do Trans braces transmit engine noise?

Plastermaster · Post by **Plastermaster** » Sat Apr 01, 2006 2:06 pm

When I swapped engines, (I'm sure for a louder one) I also added the prescot bar, your basic 3 point trans brace that goes from the frame horns to the tops of the shock towers. At around 4k cruising of under load the inside of the car really roars. I just wonder how much of the sound is comming from the trans brace. I realise the engine/tranny is isolated by rubber mounts, but they are attatched with bolts to the rear saddle and there the saddle connects to the frame horns and the trans brace. has anyone installed such a mount and noticed increased engine noise?

Thanks
Ron

500LbGorilla · Post by **500LbGorilla** » Sat Apr 01, 2006 2:30 pm

You bet it does. Every point that connects the engine to the frame is going to transmit noise.

Bruce2 · Post by **Bruce2** » Sat Apr 01, 2006 4:03 pm

But Mark, the brace does not connect the engine to the frame. Only the frame to the frame. The engine and trans will still be isolated by the rubber mounts.

Plastermaster · Post by **Plastermaster** » Sat Apr 01, 2006 4:13 pm

I guess I could take it off to see just how much. Just thought I would ask first.

The transbrace is to prevent flex in the frame horns. Usually people think of it to control wheel hop, but flex in the frame horns is what causes the wheel hop right? So the question is, with a strong engine, IF you are not spinning your wheels but just laying on the gas when you are already rolling, is frame horn flex an issue? Sure if you have Jakes 3.0 yu can spin wheels in any gear without the clutch, but that is an extreme engine torque wise. Torque will load the frame horns and wheel spin releives that load creating the up and down = hop. With 170 lbs of torque in my 2270 is frame horn flex really an issue given that I don't do launches from more than 1500 RPM. Beleive me the noise IS an issue!

No, I am not asking anybody to take responsibility for my frame horns bending.

Just asking for honest opinions.

Ron

500LbGorilla · Post by **500LbGorilla** » Sat Apr 01, 2006 5:13 pm

Bruce2 wrote:But Mark, the brace does not connect the engine to the frame. Only the frame to the frame. The engine and trans will still be isolated by the rubber mounts.

Yeah, I meant that it's another attachment point. Some of the noise transmittal is dampened by the fact that the frame horns are long, and they don't allow the engine to connect in a rigid manner to the real meat of the frame. The frame horns allow a little more vibration to remain motion, rather than having it be absorbed by the frame. I have one (real KCB) and the noise level did increase as a result of installing it.

sideshow · Post by **sideshow** » Sat Apr 01, 2006 5:31 pm

I put mine in between a tranny swap, yes it got louder. Not solid mount loud, daily driver-able.

EASY RIDER · Post by **EASY RIDER** » Sat Apr 01, 2006 8:52 pm

GB 643 on tranny and a CSP triangle set up and mine is loud also. I feel it more than hear it. I still don't have carpet so some of the noise is from that but I do feel the difference.

Plastermaster · Post by **Plastermaster** » Sun Apr 02, 2006 1:00 pm

One thing I noticed is that if I tilt up what would be the back rest of the back seat if I had one, it is noticably quieter. So today I added some dense foam to the top of the parcel shelf under the carpet, and also to the underside of the parcel shelf. I also removed the interior rear 1/4 panels and did the same to the backs of them, as well as everywhere else I possibly could in the cavity inside the wheel well/fender area. It did help a bit. People lok to dampening the ring of the sheet metal which does help, but I have fouind that bulky dense insulating materials do even better.

Easy, I know what you mean about feeling the vibration. At cirtain rpm/load situations the car feels like I'm riding a jack hammer. That can only be vibration making it through what ever measures are there to prevent it. I believe with larger displacement, higher compression, fast ramp cams the engine is going to beat the car harder. Its the difference between drumming on the car with a rbber mallet as opposed to a balloon.

I havn't taken the car for a 70mph ride yet as its raining and the car came back from the body shop with a leak

Ron

EASY RIDER · Post by **EASY RIDER** » Sun Apr 02, 2006 7:12 pm

Plastermaster wrote: I believe with larger displacement, higher compression, fast ramp cams the engine is going to beat the car harder. Its the difference between drumming on the car with a rbber mallet as opposed to a balloon.

I don't know about that. If your engine is well balanced I don't think the displacement or fast ramp cam will make a difference. I have felt the difference in many balance jobs at Jake's. When an assembly is balanced it is VERY smooth. Now before it gets there it can feel very "bumpy" on the balancer. If an assembly was not balanced I'm sure that bumpy feel would transfer into the car and only become worse with higher rpms.

Plastermaster · Post by **Plastermaster** » Sun Apr 02, 2006 9:04 pm

I have Jakes race balance, so that shouldn't be an issue. My idea is just a speculation, but comparing it to my other engine, each stroke seems much more explosive. It is a purely subjective evaluation. It is probably just sound waves.

Ron

marekv8 · Post by **marekv8** » Mon Apr 03, 2006 10:39 am

I've got a CSP Käfer Cup Brace, Berg 643 Transmission Mount, Berg 642A Nose Cone Mount, and Berg 642P Pad Mounts in a '64 sunroof Beetle with a RAT 2270. I actually have less vibration than I did with the stock drivetrain, but the noise certainly picks up over 4,200 rpm (although it's nothing like a jackhammer feeling). I have also replaced the stock tar boards with Line-X and have aluminum door and rear quarter interior panels, so I knew I was asking for some additional volume. The car also has a RLR six point cage which seemed to eliminate a lot of jiggling and vibration when first installed. The cup brace and drivetrain were installed at the same time, so I don't know how they effect the car/noise level independently. My next move will be to cover the interior area of the rear firewall and the interior portions of the aluminum panels with Dynamat-- and turn the stereo up.