Crunching gears. Help?

Skilid · 29 Apr 2014 at 17:18

Hi guys,

My 2008 Mazda 3 MPS has developed a fault with shifting. When the 'box is cold I get a crunch through the gearstick when changing from first to second. All other gears are completely fine. If I shift from first to neutral, and then into second it will go in without crunching, but is sometimes stiff. Shifting from third to second when cold is stiff, but it doesn't crunch.

Once the 'box has warmed up after about 10 - 15 minutes driving the crunch is gone and the whole 'box feels great/normal.

When sat still with the clutch depressed all gears engage completely normally with no stiffness or crunching, it's only whilst moving, and only whilst cold.

Any suggestions before I go and get butt raped at a garage to have it pulled apart?

Thanks.

EDIT: 'Box oil is new as of a few weeks ago and is the right grade, fully synthetic.

rodenal · 29 Apr 2014 at 17:24

It's usually down to the synchro's if it's a rod (as opposed to cable) shift mechanism. Might be a case of either waiting till it needs a clutch anyway to have the work done and living with it or biting the bullet and getting it sorted now.

I'm not familiar with the Mazda though, i'm sure others will let you know if there are any other potential causes

Sometimes changing the fluid can help, though you've obviously just had this done - out of interest was the issue there before?

happy_2008 · 29 Apr 2014 at 17:30

Some cars it can just be a common problem. My Evo 8 is crunchy at cold from 1st to 2nd but once warm its fine although mine is a common problem.

Skilid · 29 Apr 2014 at 20:00

The issue was there before the fluid change, although now it's worse.

It also wasn't doing it this time last year. Seems to just be getting slowly worse.

lemonade · 29 Apr 2014 at 20:24

Sounds like your 2nd gear syncro is worn, do you change gears really quick and hard?

Sounds like the car must have been thrashed in its lifetime with hard gear changes.

ci_newman · 29 Apr 2014 at 20:57

Sounds like the sychro is on the way out. Time to learn double de-clutching

TaKeN · 29 Apr 2014 at 21:02

Granny shifting, not double clutching like you should.

sovietspybob · 29 Apr 2014 at 21:08

Could try changing the 'box fluid for some redline shock stuff, that's meant to be really good in worn boxes to put off the rebuild for a bit!

Dogbreath · 29 Apr 2014 at 21:45

Synchromesh almost always gets worn on 2nd before any of the other gears. However, if the clutch is dragging even a little it will really show up weak synchro.

Blackhawk47 · 29 Apr 2014 at 22:09

Solution = pretend you have a new Golf GTi.

Mr_White · 29 Apr 2014 at 22:11

TaKeN said:
Granny shifting, not double clutching like you should.

You're lucky that hundred shot of nos didn't blow the welds on the intake...

Skilid · 29 Apr 2014 at 22:42

I'm not harsh with the gearbox or anything.

I also apparently have to be very careful with those types of oils because they can affect the LSD.

leigh_boy · 30 Apr 2014 at 09:07

TaKeN said:
Granny shifting, not double clutching like you should.

that was the first thing that came to my mind... good old 2f2f

Blackhawk47 · 30 Apr 2014 at 10:46

Mr_White said:
You're lucky that hundred shot of nos didn't blow the welds on the intake...

Somebody put in the wrench time.