JDS968

My understanding is that this sort of problem, either with no balance shafts or malfunctioning balance shafts, is limited to specific RPM ranges that create vibrations on the resonant frequency of particular parts. Either that, or it's 4 AM and I'm thinking of entirely the wrong thing...

Giantman

I thought I read somewhere (clarks maybe?) that balance shafts on these engines become usefull after 2,800 rpm? If this is indeed the case, is it even possible for a missaligned shaft to cause issues in the 1,600-1,800 range that I am having trouble with?

Please chime in any balance shaft experts out there

The DareDevil

My low-RPM vibration issues were resolved by replacing the (broken) motor mounts.

Giantman

Interesting, did your shifter in particular rattle as a result or was the vibration more an all over kind of thing?

RobE952

I have a similar rattle in my shifter. Always in the same low RPM band. Upon pulling the engine last fall I discovered a completely severed engine mount. I'm hoping new mounts will cure that problem.

Although... my new LR ultra trany mount will probably add some more vibration back in. Typical.

The DareDevil

More an all over kind of thing.

Giantman

Can engine mounts be inspected/replaced without pulling the donk?

Also, what about the tranny mount? Could this be suspect too?

PorscheDude1

Weak engine mounts usually cause viberation at idle.

Giantman

So just a quick update as I had some time yesterday to further investigate the cause of this shifter vibration between 1,600 an 1,800rpm.

As I stated before, the shift lever itself is OK. The vibration is coming up the shift rod from the transaxle. The shift rod vibrates WITHOUT the lever even attached. The vibration occurs with or without the clutch engaged. I can hold the revs at around 1,700rpm and maintain the vibration.

So I started poking around 'down there' and found that there is a lot of lateral play in the intermediate shift lever. If you watch the video (link below) you will see exactly what I am talking about.

Therefore, could this 'slop' be the reason vibrations are being sent down the shift rod to the shift lever even though it doesn't actually explain the reason fo, or source of the vibrations?

Thanks for any insight you can offer!

Link to video:

http://www.youtube.com/watch?v=fbUXlyTNMWE

Jeff N.

Not sure if that play translates into the buzz or not but you can fix the play. The plastic portion of shifter linkage wears over time leading to the lateral play you are seeing. Here's the part you need. I have one on my bench waiting to go in.

https://rennlist.com/forums/944-turb...provement.html

Giantman

THanks Jeff, I had actually read your post on this machined replacement already. I want to replace the plastic item but the whole idea of dropping the transmission to do so is putting me off big time. Especially as I don't know for sure if this will eliminate the vibration. I guess it's the source I am really aiming to fix first otherwise a lot of effort could be for nothing.

Is Stuttgart Motors still around? I was unable to locate them on the web.

Cheers.

Jeff N.

I think they are still around. (Note to self - in web age, never have the primary name of posche business the name "stuttgart" - you get lost in the 10,000 results )

http://www.stuttgartmotorsinc.com/

I have changed shift blocks without dropping the tranny. It's tight but you can do it.

I would agree this likely wouldn't replace the buzzing vibration. I had this problem for a while as well and it just sort of disappeared. The only thing I changed that was even close to the area was a weeping heater control valve. It was oozing coolant onto the clutch plate and I think causing some clutch issues. My buzzing seems to have gone away in the time that I did that fix. May be worth a look if you're loosing any coolant to check this out....long shot but who knows?!