Questions on S14 Subframe Build

[dongoesby]

Long questions short. I had a high speed slide(~65mph). The car managed to stop with only the driver-side rear wheel went up to a muddy hilly-slope (approx 2-3 feet above road pavement) while the rest of the three wheels were on pavement. There was no visual damage on the body besides trashing the driver-side side skirt. The spring of that rear driver-side corner was fully compressed and the alignment was messed up. The rear driver-side camber and toe were out of spec and the "toe" could not be adjusted back into the previous adjustment.

Situation: My S14 has Stance coilover, SPL RUCAs and Tanabe sustec sway bars. After careful visual inspection, I found the driver-side axle has a minor leak near the diff housing and scratches at the bottom of the driver side frame rail. The rear subframe and all the arms appear to be straight without any bents or snap. However, the mechanic at a local random shop (not alignment specialist) said the rear driver-side "toe" is still a degree or two off and claimed that some arms may be bented or the subframe may be potentially twisted (I highly doubt it since the arms could snap before this happens).

Suggestion: Instead of taking further inspection on my rear subframe, I have a spare subframe on another s14 (un-mod'd, accident-free) sitting in my garage and new SPL solid aluminum bushings for subframe and diff. I'm planning to do what others had done, box/weld the spare rear subframe, and swap it into my s14. However, I have following concerns:

1. How can I be sure the spare subframe is straight?

2. Could a local exhaust weld shop able to box/weld the subframe for me?

3. I like to leave some rooms for whether in the future my car would go for grip or drift. Is boxing a subframe an overall good idea/improvement for my route? or would it be causing a downside for daily driving/caynon runs?

4. Is that downside for daily driving/caynon runs as well for solid aluminum bushings? How unbearable is the noise after installing them?

Overall, I'm still skeptical about how-to box a subframe and what practical benefit gain on daily driving/caynon run with solid bushings. I want to repair my alignment and get a taste of track soon. Feel free to chime in, any suggestions are welcome!

Thanks.

[Jakob]

the benefit of solid bushings is that your subframe will be solid with your chassis!
if you take a look at how your subframe is mounted to your car you should see that the rubber allows the subframe to float, my rubber bushings are super dead and it feels like my subframe is loose and is going to break from the car! if you are familiar with bmws you know that this is a common problem, yes they loose their rear suspension at some point when it gets too bad.
anyways, by adding solid subframe bushings you are eliminating that floating and FIX your subframe to your car and it allows no movement, which is a good thing.

do you have a stereo system in your car? yes?:fruit: then dont worry about the noise
if you track your car or make canyon runs then the benefit of the solid bushings should outweight that little more noise you can hear from your diff and if it bothers you that much, there is still dynamat.

i cant help you out much about the subframe boxing because im about to pick up a spare subframe too and build it and i have to ask some suspension gurus about the subframe boxing and where the critical spots are.

and if you worry about the straightness of your subframe, you can check the fsm it has a lot of measuring points for the underbody of the chassis and you could transfer some of the to the subframe, like the mounting points etc etc and find out if its straight or not.

hope that helped :dead:

edit: what you could do is sell the spl bushings and get the PBM subframe spacers, i think they would fix your axle problem

[dongoesby]

do you have a stereo system in your car? yes?:fruit: then dont worry about the noise
if you track your car or make canyon runs then the benefit of the solid bushings should outweight that little more noise you can hear from your diff and if it bothers you that much, there is still dynamat.

Yes, the dd stuff like stereo system still intact on my car. However, I'm afraid that the noise would be alot louder than I expected:

"when I let off I can hear the diff whine. It's so loud I cant hear my exhaust, stereo or passengers. It gets louder and higher pitched with speed, and it gets a little quiter if I push in the clutch." 87Kevin from FA

I'm now astonished. And yes, I do have a 1.5 way Nismo diff. Together with boxing the subframe and spherical joints from SPL control arms, I'm seriously thinking for an alternative option other than solid bushing.

Also, I heard the solid bushing causes whine/high pitch sound on highway ~60mph. :(

[dongoesby]

anyone got more inputs?

[NiSilS14]

It's really not that bad, I have solid subframe and diff bushings. Then again it all depends on your tolerance on NVH.

[DisEpyon]

No idea for your questions 1-3, but for 4.

I am running the solid subframe aluminum bushings, but not the diff solid bushings. The rattle noise at first kind of got to me, but after awhile i get used to it. Its really not that bad at all, and as far as it being loud over your radio, you dont notice it at all, unless you want to notice it. It just becomes normal. I only have the 2 front door speakers and thats it, and i dont have a problem with it.

just one of those things you need to experience for your self to see if you care or not, everyone is different.

[kingkilburn]

"when I let off I can hear the diff whine. It's so loud I cant hear my exhaust, stereo or passengers. It gets louder and higher pitched with speed, and it gets a little quiter if I push in the clutch." 87Kevin from FA

That sounds like a bad diff.

[singlecamslam]

I dont know about you guys, but after i installed my SPL solid bushings my car sounds like a chainsaw inside. Before them i could heard the diff just a little because my car is totally stripped. Its loud to a point where you cant hear the person next to you on the freeway. And its not my diff because i put two different diffs in and no difference. I actually dont mind the noise, and the car feels awesome with the bushings. I used to daily drive it.

[Bigsyke]

Are you guys kidding me? I just threw in my solid subframe bushings in 2 days ago and with everything torqued down its about 50x quieter than without. The buzz is with the solid diff bushings. I had the aluminum collars before, it was horrid.

Solid subframe bushings is the best change I have done to my car yet. Bar none.

[atutt]

everything on my car is solid except for anything on the LCA's. Just keep a full interior and you won't notice much.

[Jonnie Fraz]

Don,

You still have full interior in your car, right? Mostly you get a lot of cabin noise if you have removed all your sound deadening. Since you have the interior it will absorb most of the noise. I have never heard the thing about the dif whine @ 60mph. I have heard that about the one piece driveline. As far as welding get a hold of me and I will do it for you.

[singlecamslam]

I made a thread about it a while back. Cant find it now, but people say after solid subframe bushings people get a lot of diff noise, of course thats because all the sound deadening is removed and no interior. I think its normal.

[aznpoopy]

i've had solid diff bushings. a little extra noise from the diff is normal. it is not unbearable. it won't drown out your music. you will notice it though, and it is a little overkill for the street. but if you have it already, fuck it and install, IMO.

noise so loud you can't hear anything else is not normal, even with solid crap. as mentioned above, that sounds like a bad diff. i've had that problem as well; shit sounded like a f1 car in the cabin. louder the faster you went. i had to wear earplugs for the last few hours of its life.

[dongoesby]

Don,

You still have full interior in your car, right? Mostly you get a lot of cabin noise if you have removed all your sound deadening. Since you have the interior it will absorb most of the noise. I have never heard the thing about the dif whine @ 60mph. I have heard that about the one piece driveline. As far as welding get a hold of me and I will do it for you.

John, thanks! I will definitely would like to talk to you more about it after my swap is done, which is, hopefully, within these two weeks.

noise so loud you can't hear anything else is not normal, even with solid crap. as mentioned above, that sounds like a bad diff. i've had that problem as well; shit sounded like a f1 car in the cabin. louder the faster you went. i had to wear earplugs for the last few hours of its life.

So what really went wrong on your diff? How did it sounded, and did you manage to solve it?

Thanks guys for the well inputs, these are great. I think I'm going to stick with my plan.