Very interesting Bill. The only time I’ve seen this mod performed the case was spotfaced, spacers made etc… But the studs were drilled all the way through the case. Studs were sealed with rtv.
I don’t have access to a CNC or even a milling machine so would need to have a good machinist do it for me which is easier said than done where I live. I wonder if I could even find someone who would be able to use a thread mill to form the threads from the inside out.
Other than the solution being much less elegant than your version, do you see any possible issue with the stud holes being drilled and then tapped all the way through the case? The one I saw didn’t seem to have any problems but I have no idea how much use it got.
I would be leery of any machinist that could not do that. Thread-milling has been a staple of CNC machining for a looooong time. I do it all the time. And milling internal threads bottom up is the normal way to do it when thread-milling. Top-down is used for external threads. In both cases so the tool is climb-milling.
I agree with you completely. Unfortunately where I live there is only one company about 50 miles away that I know has a CNC. Gotta see what they say about being able (and willing) to do it.
Just to show you what kind of area this is, last time I built an XK engine I had to take it to Atlanta (2 hours away) to find a place I trusted to do the machine work… Since then I managed to find just one place locally that even has the capability to balance a rotating assembly
Ya know… It’s a simple enough mod, you could do it manually, using hand tools. Take a piece of aluminum, and a hacksaw, and cut a block big enough to make a mounting “pad”. Saw/file/grind to shape so it conforms to the shape of the bellhousing or gearbox at the chosen location.
Use the slave cylinder as a guide, and drill the two bolt holes through the “pad”. Use the “pad” as a guide to drill thru bolt holes in the bellhousing or gearbox. Hand-tap the bolt holes. If you use a spiral flute tap, 99% of the chips will come out the top of the hole, rather than going into the gearbox. Some grease around the inside of the holes, and a rag stuffed into the gearbox should catch any stragglers. Stripping the gearbox should not be necessary. Just drain the oil first, flush the affected area with new oil after tapping, and re-fill when done.
Hello Mike,
There is absolutely no problem with drilling and tapping right through into the inside of the Gearbox. Gearboxes that have these mounting studs as a standard feature (from when the V12 was introduced into production) are drilled and tapped through into the inside of the case.
The reason I don’t go all the way through, is that some clients bring the Gearbox to me for modification and don’t want the Gearbox stripped. Accordingly, I can achieve this by not drilling through to the inside of the Gearbox and finish with more complete thread forms than with tapping a blind hole.
Not to strip the Gearbox that is from, or destined for an E Type is a retrograde step in my opinion. Unless the history of the Gearbox is well known, I routinely replace the bearings of a Gearbox when its been removed form the car, even if the removal was not due to an issue with the Gearbox. Bearings are cheap and its not a huge job to strip and reassemble; far less than having to remove the Gearbox from the car further down the track.
I’ll post the dimensions you want tonight. I copied the file to a Thumb Drive yesterday and then left it at work.
I agree with Ray, in that you could could do the job using manual tools and a home made drilling jig. You could further limit the contamination of the Gearbox when drilling and tapping through into the Gearbox by placing it upside down with the face where the Top Cover bolts to, on a horizontal surface. In this way you have gravity working in your favor with regards to any swarf that may make it into the inside of the gearbox.
Liberally coating the flutes of the drill and the tap with grease will help keep the swarf from entering the Gearbox. Just before the Drill is about to break through into the inside the Gearbox Housing, clean the hole and drill, re-coat the Drill with grease and proceed. Repeat the process with the Tap.
I installed a Quarter Master hydralic release set up in my ots with a medatronics 5 speed 10 years ago. I used one in my race car for at least 5 years before that. Very simple devices - they use an o ring to seal it and have been bulletproof. Only problem is they are not adjustable without removal from the car, and that’s a problem.
I’m totally ignorant on V12’s. Is the stock clutch slave mounted to the transmission ?
The following picture shows the Gearbox Housing from an S2 E Type showing the facility for the mounting studs missing. This is also the case for the S1 XJ6.
The following picture is of a Gearbox, with Overdrive, from an S2 XJ6 Jaguar, showing the inclusion of the facility for the Gearbox mounted Clutch Slave Cylinder. From the introduction of the V12 and the requirement of the Gearbox mounted Clutch Slave Cylinder only one style of 4 speed, all synchromesh Gearbox Housing, as used with the E Type, was produced for use with both V12 and 6 cylinder applications.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
28
Does that slave cylinder push or pull? Does the one mounted on the bell housing push or pull? If they both push, I’m guessing the lever arrangement inside the bell housing is dramatically different between the two.
