Van Diemen clutch slave cylinder

[Spengo]

I should probably just make forum threads for my dumb questions rather than bothering people in pm. Anyway, I'm going to be replacing the o-rings in my clutch slave cylinder. I have the car split and I've undone the two bolts and banjo ends. I thought it would come right out but it does not budge. Bonked it with a rubber mallet gently, also tapped with a punch to try and rotate it. Should I give it bigger whacks or is it attached somewhere else that I can't see requiring more disassembly? PB blaster maybe? I do not want to damage anything.

[Rick Silver]

I should probably just make forum threads for my dumb questions rather than bothering people in pm. Anyway, I'm going to be replacing the o-rings in my clutch slave cylinder. I have the car split and I've undone the two bolts and banjo ends. I thought it would come right out but it does not budge. Bonked it with a rubber mallet gently, also tapped with a punch to try and rotate it. Should I give it bigger whacks or is it attached somewhere else that I can't see requiring more disassembly? PB blaster maybe? I do not want to damage anything. 20230303_142258.jpg

Put the two banjo bolts back in hand tight and take a "reverse" prybar and gently pry it out. It will come out with a few wiggles. Make sure to replace all of the o-rings including the static o-ring in back.

Also make sure you are using EPDM o-rings and not Buna-n.

Also if you have a threaded and not circlip held in centertube - it is reverse threaded.

[Spengo]

Thanks, got it loose. It doesn't come very far forward though, there are these walls on either side inside the bellhousing that seem to be blocking it from coming all the way out. I got the o-ring kit from Primus so presumably they are the most ideal o-rings.

[Rick Silver]

Thanks, got it loose. It doesn't come very far forward though, there are these walls on either side inside the bellhousing that seem to be blocking it from coming all the way out. I got the o-ring kit from Primus so presumably they are the most ideal o-rings.

What year is it? Mine has an o-ring right behind the slave cylinder which you appear to have gotten loose and then further back a second o-ring it seats into which is a tube through the oil tank and bell housing into the diff. My guess is its just stuck on that o-ring and you juts have to pry a bit harder. I do not know how that tube is secured into the differential housing, although that replacement o-ring was included in the oil tank seal kit I also got from Brad.

[Spengo]

What year is it? Mine has an o-ring right behind the slave cylinder which you nappear to have gotten loose and then further back a second o-ring it seats into which is a tube through the oil tank and bell housing into the diff. My guess is its just stuck on that o-ring and you juts have to pry a bit harder. I do not know how that tube is secured into the differential housing, although that replacement o-ring was included in the oil tank seal kit I also got from Brad.

It's an RF99, I'll give it a go

[Spengo]

Got it. Messy.

[Rick Silver]

Got it. Messy.

Wow, that is amazing. I just did mine on my 1998 that has the full 2001 wide track suspension and complete body work updates. I did replace my bell housing and slave cylinder at some point around 2003. Mine came apart quite easily but I have done it a few times over the years.

My slave slides into the collar that broke off on yours with a simple o-ring as a seal. I do use a little sealant there to be safe. It looks like someone epoxied or used an adhesive on your collar to slave seal. And the tube in the picture looks like it is corroded. Is it? That would be quite strange.

[Spengo]

I think the tube is fine, it's still in there and doesn't appear to be broken. All that silver stuff is some kind of rubbery gunk. I suspect racetrack repairs. Some kind of silicone/caulking in a tube. When there was no Brad around Home Depot had to do. I guess I know why I always had clutch problems.

I wonder if I should take it apart further so I can remove that tube and see if there are any more fun surprises.

[BeerBudgetRacing]

Take the gearbox off for sure so you can inspect and reassemble without the shaft in the way.

[DaveW]

I think the tube is fine, it's still in there and doesn't appear to be broken. All that silver stuff is some kind of rubbery gunk. I suspect racetrack repairs. Some kind of silicone/caulking in a tube. When there was no Brad around Home Depot had to do. I guess I know why I always had clutch problems.

I wonder if I should take it apart further so I can remove that tube and see if there are any more fun surprises.

That RTV may have been an attempt to keep engine oil from leaking into the bellhousing, so I agree with BeerBudget that you need to properly inspect the tube and its o-rings/sealing.

