Anyone using an adjustable clutch pushrod?

[Guest]

Bought a new slave cylinder and was thinking of putting one of these on with it. I was hoping someone was using one already and if it kept the pedal good and firm like it advertises.

Moss adjustable clutch push rod

 

[TR3driver]

Adjustable pushrods were standard on older Triumphs like my TR3A. They do allow you to adjust the freeplay at the slave, as stated. Of course, you have to periodically reset it as the clutch plate wears.

But the joker is that the later system is supposed to operate with zero freeplay at the slave, meaning the highest possible pedal. If it doesn't, then something else is wrong that should be fixed (like maybe the spring inside the clutch slave that takes up any freeplay is broken or missing).

BTW, 0.3" seems huge to me. .030" is more rational, and ISTR some references say as low as .010". Since the mechanical advantage from the pedal to the slave pushrod is something like 7:1, 0.3" would cause an extra 2.1" of pedal travel. This would be particularly bad on a late TR6, since they are very short on travel at the slave anyway (IMO).

 

[TR6oldtimer]

I agree with Randall. If you use the adjustable push rod, you need to remove the internal spring in the slave and install an external spring as used on earlier TR's. The external spring will pull the push rod all the way into the slave. You then adjust the push rod to obtain the proper clearance between the clutch and throwout bearing. This is what I did on my 6.

The TR6 was originally designed to have the throwout bearing in constant contact with the clutch. Original equipment worked well. As parts suppliers moved to non-original throwout bearings and clutches, parts not designed to be in constant contact were used. This caused premature wear on the clutch and/or failure of the the bearing.

Also note:
From the Buckeye web site:

"The TO bearing in the TR250 & TR6 is also designed to be in constant contact with the pressure plate spring fingers. When the stiffer KOYO TO bearing is substituted for the OEM bearing, the force between the TO bearing and pressure plate is insufficient to keep the bearing spinning so it squeals or chirps. Many have modified the system to pull the KOYO TO bearing away from the spring fingers using components from the TR3/TR4. When this is done, it only squeals when the clutch pedal is pressed. "

 

[TR3driver]

From the Buckeye web site:

"The TO bearing in the TR250 & TR6 is also designed to be in constant contact with the pressure plate spring fingers. When the stiffer KOYO TO bearing is substituted for the OEM bearing, the force between the TO bearing and pressure plate is insufficient to keep the bearing spinning so it squeals or chirps.

A better solution to that problem, IMO, is to add an external spring to supply enough extra pressure to spin the TOB. This is included in the Gunst kit (although apparently not in some of the copies).

(Of course, I feel an even better solution is to stick with the stock bearing, but I won't argue the point.)

 

[TR6oldtimer]

Re: Anyone using an adjustable clutch push rod?

/bcforum/images/%%GRAEMLIN_URL%%/iagree.gif
OEM is the best way to go, but there is still lots of confusion here on my part, particularly when it comes to the TO bearing and the type of clutch. I seem to recall there are many articles describing excessive wear of the clutch fingers from improperly matched TO bearings or engagement systems. I will have to look more into this when the time comes to work on the engine and clutch.

 

[TR3driver]

Re: Anyone using an adjustable clutch push rod?

The excessive wear is caused by the same thing that causes the 'squeal'. The original design was for the bearing to be lightly loaded into the pressure plate fingers and hence turn all the time. The original bearings were designed to turn very easily. But some other bearings being offered/used as 'uprated replacements' take more force to spin. So instead of spinning, they rub against the fingers, causing them to wear and/or squeal.

Unfortunately, there were a lot of replacement bearings on the market a few years back that were supposed to be equivalent to the original, but were too stiff (ie defective), so that problem got mixed up with all the other woes that TR6 clutches seem to suffer. I've also heard that some books don't mention the spring inside the slave.

 

[pa297pass]

Re: Anyone using an adjustable clutch push rod?

What does everyone think about "upgrading" or modifying the stock TR6 clutch hydraulic system? I have a '74 with the 0.70 inch master cylinder.

Would it be worthwhile to change to the earlier TR6 master cylinder with the 0.75 inch bore?

BPNorthwest sells a "long throw" clutch slave cylinder ... is this a worthwhile upgrade?

The reason I ask (sorry Stirkle for stealing your thread) is my LUK/stock clutch is starting to act up with about 10 years, 5K miles on it.

Thanks as always for your help.

