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Drive train vibration

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TimK

TimK

Jedi Knight
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I removed my transmission 2 years ago and replaced the clutch and pressure plate and replaced the steady bracket rubber bushings with polyurethane bushings. Since then I have an annoying vibration which buzzes the whole car at engine speeds between 2000-2500 rpm. The vibration is much more noticeable while driving, but is much less when revving the engine at idle. There have been recent posts about damper de-lamination causing crank failure, but my damper looks fine -- it spins smoothly. How do you know if a damper is bad? Or could it just be the solid poly bushings transmitting/magnifying the engine vibrations, or could the pressure plate be unbalanced?
 
Hi Tim,
Did you put the drive shaft back in the same orientation? Or did you have it balanced while it was out? That might be your culprit.
 
I thought about that, but forgot to mention that I did not mark it and there is a 75% chance that I got it wrong. That is the easiest thing to try to remedy the situation. I guess I can rotate it one bolt at a time until I've either fixed the problem or it doesn't solve it. Thanks for the idea, Greg.
 
TimK said:
I thought about that, but forgot to mention that I did not mark it and there is a 75% chance that I got it wrong. That is the easiest thing to try to remedy the situation. I guess I can rotate it one bolt at a time until I've either fixed the problem or it doesn't solve it. Thanks for the idea, Greg.
Click to expand...


:nonod: NO NO NO, that will not correct the issue if the drive shaft was assembled incorrectly . Look on the drive shaft halves there are markings which must be aligned to in sure there is not an out of balance condition. However, at the low revs of these engines drive shaft problems usually do not occur except as noted or if replaced Universals cause the crosses to be misaligned--Fwiw--Keoke
 
I had an annoying vibration coming from my Zephyr engine (which is somewhat similar to the Healey engine) and it turned out to be the clutch being about 30g out of balance. I took out the crankshaft and had all the rotating parts balanced together and now it is very smooth.

Try putting a long screwdriver on the bellhousing and press the handle against your ear while revving the engine through the vibration zone as this will pick up any harshness = probably your new clutch is not well balanced.

Andy.
 
I did not do anything to the drive shaft except disconnect the four bolts to the transmission output.
 
There have been recent posts about damper de-lamination causing crank failure,
but my damper looks fine -- it spins smoothly. :lol:

How do you know if a damper is bad?
Well sometimes you can look at the rubber and it will look like it has been twisted.

Or could it just be the solid poly bushings transmitting/magnifying the engine vibrations,I doubt it unless they are very very hard.

It might be the pressure plate and the clutch disk are unbalanced or defective in some way.----Keoke
 
Hi Tim,

It is very possible that all that have been noted by others is causing your vibration, however, I believe your issue is how to start to eliminate the possibilities with the least of effort. It is my feeling that your polyurethane bushing may be able to transmit vibration more effectively than standard rubber bushing, however, the vibration must be present to transmit.

One point, you indicated that the vibration is present as the engine is revved when the car is stationary and with the transmission in neutral. In that situation, I would expect the drive shaft would not be engaged and contribute to a vibration. In that circumstance, I would look to the damper and clutch mechanism, however, the drive shaft could also be a contributor adding a second vibration (2 sources of vibration and not 1). Each vibration source may be small but together … annoying.

I would suggest you start by checking your damper and drive shaft’s orientation. Should these prove OK, then and only then would I address the balance of the clutch and pressure-plate.

By the way, if your damper has separated, there are a few vendors that will re-laminate your original at around $100. You may also decide to go and have your drive shaft balanced as a number of Healey owners have done when addressing this issue.

Hope this helps.

All the best,
Ray (64BJ8P1)
 
RAC68 is correct that if the vibration is at an engine rpm of 2000-2500 regardless of car speed (ie, it's at 2000-2500 rpm in all gears, or neutral) then it's not the driveshaft, wheels, etc. because they would vibrate as a function of car speed, not engine rpm. Damper or clutch balance are the most likely culprits, and less expensive to test than crankshaft imbalance.
 
Thank you all for your analysis and advice. I took out the transmission twice and hate to have to do it again, but I also no longer enjoy driving my Healey with the vibration. I am inclined to think that the symptoms point to the pressure plate since that was the biggest change immediately prior to the vibration occurring. As Keoke says, the poly bushings would only increase transmission of a vibration, not cause it of course. The fact that the vibration occurs in all gears at that rpm range seems to rule out the drive shaft. I had an out of balance drive shaft on my old MGB race car and that vibrated viciously through a wide speed range. I am, however thinking of jacking the car up and running it at 2500 then pushing in the clutch and braking to see if there is a change. I may be getting too old to deal with consecutive issues with an old LBC. The joy of ownership and driving it has kept me going for nearly 30 years, however.
 
Hang in there Tim, the problem is that the floor has moved farther away so it takes longer to get up. :laugh:
The joy of ownership and driving will keep you going for another 30 years.----Keoke-- :hammer:

OH when you get it jacked up be sure and check that the drive pinion in the diff is not lose. Rotate the drive shft by hand and shake it hard at the diff end while looking for movement of the pinion. I had a situation like this many years ago the Lock washer behind the pinion nut broke and allowed the pinion to run off center.
 
Don't even think it is the damper. The bad harmonics of the inline 6 come into play about 5900 RPM, so if you are in the 2000-2500 RPM then your damper is not even a factor.
I suspect the clutch pressure plate that you installed is way out of balance.
Since the Healey (Austin) engine is zero balanced, take out your transmission, remove your flywheel and take the flywheel and the pressure plate to an automotive machine shop and have them balanced.
 
Thanks Richard and everyone else. I am really disappointed when I do a big job to make things better and they get worse. Now I have to do it all over again and who knows what new havoc I'll cause. But then again, the joy of solving problems (if you do solve them) lasts a long time....

If I take the transmission out again, I may open it up and replace the baulk rings/synchronizers (but risk creating more problems)....

There are also leaks at every joint...
 
This is the rest of the story. Last week Michigan finally warmed up enough for me to take out the trans for the third time (twice in 2008). I got the best clue from someone on the forum who said the flywheel had a number 1 that had to be At the top when piston #1 was at TDC. I had photos showing I had replaced the flywheel 180 degrees off when I had put in the rear main seal. I removed the trans and rotated the flywheel 180 degrees and now the vibration is gone. Thank you so much forum person for that key piece of info, I wish I remembered who it was.
 
Interesting, it's a while since I did it but don't I remember a locating peg in the end of the crank which means you can only put the flywheel back on one way?
Or was that on my old ford?
Ian
 
It must be another vehicle. No peg on my bn7.
 
Hi Tim, you didn't by chance remove the flywheel did you?

If you don't align the flywheel, (It's marked for #1 cylinder at top) it will cause high speed vibrations as you described.

The shop manual explains it pretty well.
 
Yes I did remove it to install a rear main oil seal and put it back 180 degrees off. I was unaware of the need to align the #1 with piston #1 at TDC. I solved it with returning it to its correct position.
 
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