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+--- Thread: Avoiding Crunching First Gear - Is there a technique (/showthread.php?tid=4925)
Avoiding Crunching First Gear - Is there a technique - John P - 08-09-2020
Hi,
Despite fitting new linings to the clutch on my Ulsteroid, removing the wear in the toggle slots by fitting grub screws and also fitting new toggles I still can't engage first without an embarrassing crunching. Changing gear on the move is OK within the limits of my double de-clutching ability.
It's got a 3-speed box and I carefully filed the grub screws so that all the toggles were the same depth below the face of the crank-case mating face within something like 0.1 mm.
The thrust race seems OK but obviously it's housing does have some wear at the point where the toggles bear which must reduce the amount of clutch disengagement. That being said it didn't look that bad to me.
I'm hoping I don't need to remove the engine again to try to reduce this wear so firstly is there any technique to getting it to engage reasonably quietly and secondly would you expect matters to improve once the new linings have bedded in?
John.
RE: Avoiding Crunching First Gear - Is there a technique - Ruairidh Dunford - 08-09-2020
Does the clutch centre plate spline match the gearbox or is it perhaps too long and bottoming, thus preventing full disengagement?
To test this, loosen the gearbox nuts off slightly and allow the gearbox to move backwards a small amount (1/8"), if this stops the crunch you should space the gearbox back accordingly or remove material from the centre plate spline.
RE: Avoiding Crunching First Gear - Is there a technique - Julian Hunt - 09-09-2020
When I was a lad, and there was commonly no synchromesh on first gear in most cars, I was told to put the clutch down and hold it for three seconds before putting the car into first. Still works for me.
RE: Avoiding Crunching First Gear - Is there a technique - Reckless Rat - 09-09-2020
A high engine tick over speed won't help either. You are effectively trying to mesh two large straight cut gears, one of which is rotating (layshaft) and one which is static (1st gear). Even after clutch depression the layshaft continues to spin for quite a few seconds until friction from the oil slows it down. If there is any clutch drag that will affect how quickly layshaft rotation is damped.
RE: Avoiding Crunching First Gear - Is there a technique - John P - 09-09-2020
I haven't yet got around to backing off the gearbox mounting studs as suggested by Ruairidh but thinking about Reckless Rate's comment that the layshaft is slowed by friction from the oil I had a look on-line for recommended lubricants.
Although the original specification seems to call for a straight 30 oil others have suggested Castrol Classic XXL 40 or even a non EP SAE 90 oil.
I'm currently using the same oil as in the engine which is a Classic 20W50.
What do you think about changing to a Non EP SAE90 Gear Oil?
John.
RE: Avoiding Crunching First Gear - Is there a technique - Reckless Rat - 09-09-2020
All that is needed in the A7 gearbox is engine oil, not a heavier grade such as SAE90. Stick to 20W-50 or straight 30 and you'll be fine.
RE: Avoiding Crunching First Gear - Is there a technique - Rogerfrench - 09-09-2020
Reckless, I don't know if you realise it, but the SAE grades for gear oil are not the same as for engine oil. From memory, SAE90 gear oil is about the same "weight" as SAE40 engine oil. Probably fine in an A7 gearbox, though I always used engine oil.
RE: Avoiding Crunching First Gear - Is there a technique - Zetomagneto - 09-09-2020
The Tutela ZC90 in my Morgan is definitely heavier than 40 SAE engine oil.
RE: Avoiding Crunching First Gear - Is there a technique - AustinWood - 09-09-2020
Thin oils reach parts others won't. SAE 30 is all it needs.
RE: Avoiding Crunching First Gear - Is there a technique - Terrytuned - 09-09-2020
Engine oil is for engines gear oil for gears use a light gear oil 75/90 GL4 in 3 or 4spd g/boxes there was not a light gear oil in the 30's Terry.