Help, T5 swap gone bad! Please!!

Hey guys ok here is the scoop. I bought a 1990 T5 from a friends wrecked mustang. I put it in my 66 mustang which has a 351w in it. I had a very hard time finding a flywheel that supported the 10.5" clutch, while still having the 28oz balance factor. I called over 40 machine shops trying to find one that would lighten a 50oz balanced flywheel to 28oz. I know Summit has them, but I didn't want to pay $250 for one. Anyways, I found a mustang place that had 28 oz balance flywheels. After I bought it, they corrected me and said that it was only for a 10" clutch, and not a 10.5". I got scared, but decided to keep it anyways. I noticed that the 10" flywheel and the 10.5" flywheel were exactly the same in size/shape. So, I put my 10.5" pressure plate up to this flywheel, and found that 3 out of the 6 screw holes lined up. I had my machine shop drill and tap the other 3 holes, and another 3 dowel pins. The pressure plate lines up perfect...

Ok now for the problem: My mustang moves fine. forward, reverse, no problem. But it has a weird vibration. It is noticable at 2000 rpms, and seems to go away if you stomp on it a bit. It's not a insane vibration, just one enough to make me stop driving it for a while. What could be causing this vibration? My previous transmission, a C4 had no such symptoms... The best way to describe this vibration is, it sounds as if the engine is running on 6 or 7 cylendars, not 8...

What is going on guys? Do you think the flywheel is okay? Or is it causing the problem?

What else could it be?

Can someone describe an off balance engine?

Thanks!

<font size=-1>[ This Message was edited by: 66stang on 1/6/03 9:37am ]</font>

I would suggest that the vibration is an "out of balance" situation due to your flywheel. Somehow the harmonic balancer and the flywheel are out of tune at that particular RPM. It is a "harmonic" imbalance. I would suggest you take your flywheel to Summit and do a side by side with yours. this may not be enough since this is a dynamic problem (not static - i.e. "looks&quot[img]/phpBB/images/smiles/icon_wink.gif[/img]. I would talk to an Engineer at Summit and discuss your problem with them.

i had the same expereance did you use the c 4 yoke if not it will shake like that but it could be your clutch set they are balanced also i had a bad one once good luck [img]/phpBB/images/smiles/icon_smile.gif[/img]

You bring up an interesting point. My pressure plate was used (from 67stang). I'm sure its good material. I did, however get a new clutch disc. They are both Centerforce 2 products.. So, maybe this is a problem, maybe not?

First, rule out a drivetrain issue. If the vibration occurs in neutral with the car at rest, it's in the engine/flywheel/pressure plate. If it only occurs when the car is in motion, it's probably in the drivetrain.

When an engine has to be precision balanced, often down to a half gram (the weight of a single extra strength Tylenol tablet) it doesn't take much to throw things off.

When flywheels get drilled for pressure plates, they need to be PERFECT! And then it all MUST be dialed in on a balance machine. If the pressure plate isn't balanced along with the rest of the rotating assembly, the engine isn't balanced... especially if the flywheel has been re-drilled, or it's some sort of 'custom' unit.

This is where I'd be looking. I'd say the flywheel/clutch is way off. Of course, if you don't have the balance figures (my machine shop keeps them on file) you'll be hard pressed to get it re-done.

Good Luck!

_________________
Mike Burch, 66 mustang real street
302 4-speed 289 heads, 10.63 @ 129.3
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220
http://www.fortunecity.com/silverstone/healey/367

<font size=-1>[ This Message was edited by: n2omike on 1/6/03 10:38am ]</font>

<font size=-1>[ This Message was edited by: n2omike on 1/6/03 10:38am ]</font>

Well the good thing is that when my engine was balanced (using a 28oz flexplate), the flexplate was not drilled, nor was any weight added to it. So technically, my engine should be able to use any 28oz flywheel/flexplate... I never knew an engine could be thrown off by the weight of a tylenol tablet. If that is the case, then it *could* be the fact that when I was screwing down the pressure plate, I couldn't find 6 equal sized washers. So I used some that were just slightly off. Not very much, but maybe thats what is messing things up ? I really am begining to think it is the flywheel or the washers I used. (the vibration occurs during idle and movement) Thanks guys..

My other concern is this. I drove my mustang with it off balanced for about 15 miles. How much damage could it of caused to my bearings? Mind you the vibration I experienced only happend above 2000 rpms, and I seldom pulled the car above that on the way home...

Thanks,
CHris

<font size=-1>[ This Message was edited by: 66stang on 1/6/03 10:52pm ]</font>

I'm not an engineer, but the moment of inertia of 1/2G at about 5" from the axis at 2000 RPM is more than a little. My personal feeling is that once an engine is precision balanced using a flywheel and damper with counterweights, not any flywheel (or balancer) can be used even if it is advertised to have the same specs. If you had neutral balanced the engine, it would be easier to swap parts. The fact that you had to modify the parts to get them to work also adds to the idea that your components are mis-matched.
[addsig]

FWIW I use the 10" flywheel and the 10" clutch with no problem at all.

I'd go ahead and get a new flywheel that's 10" since they never made the 10.5" in the 28 ounce imbalance.

There is no way you're going to feel what you are feeling due to a 1/2 gram imbalance!

Factory 5.0L engines have an acceptable tolerance range of 6-8 grams.

Either you have a major imbalance, or as we spoke, its because the trans is touching the transmission tunnel.

I wasn't saying he would feel a 1/2 gram imbalance, just that precision balance jobs hold this type of tolerance. 6-8 grams sounds about right for an engine to be considered 'good to go'.

Where I was going with that, is that when something as heavy as a pressure plate is installed just slightly off center, the balance job can go straight to h*ll!

Anytime these parts are mixed and matched with custom flywheels, drilling, etc... the engine NEEDS to have a precision balance job. You just can't throw combos like this together and be assured things are 'within spec'.

Again, DOES IT VIBRATE IN NEUTRAL WITH THE CAR AT REST? If so, it's in the engine/flywheel/pressure plate. If the vibration only occurs when the car is moving, look somewhere else in the drivetrain.

Good Luck!
[addsig]