[Spengo]

Got the bellhousing off. As suspected, found more RTV where gaskets are supposed to be. Is there also supposed to be a fancy specific gasket between the bellhousing and transmission?

[Rick Kirchner]

there's a large o-ring that is supposed to be there.

[Spengo]

there's a large o-ring that is supposed to be there.

I think I have that I mean the outer rectangle

[BeerBudgetRacing]

I think I have that I mean the outer rectangle

Not sure where you can get an original.

I've had good luck using X seals from McMaster on the gearbox.
https://www.mcmaster.com/products/se...ction-shape~x/

I would use SOME rtv on both of the seals.

[Rick Kirchner]

shouldn't there be a plate between the box and the tank? I don't know about the later model cars, but on 90-96 there's a 1/4" plate with an o-ring groove

[BrianT1]

I wouldn't be to concerned with the o ring on the gearbox to bell housing side.The one that you have on the gearbox side seems fine. that back opening in the bell housing is a catch tank for engine oil over flow. If you have your engine oil level correct you will only spit out a small amount. Then if you drain it there will be no oil in that catch tank. So there won't be any leaks.

The silicon that's there is more than likely a precaution for the through tube. That through tube has o rings on the inside of it which keep the oil in the bell housing and the silicon is just a safety measure. Not usually needed but won't hurt either.

Brian

[BeerBudgetRacing]

The silicon that's there is more than likely a precaution for the through tube. That through tube has o rings on the inside of it which keep the oil in the bell housing and the silicon is just a safety measure. Not usually needed but won't hurt either.

On the 96 and prior bellhousings there is a plate that sandwiches between the bellhousing and the gearbox. There is a 'catchcan' there as well, but most have been modified (aka holes drilled through to the oil tank) to increase oil capacity.

So the through tube (which is built into the bellhousing) needs to be sealed from the catch can.
On the older cars the 'catch can' was essentially sealed by the plate - not the gearbox mating surface.

On the later cars (I haven't had to pull by RF01 apart yet) I understand the design changed so the through tube is replaceable.
Does the through tube go through a tunnel or is it exposed to the oil in the tank?

From these pictures it looks like it needs to seal at both ends and in the middle where 2 sections meet.

[BrianT1]

On the 96 and prior bellhousings there is a plate that sandwiches between the bellhousing and the gearbox. There is a 'catchcan' there as well, but most have been modified (aka holes drilled through to the oil tank) to increase oil capacity.

So the through tube (which is built into the bellhousing) needs to be sealed from the catch can.
On the older cars the 'catch can' was essentially sealed by the plate - not the gearbox mating surface.

On the later cars (I haven't had to pull by RF01 apart yet) I understand the design changed so the through tube is replaceable.
Does the through tube go through a tunnel or is it exposed to the oil in the tank?

From these pictures it looks like it needs to seal at both ends and in the middle where 2 sections meet.

The through tube is in 4 pieces. Each of those pieces has o rings and in some cases multiple o rings that seal the tank from leaking. But a little silicon in areas is just added protection, especially since the bell housings are over 20 years old and I bet most have not changed the o rings in a long time.

Brian

[Spengo]

BrianT is exactly right, the rear of the bellhousing is a gigantic catch can. I've cleaned out 95% of the RTV from the nooks and crannies and figured out where most of the o-rings belong. I don't think I need any fresh RTV, everywhere that it was applied liberally was missing the matching o-rings. Maybe it's worth putting some fresh RTV between the bellhousing catch can section and diff just to ensure anything that ends up in there doesn't leak out, shouldn't hurt anything anyway.



The rest of the ones from the bellhousing o-ring kit I assume go with the oil system that I have not disassembled as it has never leaked on me. I have one more from the clutch o-ring kit that is identical to the two that go inside the piston. Does this go somewhere I have not found or do some models have three o-ring slots instead of two inside? Remaining o-rings shown below:


If all is good to go I can start putting things back together.

[Rick Silver]

BrianT is exactly right, the rear of the bellhousing is a gigantic catch can. I've cleaned out 95% of the RTV from the nooks and crannies and figured out where most of the o-rings belong. I don't think I need any fresh RTV, everywhere that it was applied liberally was missing the matching o-rings. Maybe it's worth putting some fresh RTV between the bellhousing catch can section and diff just to ensure anything that ends up in there doesn't leak out, shouldn't hurt anything anyway.



