Long-term adverse effects of Whiteline chassis inserts?
 

My question pertains to the Whiteline polyurethane transmission mount insert, differential mount inserts, and subframe mount inserts.

I believe these products would increase the life of the stock bushings in their respective locations since they would ensure that the stock units are deflecting less, thus greatly reducing the chance of them tearing. On older cars, torn bushings in these locations can be common and are always a major pain when it comes to replacing them, especially the diff and subframe bushings. With these inserts theoretically increasing the longevity of the stock, rubber bushings, they seem to be a no-brainer for any twin.

What I'm wondering is whether they could introduce problems elsewhere.

Since the stock bushings are no longer absorbing the energy through deflection, the energy has to be transmitted elsewhere, right? Areas off the top of my head that could see increased abuse due to these inserts include the internals of the diff itself, the axles, suspension bushings and ball joints, etc.

Aside from potentially increasing wear on other components, are there any other possible negative effects from running these inserts from a suspension and handling perspective? Like, for a street car, is this too much chassis stiffening, or is it only helping the stock suspension work even better? Since the stock suspension bushings are still there, wouldn't they just absorb more energy and result in greater alignment changes during a corner and thus negatively impacting the handling of the car? I don't know, just thinking out loud here.

Any experience and/or insight regarding this matter is greatly appreciated. They seem to be great mods, but I want to be able to discuss possible negative effects and just gain a better understanding of them overall.

The only 2 problems I seen in my MR2 days with poly bushings is it caused a few motor mounts to wiggle loose. Since the transfer of vibrations was not absorbed by the traditional bushings. Other than that, a bit of locktight should fix it.

The other was daily confort. Many people and even me went back to oem bushings just for the better ride quality. It was fun when your a boy ricer but once you grow out of it. It's not.

Just found this highly relevant post by @NRXRaptor:
http://www.ft86club.com/forums/showp...85&postcount=4

Like he says, the diff seems to move the most; those rear carrier bushings move around like crazy. I've ran the Whiteline inserts before. The NVH didn't bother me that much, but I didn't like the clunk I got between shifts unless I was being careful. I've read that if you use just the rear bushing inserts on the diff and not the ones on the front (toward the front of the car), it greatly reduces all these negative effects. Thinking about just doing that.

As for the subframe, it definitely moves around under heavy load. This can't be good... But that car handles well from the factory and the rear end is predictable. I think these are what I'm questioning the most...

I know what you mean. I filled my 240SX's motor mounts with window weld back in the day. Iy was cool at the time, but I've definitely grown out of that. To me, it's about balancing comfort with performance now.

What I like about Whiteline's products is that it still retains the factory rubber bushings, just with polyurethane reinforcement, instead of a full poly replacement.

Honestly, not many people outside of chassis engineers would know.

When you make something solid or resonate at a different natural frequency than stock, you start opening up a can of worms... there's a reason why OEMs test so much and their stuff is so.... "conservative", because they use the easiest part to cover the widest range of use.

-alex

But some of NVH increases subjectively are minor enough to make it worth doing some of stiffening mods anyway with pros outweighting cons. So imho "it depends" on case per case basis.
Though there is also bit, that some may play reasonably well if used alone, but making overall NVH increase untolerable if used with set of other parts.

I just installed Whiteline Diff and Sub Frame inserts. Car feels much better, more solid, but way noisier. Can really hear the rear end gears whine now. I could never live with this if this was my only daily driver but as a 2nd car I'll live with the noise.

The front outrigger bushings of the differential made the most noise for myself. So much that I took them out and left the two rear bushings in instead. Even with the trans bushing, rear subframe and rear diff bushings in the NVH is very livable.

I think this is what I'll ene up doing. Did you feel a noticeable improvement in handling amd overall grip?

Would be good to hear from others who have ran these parts long-term to see if they resulted in other parts wearing faster.

The rear end is noticeably more planted in spirited driving for sure. You wouldn't think there is a slight lag in the OEM bushing settling but you will notice how more instant the weight transfer is.

As for the diff bushings, well its nice to know it isn't bouncing around anymore but you still get wheel hop at times since the OEM engine mounts are still there. However shifting is a slight bit better.

I can concur that removing the outrigger bushings, for me just the lower ones while keeping the upper ones, removed a lot of the NVH I got after installing them.

Wait so you're saying to remove the upper inserts on the front diff mounts and leave the plastic kinda ridged ones on the bottom?

This is interesting. Seems like the front bushing upper inserts could be the real source of the NVH.

I did the opposite of what you just said. I kept the upper and removed the lower. I'd start there and see what that does for you.

Another thing I just thought about though is that for me, having a trans mount insert caused more NVH than I liked, and moving to an STI mount seemed to lessen it.

i have a all the bushing you mentioned on my 2017 86. i have them for 8000km now,i drive the car hard and daily drive it. the noise is not too bad imo its just at high speed that its more noisy, but for how much better the car feels i dont care bout NVH. i dont see any problem with running those bushing.