Matt

 

[TR3driver]

Re: Anyone using an adjustable clutch push rod?

IMO, to answer your questions, we need to know exactly what "starting to act up" means. Switching to a larger MC or a smaller slave will help if the problem is lack of travel at the slave (although repairing all those worn pivots would likely fix the problem as well, without increasing the pedal effort as swapping the cylinders will).

But if the problem is a stiff TOB, or the TOB carrier hanging on the transmission nose, or the "dowel bolts" being missing, or the taper pin being broken, or the clutch plate coming apart, or rust on the input shaft, or (you get the idea); then swapping the MC and/or slave isn't going to help.

 

[Brosky]

Re: Anyone using an adjustable clutch push rod?

I had issues with the Gunst bearing and the Borg & Beck clutch assembly, which I replaced with the TRF Magic Kit, that uses the LUK and Koyo T/O Bearing. At the time, the Gunst was supposed to work well with B&B, but we all know better now. You don't have to ask ME how I know.

https://www.74tr6.com/clutchreplacement.htm

The Gunst squealed constantly as described above and the pictures in the link will show why. It is a hard bearing to turn, compared to the original, thus the squeal, again as mentioned above.

Now, how does the Koyo work in comparison? Like a charm, BUT there is a very slight noise when the clutch is disengaged and the car is idling in neutral. Nothing to compare with the Gunst.

I do have the adjustable push rod and it's a waste of money. Use the stock push rod and put a mild return spring on the lever arm to help keep it retracted away from the pressure plate and you should have no further problems.

Any clutch that is designed to have a T/O bearing ride against the pressure plate is candidate for issues in the future. There are only so many revolutions that will be available before the lubricant gives out and failure occurs. The less that it spins, the better.

EDIT: I also have the bigger bore and no problems so far. knock on wood, but I don't really expect any, since I replaced everything when I did the job.

 

[pa297pass]

Re: Anyone using an adjustable clutch push rod?

Randall:

The last few time I have driven my car the clutch doesn't seem to be disengaging all the way. The car is getting hard to shift into first gear, and the other day, I actually couldn't put it into reverse (gears would clash).

When I rebuilt it ten years ago, I put a new cross shaft, and throwout fork in it, and I'm pretty sure I drilled and pinned the throwout fork to prevent the pin from breaking.

I am hoping to shotgun this and replace the master, slave and plastic clutch line all at the same time. Just wondering if I should be changing any of the parts from stock specification.

Thanks for the help.

Matt

 

[Don Elliott]

Re: Anyone using an adjustable clutch push rod?

I THINK THAT $36.95 IS OUTRAGOUS !

Check the spares for a TR3A. Also check the price of the yoke, the rod and the link pin separately.

 

[TR3driver]

Re: Anyone using an adjustable clutch push rod?

Does the clutch also engage with the pedal very near the floor ? If so, changing to the .75 MC is probably a good move. If not, I would be thinking more along the lines of missing dowel bolts, bad pilot bearing, or rusty input shaft.

But you might try inspecting/repairing the joint between the MC pushrod and the clutch pedal. The clevis, pin and pedal lever all wear with time (especially if they aren't oiled occasionally) and just a little wear at this point can cause a surprising amount of trouble.

My Stag suffered the same problem, and I was able to make a substantial improvement by replacing the pin with an oversize one (8mm as I recall) and reaming the holes to accept it. Some day when I have the pedal assembly out for other reasons I'll fix it properly, but I expect this interim repair to last a long time.

 

[RonMacPherson]

Re: Anyone using an adjustable clutch push rod?

Brief recap on hydraulics.

When you enlarge the master cylinder bore, i.e. from .70 to .75 And do not modify any mechanical pressure anywhere else in the system. you are reducing the pressure applied to the slave, as you are moving more fluid through the same hydraulic resistance elsewhere in the system.

softer pedal, little less force down at the bottom. For a firmer pedal, and more force to the slave piston,go smaller.

One other thing is to make sure that you have the slave cylinder bolted onto the bellhousing on the transmission side, rather than the oil filter side.

 

[Brosky]

Re: Anyone using an adjustable clutch push rod?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:] But you might try inspecting/repairing the joint between the MC pushrod and the clutch pedal. The clevis, pin and pedal lever all wear with time (especially if they aren't oiled occasionally) and just a little wear at this point can cause a surprising amount of trouble.[/QUOTE]

OK, now that I think about it, this wear situation above may be the only time that the adjustable rod would be of value. Just because you could lengthen the rod. Good point, Randall.

