Powerflex gearbox mount bush insert - 996 Review & Mod.

After I fit the Powerflex gearbox mount inserts I posted about the transformation it made to the car with regards to handling and NVH and stated that after I'd been on my lads holiday I'd review them and take appropriate action. I'm back off in less than 3 week on another 2.5k trip with my good lady and the dog so wanted to be happy with them before that so yesterday I decided to remove them and do the infrasilver hack . With regards to the performance of these up to now (after 2 months and around 3k miles) they did bed in more as time/distance went on and the NVH was reduced, but over 3k rpm there was still a considerable amount of vibration through the car and when cruising above 80mph the was quite a drone that wasn't apparent around 70mph. The handling of the car was still as good as when 1st fitted and much better and sharper than with the original old saggy bush. So with this in mind and after infrasilver commenting on his after his eurohoon it spurred me on to do it. I took a few snaps whilst doing it so folk can see how it works, the issue with them and what the process is, etc. I didn't have much of an issue fitting them and the carriers were a nice solid fit over the outside of the inserts. When I came to remove them yesterday, you can see patterns on them where the longitudinal carrier has clamped around the outside of the insert and started to bed in. Also bedding in pattern on the inside of them where the gearbox casting has been tight against them. At this point I realised this was most likely the problem with the NVH and needed to be removed. The top part of the insert (where infrasilver cut out the middle section) was also showing evidence of been clamped too rigid. You can see on the photos where the inserts have gone brown where they have been clamped most (as well as indentations in the rubber surface on them - harder to spot on the photos but noticeable when looking 'in the flesh'). Once the 'hack' was done, refitting was simple enough and they went in far easier than when 1st fit. Everything bolted back up, undertray fitted, then out for a blast to review the change. Wow!! Totally different! As soon as I turned the engine over to drive the car off my ramps I noticed instantly that there was less transfer of engine/gearbox vibration into the car. Took if for a spin down the local A road and the drone above 80mph had totally gone. Turned off onto one of my local twistys an gave it some. The NVH experienced above 3k rpm also totally gone and the deceleration vibration between 4k down to 3k removed. Car still feels nice and tight and the handling just as good. Was quite pleased with the result of doing this as originally although they improved the handling of the car, the NVH was just a tad too much. Looking forward to my next trip down the SoF and will post any update after that. Here's a few snaps of the process: The inserts fitted before the modification. Carriers & insert removed to expose the original bush. Inserts after removal - notice the brown staining on the top tabs and the ring around the outside of them where the gearbox housing has pressed into the rubber. The external faces of the inserts. Also notice the depression made by the carrier that runs (on the left one) from the full width of the aperture to the top right outer edge around the 2 o' clock position. The Hack - I decided to trim a circular pattern that was within the circular clamp mark made be the casing of the gearbox so no transfer of vibration would occur. Surplus to requirement - notice the indentation where the inserts has been too tight a fit. Refitted back in position ready for the carriers to go back on. All back together and ready for the test drive. Now the countdown to the proper test drive in 3 weeks!! :thumbs:

Great post Alex, thanks. Good to know the deceleration vibration and drone >80 is normal as i was a little concerned with where it may be coming from as i did the RSS engine mounts and box oils at the same time.. I will do this mod over the winter when i get some time.. Great write-up.. Thanks, Neil

Excellent timing, mine should arrive any day now.

Excellent update and pictures say a thousand words.

Glad it has worked out , I was thinking it may have been a one off on mine and be of no use to others but great news that it works.

Cheers mate. I"m even tempted to contact powerflex and tell them about the issue.

Thanks a lot for this Alex and infra silver! I have a Function First insert that I am going to put in my car, so this is very timely for me. I would be very interested in their response. Wondering why they would have made the flange the way they did.

Must admit that I thought there was a lot of unnecessary stuff on these when I bought them (and I found NVH unbearable) If this mod does improve things greatly, might well try again!

Thanks for this Alex, I have these ready to fit and will now be able to trim them first with confidence that they will be bearable Cheers, Peter

Many thanks for this and apologies that you have had problems and felt the need to modify our part. My development guys are looking into this and I suspect given what you have found, we will modify the insert. If anyone has an old part and would like it replaced with the new design please let me know at [email removed] and when the new tooling is done we will send you the new design directly.

Hi David & welcome to the forum! Many thanks for taking the time to join the forum and give some input into the situation. If you need any help from me just ask here to drop you a mail or send me a pm. Regards, Alex.

what did you cut them with? Mine are still awaiting fitment. Not sure whether to bother or just get a new bush when a clutch goes in.

Stanley knife with a new blade in.

Many thanks. I will try to keep you informed of progress but with new tooling, moulds and production it will take a few weeks. Whether you have fitted the part, modified it already or it is awaiting fitment we will send out new parts free of charge.

You cant ask for more than that! If you could post when the re-designed items are available as I am keen to purchase. :thumb: