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Engine Mounts: Blown 964 to Rennline to 993

 
Old 01-15-2016, 01:30 PM
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MTR
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Default Engine Mounts: Blown 964 to Rennline to 993

I was jacking up the rear of my car to address an exhaust leak when I noticed a significant amount of fluid dripping from rear passenger side of the car. Upon closer inspection it was fluid from my motor mount. After 26 years in the Florida heat the rubber was easily pulling away from the mount and it finally let go.

So after some Rennlist research I discovered it's not recommended to replace the mount with another 964 part due to cost along with better alternatives. Most users recommend either the RS, Wevo, Rennline, or 993 mounts. I went with the Rennline mounts because they come with 3 sets of bushings: street, sport, and race. I figured this would allow me to dial in the stiffness depending on an acceptable level of noise, vibration, and harshness (NVH).

First off, after receiving the Rennline mounts I was extremely impressed with their quality. They are beautiful CNC'ed and anodized pieces with chamfered edges everywhere. You do have to assemble the mounts which calls for torquing the center threaded post to 30 lb-ft. Unfortunately the piece that the post needs to thread into is totally round so you can't get a open end, socket, or vise on it to stop it from rotating. Seemed like somewhat of a design flaw since adding two parallel flat surfaces would be very simple. I just used some Loctite Red and torqued it while trying not to let it spin in my hand. I wasn't sure how much of an NVH increase to expect since my 964 OEM mounts were blown and sagging, so I though I would start out with the least stiff yellow "street" bushings. After an uneventful straightforward install I went for a test drive. I immediately noticed a significant increase in NVH at idle. My car is already fairly loud so the noise increase was difficult to quantify, but in terms of vibration I could definitely feel more vibrations in the seat, shifter, and even a little bit in the steering wheel. The car did feel more together and also seemed to plant quicker after going over speed bumps, etc. But overall even the "street" caused too much NVH for my liking, given my car is used for 95% street and 5% track driving.

So I decided to give the 993 mounts a try as most users said they are a great alternative for street applications. As I understand it these mounts are a 993 part number but are also used in 996 cars as well. Also, I'm fairly certain they are a non-hydraulic mount but don't know for sure, so if someone can educate me here I would appreciate it. One thing I noticed while inspecting them prior to the install was you could press on the threaded post and cause some deflection fairly easily, meaning they were not nearly as stiff as the Rennline mounts. After installing the mounts the test drive confirmed that they are much softer and my car returned to being very smooth at idle, a definite reduction of NVH compared to the Rennline mounts.

Overall, I am much happier with the 993 mounts for my application. I'm sure not having a semi-solid mount might cost me a couple tenths at the track, but for me that's an acceptable trade-off for a nicer ride on the street. Also, I wouldn't hesitate to purchase another Rennline part given the quality and customer service I've received. So if you do have a higher tolerance for NVH or your 964 sees a lot of track time then the Rennline mounts would be a great solution in my opinion.

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Old 01-15-2016, 02:17 PM
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Interesting note about the Rennline pieces and the whole assembly spinning when being tightened. The Wevos use a long bolt, so you hold it with a socket at the top and tighten the nut with a socket from the bottom. Does the bottom surface on the Rennline pieces have any sort of key? Possibly a key that slots into the opening on the engine carrier and prevents rotation? If yes, then perhaps the problem was that you needed to jack up the engine slightly to create preload between the bottom of the Rennline mount and the mounting points on the engine carrier bracket.
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Old 01-15-2016, 02:30 PM
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Rennline provides two nuts that you torque towards each other to lock them into place on the main post then you can attach a socket and torque wrench to thread it into the top CNCed assembly. So there isn't a hex key like there would be on struts to keep them from spinning. It's this top CNC'ed piece that is totally round and flat on the top whereas it sounds like you can put a socket on the Wevos. Rubber plus a vise would probably be the best approach for the Rennlines but there should definitely be a better way.

Sounds like Wevo designed theirs a little better, but the Rennlines look really nice with the smooth flat tops.




Last edited by MTR; 01-15-2016 at 03:16 PM. Reason: Added pictures.
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Old 01-15-2016, 03:24 PM
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I did the 964RS mounts. They've been installed but I haven't had a chance to review yet. I also bought the Wevo's, but decided to go OEM. Will post a review as soon as I get my car back.
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Old 01-15-2016, 04:37 PM
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Hi,

I have the Rennline semi-adjustable mounts fitted onto my car (seen here below before they were fitted) and they are great. The gear shifts are much more direct with no sloppiness, even the engine sounds better which was an unexpected bonus.



A point of note, mine came with the three sets of adjuster dampers, the yellow ones are street setting, blue are sport and red are track. I have the blue ones fitted and they are perfect for fast road and a general firm sporty feel and occasional track fun.

Cheers,
Paul
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Old 01-15-2016, 04:46 PM
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Paul, did you assemble your mounts? If so were you able to hit the 30 lb-ft torque called for on the main post?

Also, if you engine sounds better with the new mounts it's most likely just transmitting more noise into the cabin. I also noticed that my car shifted better with the new mounts compared to the blown OEM mounts. But between the Rennline and 993 the improvement in the shifter feel was the same. Which would make sense because it's most likely not the damping but actually the angle of the powertrain that is now back in line versus sagging a half inch or so.
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Old 01-15-2016, 05:13 PM
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Hi,

I'm afraid I didn't fit them myself, so I'm sorry I can't answer about the torque setting achieved. I was originally going to do it myself but I decided to have the bushings, drop links and top mounts for front and rear all done at the same time and I thought I may as well have it all done together as I wanted it finished before I took the car to France.

There is possibly slightly more noise in the cabin although I can't be sure. It was always quite loud with the Fabspeed exhaust, however the engine notes are much more distinct music rather than a noisy mush.

The standard engine mounts I took out were in pretty good shape for 78k miles and I guess new OEM replacements would provide an improved gear shift given that they would lift the engine but there's is no mistake that the Rennline engine mounts are spot on.

Cheers,
Paul
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Old 01-15-2016, 05:22 PM
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Originally Posted by Paul284pt View Post
I was originally going to do it myself but I decided to have the bushings, drop links and top mounts for front and rear all done at the same time and I thought I may as well have it all done together as I wanted it finished before I took the car to France.
Sounds like a nice refresh. I've been eyeing the Tarett Drop Links for a while. They look like another well made aftermarket product.
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Old 01-15-2016, 05:42 PM
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Together the Tarrets and other upgrades have transformed the handling of the car, it's so much more direct and the turn-in is brilliant. Previously the car had never felt like it could be thrown about in the way say an SC or the lighter cars could be.

Best,
Paul
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Old 01-21-2016, 06:18 PM
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So the drop links make a difference. I've got a c4 on its bottom, do they rub the driveshafts?
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Old 01-21-2016, 06:46 PM
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You're not going to be able to run any aftermarket droplinks on the front axle of a C4.
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Old 01-21-2016, 07:35 PM
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Btw, I definitely give a big thumbs up to the RS mounts. I don't notice any material difference in shaking/wobbling or noise, but shifting response is significantly more crisp. Didn't get a chance to take the car around some bends to see if there's less roll, but so far, I'd highly recommend the 964RS mounts.

FYI, my original mounts were sagging pretty significantly. On startup I typically had to double clutch to get into gear and then rowing (esp. into 3rd) was a chore. Now's it's buttery smooth.
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Old 05-16-2019, 11:03 PM
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Originally Posted by MTR View Post
I was jacking up the rear of my car to address an exhaust leak when I noticed a significant amount of fluid dripping from rear passenger side of the car. Upon closer inspection it was fluid from my motor mount. After 26 years in the Florida heat the rubber was easily pulling away from the mount and it finally let go.

