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914World.com _ 914World Garage _ vibration?!
Posted by: sk8kat1 Mar 26 2007, 10:30 PM
ok .. I have the car on the road but I am feeling an unfamiliar vibration right about when it is time to shift and on decel.... but I figured that is from the newly installed solid engine and trans mounts ...right?!
but I also get a similar vibration in 5th gear and crusing at 70-ish ... is this possibly also related to the new solid mounts?
Posted by: Aaron Cox Mar 26 2007, 10:42 PM
solid engine and trans mounts do couple in more noise......
Posted by: sk8kat1 Mar 26 2007, 10:53 PM
this is more of a vibration I can actually feel in through seat bottom while driving....
and yes all the joking about my ass and something vibrating have already run through my head while I was typing this... 
Posted by: SirAndy Mar 26 2007, 11:48 PM
but I figured that is from the newly installed solid engine and trans mounts ...
uhm, may i ask why in the world one would install solid engine and transmission mounts unless it's a dedicated racecar?
ever occured to you that the factory may added rubber mounts for a reason?
Andy
Posted by: alpha434 Mar 27 2007, 12:00 AM
Metal solid mounts or poly?
Polyurethane will absorb a little bit. Enough for comfort and performance, when done right. Aluminum is too hard. Period.
Posted by: sk8kat1 Mar 27 2007, 07:03 AM
I did solid mounts by suggestion by an other 914 owner because of improved shifting.
and they are both poly .....
so based on the comments all the buzz I am feeling the mounts , right ?
Posted by: blitZ Mar 27 2007, 07:34 AM
I just switched to the Jwest nylon mounts and noticed a tad bit more noise. Not really any vibration.
Posted by: sk8kat1 Mar 27 2007, 08:52 AM
I just switched to the Jwest nylon mounts and noticed a tad bit more noise. Not really any vibration.
hmmm ... what else might cause the buzz I am feeling ?
Posted by: r_towle Mar 27 2007, 09:12 AM
You will feel it in you ass, yes.
Now, unless you have replaced these also, you have two rubber engine mounts, and that is it.
So when the engine revs, the body will vibrate, just simple physics.
Think about it...if the motor is perfectly balanced, and the whole car is perfectly balanced (wheels, tires, rotors) then you may feel less vibration.
the solid tranny mounts will product a noticable vibration, that is why there are rubber ones on the tranny, and rubber ones on the front of the motor.
Rich
Posted by: sk8kat1 Mar 27 2007, 09:19 AM
You will feel it in you ass, yes.
Now, unless you have replaced these also, you have two rubber engine mounts, and that is it.
So when the engine revs, the body will vibrate, just simple physics.
Think about it...if the motor is perfectly balanced, and the whole car is perfectly balanced (wheels, tires, rotors) then you may feel less vibration.
the solid tranny mounts will product a noticable vibration, that is why there are rubber ones on the tranny, and rubber ones on the front of the motor.
Rich
actually I replaced both engine and trans with nylon solid mounts ... so I guess that means that would just accentuate the vibration / buzz that I feel in my ass .. right... so no worries just get used to it right?......
so is it normal that and a certian speed it also seems to buzz/vibrate alot .. .. approx 70-ish mph
Posted by: SirAndy Mar 27 2007, 11:12 AM
so no worries just get used to it right?......
if you're lucky, then, maybe ...
like said above, it's simple physics. the rubber mounts absorb the vibration. now that you got solid mounts, the vibration is transfered onto the chassis.
if you're really lucky, nothing will brake or rattle lose. the reason people get away with solid mounts on a race-car is that the race car get's inspected for cracks and lose items on a *regular* basis.
are you planning on dropping the engine every other week to inspect for damage?
improved shifting? sure. you just added a bandaid without fixing the problem.
the 914 shifted tight when they came out of the factory. with the stock rubber mounts, that is.
think about it, if everything in your shifting system was in good working order, why the hell would you need solid mounts?
if it was my car, i'd say, fix the shift bushings/linkage and get some 911 sport mounts ...
that's what i did on my car. shifts like new ... and no ass-massaging vibrations either ...