The rest of the ones from the bellhousing o-ring kit I assume go with the oil system that I have not disassembled as it has never leaked on me. I have one more from the clutch o-ring kit that is identical to the two that go inside the piston. Does this go somewhere I have not found or do some models have three o-ring slots instead of two inside? Remaining o-rings shown below:


If all is good to go I can start putting things back together.

The extra oring goes in the slave cylinder and the tube that you did not remove needs to be removed and you will see where the oring goes. Note that the tube, if it is the threaded type (they make one that has a circlip also), is LEFT hand threaded. You may need to make a tool to fit the two slots.

I put a small amount of sealant on the oring that does the slave to belhousing seal and same for the one that goes between the slave and tube - a small amount as an extra precaution.

[Spengo]

The extra oring goes in the slave cylinder and the tube that you did not remove needs to be removed and you will see where the oring goes. Note that the tube, if it is the threaded type (they make one that has a circlip also), is LEFT hand threaded. You may need to make a tool to fit the two slots.

I put a small amount of sealant on the oring that does the slave to belhousing seal and same for the one that goes between the slave and tube - a small amount as an extra precaution.

Gotcha, I see how it goes. I think a pin spanner wrench will work.

[Spengo]

A machinist friend made me a tool but this is requiring way more force than I would expect. It's not budging even with a half inch drive breaker bar. Could there be red loctite involved? It's definitely left-hand threaded meaning turn clockwise to remove right?

EDIT: Got it! baked it in the oven for half an hour, came out like it was nothing.

[Spengo]

Made a crappy video

[alangbaker]

Made a crappy video

Cool!

This may come in very handy for me in the next couple of weeks as my clutch slave seems to be misbehaving; albeit it somewhat differently. When I lift my foot off the clutch pedal when the car is cold, the slave cylinder sometimes sticks and takes a moment or two to let the clutch engage...usually resulting in a stall just as I go to drive down to pre-grid.

[Messenger Racing]

Alan,

It sounds like you have a different issue common to Honda/VD applications - give me a call tomorrow to discuss if you like.

Jay

Cool!

This may come in very handy for me in the next couple of weeks as my clutch slave seems to be misbehaving; albeit it somewhat differently. When I lift my foot off the clutch pedal when the car is cold, the slave cylinder sometimes sticks and takes a moment or two to let the clutch engage...usually resulting in a stall just as I go to drive down to pre-grid.

[Spengo]

I have forgiven whichever of the previous owners RTVed the crap out of the slave cylinder and through tube. I have now broken the car in half and put it back together four times. I am 99% sure the oil tank will retain oil now.

[Spengo]

The slave cylinder o-rings blew again when I raced last weekend. It lasted all of the first day and half of the second. By the third day it was visibly squirting fluid out when I pressed the pedal. I have been given a few ideas for why it failed.

1. The o-rings require grease such as Lucas Cylinder Grease to last
2. The throwout bearing needs .010-.015 clearance between it and the clutch spring fingers when disengaged, I guess the engine spins so fast that it causes it to heat up if it's touching? Or maybe even spins the slave piston?
3. The clutch pedal needs a stop so you don't press it too far, 3/16" past disengagement. Not sure how this causes a problem though.

Of these, #2 seems most likely since it has always seemed like heating the car up is what made the clutch stop working though I would have thought it would self adjust. My plan is to measure the face of the engine to the face of the fingers on the clutch using a board across them, then push the slave all the way in and measure from the face of the bellhousing to the face of the throwout bearing to determine how much clearance there actually is. If there is no clearance it doesn't seem adjustable but I guess I can either give the slave cylinder housing to my lathe bro to give it the ol' spin treatment or shim the bellhousing away from the engine either with washers or perhaps even a laser cut shim that goes all the way around. Any other thoughts or ideas?

[DaveW]

#1 - Brake-compatible grease dissolves in brake fluid quickly. Brake grease aids assembly, but doesn't stay there for long, so that's not likely.

#2 is a slight possibility. Excess heat from any cause can cause issues with short seal life. Normally the TO brg spins (unless it's binding), but the slave piston does not. Usually, the symptom of lack of clearance is a slipping clutch, not seal issues.

#3 - The pedal needs a stop to keep the spring from over-deflecting and yielding, but that doesn't often cause a slave-seal issue. However if the slave piston moves way too far, one of the seals can lose contact and leak, or cause it to bind and be damaged as it retracts.

