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Strange gearbox prob (5th gear)

dangerous_daveo
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dangerous_daveo Grand Master

dangerous_daveo

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Ok! Went for a drive last nite, everything huckydory. No probs. Missed 3rd, kinda hit the selector wall thingy, big loud crunch noise. Then put it in 5th, kept driving, all gears work.

Then come this morning, go for a drive, no problems. Go to get on the highway, go to put it in to 5th, wont go in, (wont go in being it will go in its little slot all the way, but wont actually engage the gear properly) it then crunches as if the gears are JUST touching, going by the noise and the feel thru the gear stick. But all other gears are fine, no different.

The engine is an RB20DET, and the RB20 box. Car is a cefiro but I dont see how that would matter.

Any help would be REALLLLLY nice, cause I have NO idea, other than maybe not enough gearbox oil, or maybe the selector.

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wrxhoon Grand Master

wrxhoon

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It sounds like a selector problem to me . You will find that the selector runs out of travel , it wont go down enough to select 5th or the fork inside the box has let go , there is a roll pin holding it in place .

Try putoing it in 5th while stopped with the engine off then strt it up and slowly let the cluth out to see if it engages , if yes then its the selector .

wrxhoon Grand Master

wrxhoon

Posted
Posted

It sounds like a selector problem to me . You will find that the selector runs out of travel , it wont go down enough to select 5th or the fork inside the box has let go , there is a roll pin holding it in place .

Try puting it in 5th while stopped with the engine off then strt it up and slowly let the cluth out to see if it engages , if yes then its the selector .

wrxhoon Grand Master

wrxhoon

Posted
Posted

It depends on what it is , at the very least you will have to remove the gearstick and see if the selector operates , it should as it engages the other gears .

The box may have to come down if the fork roll pin is off or the fork has jumped the 5th gear hub ( possible ) but hard to say without seen it .

wrxhoon Grand Master

wrxhoon

Posted
Posted

If thats right he should still be able to engage 5th but crunch as it goes in and egage normal when the car is stopped .

I reckon it sounds like your 5th syncro is now in a pile at the bottom of your gearbox...

This might help you make up your mind

http://auto.howstuffworks.com/transmission.htm

SteveL Mentor

SteveL

Posted
Posted
Ok!  Went for a drive last nite, everything huckydory.  No probs.  Missed 3rd, kinda hit the selector wall thingy, big loud crunch noise.  Then put it in 5th, kept driving, all gears work.

Sounds like you missed 3rd and grabbed 5th instead.....but hard.

I'd say most likely a broken 5th selector fork. One 'arm' is probably broken off, which would allow only near or partial engagement. Seen it before with RB30 gearboxes (v similar design), they have an alloy selector fork, which can break under hard/harsh shifting.

dangerous_daveo Grand Master

dangerous_daveo

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Sounds like you missed 3rd and grabbed 5th instead.....but hard.

I'd say most likely a broken 5th selector fork.  One 'arm' is probably broken off, which would allow only near or partial engagement.   Seen it before with RB30 gearboxes (v similar design), they have an alloy selector fork, which can break under hard/harsh shifting.

Yep, Id agree with that after talking to a few very helpful but rather booked up gearbox shops today. That or the gear has posibly come loose.

SteveL Mentor

SteveL

Posted
Posted
Yep, Id agree with that after talking to a few very helpful but rather booked up gearbox shops today.  That or the gear has posibly come loose.

It's also possible the mainshaft nut has come loose, but usually when that happens the first signs are that the gearbox starts jumping out of 5th gear and gets progressively worse. Since your problem started happening rather suddenly it's more likely somethings broken.

I'd also recommend looking closely at the condition of the bearings....particularly the countershaft bearing in the steel sandwich plate. It's not uncommon for this bearing to fail in gearboxes used hard. I've actually got an R32 GTSt gearbox apart at the moment that seemed in OK condition, but disassembly has revealed the CS bearing cage has disintegrated and the balls literally fell out. I've seen this before and others have reported similar problems. In fact I'd recommend replacing these bearings while its apart (the CS bearing is only $10...retail), but the labour cost might be high since to get at it requires complete dis-assembly.

dangerous_daveo Grand Master

dangerous_daveo

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Quick up date. It is the selector fork. Whats happened is its partly broken/bent, hence it would go in to gear the night before, and not in the morning, posibly due to heat in the gearbox, etc making it easier or harder to go in to gear. So thats a big NO to gearbox fairys.

Anyway, while the gearbox is out its going to get a reco, all bearings and seals done, as its saving me $300 by doing it now instead of later.

Now a big plug for the gearbox shop! Im in QLD, and I went to Springwood Gearbox repairs. The guys were unbeliveably helpful, friendly, happy answer my stupid questions (I actually mentioned gearbox fairys to them) fair priced, and actually are doing what I asked, fully recomend them. (atm anyway, I havent got my car back yet, but they said tomorow no worries)

dangerous_daveo Grand Master

dangerous_daveo

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  • Author
Posted

Just the update.

It was the selector fork, it had partly broken/bent, hence I could get it in to 5th the night before, and not the next day, probably heat being the factor there. (no gearbox fairys)

Im going to get all the seals and bearings replaced also (with stronger items) as its $300 cheaper to do it while the box is out and half apart than do it in 6months time.

Also a big thanks to the gearbox shop (free plug!!!) Springwood Gearbox Repairs in Brisbane. The guys were really helpful, quick to get back to me, had all the info and prices ready before they called, basically did what I asked, and more. And answered my stupid questions without treating me like a tool. They also seemed well priced.

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