1985 240ti M46 having vibration through gas pedal,clutch and shifter. Seems to be stronger while pushing in clutch as going through gears but still appears while cruising but not as strong.

I replaced the motor mounts and no change.I am going to pull the belts of the a/c compressor and power steering to see if it is one of those.I know it's not the alternator because that is new.
I was thinking it could be the transmission but I have never head of that causing that vibration between 2000 and 2800 RPM range. Then my other thought was the flywheel being out of balance. Anyone have any thoughts on any of above?

Hi,.? Trying to think about this, tonight!

This maybe more about questions than any answer to your vibration.

When you said you changed automatic transmission out in favor of a stick shift!
What did you do about drive shaft lengths or types?
I'm thinking the two are not the same length overall by only a couple inches or so?

I'm not familiar with what come underneath the 1985 sedan at all!
1986 wagon is in two pieces and has a sliding member that telescopes.
As I'm trying to remember reading somewhere, that my wagon, being a stick shift, has a rubberized spline within that section.
What did the automatic 1985 come with in either model? This might explain if or why the 1986 could be different.
Some other driveline guys might know the how and why something is not working together.

I might be totally wet in this thought but, if you put a different drive shaft in there or your own combination then maybe the two are halves are out of phase.

I have never heard of a flywheel itself going out of balance. That's one solid chunk of steel.

The possibly of a clutch assembly having a cracked finger of the spring diaphragm pack or a shock absorber spring being dislocated from inside the friction disc can happen. The latter usually locks up the clutch action though.
A piece of a spring finger could have relocated to cause "some" imbalance. The whole affair is a riveted assembly of many segments of spring steel.
One would think that you would have a vibration as the rpm changed whether it was pulling on a load or not.

Going down the road brings in the driveshaft components and of course infamous U-joints, that are a lot more dynamic!
A whole bunch more than drive belts on some engine accessories. That is! Unless you throw in the "harmonic balancer" on the crankshaft. That causes a rumble!
Have you marked it, with a streak of white paint, to check to see if it's spilt and turning under those belts?

Like I said, more questions than a direct answer. There is an answer to this, if we get enough clues, and massaged them into this here.

Phil

Hi Phil,
The drive shaft and M46 cam out of a 1984 244,the drive shaft has metal flange that mounts to the transmission metal flange also has the sliding member.It is a 2 peace drive shaft.
The drive shaft that came out of my car was 2 peace and yes I marked it before pulling same when I pulled the drive shaft from the donor but I think it was shorter,I also used the cross member that came out of the 1984 donor. When I put the 2 cross members side by side looked the same except there was a hole on the right side for the clutch spring.
On the cross member when I pulled it from my car had 2 blocks maybe 1/4" between the cross member and frame but when I pulled the cross member from the donor car there wasn't any blocks.
When I installed the m 46 and cross member and the top of the transmission would hit the tunnel on start up so I had to use the blocks.
When I drive the car and in the range of rpm's that cause the vibration I had someone sit in the back of the car to feel around where the drive middle rubber doughnut is and there isn't any vibration in that area. all the U joints and center bearing are new.
I don't remember if I said that the vibration is the same sitting in neutral. Thanks for all your questions,Charlie

Hi, Charlie

It seems that you have narrowed the vibration down to engine area if you can feel it in neutral.

I looked back into your post and you said you can feel the vibration through the clutch pedal.
So when you have to the play out of the top under your foot you are actually feel the lever shaking.
That would indicate that the fingers of the diaphragm must be moving laterally.

So there must be something not flat and parallel with surface of the flywheel.
The flywheels don't normally warp but can get hot spots just like a pressure plate from excessive heating. This can cause the friction disc to glaze just like brake pads.

When installing the donor clutch and flywheel did you notice and discoloration areas as in a slight yellowing or patches of blue spots? The very top surfaces will turn into hard spots. These will lead to chirping upon engagement.

Machining by turning or grinding evenly just below these areas can remove this scorching on the flywheel. The pressure plate is another story. I imagine it can be done but you are still left with the unknown power of tension in the spring fingers.

The chirping will come and go on how you release the clutch and the temperature of the assembly.
The less you keep your foot pressing on a clutch, the less it will chirp. That's my experience, especially on a high mileage unit.

Unfortunately, It's also a sign of things worn or a weak application of even pressure around the pressure plate.
This does not mean you are using the clutch incorrectly but the spring diaphragm as a whole is weak. The pressure plate is held to the spring fingers by linkages in a ring around it.
Those links are suppose to settle to an even distance in space thickness between them and the attached finger.
Either a spring finger or two or a link may have suffered tempered stress relief, warpage or breakage.
The inner circle of fingers that touch the throw-out bearing pushes against are probably not even to each other. It's a compounded event.

Trying to explain a vibration at those raised speeds when you are not pressing in on the clutch and in neutral. It's got to be something but I can not come up with it.
Weight, a missing bolt or a wobble has to be causing it.
I can tell you from what electric motors and centrifugal pump impellers balancing I did in the Navy, a few grams of displaced weight can get do wonders to mess things up.

It's my thinking that it's either shroud of the clutch, that's is holding the fingers or the pressure plate, is not parallel to the flywheel and the shroud.
The friction disc floats or is suppose too, between the pressure plate and the flywheel.

Do you have any idea how many miles were on the donor car or did it look mistreated or as we say "run in the ground" from the lack of maintenance? Excessively oily engine?

I'm thinking you had no heads up and you wanted to work the gold mine you found for all its worth!
I would but I'm always expecting to get bit or nibbled as used is used!

Sorry, for what I think is bad news, but a tear down inspection is only logical.
Inspect the flywheel with and use dial indicator. Then go with a new complete clutch assembly.

I'm really curious to what you are going to find and hope you post back even though I know winter is coming.

Phil

Thanks Phil,
I also think it's the clutch and or flywheel is in play. At this time I will wait for a while since it's getting colder and at 70 my body doesn't like the cold, it hasn't got any worse so I can wait until spring.I will repost when I start up again. Thanks for your help.
Charlie

In addition to the other excellent suggestions that you have already received, put the car up on a rack (or slide under on a dolly if you can - I can't!) and check your center carrier bearing and the rear u-joint for play.

Bad/failing u-joints can do weird things. Mine started with a metallic "ping" when I released the clutch in 1st. It progressed to a rumble in the driveline, and then a full-on vibration that felt like the car was going to burst apart right before I had it replaced. This was the u-joint where the driveshaft goes into the differential.

Thanks for your reply but already checked them and bearing,rubber support and u joints are Good.

Sagging or broken transmission or motor mounts can cause all those symptoms. -- Dave

Well I changed the transmission mount but no change.I ordered engine mounts and will see if it solves the problem.
This didn't just happen,it started back when I changed from the AW71 to M46 transmission.Could a flywheel that is not balanced cause this problem? The vibration starts between 2000rpm's and 2400rpm's but it will still do it in neutral.

I would think it's not likely that the flywheel itself is out of balance - but possible I suppose. Maybe the flywheel isn't seated completely? Or the clutch is out of balance - broken finger? or not centered - dos the flywheel still have its locating pins? -- Dave

Yes it has the locating pins.When the car is cold on take off the clutch chatter's a bit but after it warm no chatter. At some point I am going to replace it.
I have had clutch chatter in other cars but it didn't cause the vibration that I have now. I guess I will have to wait until I get the motor mounts on Friday.

Thanks Dave I will have to check them.They where new after I rebuilt the engine about 2 years ago.
Charlie

Inspect you driveshaft also for bolt tightness.