More thoughts:

It's a requirement to leave some clearance (about 0.2") when the slave piston is fully compressed so that any time the pedal is not depressed, the TO brg can relax away from the spring and does not contact the spring with any force. That should not compromise release, but does allow some room for thermal expansion, disk wear (which makes the spring contact point move toward the slave), etc.

I also have had issues with off-spec slave seals that were cured with the wrong cure agent (peroxide cure is required). That can cause the seal(s) to take a set at too low a temperature causing leakage.

One time I had a SS braided clutch line split its Teflon liner and leak, maybe due to too tight a bend in the line - that wasn't obvious on first inspection. I initially thought the slave was leaking, but it was the line to it.

[Rick Silver]

The slave cylinder o-rings blew again when I raced last weekend. It lasted all of the first day and half of the second. By the third day it was visibly squirting fluid out when I pressed the pedal. I have been given a few ideas for why it failed.

1. The o-rings require grease such as Lucas Cylinder Grease to last
2. The throwout bearing needs .010-.015 clearance between it and the clutch spring fingers when disengaged, I guess the engine spins so fast that it causes it to heat up if it's touching? Or maybe even spins the slave piston?
3. The clutch pedal needs a stop so you don't press it too far, 3/16" past disengagement. Not sure how this causes a problem though.

Of these, #2 seems most likely since it has always seemed like heating the car up is what made the clutch stop working though I would have thought it would self adjust. My plan is to measure the face of the engine to the face of the fingers on the clutch using a board across them, then push the slave all the way in and measure from the face of the bellhousing to the face of the throwout bearing to determine how much clearance there actually is. If there is no clearance it doesn't seem adjustable but I guess I can either give the slave cylinder housing to my lathe bro to give it the ol' spin treatment or shim the bellhousing away from the engine either with washers or perhaps even a laser cut shim that goes all the way around. Any other thoughts or ideas?

Both surfaces the orings ride on must be perfect

The orings must be epdm (iirc) and not buna n

The gap needs to ne 0.1 to 0.15 NOT 0.010 as you wrote

The inner tube needs to be tight and properly seated

After 3 complete rebuilds last year i put in a tilton and its been perfect for four races. Once they start acting up people often say you must replace the entire slave cylinder. At this point i would strongly recommend a new tilton unless you see something obvious. Move on and never look back

[BrianT1]

You and Rick were probably the last two that still have the original VD slave in their cars. I would bet every other one in America has switched to the Tilton or SAAB style slave and now that Rick changed your probably the only one. I would just bite the bullet and switch. You will be glad you did. These were a problem from the get go hence the reason they were eliminated.

Brian

[Spengo]

Guess I'll pony up for a tilton. I assume I still have to measure the gap and make sure I have clearance? Glad to hear it's 100-150 thou instead of 10-15, I was wondering if I'd even be able to measure that accurately haha.

[Lyngengr]

Guess I'll pony up for a tilton. I assume I still have to measure the gap and make sure I have clearance? Glad to hear it's 100-150 thou instead of 10-15, I was wondering if I'd even be able to measure that accurately haha.

Tilton gives you their recommended clearance, and as Rick says, it will be the largest with a new clutch disk. I have a good set of dimension in a 2D drawing if you want that, let me know. I haven't had any issues with the Tilton slave cylinder, but I do replace it every couple of years. You can get it from Pegasus.

[Spengo]

Tilton gives you their recommended clearance, and as Rick says, it will be the largest with a new clutch disk. I have a good set of dimension in a 2D drawing if you want that, let me know. I haven't had any issues with the Tilton slave cylinder, but I do replace it every couple of years. You can get it from Pegasus.

That would be great. I've ordered a Tilton slave cylinder from Brad and he tells me I need to modify the housing slightly to make it fit. He also told me to ask Rick Silver about what to do.

[BrianT1]

That would be great. I've ordered a Tilton slave cylinder from Brad and he tells me I need to modify the housing slightly to make it fit. He also told me to ask Rick Silver about what to do.

Yes you will need to modify the housing. The tilton will need to sit flush against the aluminum mounting plate. Honestly, I am not sure it can be done on yours, since it was originally the housing for the original VD slave. Most kits replaced that whole plate. Either way the face will have to be flat, so the bevel will need to be machined flat.

