Strange clutch issue - not disengaging properly

[Gareth87]

Hi all,

 

Just fitted a fully rebuilt R34 RB25 box behind my FJ20 and went for the first drive today but had an issue..

If I put my foot on the clutch fully and try to engage 1st, it doesn't seem to be disengaging the clutch fully as it starts to creep forward without being in gear.

Once I actually push it into gear, the clutch bite point is very high in the stroke which I thought would be the oppsite?

It also shuddered when clutching off from standstill.

Any ideas?

Facts are..

R34 Neo box - pull type clutch

FJ20 billet lightweight flywheel - fresh facing

Nismo slave cylinder

Master cylinder is original nissan bluebird

 

[BK]

Does sound very strange. Your "fully rebuilt" gearbox could've been stuffed up on the rebuild and it's hanging onto the synchro baulk rings which means it's not fully deselecting the gear engagement. Could also be a selector problem. If either is case the problem is within the gearbox  Could also be just very tight synchro engagement and will go away once worn in.

One thing I would be doing for a start is getting rid of that Nismo big bore slave cylinder and going back to the standard one, as the smaller bore Nissan pull slave has more travel than the Nismo - been there, done that years ago.

The Nismo slave cylinders push or pull are pure shit because of their shorter stroke length and only cause problems.

[Duncan]

Unless you can fix it with pedal adjustment, I believe the issue will be related to the release bearing not having enough movement to release properly. The only way to understand and fix that is box off and measure the movement. I've never had to do it but there will be DIY guides out there somewhere

[BK]

On 31/03/2022 at 6:16 AM, Duncan said:

Unless you can fix it with pedal adjustment, I believe the issue will be related to the release bearing not having enough movement to release properly.

That's right and Nismo slave reduces this movement for a start, so unless you can change the stroke via clutch pedal movement theres not a lot you can do. Being a pull clutch there's really no way to change it at the release bearing end or release fork hinge point - everything is at a fixed distance. You can't change bearing carrier lengths or pivot fork heights like you can in a push setup to correct problems like this. Have used a custom longer rod at pull slave cylinder once before, but again was to temporarily get around the incorrect clutch as you shouldn't have to do that.

On another note, being an FJ the clutch would surely have to be custom height too when using a pull setup, and not a Skyline based pull clutch (assuming, as no clutch type was stated) as I can't see it being the same.

I must have misread initially though as my comments regarding the gearbox were more aimed as interpreting the car creeping while in neutral using the clutch, as I don't think thats what was meant.

[Gareth87]

Hey all.. thanks for the replies.. yep. I'm guessing the clutch height is out of wack. I had the rb flywheel next to the fj flywheel and the FJ fly is thinner I'm pretty sure.

I should of picked this up but It makes sense now i think about how the pull type clutch works..

We lengthened the slave shaft today as a test and popped the centre ring off the clutch so the box has to come out anyway now.

I'm guessing this is something that can be machined and fixed? This is all a bit new to me with a pull clutch.