Discussion: Upgraded Bushings & Mounts
 

First off, I realize there are multiple topics discussing the various upgraded/stiffer bushing and mount options for our cars. What I want to do is to create a discussion about the benefits and downfalls of replacing the stock components.

My only big complaint with this car is the elastic and unsettled feeling under acceleration and when hitting bumps while cornering. As much as I want to resolve that by upgrading these parts, I want to know the side effects of doing it. For example, if I start with a differential bushing but don't change out the other parts, are the other rubber parts tied in going to be forced to take up the lost movement of the one stiffer component and as a result wear out quickly? On the other hand, if all driveline mounts are replaced, I'm assuming there will be a significant increase in vibration.

Basically my thoughts on this are that with multiple mounting points you can't just replace one and see the desired result. I've watched the videos showing subframe movement and heard the reviews of bushing inserts or replacements, but I can't see how you can truly improve on the problem by only replacing one point in the system.

Who has experience with this? Is there a good option that won't significantly increase vibration but does remove the elastic feeling? I'm fine with saving up a bit longer to get all of the necessary parts at one time if that's the correct approach. It seemed worthy of a discussion, so that anyone else that wants to make these changes has a resource to read through that offers opinions as well as facts on the matter. Thanks in advance.

rear subframe bushing inserts will give a much better feel that stock, and not increase NVH much if at all. I say inserts, because full replacements with harder material will definitely increase NVH. This to me is such an easy and effective way to improve the feel of the car. One of the first, if not the first, mod I would recommend people do.

I have also done the transmission mount insert (whiteline's "positive shift kit"), and it does increase transmission noise a bit, but shifter feel is improved.

Lastly, I have done whiteline's differential outrigger kit. It's not metal replacements, it's still plastic, but this is definitely where most of my additional NVH comes from. That said, I live with the differential whine because it provides such an immediately response to acceleration now, especially with all three of these mods installed. Not everyone can deal with the additional noise, especially at certain speeds on the highway. But if you can live with the whine... it's definitely worth it.

Thanks for your input. I take it that you added each of these separately?

My only drivetrain mod is the whiteline rear subframe insert kit, and it really improved the feel from the rear end under accel / decel. I've heard the TIC aluminum bushing provide a nice improvement in steering feel.

I might do the diff insert kit next. In this video I took at autocross (street tires) you can see how much diff moves in the mounts.

[ame="https://www.youtube.com/watch?v=ttAEZZkUplU"]VMI 2013 Points Event #4 - Atkinson - Run 3 - Rear Suspension - YouTube[/ame]

You may be right about other bushings "down the line" wearing quicker with hard bushings installed in select areas, however bushings usually have a pretty long service life so it's not worth worrying about IMO.

Ive only replaced two points so far so I can shed a little light on those:

Shifter bushing - No NVH increase what-so-ever. Shifts are much cleaner and there is much less play in the limits of shifter movement than before. Shifting feels more precise. There is no reduction in gear "crunchiness" as others have claimed

forcedfab transmission stiffener - Definate increase in NVH. If I had the stock exhaust, it would drive me nuts. The transmission definately stays more planted than before and it does not move; but this comes at a price. The positive side to this is that I cannot hear the crickets with the car in neutral at a stop. Just gear whine...

I have the whiteline rear subframe, diff, and trans mount bushings in the car, along with rear LCA and whiteline swaybar, swaybar bushing and endlinks. With just the subframe bushings and trans mount there was no added noise. But after installing the diff inserts today, the car makes a lot more noise. Clunks when shifting occasionally, which I thought was a bit strange, so I'll have to check that out tomorrow. It almost sounds like its coming from the trans mount area by where the driveshaft joint (connecting the two part driveshaft) is. Not sure if anyone else has had this issue.

I did only the rear subframe inserts. It helps the responsiveness of the rear end by a considerable amount, with no additional NVH that I noticed. I've heard doing these in combination with the diff inserts can add some NVH.

The subframe inserts are cheap enough and the install is easy enough that it's something that you can do and undo if you don't like the result. From the undercar videos I've seen of the rear suspension the majority of the movement comes from the rear subframe and the swaybar bushings - I will be doing swaybar bushings soon (if I don't completely replace the bar).

I did the subframe inserts, cusco sway bar, and diff brace. I kept the diff bushings stock. It did add a minimal NVH, but nothing too bad. All these mods resulted in a more responsive rear end.

Good info! Thanks again. :)