Vibration

[MRITTER]

Put a Tremec 3550 in my FFR this past weekend - boy, talk about a tight squeeze - and now I have a vibration problem. It starts arouns 2100 rpm and lasts until about 3200 rpm. Seems to be worse on decel than accel. Shakes the whole damn car. Really pissing me off. Also put in a new Ford Motorsport clutch & pressure plate and had the flywheel turned. The vibration is felt with the clutch in or out, in gear or in neutral. What have I done wrong???

Any ideas will be appreciated. I really do not want to take that trans back out, but I think that it has to have something to do with the clutch and/or flywheel.

Mike

[Cobra20646]

Mike,
I take it that it's all RPM related and not speed related right? Like it still shakes when sitting still and just reving the motor?
I also assume that the the flywheel. clutch, plate and tranny was changed all at the same time too?
If thats the case, I'd check the flywheel for proper balance. You didn't say, but early motors used 28 oz ext balance, and later motors used 50 oz. If the motor was balanced by the builder, you may need a neutral balance wheel.
You might also check the crank damper for proper balance.
- Jim -

[Mike Braddock]

Mike,

Did you install the dowel pins that orient the pressure plate in the proper location on the flywheel? One of my friends installed a T5Z and a new clutch setup and ended up with a very similar vibration. He didn't know about the dowel pins and they weren't included with the new clutch. After disassembling, installing the pins and reassembling, no more vibration...

Good luck.

Mike

[Bill Wells]

I don't know about the referenced dowel pins, but I put a new Tremec T5 in my 65 Stang Hi Po (289 K bored + .040 to 294)with new fly wheel , clutch and throw out bearing. Had to have the new flywheel 'balanced' to match the old one , they drilled several indentations in it on one side taking out several ounces in total. Then no more vibrations. Not sure this is apples and oranges here or not, but an out of balance flywheel will make ya shake rattle and roll ! B

[MRITTER]

When we removed the old clutch there were no dowel pins in the flywheel, but we put the pins in before we replaced the clutch. I am wondering if the pressure plate could be the culprit. It is a brand new HD Ford Motorsport clutch though.

Thanks for all the input.

Mike

[Bob Putnam]

Mike,

Make sure that no part of the engine/transmission assembly is resting on the chassis too. Sometimes a small vibration will really show itself when it's transmitted through the whole car.

[Jeff Frigo]

Mike:


I think it is very easy, I can't believe nobody else suggested this. Try unbolting the drive shaft from the rear end, rotate the yoke 180 degrees, and bolt it back together. I have had this happen to me and also to my friends on other cars. Let me know if this works.



Jeff

[poorboy]

Jeff:
Mike stated the vibration is without the car moving, witch elimates the drive shaft as the trouble.
Poorboy

[CobraEd]

Bob has an excellent point about any part of the engine/bellhousing/transmission touching the frame. He is dead on!! To take his thought one step further, is the tailshaft mount (transmission mount) centered properly so that there is full movement within the rubber. If you had to jam the mount in for any reason, or cock it in such a way that there is no free movement within the rubber, this will emulate the driveline touching the frame and send all of the small vibrations directly into the car.

Ed

[MRITTER]

The trans is not touching the frame anywhere. The tail is about a half an inch above the cross-member. We used a urethane trans mount. It is really close to the cross-member and I am not sure if it is touching. If any part is touching it would just be the urethane block on the side of the cross-member.

The vibration feels more "harmonic" the way it starts and stops at a certain rpm. I think that it is either an out of balance pressure plate, a first for me, or the machine shop got the flywheel out of balance when they turned it. I have a new pressure plate on the way and we are taking a different flywheel to a different machine shop to get it turned. We will remove the trans Sat. and install the new parts and hope for the best.

Thanks for all the input. Keep posting if you have more ideas. I will let you know the results of our re-installation.

Mike

[Jeff Frigo]

Poorboy:

Mike says nothing about the car not moving, he said in or out of gear, clutch in or out.

Mike:

Please clarify, do you get the vibration when the car is parked, or when it is moving? If it is when the car is at a stand still, ignore my idea, if it is only when the car is moving, try what I said. It is very easy and as I stated, it worked for me. Just trying to help.




Jeff

[mr0077]

Mike, if the vibration DOES occur while the car is moving, check your driveshaft length also...had a very similar problem on a conversion project with a short shaft. If it's while sitting still, pls ignore this suggestion. LOL

[MRITTER]

Hey guys. Yes it vibrates moving or sitting still. Rev it to 2500 and it will rattle my cell phone around in the holder. It seems to be worse on decel rather than accel. Kind of a shudder as the revs come down. Really weird??

Thanks for the ideas,

Mike

[Coloradocobra]

Plug wires? Might want to check that you didn't knock one loose when you were wrestling that transmission in there. Also check to see that you didn't put the headers/sidepipes in a bind with the new transmission mount. You might be fighting a resonance condition. I'll place my bets on the flywheel or pressure plate, though.

Good luck,

Gary

[Mark Morrison]

Mike

We usually put the car up on jack stands. Run the car and start taking one thing off at a time. Its a drag but you can start to elimanate one pieace at a time. Just an idea.

[aumoore]

From Reading your first post I gather you just put the new trans, clutch in and had the flywheel turned. Turning the flywheel should not have caused this unless: they gave you someone elses flywheel or it is not machined true. The flywheel mounting holes should only line up one way so it is almost impossible to put it on wrong.


Have you checked your harmonic balancer? Maybe it was about to go bad before you put the new trans/clutch in? FMS sells a new one for about $65 and it is not a bad idea to change a old one out as the elastomer is subject to going bad with age especially with motors with a lot of HP.

[MRITTER]

I put a new harmonic balancer in about 1000 miles ago (3 months). Rules that out. I'll let you know what we find on Sat.

Mike

[Coloradocobra]

Mike,

Just remembered a story from an old balance shop guy. He had balanced an engine but when the owner assembled it, it had high vibration. They traced it down to a metal shaving that had fallen between the flywheel and the crankshaft flange causing the flywheel to have excessive axial runout. You might want to set up a dial indicator and check axial runout at about 4 or 6 locations on the flywheel. Just make sure you keep the crank loaded forward against the thrust bearing each time you rotate the crank. This will also identify a poor surfacing job. The axial runout creates a high couple unbalance force that is difficult to trace because when you put it on a balancing machine it may check out OK.

Unbalance force increases as a function of the square of the speed (e.g., force at 4000 rpm is 4 times the force at 2000). If the vibration is "gone" at 5000, it points more towards a resonance or a "grounding" of the engine to the frame or body.

Just a few more things to check in your quest for smoother operation,

Gary

[MRITTER]

Well, the second time you install a Tremec is easier than the first time, but it still isn't a whole lot of fun. We identified the culprit as the flywheel. The machine shop must have thought that we wanted the special "angle-milled" job because that is what we got. Good thing we had an extra flywheel.

Thanks for all the input. Now on to the next task - Upgrading the cooling system and ignition in preparation for the twin turbo setup. Can't take it with you.

Mike

[aumoore]

Glad you found out the problem. I guess I win as my second guess was "they gave you someone elses flywheel or it is not machined true"