[paul289]

Just completed my T5 swap enough to get going down the road. On the test drive, I noticed that there's an RPM dependent vibration. I remember there being one before, after I had installed a '72 C4, but changing the torque converter had helped. It was not present before the '72 C4, so I know that the engine internals are not to blame.

When performing the swap, I had sent the flywheel out to be balanced to match the flexplate at a reputable shop, so I doubt that's the issue. However, the SPEC clutch kit didn't have dowel pin holes in the flywheel, so I had to just use bolts to hold it. Could that be the issue? How would I go about fixing it if it is?

Or could it be an issue with the transmission not being lined up properly? I kinda doubt that, especially since I'm using a brand new Ford Racing bellhousing.

 

[Ironhorse302]

Paul, please do not quote me on this, but it is possible the driveshaft is causing your harmonic. I don't know enough about the flywheel to tell, but I thought a flywheel vibration would be felt across the range of RPM rather than within a specific range. But I am curious; when you said you had the flywheel balanced to match the flexplate, did you mean the front damper? I didn't think there was a balance to the flexplate, as the torque converter would do that job.

 

[paul289]

It isn't the driveshaft, because that would cause the vibration to change with speed, not RPM. Clutch in versus out doesn't change it either. The vibration is minor at low rpm, but comes on strong at 2000 rpm and doesn't really appear to get worse from 2500 on. Flexplates are balanced, since all engines use the same internals between manual and automatic. Mine was originally a 28 oz imbalance, but my machinist custom-balanced a new flexplate when he balanced my rotating assembly. So when I go a flywheel, I had it balanced to match the flexplate. I didn't notice any weights missing from the flexplate, and it was revving smoothly before, so if the flywheel was accurately matched to the flexplate, then that's not the issue. Could also be that the harmonic balancer spun, or the rubber is failing, but it's only 8 years old so that also shouldn't be an issue.

I kinda doubt that the pressure plate being some small fraction of an inch off axis from the flywheel would cause this sort of imbalance.

I'm still not entirely convinced that the issue is a balance problem. Could be a misfire on one cylinder, or something.

Now watch. I'll fix the vacuum leak and the problem will go away. Seems to be how most of my issues get sorted.

 

[Ironhorse302]

Sorry, Paul, you're right about the driveshaft...I was thinking back to when my son had a similar problem with a C4 > T5 swap. I went back and read your first post; you didn't say whether the vibration was present with the car in neutral (at rest) and just bringing the engine RPMs up slowly. It seems a little far-fetched to think that the balancer would've shifted while you were installing the new trans; very coincidental.

 

[VirginMuscleMan]

What car are we talking about here ?

 

[paul289]

It's the '65 Mustang in my sig. I don't see how the balance could have changed, so I don't think that's it. At the moment, I'm leaning towards a dead cylinder, since the vibration doesn't really get worse. I'll check the plugs to see if they fouled any. I think the vibration was present with the previous C4, and it resulted in the front bushing on the transmission (that supports the torque converter) seriously wearing out. I attributed that to an out-of-balance torque converter, since there was no such damage or vibration with the original C4.

 

[duke65kode]

I have to ask cause I don't see it in any of your posts but did you install the pilot bushing in the end of crank? If worn or not installed it will cause a vibration.

Duke

 

[paul289]

I have to ask cause I don't see it in any of your posts but did you install the pilot bushing in the end of crank? If worn or not installed it will cause a vibration.

Duke

Yeah, brand new pilot bushing that was included in the kit.

 

[paul289]

Think I might know what the problem is. Since the issue started after I swapped in the newer C4, it should be something that I changed during that. The only other change that happened was switching to a polyurethane transmission mount. The engine mounts are still rubber, so that could contribute some weird harmonics. I still have the rubber transmission mount, so I might stick that back in to see if that helps.

 

[paul289]

Haven't yet put the rubber mount back in, but it's going in soon. Had to yank the T5 to check out a noise. I think the poly mount contributed to its own loosening, as well as loosening a few other bolts.

Main question: Do 289s generally move or vibrate a bunch as is? If mine is balanced properly, will it just shake anyways, regardless? Mostly I just don't want to just throw a blanket over the problem without actually fixing it.

 

[Beechkid]

No, the SBF's are very smooth engines..............

 

[silver69]

Paul the dowels do make a big difference and should be installed in the flywheel to align the clutchpack and pressure plate. Pull it all down, install the dowels, install the clutch and pressure plate and finally the retaining bolts(in a star crisscross pattern which im sure you already knew).
Did you perform the runout check on the bellhousing as indicated in the enclosed paperwork? If its off enough it will cause your vibration too so dont discount that small step.
Also the flywheel can be purchased to match the engine 0(neutral),28 or 50oz designation and unless you are running a internally balanced neutral setup or late model 86+ 5.0 you shoud need a 28oz counterbalnce flywheel.
I really think if you indicate the bellhousing and find it within tolerance the culprit may very well be the lack of alignment dowels in the pressure plate all with assuming the flywheel was correctly balanced.
Think of it in these terms: you can feel a tire out of balance as little and .5 ounce and at 60 mph and it will only rotate about 650 to 800 times depending on its size, through rubber insulators sway bar bushing and a host of suspension parts. Now imagine .25 oz bolted to the engine idling at 800 rpm then 1500 then 2500. The vibration will be exaggerated exponentially and a urathne mount is more condusive to transmit harmonics because its job is to limit movement where a rubber one soaks it up.....I will however gladly laugh at myself if its a bad plug/wire lol. Good luck man this is how I would proceed based on what you have presented...regards

 

[paul289]

The reason why I don't think it's the flywheel is because it was vibrating before, with my second C4. Perhaps it was even vibrating before then, and I just never noticed it because I didn't have the poly trans mount. The flywheel was a 28 oz. imbalance, which was balance-matched to the flexplate, so I highly doubt that the flywheel itself is the issue. I will be checking the bellhousing runout while the transmission is out to make sure that's not causing any transmission issues.

The cap, rotor, and plug wires are all new, and I'll be checking the plugs to see if one is running rich or lean or something. A while back, however, I did have a lifter fail on me. It's possible that another lifter isn't doing so hot, and one cylinder is down on power, and the poly mount was just making it seem worse than it really is.

 

[silver69]

I understand but keep this in mind Paul, new does not mean good, treat the ignition system like anything else no matter how "new" it is....stuff is bad out of the box all the time. I have a "new" efi coil, a set of 8.8mm Taylor wires, Areomotive 1142 in tank efi pump, 10" alpine Sub......all with less than 4 hours run time... the list goes on and on..just shipped back 1 pair of wilwood 6 piston calipers never even run but leaking around the piston seals sitting overnight on my lift to prove it.

 

[sp66stang]

paul check your motor mounts one could be going bad.