AndyPosted by: sk8kat1 Mar 27 2007, 12:54 PM
so no worries just get used to it right?......
if you're lucky, then, maybe ...
like said above, it's simple physics. the rubber mounts absorb the vibration. now that you got solid mounts, the vibration is transfered onto the chassis.
if you're really lucky, nothing will brake or rattle lose. the reason people get away with solid mounts on a race-car is that the race car get's inspected for cracks and lose items on a *regular* basis.
are you planning on dropping the engine every other week to inspect for damage?
improved shifting? sure. you just added a bandaid without fixing the problem.
the 914 shifted tight when they came out of the factory. with the stock rubber mounts, that is.
think about it, if everything in your shifting system was in good working order, why the hell would you need solid mounts?
if it was my car, i'd say, fix the shift bushings/linkage and get some 911 sport mounts ...
that's what i did on my car. shifts like new ... and no ass-massaging vibrations either ...
Andyon PP they said the sport mounts are only for 1970-72 -- ?! my old trans mounts were shot and I did replace all the bushings... so the general thought is that sport for trans mounts and stockers for engine ...
or will I still have issue running solid trans and stock engine
Posted by: SirAndy Mar 27 2007, 12:58 PM
on PP they said the sport mounts are only for 1970-72 -- ?!
i should have clarified ...
i used the 911 sport mounts as *transmission* mounts, not engine crossbar mounts.
my engine mounts are bone stock rubber. you can buy those new ...
Andy
Posted by: John Mar 27 2007, 04:17 PM
Bla Bla bla...
If the vibration you are experiencing is speed related and not engine RPM related, what do you suppose it could be?
I'm guessing that it is wheel balance.
It also could be something between the trans output flanges and the road. (Wheel Bearings, wheel balance, CV joints, axle shafts, etc.)
If it was engine vibration, it would vibrate at similar RPM in any gear. I once had a resurfaced flywheel that was out of balance. It was immediately obvious upon startup.
These engines don't typically dance around when running (if they did, you'd have other issues).
I have run 4-cyl 914's and 6-cyl 914's with solid mounts for years without issue (Track car and street car alike). I have noticed no increased vibrations. More noise transmitted, but no excessive vibrations.
I don't think your new butt vibrator is due to the plastic engine/trans mounts unless something is loose.
just my opinions.
Posted by: 914nerd Mar 27 2007, 05:25 PM
What did your old mounts look like?
I know that my old mounts were completely shorn and that was allowing a fair bit of movement
I went to the hard nylon mounts and there was some increase in noise (and a little vibration due to the fact that the engine was again attached properly)
It itn't anything too substantial, but it is noticable
So is the shifting improvement from having things held together right again
Posted by: sk8kat1 Mar 27 2007, 05:37 PM
What did your old mounts look like?
I know that my old mounts were completely shorn and that was allowing a fair bit of movement
I went to the hard nylon mounts and there was some increase in noise (and a little vibration due to the fact that the engine was again attached properly)
It itn't anything too substantial, but it is noticable
So is the shifting improvement from having things held together right again
my mounts were in my opinion trash ... and the buzz is noticable but not like it is shaking the review mirror bad ...
Posted by: sk8kat1 Mar 27 2007, 05:38 PM
...and the buzz seems to be around 3000- 4000 rpm
Posted by: JohnM Mar 27 2007, 05:42 PM
just a something to check-- non-original trans mounts may move your exhaust up and something could be hitting at certain rpms, torque.
Posted by: 914nerd Mar 27 2007, 05:43 PM
That sounds fairly similar to what I was feeling and it seems to have been due to the better attachment between the engine and the body of the car
Personally, I wouldn't worry about it too much
Posted by: SirAndy Mar 27 2007, 07:42 PM
These engines don't typically dance around when running
is that so?
i've seen 'em jump, not just dance ...
that was with broken motor mounts. it shows just how much force is generated.
there's a *lot* of twisting going on when you hit the gas.
the rubber mounts absorb much of it, the solid mounts transfer it to the body.
you do the math, the force has to go somewhere ...
Andy
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