synchros

[Javed]

Hey guys,

Started noticing my car crunches into 4th gear while revs are high or shifting too quick. It obviously points to the synchros. How much does it usually cost to change them?

Cheers,
Javed

[wynode]

2 Options

1. Gearbox rebuild - Labour is your biggest killer here
2. Find a second hand box and swap that in.

[SPEEDCORE]

How long has it been since you changed your transmission fluid?

I just ask cause I had not bothered to do it for around 6-7 months and I was noticing grinding into second (cold and hot car), also 2 weekends ago had a track day and I was crunching 3rd at high rpm operation quite frequently which was a bit concerning.

Anyway changed the g'box oil and it was a day and night difference. I am so going to change the tranny fluid like every 3 months/ 3 track days.

Maybe try that first if hasn't been changed for a while.

[Javed]

cheers, yeah i dont think its been changed for a while!

[Kit]

yeah, as mentioned by speedcore, change your tranny fluid! very important.

Thats the first thing you should do before you take any further action.

I recommend Castrol Syntrax.

change it every 10,000km.

and then see how it feels

[JohnCRX]

Hey guys,

Started noticing my car crunches into 4th gear while revs are high or shifting too quick. It obviously points to the synchros. How much does it usually cost to change them?

Cheers,
Javed

I recently installed a JDM B16 / Y1 in my CRX and 3rd and 4th were crunching.
Sent the tranny back to importer under warranty, they fixed it for free.
Guess what, they did not replace any parts. Apparently the bronze from the sunchro rings deposits on the ramp of the gear causing it to "glaze". the mechanic "deglazed" the ramps, presumably by using some emery paper, and the synchros are like new.

[Kit]

I recently installed a JDM B16 / Y1 in my CRX and 3rd and 4th were crunching.
Sent the tranny back to importer under warranty, they fixed it for free.
Guess what, they did not replace any parts. Apparently the bronze from the sunchro rings deposits on the ramp of the gear causing it to "glaze". the mechanic "deglazed" the ramps, presumably by using some emery paper, and the synchros are like new.

John,
so was that because they were glazed, there wasn't enough friction for the syncros to match the revs correctly?

Chris

[FR33K]

hmmm
i thought that your 2nd/3rd gear synchros would go before 4th ??? coz you use them and slam it into those gears more often hehehe

[JohnCRX]

Seems the glazing reduces the friction required to match the gear speed.
I pulled the tranny appart after it was repaired by the mechanic as I was sceptical...thought it would really need new parts.
What you see is the 1st gear synchro is largest, 2nd gear sunchro next largest, then 3rd and 4th and 5th are all the same size synchro...and are infact interchangeable. Ask me how I know how thay are interchangeable...because I swapped 5th and 3rd around to extend the life as 3rd was slightly worn thinner.
I think this is why everyone wears out the 3rd as the 1st and 2nd are adequate design, then 3rd is too small.

[Kit]

ahh ok thats interesting. any idea on what causes glazing?

Freek: yes, 2nd and 3rd are normally the first to go, not only cos people tend to slam these gears, but also because 2nd and 3rd have the greatest difference in revs from the gear before.
thats why certain hondas have double and even triple cone syncros on these gears.