Flywheel / Flexplate (AUTO) balance........how important?

Discussion relating to the Scirocco 1982-1991 - - please ask technical questions in the technical/trouble shooting section
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kidcrewbob
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Flywheel / Flexplate (AUTO) balance........how important?

Post by kidcrewbob »

Anyone have experience of a problematic flexplate (the flywheel on an auto) whereby when stopped on the footbrake at tick-over & in gear (D or R) there is quite a noticeable vibration transmitting to the dashboard generally possibly due to balancing or some other weight related deterioration ? The rate of vibration reduces somewhat when the transmission is properly hot and disappears completely when you start to actually move OR when slipped into either P or N (so nowt to do with the engine mounts) .

I removed the flexplate to install a new crank seal when swapping a (brand) new transmission and torque converter and and didn't give much thought to it being balanced or not. Now I am wondering that when stopped at junctions in D it is amplifying a very slight imbalance in flywheel when the TC is obviously engaged (like holding a manual on the clutch / handbrake I guess).

It's a big job to remove it so wanted to get a few soundings as to the likelihood - particularly keen to hear from other auto owners re their experience of stopping at junctions in D and whether they have noticed similar - and I am certain that this would never have been an inherant "characteristic" of an auto!!


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unknownmale
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Re: Flywheel / Flexplate (AUTO) balance........how important?

Post by unknownmale »

Sounds 100% like your engine mount. I've experienced this in two autos i've had in the past. Both times the drivers side mount was shot. You would only feel vibration when the gearbox is loaded up. In both cases the car drove smooth. Only when loaded up.

You can reduce this a little by reducing the load when in Drive/ Reverse by loosening the throttle cable from the gearbox to the carb. But I guarantee you need to replace at least the drivers side engine mount


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kidcrewbob
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Re: Flywheel / Flexplate (AUTO) balance........how important?

Post by kidcrewbob »

Thanks but I’ve replaced all 4 mounts in last 6 months & the drivers side was the last one and a tw4t to get at - also, the main source of the vibration seems to emanate from the near side / transmission side ......maybe I need to check all the torques again?

An interesting observation you make re the throttle cable from box to carb - something I’ve never looked at nor fully understand I must say.....


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unknownmale
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Re: Flywheel / Flexplate (AUTO) balance........how important?

Post by unknownmale »

I think your flexplate is fine, if it was unbalanced it would get worse with revs. Small chance of a failing torque convertor, but they're pretty bullet proof!

If it were me id run through all the mounts again. Get them all a bit loose on level ground, then tighten them all up again, Front and rear gearbox mount first, then the drivers mount and top gearbox mount, just incase they're tweaked over a bit.

Yeah, if you take your foot off the brake in D, it should just slowly creep forward, if it wants to really go when you let of the brake then the cable is too tight. Another sign of this is if it slams into gear when your stationary and put it in D. If it's well set up you barely feel it engage. If you follow the throttle cable to the gearbox you should see a black adjuster. You'll just need to loosen and tighten this to get it just right, doesn't take long to set up. But because of the kickdown mech the cable will run from your pedal, to the gearbox, then another cable from the gearbox to the carb, thats the one which needs adjusting...If your car has a weber in it, it's fairly common for people to mod this, remove the kickdown spring due to fitting a manual carb with the wrong linkage.

Also, just incase... test the ATF level and colour, on level ground with the engine running in Park, check the level. Some people check the levels without the car running and end up adding too much fluid!.

Let me know how you get on!


- David
kidcrewbob
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Re: Flywheel / Flexplate (AUTO) balance........how important?

Post by kidcrewbob »

Many thanks for the tips - I will check accordingly and report back - and a good logical point re the balancing of the flexplate.

ATF is pretty fresh and still a nice shade of uncontaminated pink - could be a tad overfilled - again I’ll do the check whilst running and see.


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