Clutch choice, which is best?


D

dtomaso1

GT Owner
Dec 6, 2006
184
Phoenix, Arizona
Team,

May need a new clutch. I see three ways to go:

Stock


Stillen. Clutch and flywheel

SPEC, super twin. Clutch and Flywheel

Any suggestions? I have stock car with no mods. I would like to keep stock pedal pressure and performance (or better). Seems the regular kit is flywheel and clutch. Don't you also need new flywheel bolts, and TO bearing? What about halfshaft bolts that need to be R&Rd? Do those need to be replaced as well?

Thanks for your comments.
Tom
 
Stock or Stillen. Both are great. Spec will be much stiffer in the pedal. Stillen will be a later engage than stock. Stillen is more like an "ON/OFF" switch, but once you get used to it, is great.
 
And yes, you will need new halfshaft bolts for sure as they are a ONE TIME USE only bolt
 
shelbyelite said:
Stock or Stillen. Both are great. Spec will be much stiffer in the pedal. Stillen will be a later engage than stock. Stillen is more like an "ON/OFF" switch, but once you get used to it, is great.
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Later engagement? As even higher off the floor? I thought it was the other way around. Honestly, I'm not sure how it could be any higher than it is now (on my car at least).
 
Sorry, I really have no opinion on which clutch assembly to install as my OE clutch (which I believe is an AP unit from Ford?) still works just fine. Just watch those 3rd gear starts which have been proven to shorten clutch life.

I would think replacing the "flywheel" bolts (not sure if you are talking about the bolts which secure the flywheel to the crankshaft or the bolts which secure the pressure plate to the flywheel) is certainly OK, but not necessary. These bolts are not TTY pieces so what "wears out"? Actually if the bolt preload is sufficient (designed, calculated and applied) the bolts never know there are any alternating loads on the fastener to fatigue the bolt. Ie, the bolt just sees a constant pre-load tensile stress.

TO bearing is also a replacement candidate if it does not cost too much (I really do not know) but just as easy to replace now while everything is apart then to have to tear the clutch assembly apart if the bearing needs replacement in the future.

The axle bolts have nothing to do with the clutch change out and once replaced with either the Ford or Accufab replacement bolts should be good for the life of the vehicle. No further "R&R" is necessary.

Hope these opinions help...
 
Indy GT said:
The axle bolts have nothing to do with the clutch change out and once replaced with either the Ford or Accufab replacement bolts should be good for the life of the vehicle. No further "R&R" is necessary.

Hope these opinions help...
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Yes and no. Yes the axle bolts don't need to be changed, but the 6 coupler bolts do if they are Ford bolts. Ford bolts use a Torx bit, Accufab use a 18mm 12 point socket.
 
Ice, thanks for the clarification to my post. I agree.

The termonology needs to be specific. Axle bolts do not need replacement but the Ford Torx coupler (TTY) bolts do need to be replaced with new units. Accufab coupler bolts are reuseable.
 
Thanks for the clarifications around axle bolts. The car currently has accufab coupler bolts. Is it correct that they can be reused?

Also, Why does ford racing refer to their clutch as a kit? Maybe it comes with some other parts? E.g. Flywheel, bolts, TO bearing etc.

Thx, tom
 
Yes, Accufab bolts can be reused. I don't know about the kit.
 
Having driven cars with virtually ALL of the clutches available, for a stock car through about 950 lb-ft TQ, I would highly recommend the Spec SS Trim clutch. Their kit includes the entire assembly including the flywheel. The pedal effort is a little more than stock but nothing that would concern you. Engagement feel and take-off are superb. Each owner where we have installed this clutch just raves about it. In a previous post Shelby comments on the high pedal effort of some of the Spec clutches and this is absolutely true of their P-Trim and ST-Trim series. The pedal effort is enormous! But, the SS-Trim clutch is just right and my favorite recommendation.
 
How is the engagement of the SS trim clutch compare to the OEM and Stillens? Is progressive like OEM or a grabby on/off switch?
 
Thats some great info. Is online the best place to purchase, or is one of our forum vendors a disti for spec?

Thx again
Tom
 
spec
 
The spec is a good piece for these cars. SS trim is a waste imo, probably no better than stock or the entry level Stillen.....I would go directly to the ST trim. It is a bit more agressive, and pedal feel is slightly heavier...but a much better clutch for what these cars are capable of. Not sure if any supporting vendors carry it, but if not I suggest calling Van at Revan Racing.
 
How is the engagement of the SS trim clutch compare to the OEM and Stillens? Is progressive like OEM or a grabby on/off switch?
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Ice - This is the best attribute of the SS-Trim, IMO. Engagement is more crisp than stock but it is NOT the on/off switch of the more aggressive Spec clutches. This is definitely the clutch that I would install in my own car.

SS trim is a waste imo, probably no better than stock or the entry level Stillen.....I would go directly to the ST trim. It is a bit more agressive, and pedal feel is slightly heavier...but a much better clutch for what these cars are capable of.
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I couldn't disagree more. The ST-Trim is a HEAVY clutch. Also, it is prone to have a bit of shudder/chatter on first gear engagement. We have installed at least 8 of these clutches- so we know of what we speak. It is our sole recommended clutch for the TT cars. Other than a heavy spring feel and this occasional first-gear chatter, it is a nice set-up and it can certainly hold the power. All told, we have literally hundreds of 1-mile sprints on this clutch and never a sign a slip or failure.

BUT, back to the OP's question. What clutch for a car with 900 or less lb-ft of torque? Why deal with an ultra-heavy clutch feel and a chatty on/off first year engagement if you dont have to? This is why I would recommend the SS-Trim. It has a better feel than both the Stillen and OEM (IMO) and can still handle the power easily up through and including Whipples at 19 psi. Thus, my recommendation. For the record, we have done approximately 6 of these installs - so we have ample experience and owner feedback of each clutch. Oh, and it is also $1000 less than the ST-Trim.

Finally, we can supply the SPEC clutches for anyone that needs one.
 
Maybe I should have worded my response a bit differently. First off....1000hp/tq clutch cars are very common in my shop, and I do literally dozens of clutch installs on these types of cars every year. I have used all forms of the spec twin disc units, and personally, based on experience and failure rate, I am not a fan of the ss clutch. Doesn't mean the ss isn't still an acceptable choice in certain situations...I just prefer the st. To me, a slight trade off in pedal feel and some minor chatter is worth it for a clutch that will actually perform and take a beating.

Again, just my 0.02.....
 
What is the weight of the SPEC clutch compared to the STOCK clutch?
 
Amazing how these threads get hijacked. The OP has a stocker. IDK why he needs a clutch, but why shouldn't he get an OEM replacement?
 
Xcentric said:
Amazing how these threads get hijacked. The OP has a stocker. IDK why he needs a clutch, but why shouldn't he get an OEM replacement?
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Excellent question. I'd go back OEM unless I knew I was planning some huge torque increase, heavy track driving or some other radical change in driving style. The OEM clutch is a great piece of gear.
 
AMB said:
What is the weight of the SPEC clutch compared to the STOCK clutch?
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About 9lbs lighter (approx. 36lbs vs. 45lbs for oem).
 
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