Gear Crunching 3rd To 4th? - ZRE Sedan

[iVaz]

Hey All,

Just a quick one, I've noticed that since new, my Corolla, get's crunching gear's under FULL THROTTLE but ONLY when changing from 3rd Gear into 4th?

Should I change the manual gear oil? maybe add something? Or is it something else?

I've also noticed, that not very often but lately, it's slowly started happening even when driving slowly?

Only from 3rd gear moving into 4th.

Edited July 11, 2010 by iVaz

[SuperDave]

If it's still in warranty try your luck for that.

Crunching gears (it's actually the synchros) is a sign of an imminent gearbox rebuild.

[johnnieboi]

2yrs on.. gearbox still going good ivaz. sometimes i do punish her though.. quickshifting and not finding the gears and all.. but crunching doesnt sound good and shouldnt be happening. esp new car.. warranty issue for sure.

have you driven it for a bit first? let the transmission oil warm up?

[Guni]

clutch drag?

[iVaz]

My local mechanic say's it's because the clutch is dying, but then he's seen how I drive, and also says that it can't be that because, I don't ride on the clutch or do anything of a common clutch problem. He just said take it back to Toyota, they messed up somewhere...

But I can't :( Take it to Toyota.

And nope, not under warranty :(

[Rolla24]

Yea look after thoes gears cos i've had synchros go between 3rd and 4th

and ended up loosing 4th completly then you'll need a new gear box... good luck

[Kozmo]

Engine RPM and the time (or lack of) it takes to change gear after the clutch pedal has been fully pressed is what it is all about.

High throttle is obviously linked to high RPM... but the throttle position is irrelevant.

If you slam any vehicles gear stick from 3rd to 4th at light speed it will cause a "crunch".

Reason: Put simply... your gearbox operates at one speed and the engine at another.

The job of the synchro is to match the speed of both before a gear is selected. This always takes some amount of time.

There are a few things that can increase the amount of time this takes:

- Wear

- Incorrect trans oil (too thick)

- Cold weather (makes oil thicker than usual therefore exaggerating other issues).

If you have the time to read... here's my life story .

Thought you might appreciate hearing someone else's personal experience...

[story]

I had a lot of trouble with gear crunching in my own car when first I started driving it.

Some of this I admit would partially be due to me learning to drive. I think sometimes I probably didn't have my foot fully on the clutch pedal until I was already starting to shift into the next gear. I don't know for sure as whenever this was *possibly* happening, I was too busy accelerating, watching the taco and traffic to take extra notice of my clutch operation .

Anyway, enough with my crummy driving...

Even when I did take that extra notice and made sure Mr. Clutch Operator was doing his job properly I found that there was a point I couldn't push beyond in terms of shift speed without causing gear crunch. So... I hopped on the google and went looking for reasons behind this. After reading about the things I have mentioned above I decided it was time to change my trans oil.

I had no idea what was in my transaxle at the time, or how long it had been there so that was the most obvious and cheapest place to start.

As I'm going to own my car for some time and there's a long time between service intervals for trans oil, I went out and bought some fully synthetic fluid (not cheap).

One fluid change later and I had a totally different car - the shift was so much better.

[/story]

So everyone lived happily every after? No, not quite...

The shift was so so much better than before, but I still know there is a point that can't past.

I only get little "clicks" rather than a "crunch" if I push past this point. I don't want to reco gearbox, so its something I've learnt to live with (taking an extra fraction of a second on changes).

This is something to be expected in old cars (my corolla: 18yo, 190,000kms) but not in a car that is only couple of years old... unless it's driven like a drag-car... every day.

So, long story short.

A) A: An oil change is the cheapest thing to try.

Side note: if you choose to change your oil and then later the clutch, it is possible to change the clutch without having to draining trans fluid again (no $ lost). However mechanics normally want to drain the oil to make the job easier and so they can sell you some new oil.

B: A: There are additives out there which can reduce the time for the synchro to do its job. ie: http://www.nulon.com.au/products/Manual_Gearbox_and_Diff_Treatment/

I purchased this Nulon additive, but still haven't got round to putting it in (I don't have a big enough spanner ).

C) Q: Does your definition of "lately" coincide with having colder days?

D) The clutch shouldn't be a related problem until you start to notice clutch "slip". That being said, it is still preferable to change the clutch before clutch slip occurs.

At the end of the day, honestly - it is impossible to diagnose (with more than 60% accuracy) this sort of problem from behind a computer.

The only way of telling is being behind the wheel. As the local mechanic is the only other party with this diagnostic advantage...

If they are genuinely interested in helping you, then he will know by experience that a clutch and fluid change will fix your issues.

On the other hand...

If he's desperate to pay rent at the moment, then he'll be after you're money for a quick service - after which you will be left the headache of reco'ing your gearbox.

Ahhh, just re-read your last post: "He just said take it back to Toyota, they messed up somewhere..."

In that case seems you've found a genuinely honest bloke. I think the best thing to do would be to ask him whether or not he could do all the work and ask for an estimate. Most wshops aren't set up to do gearbox or internal engine work because of the "fiddly" nature of the work, not to mention all the extra special vehicle specific servicing tools required. Most likely the case will be happy to do the oil and clutch but will then point towards a local transmission reconditioner. In that scenario, if you're lucky you might be able to get the trans fixed by the local reco mob whilst the mechanic still has your car, and then it can all be re-assembled all in the one hit... can't hurt to ask. It all depends on what wshops are set up for what. One thing that can be said... Toyota will be setup for it all.

Sorry, I've gotten a little too carried away in one post, the long story really is almost over... (how did 5:00 AM creep up on me so fast)?!

In the mean time, treat the car gently. The more the crunching happens, the more worn your gearbox will become.

Any friends/family in the automotive trade to ask to have a drive for diagnostic purposes?

Edited July 17, 2010 by Kozmo