Powerflex gearbox mounting bush insert kit - WOW!

[infrasilver]

........and my idea, in this order, was to take most of the sidewall of the bush away as this is not really needed and see what result that brings.

I was thinking about this last night and why the sidewall is the thickness it is. It then dawned on me that they're that thickness as the distance across the outside faces of them when both inserts are fully depressed into the mounting bush are the same width as the carrier that goes over them. This is so that the outer faces act as stops and prevent the inserts from moving out from the apertures in the bush, thus ensuring they are fully encapsulated in their designed position.

Mine do seem to be less 'vibrant' since I fitted them on Friday. Think they'll be getting left alone for the foreseeable future and see what happens.

Edit: Sorry Chris, I'm presuming you meant thinning the walls down of the inserts? Correct me if I'm wrong.

Yeah they are that thickness to hold the insert in place as you say but I think there is probably too much on them just to replicate the original outer rubbers shape and I don't think it needs that much. I was thinking of cutting it down to the diameter of the actual bush so there is just a circle of poly and as this will be minimal to the NVH I may then chop off one of the insert sections off and see how that is.

 

[Alex]

Gotcha! :thumb:

 

[demon]

Anyone who fitted these inserts and didn't notice a difference would need to get themselves "checked"...!
- they make a big difference to the car - you do need to be the type who would eat marmite straight out of the jar if you plan to fit them

There's definitely more vibration. But it depends somewhat on how you drive. There is likewise definitely a firming up of shifting - second to third coming out of a deep sharp lefthander is now guaranteed, rather than requiring so much knack and timing...

My entire car is polybushed including the subframe mounts, but as a result I run standard engine mounts, rather than the RSS... so maybe this influences things.

For the first time I'm suddenly conscious I drive a 6 cylinder boxer engine, rather than just a smooth 6 cylinder....!
- there's not much exhaust note now (from the cabin), as it has been blended with more mechanical transmission and engine noise....... which I like! there's an element of "cup car" to it!!! - so yes, definitely only for those who are looking to intentionally compromise the out of the box road going manners of the 996 Carrera into something else

My main hobby this summer is going to be putting sticky backed felt and 1.5mm foam behind things.... but everyone needs a hobby and this one's pretty cheap...... in 996 terms!

 

[EGTE]

Good summary, although it seems odd that you should be worrying about rattles/buzzes, while being keen on the vibration of these mounts :?:

 

[demon]

Good summary, although it seems odd that you should be worrying about rattles/buzzes, while being keen on the vibration of these mounts :?:

I don't think the lid of the centre console "buzzing" at 4.5k really adds to the overall aural experience - vibration and mechanical noise is one thing, plastic on plastic noises in the cabin due to age and overall fit of interior trim bits is another.... these noises were always there to a degree before, but now its with a bit too much vengeance....

If I were to strip the interior it would be all pure mechanical noise, but I'm fighting for the "impossible" plush air conditioned leather interior, understated external appearance (aka "the one that looks like a Boxster") and hinting towards GT3-esque mechanical underpinnings....
- personally I think a really well considered/sorted Carrera (with a degree of compromise) can eclipse a GT3 as a really good everyday performance road car.......

Track car = awful road car
Fast road car = pedestrian uninspiring track car

My cars aspiration is firmly "fast road car"

 

[infrasilver]

I was fitting my insert today when refitting the gearbox and as it was too tight to fit in easily I removed it and decided to modify it to how I was going to do fairly soon anyway.
As you can see I just couldn't get the gearbox to fit in easily with all the side section of the insert, I think my original rubber mount has some extra rubber in the middle from the manufacturing process that won't let the insert fit fully into it.









Hopefully this turns out to be about right and not too harsh.

