I did put in a new clutch with the new flywheel.  10.5" dual friction centerforce.  I had the same setup on my 4 speed but with the old flywheel and a 10" clutch.

I could always bolt the old flywheel and clutch back in as a test but that's quite a bit of work.  I had planned on putting together a 347 in the next few months anyway, I might just jump that plan up a bit.

It stinks that I can't enjoy it now that it's back together though!

I'll check the exhaust and RPM range vibration.  Pretty sure it got worse as RPM increased.

I think if you line up the crank bolt holes properly you'll find that the holes drilled in the outer diamter of the new flywheel are 180 degrees across from the weight on the old flywheels.  Removal on one side or addition on the other accomplishes the same thing.  The holes at a greater radius also helps since it is oz-in of unbalance.  The greater the in, the smaller the oz.  To use the new flywheel and pressure plate you could remove them and take old and new to a balance shop to have them matched.  I would eliminate other sources of vibration or resonance before going to the trouble of yanking the transmission.  Unfortunately a lot of rotating components are not bolt-on.

That new flywheel did come from Summit.  They assured me by part number that is the correct part.  That's my main area of concern.

When I drove the car to the muffler shop I didn't notice a huge vibration but I was keeping the RPMs well under 2k due to the open headers.  I made sure before they took it off the lift that everything was cleared.  New tranny mount, E-brake bracket and lever, etc.  This muffler shop has a great rep around town for doing good work.

I know the old removable weight flywheel and 10" centerforce clutch are fine with this motor.  No vibration.  At this point I pretty much have to start tearing stuff down no mater what, no it's not the end of the world.  I might take both flywheels to a machine shop and have them checked.  If the brand new one isn't 28 oz or balanced wrong, Summit is going to hear from me .

Steve, I agree.  It doesn't look right to me.  I'm normally pretty good at spacial judgement and the material removed doesn't appear to be enough to create a 28 oz offset.  But I'm not a pro, so I trusted the folks who sent it.  I hate having to second guess people and make sure they send the correct stuff.

Thanks for the replies and I'll let everyone know how it goes! 

Last edited by JVince (10/27/2013 2:15 PM)

I just ran the car for about 10 minutes in neutral.  The vibration seems worse right before 2k.  It actually seems to smooth out closer to 4k.  So it's probably not the flywheel.  I think my headers are hitting the shock towers though.  I need another 1" or so.  I'm guessing since I had part of my TCP brace kit remove the towers sagged a bit over the months.  I'll get it pushed out to stock and see if the clearance helps.  Also I noticed that the t5 pro 5.0 shifter seems to be touching the tunnel under load. I can see the motor torque a bit when I rev, but no nearly as much as before.  I'm hoping the combo of the headers and the t5 touching is transmitting that vibration.  That's a hell of a lot easier to clear than yanking the tranny out again!

UPDATE:  The guy that picked up the parts for me just delivered the bad news.  He kept telling me it was a centerforce flywheel.  But he dropped it off in a Summit box. The part number on the flywheel and box reference a 28oz.  Turns out it IS a 50 oz flywheel that was put in a Summit box.  Heh.  So I have a nice unbalanced motor beating the crap out of my bearings .

No biggie.  It's a bit of a relief at least knowing what's wrong.  I'm guessing with the late model bell housing and the T5 I cannot use my 157 tooth 28oz that's sitting on my bench eh?  I don't think the starter will line up correctly.  I'm rapidly getting a collection of flywheels.  I bet they make nice clocks.

Last edited by JVince (10/27/2013 4:41 PM)

If you have a 157 tooth flywheel with 28 ounce balance laying around, you can certainly use it.  You may have to use the early style manual tranny starter (5.0 uses automatic starter whether manual or auto) to reach the teeth correctly.  The 5.0 bell positions the starter exactly the same as the original 289 bellhousing would have positioned it.  Only the distance front-to-back for the starter to reach the ring gear is different.

That's great news!  I was going to compare the flywheel that's in there now (that we suspect is 50oz) to the one on my bench.  Dimensions, tooth count, etc.  I was also going to mark where the teeth reach on the back plate with a marker and compare with my old 28oz.  I have a hunch it will work.