Hello Kirbert,
They both push. The V12 has the pivot on the far side from Clutch Slave Cylinder, on the outside of the Bell Housing in fact, whilst the pivot for the 6 cylinder application is on the same side as the Cylinder.
That’s a good idea Ray. I had also thought about making a similar plate/pad that mounts to 2 of the shift cover bolt and one of the flywheel bolts so maybe I could get away without drilling anything… might be just a crazy thought though. Wishful thinking. I love your thought of not having to strip the gearbox too!
I think my biggest concern with pulling it apart is probably irrational. I’ve become afraid of replacement parts. It seems like every single aftermarket replacement has some kind of problem. What brand of bearing do you use? And have you had any issues with new synchros? This box I’m going to use is not completely unknown to me cause I had it in another car. It does have wear but nothing terrible. It has some of the 'ol reverse idler roar though. Definitely gonna rebuild the O/D though.
Hi Terry - that was the setup I was thinking about when I started the thread. The XK engine medatronics bellhousing is already drilled to accept a concentric hydraulic throwout bearing (forget the brand now). I wanted to sort of mimic that although the Jag box isn’t sealed at the front like the JT5 so I’d have to make something to position the throwout above the back of the bell to maintain the bearing retainer area. But with all the good input about using the original style slave I think I’m convinced to do it that way.
Thank you very much Bill! that’s perfect!
Thanks again guys! I should have the V12 bellhousing this week - will let you know how it goes.
Best,
~Mike
I think my biggest concern with pulling it apart is probably irrational. I’ve become afraid of replacement parts. It seems like every single aftermarket replacement has some kind of problem.
No Mike not irrational, not irrational at all.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
33
If they both push, I find that spring in one of the photos a bit disconcerting. Seems to me that could pull the lever and slave cylinder too far back, perhaps all the way to the retracted end of its travel. Then you’d have no clutch, you’d have to pump it up. I always understood it was the clutch itself that needed to push the throwout back.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
34
Probably just the engineer in me, but it bugs me to see that slave mounted with just two bolts. It looks like everything is iron so perhaps it’s not a problem, but I visualize the slave rocking a bit with each actuation, stressing the mounting bolts and lugs. That bottom picture seems to show a pad of sorts to the left of the two mounting bolts; I’m wondering if that’s intended as a foot for the tail end of the slave to keep it from rocking. If it is, it might be a good idea to replicate that pad on the retrofit jobs.
Hello Kilbert,
Its supposed to pull the piston right back. Free play of the clutch is then adjusted via the threaded coupling and the Threaded end of the piston rod.
Yes, its a pad that a corresponding pad on the Clutch Cylinder body rests on to oppose the moment applied by the push of the piston. The two bolts and the pad is a system that has stood the test of time with the Jaguar.
Regards,
Bill
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
38
Ah, that makes sense. Having to adjust it didn’t occur to me. All of these things I’ve fiddled with just moved down the length of the slave cylinder as the clutch wore.
My dad is the e-type expert in the family, but as I understand it the factory throwout bearing is some sort of carbon block which must not ride on the clutch fingers unless one actually is releasing the clutch. Sitting at a stoplight with the clutch in = bad. Resting your foot on the clutch pedal = bad. The spring affair guarantees enough free travel to prevent excess wear on the TO bearing, the trade off being that the clutch does not self-adjust. I am sure someone more knowledgeable than myself can correct me where I have that wrong… Our e-type went straight from BW autobox to T5, so I’ve never worked on the factory setup.
1 Like
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
40
Am I to presume that the bellhousing in question is from a manual transmission car and already has the opening and the lever? The OP’s question merely regarded whether or not it would be necessary to drill the mounting holes in the transmission itself for the slave cylinder mounting?
Even so, I’d be sorely tempted to do away with that carbon throwout bearing. There’s a reason they don’t use those things any more. Now, is it possible to replace the carbon throwout bearing with a ball bearing while still utilizing the original lever and external slave cylinder? If so, that might be a good way to go. If not, that would be another argument for going with the concentric slave cylinder idea.
It might also depend on the clutch itself. I understand you can either get a 3-lever thing or a bellville spring clutch, with the bellville spring style being easier on the left leg. Will either type clutch work with either type throwout bearing?
One more factor: I’m pretty sure the concentric slave cylinder never needs adjusting.
Lotsa cars use those concentric slave cylinders. Seems to me it should be a simple matter to figure out how to make one work reliably.
