going into 2nd from 1st

[tomkidd]

Hi gents

I'm running a KAD internal gear linkage and a SCCR gear box using a clubman gear set.

Whilst doing the trackday at Blyton my KAD gearstick kept on losing the plastic ball on the end inside the linkage box... it turned out it was the circlip that holds the ball in place that kept on slipping up the shaft. KAD have since replaced the stick and refunded me the postage etc so they've been good to me.

The new stick has arrived and now I am getting crunching going into 2nd from 1st when I accelerate hard. The engine is solid mounted and has extra steadies on both sides underneath, I can't see any engine movement either. If I am gentle (and slow) the crunching doesn't happen. At Oulton park yesterday it did the same going into first but that has only happened once.

The crunch happens just before the gear engages... I'm concerned it might be a gear box issue but I'm wondering whether it might be a clutch throw setup or linkage setup?

Can anyone help out with a list of things to try to before taking the engine out?

Cheers

[Simon776]

Sounds like the sycnhro on 2nd gear is on the way out.

Quick shifts are hard on synchros.

[Spider]

I have heard that it could be that style of shifter being too fast for the synchos, but I have to say, I doubt this, especially since you are running a CR Gearbox, so the speed difference isn't as great between gears as a normal roadie, in any event, my own experience has shown me that when the Gearbox internals are in good order, you can shift very fast indeed and still get reliable synchronisation.

I'm more inclined to say that it could be one of or a combination of Baulk (Synchro) Rings, the Synchro Cones on the Gears themselves, Worn Synchro Hubs, and / or poor spring pressure from the Detent Springs in the Syncho Hubs, more likely these last two items.

edit> another thing to consider is the oil you are using and it's temperature when running, if it's too cold or friction modified, that'll also do it.

[mini63]

do you run nitrided syncromesh rings?

[rich@minispares.com]

tom


if its crunching, then either the baulk ring has failed/failing or the small dog teeth are failed/failing, as the crunch noise is the syncro hub 'fighting' with them as the gear speed is not been controlled by the baulk ring to match the speed of the mainshaft.

once it starts doing it, it never gets any better.

I have seen cars with internal gear mechs suffer premature wear like this when the lengths of the operating rods haven't been checked and set right, so as the lever is pulled back into second its not pulling the syncro hub fully into mesh with the dogs.

I wonder if the damage occurred when the plastic button fell off at blyton, as that would have altered the amount of throw that the lever would have had?

[tomkidd]

tom


if its crunching, then either the baulk ring has failed/failing or the small dog teeth are failed/failing, as the crunch noise is the syncro hub 'fighting' with them as the gear speed is not been controlled by the baulk ring to match the speed of the mainshaft.

once it starts doing it, it never gets any better.

I have seen cars with internal gear mechs suffer premature wear like this when the lengths of the operating rods haven't been checked and set right, so as the lever is pulled back into second its not pulling the syncro hub fully into mesh with the dogs.

I wonder if the damage occurred when the plastic button fell off at blyton, as that would have altered the amount of throw that the lever would have had?

Maybe... I'll be pretty peeved if that is the case. Wonder if KAD will do me a favour for a rebuild?

[tomkidd]

do you run nitrided syncromesh rings?

I have no idea!

[ivor badger 2]

The bottom line is that it is an old box design and your hand can beat the box even with the standard gear change. All that a quick shift will do is give you a heavier gear change that beats the synchro totally. How much time do you consider might be saved with a quick change? It's not exactly going to fall of the turbo, is it?

[boxofbits]

Baulk ring, and maybe even the gear where the baulk ring runs. It would be wise to replace all baulk rings in the event of a rebuild. But before that it is worth checking the clutch is disengaging fully, and the clutch fork pivot is not worn.

[rich@minispares.com]

. It would be wise to replace all baulk rings in the event of a rebuild..

why would you do that?

if the horns are in good order and the amount of stand off is within the expected tolerance, then there is no need.

a baulk ring that has bedded into its gear and is working well is fine - you can sometimes cause more problems by swopping them.

[ianh1968]

if the horns are in good order and the amount of stand off is
within the expected tolerance, then there is no need.

I've often wondered about this - How much of a gap would
one expect to see? Would 40-60thou be about right?
How small can you go before it's deemed too small?

Ian

[Spider]

I've often wondered about this - How much of a gap would
one expect to see? Would 40-60thou be about right?
How small can you go before it's deemed too small?

Ian

Typically with new Rings, about 50 - 55 thousands. According to the factory, the minimum wear limit is 30 thousands, however in many case 'crunching' will start to occur before they wear to 30 thousands.

[6604KF]

I feel for you Tom.

My first gearbox build lasted 3000 miles before it was crunching between 3rd and 2nd. We stripped it down and a new set of baulk rings were worn out, Worse than that it had worn out a set of clubman sc gears where the baulk rings sit.

The only thing we could put it down to was a long gear lever I was using so using the standard one now and it's lasted about 2000 miles and crunching into first! Just going to live with that for a while!

Does anyone know which are the best baulk rings to use? We ended up using some ok old ones as didn't trust new ones.

Luke

[mk1]

NOS original Baulk rings are MUCH sought after for their reliability & robustness.

I think MS have some new offerings in the pipeline, but feel sure that Rich will have something more to say about this.

[rich@minispares.com]

the new comp baulk rings we are selling are bang one.

much design and investment has gone into these cnc beauties.

they are made from a long length of special material bar stock and have the minimum amount of heat treatments - so they stay far flatter than any other previous offerings.

in test they have done 2500 plus gear changes in race conditions without showing appreciable signs of wear

ive got a few sets out 'on test' with 'hard' drivers and they have all reported that they last far longer than other ones


the only person to really complain about them and slag them off, discovered to his horror (after I had told him he was talking utter rubbish) that he had built his gearbox back to front...........

[6604KF]

That's good to know Rich! I must have re built my box at a bad time for baulk rings. Still, you gave the best advice you could at the time...'buy the cheapest ones so you'll not be as disappointed when they only last a few miles!'
Cheers.
Luke