Having just replaced all of the hydraulics, including the steel upper line and adding a stainless lower, travel is not an issue. I did convert to silicone fluid at that time as well.

 

[piman]

Re: Anyone using an adjustable clutch push rod?

Hello Stirkle,

as the TR6 has an overlong slave cylinder, I see no advantage in an adjustable push rod, and the system is designed this way so that no adjustment is necessary as in older designs.
I also see no reason to have the thrust bearing spinning all the time, and as there is no pressure on it how can it turn?

I have Triumph 2.5 injection saloon but it is essentially the same engine and gearbox as the TR. On the saloon there are two different diameter slave cylinders, 1.00" and 0.75" with the latter giving a longer throw to the slave pushrod. There is also the three holes in the clutch actuating arm which will also affect the clutch release.

Ron,
I think you are getting your hydraulics back to front, bigger diameter at the master cylinder gives more pressure, not less. However if you are not pressing to a dead end (as the clutch pedal limits the throw) then the pressure in the line is a reflected pressure from the clutch itself, so master cylinder diameter is irrelevant?

Alec

 

[TR3driver]

Re: Anyone using an adjustable clutch push rod?

OK, now that I think about it, this wear situation above may be the only time that the adjustable rod would be of value. Just because you could lengthen the rod.

Might be useful at the MC, if it will fit. But at the slave, the stock arrangement automatically compensates for wear in the joint, so no help there I think.

And since the original MC pushrod is trapped by the retaining washer and circlip, I'm not sure if substituting a slave-type pushrod is a good idea. Might be better to find a TR2-4 MC pushrod (which is adjustable and I think has the right end to mate with the MC).

Assuming the force required at the slave pushrod and the distance the MC pushrod moves remain constant, a larger bore MC will increase pedal effort and cause more travel at the slave. A smaller MC bore will decrease pedal effort and reduce travel at the slave.

If nothing is moving (you're holding the pedal down), the pressure on the fluid has to match at both ends. The relevant equation is (force = pressure times area) which can be rearranged as (pressure = force / area).

So if, for example, we assume a 1" slave and 100 lbf applied to the pushrod; then the fluid pressure is 100 / .785 (the area of a 1" piston) or 127 psi. That means that, with a .70" MC, the MC pushrod must be applying 127 * .385 (the area of a .70" piston) or about 48 lbf.

But if the MC area is changed to .75", the MC pushrod must be applying 127 * .442 (area of a .75" piston) or about 56 lbf. Not a huge difference, but enough to notice.

 

[Brosky]

Re: Anyone using an adjustable clutch push rod?

Just for the record, I have my adjustable push rod set at the exact length of the stock unit.

I looks nice and shiny down there, if nothing else.

 

[Geo Hahn]

Re: Anyone using an adjustable clutch push rod?

...Might be useful at the MC, if it will fit... And since the original MC pushrod is trapped by the retaining washer and circlip, I'm not sure if substituting a slave-type pushrod is a good idea. Might be better to find a TR2-4 MC pushrod (which is adjustable and I think has the right end to mate with the MC)...

I actually made an adjustable clutch push-rod for the TR4 M/C in a desparate attempt to resolve a clutch problem. Worked and did increase the action but turned out I had a broken pressure plate so now it's just another of my 'good luck charms':

 

[Guest]

Re: Anyone using an adjustable clutch push rod?

Just for the record, I have my adjustable push rod set at the exact length of the stock unit.

I looks nice and shiny down there, if nothing else.

Thanks Paul,
That picture was all the info I needed about my purchase or non purchase.

 

[DNK]

Re: Anyone using an adjustable clutch push rod?

Brief recap on hydraulics.

When you enlarge the master cylinder bore, i.e. from .70 to .75 And do not modify any mechanical pressure anywhere else in the system. you are reducing the pressure applied to the slave, as you are moving more fluid through the same hydraulic resistance elsewhere in the system.

softer pedal, little less force down at the bottom. For a firmer pedal, and more force to the slave piston,go smaller.

One other thing is to make sure that you have the slave cylinder bolted onto the bellhousing on the transmission side, rather than the oil filter side.

This brings up a question a asked earlier and didn't get a response. The TR7/8 clutch master looks identical to the 6's. It has a 5/8 bore and was wondering if I went to a TR6 M/C if it would lighten the pedal some??