My 1974 has been plagued with poor clutch operation. I have read the Buckeye Triumph website several times as they have several tech articles about the TR6 clutch problems, as well as a lot of other good articles. General opinion is that the B&B pressure plate is too strong. Replacing the Borg & Beck clutch and pressure plate with a new Luk set gave only temporary relief. Almost all the other related parts were replaced, but the operation remained poor, with excessive force required, and very early and rough clutch engagement. I tried several band-aid fixes to get through the summer. The most effective was to replace the .70" dia. master cylinder with a .75" dia. cylinder from an earlier TR. This can give more slave cylinder travel, but requires more force.
There was also an article about a custom made TOB sleeve assembly being made in Germany that was supposed to solve these problems. It is referred to as the "Gunst" TOB. There was a group order organized to import a number of these TOB’s and I decided to get one. It arrived in February 2003.
The strange thing about the legendary TR6 clutch problem is that it uses the same basic design as earlier TR models, and there were not chronic problems with them. Several manufacturing changes were introduced over the years, which collectively must have caused the nagging problems of the TR6 clutch. The older TOB’s had a brass sleeve. The cross shafts had grease fittings. The specs of the pressure plated changed. The Gunst TOB sleeve is made of machined brass. It also uses a preload spring to keep the TOB in contact with the pressure plate all the time. This will minimize wear on the pressure plate spring tips. Gunst also recommends putting in an early TR cross shaft with grease fittings, and using earlier bushings which were twice as long.
So I decided to make all these improvements while I had the car apart. I did notice one problem when I was assembling the new components. The cast iron fork was about 1/8" too wide, resulting on excessive wear on the one round pin that engages into the sleeve. So I replaced the fork. This had been replaced just before all the clutch problems started and may have been the main culprit. Lesson learned – Never assume that new parts are good parts.
Also pay close attention to the tapered pin. It should protrude through the cross shaft and into the far side of the fork. The new parts I had did not fit properly, so I filed out the hole in the cross shaft a few thousandths until they did fit. I also cross drilled the assembly and put a spring pin through the assembly. And don’t forget the safety wire.
The fact that the new sleeve is brass eliminates the steel to steel contact in two areas – the front cover to sleeve, and the sleeve to fork pins. Brass has a much lower coefficient of friction than steel. I also applied more grease this time to the sleeve and transmission front cover. I also made certain that the fork was centered on the sleeve, so that the contact pressure would be uniform side-to-side.
I installed the new brass bushing for the cross shaft. The old bushings were white metal. Having brass bushings with grease fittings to provide future lubrication renewal should improve the long term operation of the cross shaft.
I carefully tested the operation before re-installing the transmission. The initial results are good. The operation is much smoother. The engagement point is good. The pedal pressure is still a bit high, but not bad. If I were to buy a new clutch, I would opt for a Sachs with lower pressure than the B&B or Luk.