crunch into fourth

[maserati mick]

My foz is recently started to crunch when shifting(faster then usual shifs )into fourth gear it doesn't appear when driving casual but when shifting in a faster rate it crunches just wondering if there is anything that canz fix this or would it be wise to replace gbox? ?pretty surevmy box number is Ty755vb1aa 4.444 is it a easy swap would I need to change diffs? I'm wanting to get a sti v5v6 box or maybe even v4sti if possible

[Joker]

mine has always been a pain on down shifts for the last 100,000 or so kay's

oil level?

[maserati mick]

Is it a common problem for subi boxes??pain up the arse mate argh changed oil recently will top up and see what happens

[maserati mick]

Do all sti impreza models(v3-v6) have dccd. Or just ra sti model

[aim]

Your synchro is worn, replace it. Splitting a g/b is spency as though.

[Johnnynz]

Currently having the same issue. Mine has been like it for about 20,000 KM and slowly getting worse but still very driveable.

I have just purchased a GTB Box to replace mine then I'm going to fork out for a full rebuild of my STI Box. I'm expecting in excess of 1k rebuild cost.

[maserati mick]

Johny boy wot car you got mate??is the gtb box up to it???1k dayum might aswell get a second hand good condition???

[Johnnynz]

v5 WRX, The GTB Box is a stop gap for me so I can drive the car etc, do the modding I want to do then I will get my current box which is an STI one rebuilt completely. TBH I wouldnt have a clue if the GTB Box is weaker or stronger than any other.

I have broken 4 boxes now I think so I'm kind of over the whole second hand deal. No matter how good people claim them to be I want to go new internally this time for the Box I plan to use long term.

If your not to rough though and want to go second hand there's a few wreckers in Auckland who sell through Trademe, between 500-800 for boxes with warranty. There usually imported crashed front cut boxes.

Also if yours is only crunching on faster shifts you might get 20,000 - 30,000 KM out of it if you aren't rough.

[WRXONP]

whos split open a suby box before ? because as far as ive know 4th gear is the "straight through" gear where the input shaft speed is exactly the same as the output speed - ie 1:1 gear ratio - being done by locking the counter shaft and main shaft together (using no gears) so which synchro is it that wears?

[WRXONP]

as for lasting 30k -- itl last forever - its only a synchro - it can only get worse and not mesh the gear - the boxs die from shock loading - not grinding gears

[Guest]

 WRXONP said:

whos split open a suby box before ? because as far as ive know 4th gear is the "straight through" gear where the input shaft speed is exactly the same as the output speed - ie 1:1 gear ratio - being done by locking the counter shaft and main shaft together (using no gears) so which synchro is it that wears?

wrong ! - Subarus use gear sets for EVERY gear

Scynros can often be bedded back in and deglazed during a road test,

But if they are worn out then graunch all the time unpon engagement then replacement is needed of the syncro (s)

I can rebuilt these for members - all you need to do is ship it to me and i'll fix it and ship it back

I also have a few gearbox parts around to help keep costs down

[WRXONP]

so theres actually 5 sets of gears in a suby box ? so there isnt actually a straight through gear like most manual trans have ?

just very interested is all - maybe thats why 4th can just do 180 in a suby when 4th in a RB gearbox is well beyond that when 170 is the top of 3rd

[Guest]

correct-no straight thru drive in 4th

5 pairs of gears in the box

you really need to see one apart to appreciate the engineering

Front pinion runs inside counetshaft !

As for ratios/speeds etc 4th is normaly around 1.088 / 0.972 (so slightly under or overdriven - depending on the gearset)

I'd expect a RB would run slightly taller diff gears - hence the greater speed you state

But no point comparing two diffrent cars really

[DRFVDR]

To negate any other issues with the gear train you can try double declutching and rev matching into that gear,if it goes in smoothly then you can guarantee that it is just a syncro

Must congratulate Mr WRXONP for his new attitude on here, seems like young Brad has grown up some in the last month or so

[Guest]

 We are borg said:

Must congratulate Mr WRXONP for his new attitude on here, seems like young Brad has grown up some in the last month or so

+1

[WRXONP]

haha thanks lol - but yeah thanks for that was just curious -

ive seen the pinion coming off the counter shaft - just never really looked at the gearsets lol

wierd how they didnt want a 1:1 ratio - really means u cant get a true dyno figure ? cos u should really be dynoing it via the 1:1 gear ratio - so going 3rd will raise KW (under driven) and lower torque but 4th will lower KW and raise torque if its 1.088 ratio - spose its close enough though lol - getting side tracked here sorry haha

[Guest]

thats why you see ratio on a dyno sheet

They set that up first before they do a run, its all taken into account (then gearbox and diff do effect results)

I've had cars dyno'd 5th when dyna paks where new to stop them shutting down

[mondo]

If the wrong oil has been put in, it only takes <1000kms for the syncros to wear in subi boxes.How many home mechanics have done this, then found this out and put the correct oil in, but its to late?

[Guest]

honestly not many would have done this? and with the wrong oil, syncros will graunch straight away

[WRXONP]

from reading various websites - the wrong oil can polish the synchros - which ichi knows how to get them working again (bedding them in or some thing)

[mondo]

It makes the syncros stick, ie not seperate from metal contact, depends what sort of unsuitable oil is put in .