Anybody know if someone makes a aftermarket stronger than OEM clutch
fork? I have an ACT strip/street pressure plate and disk and I replaced the
original clutch fork with a OEM clutch fork about 6,000 miles ago and that
one is now broken. Or what about shot peening or heat treating the OEM
clutch fork for added strenght? How do you really big horsepower guys with
race clutches deal with the weak OEM clutch fork?

Thanks

jaj1

 

Any photo?

BC

 

Photo of what, the clutch fork? It's still in the trans. I can see through the inspection hole the clutch fork is cracked right by the roll pin.

 

I bought a new one recently for a customer's clutch job - he had the ORIGINAL clutch, everything on the car (original owner!). Anyhow, his clutch fork was fine, but I noticed no difference between the original part and the new part - they looked identical. Dunno if Mazda did some sort of treatment or something.

Are you doing a lot of drag racing or something? I just can't see how one can break again THAT quickly.

That said, I don't know of an easy replacement. I almost want to say I've seen Japanese tuners with an aftermarket part, but you'll have fun finding it and finding a good source to buy it from.

You could also consider going with a multi-plate clutch. Tons of clamping power, but less stress on the engagement/release system.

Dale

 

Dale, I don't drag race the car at all. I like going around corners. (g)
I know, I find it a little weird too that I have broken another clutch fork so soon. I thought I read another thread that said Mazda reengineered the clutch fork in later years. Evidentially from what you are saying you did not see any difference in the
old and new forks. Can someone else confirm if Mazda made changes in later
clutch forks?

 

So I take it no one has tried heat treating and or shot peening the OEM
clutch fork for added strenght?

 

It's a cast part - there is only so much you can do with cast iron to make it more resistant to cracking and breakage. It seems to me that the second one you got was unlucky. Heat treating/cryo/etc will cost as much as a new one, I would guess, but if it last longer it may save on the future labor cost.

Dave

 

Yep, that's the prob w/ cast iron parts. I was 100 miles from civilization, changing my clutch at Rikki's, when we found out the clutch fork was snapped in two. Cast iron = welding it back together was out of the question

I had an interesting situation w/ mine tho, cuz there was a throwout bearing flying around in the cluch apparatus, and it eventually got in the clutch fork, and thus pressing the clutch put enough pressure to bend the throwout bearing, and break the clutch fork from one side! Man, that was a sight to see...

Will cryotreating a cast iron part help much in strength?

Also, IIRC, Mazda did indeed upgrade the part in recent years...supposedly stronger. The forks almost always break when you're using a heavy duty aftermarket clutch. I don't think I've heard of them breaking on a stock clutch. I'd be all ears if someone else makes an upgraded fork.

Dale, that's a real good idea...a twin disc = less stress. Hadn't thought of that.

 

Everyone says the part is upgraded, but I didn't see anything substantial. No extra bracing or anything obvious. Could be a better grade of iron, heat treated, who knows.

Really, I'd just toss in another new one and chalk the last one up to bad luck.

Dale

 

Thanks guys for your input. Looks like no choice but OEM.
I just hope this one last longer than a few thousand miles. (geez)

jaj1

 

I had the same problem with clutch fork busted with the Extreme pressure plate and ACT clutch.

I had a buddy at Lockheed toss in their heat-treat oven and so far ZERO problems after 25k miles and still going strong.

 

If the casting is a martensitic steel, yes. It will still be a brittle steel (breaks without bending), but it will be less likely to break to begin with.

If it's not a martensitic steel, the cryo won't do anything.

It's possible that Mazda switched the casting heat treatment or material without any visible difference. It would take a composition or hardness test to begin to determine if there is any difference.

Dave

 

hmm?

I have 9.5 aluminum flywheel
ACT street strip pressure plate and Clutch

I find it hard to get into 1st at a stop after it gets hot after spirited driving and on track days it's a Bit$h , it gets locked out from 3rd to 4th I have to wait for the rpms to come down and pump the crap out of the clutch pedel !

I did find the mounting bolts for the pressure plate to the flywhele to be loose
I retighted them through the service plate an used locktight red.
it seem to help but it still comes back.
I was thinking SS braide clutch line , or pressure plate springs were too soft when hot !

 

25k is nothing. Until it lasts 250k we can't be certain heat treating was a help.

My guess is the replacement forks are already heat treated because the casting itself looks exactly the same, yet a new part number was issued.

 

That sounds like more of a hydraulic problem than a clutch problem to me. Yeah, I would definitely start with a braided stainless line and a good bleed/flush of the clutch hydraulics. If that doesn't totally help, look into a new master and slave cylinder, especially if you've got high mileage on the parts.

Dale

 

I was gonna mention that, but I hadn't seen the new part # myself, so I didn't want to go on heresay...but yea, I recall hearing it was given a new part number.

I assumed Mazda made it out of a stronger material (or heat treating, which I wasn't aware of), hence the new part number.

 

The tips of the fork are heat treated from Mazda. My guy did the entire fork.

When the original fork busted it wasn't near the heat treated area.

 

On mine the arm on the on the clutch fork cracked where the roll
pin goes into the the fork shaft. It is a very small crack but if you
have someone else push the clutch pedal while you look through
the inspection hole you can see the crack spread open a bit.

Again the symptoms are more free pedal travel at the top of the pedal,
the clutch grabs very close to the floor and there is clutch chatter when
first engaging the clutch.

 

I welded around the pin holes to build up the thickness of the part with nicad rod . I removed the plastic bushings and made new ones out of oillite brass .That was about 6 years ago and still good .

 

I did replace the slave cylinder w/ a new one from Mazda, the braded hose seems
the next fix. I have 53k on the body , I would hope it was not the master cylinder !

I'll let you guy's know.

 

Def. bleed the system first...the whole pumping thing sounds like there may just be an air bubble in the lines...hopefully that's all it is...