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chriz

skyline gearbox conversion in 180sx rattle/vibration on deceleration

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Hi all

 

Just completed my skyline gearbox conversion in the 180sx. Used the space plate adaptor from just jap.

It all went in fine and legit... Got the tail shaft professionally done/doglegged shifter/everything went in fine etc

 

Drove it... Massive rattle/vibration on deceleration... mainly around 2500RPM but constantly rattle/vibrates in 4/5th gear on low revs

 

Took it to a transmission shop, was told to replace gearbox.... So I did... Another $1000 down the drain...

 

Same problem...

 

Ps Im running a single place orc clutch with the lightened flywheel

"Ran fine with original sr20det gearbox"

 

I'm out of ideas at the moment and need some fresh thinking

 

Thanks guys

-Chris

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Have you checked the center baring?

Engine mounts?

Replaced the spigot bush?

How far does the input shaft sit in the spigot bush with the adapter plate?

If you're sure that the balance on the tail shaft is right then I'm not sure what else it could be. A mate of mine converted his old r32 to rb25 gearbox and his did the same thing.

Edited by essare

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engine mounts should be sweet

spigot bush no i didn't replace that :/

new centre bearing

 

Basically everything in the car including the clutch was fine before the skyline gearbox conversion

Since the conversion it makes this rattle

 

Ill try to get it up on a hoist tomorrow and maybe try to pinpoint where its comming from exactly

 

Thanks for the ideas

Let me know if you think of anything else

 

PS did they fix your mates skyline? what was the issue?

Edited by chriz

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I've always been a little skeptical with how well the input shaft would sit with the conversion plate spacing it back. Getting an idea of where the vibration is coming from should help work out what it could be. nah we thought it was the tail shaft that was out so he got it re balanced and it helped a bit but didn't fix it. he gave up sold it and bought a GTR instead haha. good luck man.

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it wouldn't be the spigot. your tailshaft probably isn't balanced right. is the gearbox shifting properly? and does the clutch feel normal?

 

if its always happening at exactly the same revs i'd be looking at the tailshaft first.

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Sounds like tail shaft isn't balanced right

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I have the same issue with my Z33 6speed conversion. Tail shaft vibrations are speed dependent, not rev dependent, so that can be ruled out. I have the same brand of clutch, but twin plate, and after a fair bit of research, it seems to be gear chatter due to poor damping characteristics of the ORC clutch plate. It sounds exactly the same as gear chatter on large trucks (I am a heavy diesel tech), which occurs due to pulses in the drive line power.

 

I have replaced all gearbox bearings, tried a new gearbox ($2k), re balanced tail shaft, new eng/box mounts, beaten out the gearbox tunnel to make sure it doesn't touch. I have also triple checked spigot/clutch plate engagement and tried 3 different oils. So I have pretty much ruled out everything suggested. I am now considering either a new clutch, or getting the damper springs swapped out for a set of much softer items. I have been dailying it for 30,000km and a couple of track days, no metal in the oil, its just annoying but wont hurt anything.

 

Stephanie

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Gearbox shifts great and everything drives fine!

 

Ill get the whole tailshaft rebalanced and go from there, thats the only thing that has been modified

as I had the front half modified and rebalanced but not the whole tailshaft rebalanced.

 

Thanks for everyones input all I can think of is it would be the tailshaft out of balance or the clutch

I wouldnt understand it being the clutch as it was fine with an sr20det gearbox.

Im not too keen on replacing the clutch as the orc holds up good and most other clutches in my experience are rubbish

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both our boxes are designed for a 6 cylinder engines, which have a much smoother torque pulse. If re balancing doesnt fix it, I would be talking to jim berry or NPC about getting softer springs in the clutch disc. When I can be bothered pulling the box again, this is what I will be doing.

 

Steph

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Ok so the whole tailshaft was out of balance by 80grams. Im waiting on them to re-balance it for me and I will let you guys know later this evening on how things go.

Thanks so much for the help

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Ok so the whole tailshaft was out of balance by 80grams. Im waiting on them to re-balance it for me and I will let you guys know later this evening on how things go.

Thanks so much for the help

 

Also when u Pick the tail shaft up ask them what speed they had it balanced to

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f**king hell! thats heaps, considering you don't usually need that much on an average wheel when you balance them...

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f**king oath its heaps... i used to work at a tyre joint and that on a rim is crazy

the first guy who did my tailshaft butcherd it, i took it elsewhere and got the whole tailshaft done now :)

 

so i took the beast around the block 90% of the vibration is gone

there is a little there now but nothing to really worry about, maybe its the type of clutch and gearbox together

 

it only does it slightly in decel in 2nd

no more every gear on decel or constantly low speed 4/5th gear

 

im content with it now

as before the vibartion would have been to kind to ruin a gearbox

where as now it kinda sounds like my old manual soarer in 5th when driving too slow

 

thanks for all the help

 

im taking for a decent run tonight and will let you know how it goes

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Just took her for an epic drive

Rattle on decel still there although not as bad still 30% there but not as aggressive

It must be the type of clutch as Steph has said because by the sound of things I have ruled out everything else

 

Noise is till fairly annoying but I guess thats the price you pay for a modified car...

Either I put up with it or change the clutch and go back to a std flywheel

 

Cheers

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If anyone has any other ideas how to fix this properly let me know

Ive had a few guys pming me saying they have the same issue with the conversion

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It's possibly an alignment issue.

 

You'll need to remove the gearbox and clutch assembly, and inspect them for unusual wear.

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What clutch are you using? and what diff are you using? I'd still say something is out of balance or alignment.

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and I dare say it but it could be something really stupid.. like a bracket loose somewhere under the car that on that rev it makes a vibration.. I've seen this happen before.

 

Have you tried putting it up on a hoist and going through the gears?

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I did a Z32 conversion with a single plate ORC 409D non dampened and had the exact same problem, could not work it out. I tried flipping the tailshaft and spacing it in case the angle was wrong, changing mounts, bashing tunnel out, checking all bolts etc but made no difference.

My motor popped so I've decided to change the clutch while its out being built. I chose a NPC custom 10" single plate dampened clutch rated to 400kw as its a daily driver with track duties on odd weekends. I will let you know the results in a week or so if the noise is gone in the drive train.

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thanks guys

 

ok so i have found out that skyline and silvia thrower bearing carriers have diffrent lengths

im using the silvia one on the skyline fork which is shorter that a skyline one "the thower bearing carrier"

this could cause a rattle

 

on top of that i need to check my spigot bearing i have a feeling it could be one or the other

the gearbox input shaft might not even be sitting in the spigot bearing due to the space plate adaptor

 

ill keep you guys updated

ripping the box out for the third time tomorrow

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You're a better man than me. I would have burned it down and sat in the corner rocking back and forth after the second time pulling the box out.

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I have had the box in and out about 10 times now, rebuilt it once, and tried another 2k gearbox. Just driving till it breaks now, when it does, I will put the spare box and different clutch in :P

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i almost parted it! this is like the third time i almost gave up on it

hate working on it... love hacking it...

 

ill keep you peeps updated

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OK GUYS

DONT USE THE SR20 THROWER BEARING AND CASE ITS SHORTER THAN THE RB

 

"by at least 1.5cm"

 

this was causing the rattle... for me in this case anyway

 

parting the car had enough of this shit and the cops in nsw f**king pigs

 

going to something more newer/cleaner/reliable and stronger from factory

plus something less defectable and stdish

 

sorry to hijack the post but here goes.... ;)

Edited by chriz

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