So after some Rennlist research I discovered it's not recommended to replace the mount with another 964 part due to cost along with better alternatives. Most users recommend either the RS, Wevo, Rennline, or 993 mounts. I went with the Rennline mounts because they come with 3 sets of bushings: street, sport, and race. I figured this would allow me to dial in the stiffness depending on an acceptable level of noise, vibration, and harshness (NVH).

First off, after receiving the Rennline mounts I was extremely impressed with their quality. They are beautiful CNC'ed and anodized pieces with chamfered edges everywhere. You do have to assemble the mounts which calls for torquing the center threaded post to 30 lb-ft. Unfortunately the piece that the post needs to thread into is totally round so you can't get a open end, socket, or vise on it to stop it from rotating. Seemed like somewhat of a design flaw since adding two parallel flat surfaces would be very simple. I just used some Loctite Red and torqued it while trying not to let it spin in my hand. I wasn't sure how much of an NVH increase to expect since my 964 OEM mounts were blown and sagging, so I though I would start out with the least stiff yellow "street" bushings. After an uneventful straightforward install I went for a test drive. I immediately noticed a significant increase in NVH at idle. My car is already fairly loud so the noise increase was difficult to quantify, but in terms of vibration I could definitely feel more vibrations in the seat, shifter, and even a little bit in the steering wheel. The car did feel more together and also seemed to plant quicker after going over speed bumps, etc. But overall even the "street" caused too much NVH for my liking, given my car is used for 95% street and 5% track driving.

So I decided to give the 993 mounts a try as most users said they are a great alternative for street applications. As I understand it these mounts are a 993 part number but are also used in 996 cars as well. Also, I'm fairly certain they are a non-hydraulic mount but don't know for sure, so if someone can educate me here I would appreciate it. One thing I noticed while inspecting them prior to the install was you could press on the threaded post and cause some deflection fairly easily, meaning they were not nearly as stiff as the Rennline mounts. After installing the mounts the test drive confirmed that they are much softer and my car returned to being very smooth at idle, a definite reduction of NVH compared to the Rennline mounts.

Overall, I am much happier with the 993 mounts for my application. I'm sure not having a semi-solid mount might cost me a couple tenths at the track, but for me that's an acceptable trade-off for a nicer ride on the street. Also, I wouldn't hesitate to purchase another Rennline part given the quality and customer service I've received. So if you do have a higher tolerance for NVH or your 964 sees a lot of track time then the Rennline mounts would be a great solution in my opinion.

Iím just wondering why the Porsche specified mounts at Ďnot recommendedí? I would have thought the fluid filled 965 part would have been the best option here. The 993 part is 993 C4 and far stiffer than the 965.
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Old 05-17-2019, 01:44 AM
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People use the 993 mount because itís a simple rubber design and far cheaper that the expensive and complicated 964 part. Similar to RS/Wevo/Rennline, but softer. Donít know about 965 parts but would assume itís the same, issue as 964 parts (otherwise it would have been mentioned on this forum many times). Plus there were two different engines in that car and the engine carrier is probably different. Whole Ďnother animal. Hey Cobalt?!

Timely thread refresh as Iím going to be ordering new MMs and thought about Rennlines, but will mostly likely get Wevos again.
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Old 05-17-2019, 05:48 AM
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Originally Posted by 911Jetta View Post
People use the 993 mount because itís a simple rubber design and far cheaper that the expensive and complicated 964 part. Similar to RS/Wevo/Rennline, but softer. Donít know about 965 parts but would assume itís the same, issue as 964 parts (otherwise it would have been mentioned on this forum many times). Plus there were two different engines in that car and the engine carrier is probably different. Whole Ďnother animal. Hey Cobalt?!

Timely thread refresh as Iím going to be ordering new MMs and thought about Rennlines, but will mostly likely get Wevos again.
Yes I realise the 993 part is cheaper. Point is if you want to minimise idle noise and vibration you should spend the extra and buy the part Porsche specified for the 993 C2 which is the 965 part. If you have a 993 C2 and you fit the 993 part which is for 993 C4 and Turbo youíll save money but get more idle noise and vibration. 993 C2 = 965 mounts = min noise.
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