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240z gearbox issues


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#1 cracker

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Posted 19 June 2013 - 09:33 PM

Hi All,

I'm looking for some input on a problem I've just had with a 240z I've just purchased - fortunately made it back from Vic before the box sh*t itself!

In the last day or two I had noticed occasionally first gear was "hard to find" and then earlier today I had to really shove it in. When this was the case the take up point was very short and almost caught me off guard to stall the car. Then, whilst driving around today, I was coasting in neutral down a hill at about 60km/h when what I thought may have been diff or box created a massive clunk and hampered the cars progress and was very clunky and noisy. I clutched in quickly which allowed me to continue rolling but I hit problems as soon as I attempted to get back in gear. I can start the car with the clutch in but now can't get the car into gear at all. "Neutral" seems to be stuck slightly in a low gear because when I try to take up the clutch the car tries to move forwards as if in first gear, but wont take off properly.

I'm nearly certain the problem is the gearbox but I wonder if anyone may be able to shed light on what specific issue may be and how serious it is? (possibly having experienced the same problem?)

I'd like to guage the damage as best possible so I can either look for a new box, fix this one, or have it rebuilt. Working with the gearbox is beyond my skillset so I would need to outsource, unless it was fitting a new box which I could attempt... (maybe!)

#2 1600dave

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Posted 19 June 2013 - 09:52 PM

Sounds like clutch hydraulics are leaking - either master cylinder or slave cylinder.

#3 Lurch ™

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Posted 19 June 2013 - 10:20 PM

+1 to what Dave has said.

Second option is that the Nut on the end of the Mainshaft has come loose...

#4 Cozza

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Posted 19 June 2013 - 10:29 PM

Can you select gears easily when the motor is NOT running?

When the motor is running, does it make it any easier to select first if you pump the clutch pedal a bunch of times first?

#5 cracker

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Posted 19 June 2013 - 11:09 PM

It seems to be stuck in gear so that if I release the clutch while the gear position is neutral the car will attempt to accelerate then clunk noisily and stall.

I can select first quite easily while the motor is running but while first is selected it seems almost like a high gear is actually selected as I can't take off and the car stalls.

#6 Six_Shooter

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Posted 20 June 2013 - 08:26 AM

Sounds like there may be a couple of issues.

First check the clutch hydraulic system as suggested. low fluid can cause the clutch to not disengage properly and making shifting difficult to do.

It also sounds like there might be an internal issue with the trans, such as a broken shift fork. In my 5-speed, I had the 1/2 shift fork break on me in such a way that it would still allow the gears to be shifted, but there was a lot of slop to the motion and would cause 2nd gear to pop out on engine brake decel. I replaced the 1/2 and 3/4 shift forks with 4 speed shift forks, since they are made out of cast iron, or similar material, where as the 5-speed had forks made from aluminium.

#7 Agno

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Posted 20 June 2013 - 10:17 AM

Sounds exactly like the problem I had. It turned out to be the hose from the clutch master to the slave was leaking slowly when the pedal was pressed and not holding pressure. A new braided line and a quick slave bleed and I was ready to party again

#8 Patch

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Posted 20 June 2013 - 11:35 AM

Sounds like it is jammed between 2 gears, you need to pull the top lever off and unjam them manually on each fork to be able to get neutral, you may find it is caused by the gear level being sloppy.

#9 luvemfast

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Posted 20 June 2013 - 12:32 PM

I'm reading the issue being that even in neutral, while car is running and releasing clutch, car tries to drive? ???
If so. Nothing to do with clutch as its stuck in gear.
You'll need to pull it and rebuild if that's the case.  As stated, 5th nut may have come loose and maybe selector forks have failed.
Good luck.

#10 1600dave

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Posted 20 June 2013 - 01:01 PM

Yep, bit of a mix of symptoms.

This one points to clutch issues, is the easiest to troublehsoot / try first.

When this was the case the take up point was very short and almost caught me off guard to stall the car.


Maybe even clutch issues first, followed by

I had to really shove it in.

,


which in turn broke something internal to the box (selector fork, etc)





#11 luvemfast

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Posted 20 June 2013 - 01:55 PM

Too true

#12 mjfawke

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Posted 20 June 2013 - 04:11 PM

I'm reading the issue being that even in neutral, while car is running and releasing clutch, car tries to drive? ???
If so. Nothing to do with clutch as its stuck in gear.
You'll need to pull it and rebuild if that's the case.  As stated, 5th nut may have come loose and maybe selector forks have failed.
Good luck.


+1, it's a box-out job.  For whatever reason, a selector sleeve isn't where it is supposed to be.  And don't try and tow the car, I'd jack it and pull the tailshaft before trying to move it. Or disconnect a half-shaft.

Plus... fix your clutch.  Most likely that the master or slave has leaked fluid, or the clutch diaphragm has failed (unlikely).  Even more unlikely... someone unlocked the nut on the clutch master push rod and it's wound itself in.


#13 dat2kman

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Posted 20 June 2013 - 06:27 PM

You have worn, and bent, nown, selector forks, also the selector rod through centre plate hole is sloppy, and baulking.

Ensure that, when depressing clutch pedal, the clutch fork, at bellhousing, moves sufficiently to fully disengage clutch, ie at least 20-25 mm from take up ( not slacky)

Is it an early 3 piece housings box, if so expensive to reco, due to hard to get and pricey bits.
If it is a later 2 piece housing box, bits are more available.
Sticking in another box, cond unknown, can be a temp get you going, giving you time to reco, and you have a spare.

#14 cracker

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Posted 21 June 2013 - 09:34 AM

Thanks everyone for your EXTREMELY helpful advice... show's how useful and awesome this forum is.

I've had it towed (on the back of a truck not with wheels trailing) back to my place and will hopefully find some time next week to pull it apart and try to find the issue(s). I believe it is the later box (73 car) so hopefully not a bank breaking fix.

Would not have had a clue what to look for without the comments above, much appreciated all!

James

#15 mjfawke

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Posted 21 June 2013 - 03:12 PM

And if you do swap a box, just remember... not all the tailshafts are the same.  There were two-piece tailshafts for the really early boxes, and (on the later ones) some gearboxes have the dustshield and some tailshafts had the dustshield.  You also need the shifter to come out in the same location unless you want to end up trimming the floor and finding a new way of doing the shifter boot.

#16 cracker

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Posted 03 July 2013 - 12:28 PM

I'm becoming a little time poor in the next month or so I'm going to take the box out and have somebody else take a look for me - can anybody recommend a good workshop that knows L series gearboxes?

I am just South of the CBD but if there is quality workshop somewhere in Adelaide I'll use them.

I'll also posted in the business directory.

Cheers,
James

ps. apologies if this information has been posted somewhere previously - I did try quite a few different searches of the forum!




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