 

[Alex]

Groundhog post :lol:

 

[Marky911]

Good summary, although it seems odd that you should be worrying about rattles/buzzes, while being keen on the vibration of these mounts :?:

I don't think the lid of the centre console "buzzing" at 4.5k really adds to the overall aural experience - vibration and mechanical noise is one thing, plastic on plastic noises in the cabin due to age and overall fit of interior trim bits is another.... these noises were always there to a degree before, but now its with a bit too much vengeance....

If I were to strip the interior it would be all pure mechanical noise, but I'm fighting for the "impossible" plush air conditioned leather interior, understated external appearance (aka "the one that looks like a Boxster") and hinting towards GT3-esque mechanical underpinnings....
- personally I think a really well considered/sorted Carrera (with a degree of compromise) can eclipse a GT3 as a really good everyday performance road car.......

Track car = awful road car
Fast road car = pedestrian uninspiring track car

My cars aspiration is firmly "fast road car"

+1 on the summary.

Fair play to you Demon, you seem to have found the experience you're after. Proof that we all like things different.
All I'll say is you'll be chasing rattles for the rest of your days now. :grin:
That bush makes things feel like the whole car is mounted around the gearbox.
The rattles on overrun from high revs are the worst. The roll cage buzzes, coins in the ash tray go beserk.

All I'll say is what I mentioned earlier. Don't confuse vibration with "race car".
A bush that makes everything shake and rattle does not make a GT3.
Despite having a mega stiff shell and cage (in Clubsport trim) a GT3 interior is still a comfortable rattle free place to be. The chatter from the single mass flywheel gives a hint at what to expect before you set off but after that the screamr of an engine does the talking. The buckets and stiff suspension keep you focused and the whole experience is simply gorgeous.

I agree that a properly set up C2 with some good mods and fresh suspension can feel like 90% of a GT3, although that probably drops to 80% once the engine comes into play.

Anyway bush or no bush enjoy the cars peeps. :thumb:

It's always interesting to see who gets on with certain mods and who doesn't. That's why I'm interested to see how Alex and Infra find it.

 

[Phil 997]

I was fitting my insert today when refitting the gearbox and as it was too tight to fit in easily I removed it and decided to modify it to how I was going to do fairly soon anyway.
As you can see I just couldn't get the gearbox to fit in easily with all the side section of the insert, I think my original rubber mount has some extra rubber in the middle from the manufacturing process that won't let the insert fit fully into it.









Hopefully this turns out to be about right and not too harsh.

opcorn: opcorn: opcorn:

 

[Harv]

There are a few different types of these inserts out there and thought I'd share pics of the ones i have.

Noticeable differences are the flanges on this version are much smaller and more in line with what Infrasilver has modded into.

But something of note is that the thickness of the flanges on mine do not protrude past the thickness of OE bush central metal section. I would say the the flanges need to float like the OE rubber spacers (that need to be omitted when fitting these inserts) and if they don't and are wedged in between the gearbox nose and the horseshoe support then that is where all the NVH is coming from.

 

[Phil 997]

Harv, Thats a very interesting observation and the fact some might remove and others dont might explain the differing opinions of thesebushes. :?:

 

[infrasilver]

I would like to see the differences between all these manufacturers.

 

[Harv]

Chris see if you can thin the flange width with a clean and strip disc before fitting (if your bushes need it).

I think my kit is possibly the harder urethane version but sadly I cannot give any another feedback yet with my engine is still in bits

 

[thecarfixer]

I'd agree.

You don't want to preload that bush, as you'll cause it to wind up if nothing else - bear in mind the engine and gearbox will be rotating on the axis of the driveshafts in response to torque reaction, so the axis of movement that the gearbox mount will move in is a sort of arc.

You want the inner parts of the bush to be doing the work, rather than the side buffer pads.

 

[911munKy]

The more I read of this thread the more I think that poly-filling the original gearbox mount (if in decent condition) with, say, 60 shore is the way to go for a daily driver road car.
Just got to pull my finger out and do it now, maybe towards the end of June when I get some time off, in the interim I await you modified mount results.