I am a little confused about the vibration though.  I've experienced a poorly balanced flywheel before.  A machine shop that shall remain nameless cut one at a less-than-zero angle for me about 10 years ago.  That was an awful shake.  This "feels" the same as this current issue but it's not as severe.  The frequency of the vibration is absolutely tied to the RPM range.  But wouldn't a 50oz flywheel be a huge imbalance?  I would expect the motor to be oscillating like crazy.

I hope to get it all apart this evening.  I wonder if there are any local places that can spin a flywheel for a balance check.  I know O'reilly used to cut drums and discs years ago.  Before I reassemble it would be nice to know that the one in there really IS 50oz or poorly drilled.

Thanks everyone.

I just got the clutch and flywheel off last night.  Before I put the T5 in I had about 1000 miles on a centerforce clutch/flywheel combo that was perfect.  I still have those sitting on my bench so I compared them to what I just pulled out.

The clutch pressure plates are the same size, but the hole pattern and hole size on the flywheels are slightly different.  I'm almost certain that's a 50z flywheel for a late model mustang.

The clutch discs are identical.  I'll be using the almost brand new one .

Aside from the bolt pattern and size, the flywheels are the same diameter and tooth count.  I plan on putting in the older flywheel, older clutch plate and newer disc.  So basically the only "new" things that will be installed are the T5, headers, rear end and drive shaft.  If the vibration is still present at least I'll know it's not flywheel related now.

look at the 28 and 50oz flywheels on fordracingparts and you'll see the one you have looks just like the 28oz pictured.  the 50oz unit has more (9) balance holes drilled in it.  They are like someone mentioned above, instead of adding weight to one side they took weight off the opposite side to accomplish the same goal.

http://www.fordracingparts.com/parts/part_details.asp?PartKeyField=11022

Update:  I put the old 28oz flywheel and centerforce from my 4 speed back in this weekend.  I started it today and the vibration is almost gone.  I have a little bit of a shake at 2k rpm but as soon as I hit 2100 or so it's gone.  I'm thinking that's probably where the headers are touching the shock towers.  I tested this with the tranny in neutral an no drive shaft attached.

However.  I found out that a clutch plate that's meant for a mechanical clutch has a different throw out height than a cable clutch.  The cable is about 2 inches from reaching the fork now.  The fork isn't bound up against the bell housing and it does have play, but it's way higher.  I read a little about it on line last night and it appears that mechanical linkage clutches are designed that way.  Joy!

So to recap, I have a good flywheel but can't use the matched clutch.  I have a good late model clutch that works with the cable, but the flywheel it fits is unbalanced.  Whew.  I'm taking the bad flywheel to a machine shop this week with the clutch to see what they can do for me.  While I'm waiting I plan on pushing out the shock towers back to stock for a little more header clearace, to see if that clears up that vibration.  What a mess!

Seems easiest to just get a 10" diaphragm clutch and install it.

Karma strikes in the oddest of places.

My mechanic friend that sold me the T5/clutch/flywheel felt bad that I couldn't use the flywheel so he ordered me another one through his local Ford racing contact.  I picked it up yesterday at will call.  It was supposed to be a billet steel replacement, part M-6375-A302B.  28oz balance, 157T, drilled for a late model clutch plate.  They sell for about $250.

When I picked it up it felt a little light, but I was in a hurry and didn't really think about it.  Then after work I opened the box:







It looks like a mix up or mislabeled box.  That's the aluminum version of the same part.  Maybe there's a silver lining in all these setbacks I've had.

6sally6 wrote:

Let us know how the Alum. wheel works fer ye.
I've always liked the idea of an Alum. wheel.
Just never been brave/rich enough to try one on the street.
6sal6

My sentiments exactly.  Billet steel has always been my choice and you can normally pick those up for $100-$200.  The benefits of an aluminum flywheel on the street always seemed negligible compared to the price tag.  I know a few guys that use them and they all like them after they get used to the rev difference.  If nothing else it should be exciting the first week or so .