Gav

Hi,
Been putting up with hard to shift issues from the start.
Ls1 t56 combo.
Dont know what clutch is but its a kit car the swap is in.
If i bleed clutch and flush master cyl (master is 0.75) the clutch fluid stays ok for a while and shifting improves very... slightly. Even switching to dot 5 non synthetic helped for a bit... After 100 miles or so fluid is black again in master.
I suppose all i can do is drop the trans and have a look at clutch and slave and pilot.?
My main question is that can the slave be dead and not loose any clutch fluid, i never have to top up at all the master...
Initially it was just hard to shift 2 to 3 or high rpm shifts, gears sometimes dropping out especially reverse. Just wondering if slave is sticking or something.
Hope someone please could give me some guidance.
Regards
Gavin

Gav

110 views and i bet over 100 of you know more than me...

jmd

iTrader: (4)

Black shoudn't happen in 100 mi, though it does happen over time.
Air can enter at the hose from reservoir to master. I like EFI clamps around that hose's junctions. You should also try and use the OEM style reservoir lid gasket, which disallows fluid contact with air for the most parts.
Other system areas are going to leak under pressure, not introducing air.
If you have no leaks, and that's all good, a slave replacement isn't a bad troubleshooting step. If you've a brake and clutch rebuilder, you might have the, review your app for proper operation while you can easily pull it.

Gav

Thanks for reply.
My master has no external reservoir, its part of the main body.
Just a massive job to drop the trans myself..
Regards
Gav

xny1989

iTrader: (1)

fluid turning black so quickly may be from excessive heat on the braided line from the master to the slave. If that line is stock, you may benefit from doing the "drill mod" to widen the internal diameter of the line exiting the master. See sticky in this section for more info. on this. If heat is the issue, wrap the line with heat barrier.

Gav

Hi, its an ls swap no nothing master wise is stock, hence suppose no restriction in master line from a generic master cylinder.
Got trouble going from 5th tp 6th as well, shift fork bent? Starting to think total stripdown of t56 and check internals if i drop the tranny to check slave, pilot bearing, clutch etc etc.
Reg
Gav

stevieturbo

Removing the trans should be very easy in most cars ?

If you're having issues with shifting in most gears...then you'd best be looking at clutch issues before the box itself.

Jack driven wheels up, run the engine and try the car in gear, foot on the clutch. Do the wheels try to turn ?

You say it's a swap....and a 0.75 master. But how much travel do you have at the master ? Or more importantly at the actual slave ?

If you dont have enough, then you'll never get it to work

gnx7

iTrader: (28)

The Wilwood 7/8" bore MC have had issues recently.... if you are running one. It may have failed.

Gav

Hi,
Removing trans may be a nightmare as may not have enough room to pull trans back to clear clutch...its tight....which may mean engine out or disconnecting engine parts to move forward one inch....dont know yet but will try this autumn winter....
I dont know about the travel from master as havnt tried it.
As was given engine and gearbox with clutch on it and slave, i have no starting point on what clutch it is, how old it is, same with slave and gbox..
Clutch pedal feels ok though
Will jack car up and rev in gear next chance i get with clutch in.
Regards
Gav

stevieturbo

If you do not know that you have adequate travel available at the slave from your pedal/hydraulic assembly, then you're wasting your time with any clutch, as that's some basic first and vital steps.

It can sort of be overlooked on a standard application with all factory parts, but for a custom application, it must be known to be ok.

Gav

I suppose in that case i have got to drop the box then anyway?
Regards
Gav

Gav

The master i bought is this
https://www.merlinmotorsport.co.uk/p...68606-gmc-12-i

stevieturbo

The master is only one part. The slave is only one part. The pedal is only one part..etc etc

If you have sufficient travel at the master rod, then yes it may be fine, but that depends on the pedal and what leverage is offered by the master rod position relative to pedal travel.

A 3/4" bore master will probably need around 1" of travel to operate the slave correctly.

The actual slave/release bearing, probably needs around 12mm, but that can vary a little depending on clutch. If you had 12mm, then it's a fairly safe bet your clutch should be clearing.

But jack the driven wheels up and do that test first, it's a lot easier than getting upside down trying to work at a pedal box !

Or get a small USB scope camera to view what's going on inside the bellhousing when you press the pedal, but it's hard to get any measurements from that.

Gav

Thanks Steve,
Will jack up rear at weekend put clutch in and rev it. Stupid question but how high should i rev because the problems are mostly high rpm orientated
Regards

stevieturbo

You dont really need to rev it much, you're just testing to see if the clutch is dragging, or whether it may be clearing correctly.

But basically the wheels should not try and turn at all if the clutch is fully released ( and make sure the handbrake is off etc lol )

Gav

Thanks, will do and update.
Regards
Gav

Gav

Ok, just tried this. Rear wheels jacked. Engine ticking over. Handbrake off. Clutch pedal down, selected first and revved to 1500rpm, no rear wheels turning. Slowly let out clutch and wheels start to turn when clutch pedal approx 2/3rds out .Repeated and about same bite point.
Regards
Gav

stevieturbo

That would be a good sign that the clutch system itself is working reasonably well, and not dragging.

So less likely to be the cause of poor shifting.

A dragging clutch or any similar issue will be more apparent on downshifts than upshifts, as upshifts naturally tend to be easier ( normal driving of course )

Gav

Gonna drop the box in a month. Replace the slave and clutch Diamond stage 2. Fit an easy bleeder to the slave. And open the box up and check synchros and internals.
At least i will have a baseline then and know how old things are.
I do have a slight oil drip from the rear flange of the gearbox anyway, oil level is ok though, so will have to remove to seal that up.
Regards
Gavin