Send me you email and I can send photos. I am having issues uploading images at the moment.

Also you will need to measure the gap. There are plenty of videos on YouTube on it. Not necessarily for a vandiemen but it shows you how to measure for the gap.

You dont want to get this wrong or you will blow your motor by messing up the thrust bearings.

Brian

[Rick Silver]

That would be great. I've ordered a Tilton slave cylinder from Brad and he tells me I need to modify the housing slightly to make it fit. He also told me to ask Rick Silver about what to do.

im sitting in an airplane in montrose co. Ill post some details tomorrow. What Brian said is correct with the addition that you can modify your existing housing by maching the bevel flat. Ill post pics and details tomorrow

[Spengo]

Doesn't sound too hard, can probably accomplish it on the tabletop lathe a friend of mine has in his garage. I'd appreciate anything either of you guys have, you can send it to srogers@zizin.racing if there are technical difficulties posting it to a forum. I also read on the product description that a stop for the clutch pedal as someone described to me before is required for this slave cylinder. Any info on how to set that up properly would be appreciated as well.

[Rick Silver]

Doesn't sound too hard, can probably accomplish it on the tabletop lathe a friend of mine has in his garage. I'd appreciate anything either of you guys have, you can send it to srogers@zizin.racing if there are technical difficulties posting it to a forum. I also read on the product description that a stop for the clutch pedal as someone described to me before is required for this slave cylinder. Any info on how to set that up properly would be appreciated as well.

This is for a ULP 8000 series Tilton hydraulic release bearing (HRB) for a 5.5 in Tilton clutch that uses a 38 mm bearing. Clearance from bearing-to-diaphragm fingers must be between .170" and .230" for a new clutch. Clearance will decrease as the clutch discs wear. I needed the 1.44 in tall HRB to get the correct clearance. You will need a pedal stop.

The original slave cylinder face needs to be machined flat. That is you need to remove the bevel on the surface where the new hydraulic actuator will seat.

The new hydraulic release cylinder will need a spacer to get the correct gap between the bearing and the clutch cover diaphragm springs.

Once the surface is machined flat you will need to make 2 holes for the HRB bolts. This needs to be done carefully so the HRB is radially aligned with respect to the clutch cover – the tolerance should be less than 0.010 in. I rigged up a shaft and used the old piston to align the new HRB to the old slave cylinder resulting in 2 radially symmetric mounting holes.

I drilled and tapped these two holes. I threaded a socket head cap screw from the back and used thread locker. When marking the two holes the HRB needs to be rotationally aligned so the bleed hole is at the top. You will need to replace one of the two hydraulic lines as one of the old ones will likely be too short. I used aero lock nuts on the HRB side, but the threadlocked threaded bolts allow the HRB to be removed in the future without removing the original slave cylinder.

Now you need to make a spacer based on the release bearing to clutch cover spring clearance. This should result in a .170 to .230 inch clearance for a new clutch. The clearance can be measured by taking a flat bar and measure from bellhousing mounting surface to the bearing contact surface. Then measuring engine mounting surface to diaphragm spring surface. Difference is the clearance. I used a 12 in sliding combination square. I needed a .190 inch spacer made from an aluminum plate with a large cutout in the center for the input shaft.

After assembly and bleed you need to set the pedal stop. Depress the clutch pedal until the clutch just starts to disengage. The pedal should then travel about 0.25 inches more to fully disengage. You want no more than 0.200 in of actual bearing travel once the bearing first contacts the diaphragm fingers.

[Spengo]

Thank you Brian and Rick for all the directions and pictures, it was super helpful. Lathe bro faced off the old housing and made a post that fits perfectly inside where the old piston went and perfectly inside the new one so it can be perfectly centered. He also made a little bushing for drilling perfectly centered.

Now we just have to make the spacer. Used a piece of bar stock and measured from the face of the engine to the top of the clutch, then from the top of that to the springs to get the distance from the face of the engine to the springs. Then measured from the face of the bellhousing to the top of the tilton bearing. We came up with a measurement of .190" of space between the face of the bearing and the spring which is in between both measurements given, no spacer needed.

Should be rolling again soon, hopefully finally with a reliable clutch.

[Spengo]

Made another crap video so the info in this thread doesn't get lost.