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I have a 1973 GTS that has been highly modified with a stroked 351 with fuel injection, coil packs, twin turbos and a motec ECU.  Just had it dynoed and it puts out 525HP at 5# boost and 625 at 10# boost.  Unfortunately, I did not replace the clutch when I had the engine and trans out of the car.  I blew out the clutch,  and now need to replace it.  I don't ontend on racing the car but do plan to get heavy into the throttle from time to time on the road. I have 2 questions:

1. Is it possible to remove the transaxle and replace the clutch without removing the engine?

2.  What clutch (and where can I get it) would be a good match for this HP level and modest (non-racing) driving style?


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  • IMG_2581: 1973 GTS
  • JRYI4520: Twin Turbo
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Your engine bay is amazing!  The clutch can be replaced without pulling the engine.  My clutch is slipping and I spoke with Wilkinson about such this week and he said it is relatively straightforward to pull the transaxle while leaving the engine in place.  He succinctly explained how to do it.  It could be helpful to call him and ask for guidance.  He can also suggest a clutch solution.  He said he will be away until Tuesday next week.  Sharky (Pantera Miami - one of our forum sponsors) can help and takes phone call.  And as Jimmy wrote, Jerry Sackett and Dennis Quella know the cars and can help as well.

Last edited by stevebuchanan

I just redid the clutch in my car. Many of the modern ford style 10 1/2 inch clutch casings have a higher sharper shoulder profile than the older shapes bringing  them closer to the inside surface of the standard bell casing.

The two internal standard bell casing to gearbox machine screws at the bottom of the bell case  are around 3mm closer into the rotational arc of the pressure plate case than the rest of the bell housing. If these are replaced with a low profile head ( still high tensile) machine screw the overall swing clearance can be increased by 2-3mm which can be critical to fitting a particular clutch.

Once its fitted  make sure the entire clutch assembly will swing through the full orbit without touching anything internally.  I had one spot hang up on those internal machine screws and had to pull the entire lot to fix it.

You can also burn out your starter motor solenoid in short order if it binds .

Don't ask me how I know,,,!

On a standard set up , release the rear gearbox mounting bolts , loosen the exhaust and gearbox linkage   , jack up the car at the rear , two timber toms onto the rear of the sump casing of the engine from the floor and carefully ( really carefully ) lower the car until the rear gearbox mounts clear the chassis mounting ears. The rest is straightforward.

No need to pull the engine just watch like a hawk the front clearances on the fire wall.

In your case there is the issue of the very fine turbo set-up which will require separate consideration.

A vintage 11" Schiefer pressure plate should be good to about 600hp.   About 2800# Long design.  They have short counterweights that clear inside the bellhousing.  I've been using the pressure plates with aluminium internals that have a hardfaced metallic coating.  Try to mate it with a 100% organic disc.   These discs are slightly lighter than the metallic combo discs and are easier on the transaxle synchros.  Pressure plate is Schiefer part # 625-0054 or 625-0057 vintage 1980's and 1990's.  I've been saving a couple of NOS ones if you interested.  They also work well with a litewight aluminium flywheel, but watch out for the balance (if original external) on the liteweight flywheel.  Pressure plates are neutral balance.

Dan, it is quite possible to just pull the ZF, leaving the engine and its accessories in place. The only tricky part, if you have a later model car like yours is getting the rear ZF mounts out of the way. I recommend removing the nuts on the 3 studs (each side) holding the rear mounts to the ZF cases and double-nut them so as to remove the 6 studs.

Then replace the 3 studs with hex bolts. Otherwise, you will need a long pry bar or maybe a 6' long 2x4 to pry the cases sideways without damage so the aluminum mount castings can be pulled away from the OEM studs, one side at a time.  With hex bolts, the next time will be even easier.

Some of my single DIY friends with no engine crane do not actually 'pull' the ZF. Instead they simply unbolt everything and slide it back about 8" from the bell housing. Thats enough space to R & R a clutch. The ZF without a bell housing weighs about 155 lbs so you'll need yourself, two husky friends and some good straps or ropes to lift the bulky oily lump high over the rear body.

While you're in there, its considered wise to also replace the pilot bushing and the throwout bearing, because they are wear-out items and its a lot of trouble to replace them singly. 

The McLeod Street Twin is rated to 1,200 HP, your application is probably more focused on instantaneous torque and clutch clamping power as the turbos kick in, then again not having the ZF as the weakest link may not be bad thing!

Everyone may be clear here, but in some clutch conversations I see interchange between the use of terms; dual friction (a single friction disc with different friction materials either side) and dual disc (multiple friction disc).

Many if not most designers of devices include a fuseable link.

It's there to protect the device from an overload.

A clutch has been and can be a fuseable link. Putting in a clutch capable of 1,200 hp could be the death toll of a ZF.

Clutches are cheaper then ZFs by at least a 10 to 1 ratio, if not more.

If you need a dual disc, you are definitely over the capabilities of a ZF.

I forgot: not all clutch covers will bolt onto all Cleveland flywheels. That's one reason why aftermarket flywheels (steel and aluminum) have several clutch bolt patterns drilled into them. Some that are the same pattern use different thread sizes & lengths, further complicating things for DIY-ers. Finally, a lot of OEM Ford flywheels 289 to big block will bolt onto Ford V-8 crankshafts but many are drilled for 10-1/2" OD clutches, not 11" as used in the 351-C, 400, 429 & 460 engines.

And no- you cannot predictably redrill and tap your own flywheel. Just a few thousandths off will have your engine shaking like a wet dog at 6000 rpms. Just before something lets go like a grenade in your bellhousing! That doesn't even touch on the strength of OEM gray-iron flywheels when home-modified for use above stock Cleveland redline of 6000. I'm all for DIY, but not with flywheels! I used to have photos of that Texas Pantera that exploded a flywheel (drag-race or road race?) and it nearly severed the rear subframe & blew a tire, also wrecking a rear fender & decklid.

^  Yep. Do not redrill an iron flywheel. In fact, best not to reuse them. You want preferably a billet steel flywheel.

The factory used iron flywheels because the clutch linings on the discs grip better on them then steel, i.e., less slippage.

The simplest thing to do is buy a matched flywheel/clutch set.

The iron units have been known to explode and throw shrapnel as BW stated.

Personally I'd stay away from aluminum ones as well. They are two piece and there is no guaranty that the bronze insert won't come loose, so same reasonas the iron, you could blow it up.  Plus often you need to pump the clutch pedal to get the car to launch because the flywheel has lost so much inertia. That means you are slipping the clutch repeatedly which isn't a good idea.

Last edited by panteradoug

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