I'm about to install a ACT 2600, TSS shift fork and a ACT flywheel. Should I shim the pivit ball or not? This is on a 90GSX.

It depends on how many times/how much your flywheel was machined. In general, 1mm washer won't make the clutch fork overextend and will result in better clutch disengagement.

, of all people to respond Anyway all the parts are new, clutch,flywheel,fork,pivitball,slave,master cylinder and clutch lever. I was just wondering since the TSS fork is not original OEM stuff that shimming the ball might help or hinder things. Taboo would you shim it in my case

That's a tough call... If you shim the pivot ball too much (or if you shim it and it doesn't need to be shimmed), the fork will overextend and the fingers of the pressure plate will hit the springs of the clutch disc. The cruscial specs of the TSS fork are exactly the same as the new OEM unit. The question that remains is how far the fingers of the pressure plate are located from the block (which is affected by the flywheel machining). You "should" be OK with 1 1mm washer even with a brand new flywheel, new pivot ball and new fork... I'd go for it.

Taboo said:

That's a tough call... If you shim the pivot ball too much (or if you shim it and it doesn't need to be shimmed), the fork will overextend and the fingers of the pressure plate will hit the springs of the clutch disc. The cruscial specs of the TSS fork are exactly the same as the new OEM unit. The question that remains is how far the fingers of the pressure plate are located from the block (which is affected by the flywheel machining). You "should" be OK with 1 1mm washer even with a brand new flywheel, new pivot ball and new fork... I'd go for it.

Click to expand...

I've done just that, shimmed a brand new clutch setup.
I have just installed a brand new Competition Stage 2 clutch, Competition Clutch Lightweight Flywheel with a new OEM release fork, pivot ball, TOB and clip with the help of KillaDSM and a friend.

Given that I've had clutch issues since ..well, since forever, I wanted to go the safe route and put a single 1mm washer under the pivot ball. Just in case.

The fork now sits near perfectly in the center of the inspection window on the bottom of the bell housing. But the problem is, I get a horrible, horrible sound from the transmission when I fully depress the pedal. The fingers of the pressure plate hit the springs of the clutch disk. Exactly as described above.

To remedy this, and make the car drivable, we adjusted the clutch rod in nearly as far as it will go while still disengaging the clutch but without extending the clutch so far that the fingers hit the springs. However this leaves me with more than half the pedal travel being "free-play" and does not allow the pedal to return to the cruise cut-off switch. The pedal doesn't even come remotely close to hitting that backstop with the cruise switch.

In fact, that solution was not really even enough to prevent the fingers/springs from hitting each other upon full depression of the clutch pedal. So, running out of options, we shimmed the slave cylinder, itself, out about 1/2". This allowed us to entirely avoid the springs/fingers hitting but to achieve this the clutch still has to have ridiculous amounts of freeplay, still sits far from the backstop and as a result the clutch engages right off the floor.

The car was now driveable.
Once I got the vehicle home I went into my "secret DSM stash" and pulled out the shortest slave cylinder rod I had at my disposal. The rod is roughly 1/4" shorter than an OEM rod. This helped out some too, since I would need longer bolts to shim the slave out any further.

All of these "tricks" to bandaid my poor judgment have improved my situation with every step, however, the pedal still engages right off the floor and still doesn't allow enough adjustment to allow the pedal to rest on the back stop without incurring the dreaded spring on finger action.

I'm shocked that a single washer could throw things off by so much. Especially since the fork position is neutral in the inspection window. So much for "playing it safe".

I'm trying to envision this in my head, but, will my problem only get worse as the clutch disk wears?

Any advice or suggestions would be greatly appreciated.



EDIT: We also installed the TOB clip upside down, the opposite of what these pictures show. I've read a couple of posts that indicated that while incorrect the clip and TOB still function as intended. I don't feel this has significant impact but I'm mentioning it for completeness.

this is on Tre's Website


The reasons behind shimming the clutch pivot ball are often misunderstood. Ultimately what you're doing is correcting the offset geometry of the clutch fork so that it's optimized for the clutch you are using. When it comes to aftermarket flywheels, clutch discs and pressure plates there tends to be some variance in the final offset distance of where the spring plate fingers are in relation to the throw-out bearing. This distance will also vary whenever the flywheel is resurfaced. If the machine shop had to take .030" off your flywheel, your whole clutch assembly will now be .030" further away from the transmission. This is when you need to shim the clutch fork pivot ball .030" to compensate.

When to shim the pivot ball? During the transmission install but first things first: Inspect your clutch fork for excessive wear. Inspect the clutch fork finger tips that push against the throw-out bearing. They should be round, without any flat spots. The clutch fork pivot ball socket should not show signs of wear. If it does, replace it. 1st gen owners take note: You can upgrade to the 2nd Gen clutch fork, part# MD770506. It's much stronger than the 1st Gen fork and we have them in stock.

Why shim the pivot ball? Because you want to keep the clutch fork at the optimum angle so that it sits in the proper location and doesn't make contact with the transmission case when you push the clutch pedal down. If it does make contact you will risk breaking the transmission case where the slave cylinder bolts on. Another benefit of shimming the pivot ball is reduced thrust load on the throw-out bearing post.

Wow, Taboo...

I'm thinking the new clutch/flywheel setup may put the assembly further out from the engine to begin with. So adding the washer under the pivot just compounded the matter. I know it's a pain, but take the shim out and see how well it does then.

I've never seen that comment about the 2g fork, either. Maybe I don't pay enough attention. Do other people recommend it as well?

Edit: Straight from JNZTunings OEM Catalog: "Part number MD737767 was superceded by part number MD770506." I guess Mitsubishi recommends it.

Man, I'm torn on what to do with my setup. When I had my engine rebuilt, I threw on a Stage 2 TRE transmission, 2100 clutch kit and streetlite flywheel. The ACT TOB was used and apparently TRE shims the pivot ball when they rebuild the transmissions. Shifts seemed fine, occasionally I would get a little grind going into 3rd, but one thing I noticed right away was an annoying sort of rattle at idle and low speeds that would go away when I pressed on the clutch pedal (even slightly).

It has been 30k since I had it all installed, I haven't launched the car even once and I baby it (never even hit anything past 5k). I don't plan to resurface the flywheel, but I do plan to buy a new fork, pivot ball, and OEM TOB. Once I get home, I'll check to see if the shim is actually on the pivot, if it is I might just leave it out when I put everything back together.

*UPDATE*
I just mounted the tranny with a new OEM TOB, fork, and pivot ball. After I had it fully mounted, I checked the alignment of the fork in the boot and it was slightly off center to the right. The pivot ball that was already in the tranny did have a shim (like it says on the TRE page) but I removed it and fortunately I did or I would have risked ruining something.

The pedal pressure sees to be the same and functions as it did before the job, but we will see how the engagement is once I take it for a test drive in a few days.