- On a big cruiser skateboard like this, the bushings and the trucks
are usually pretty soft so that when you lean on it, it effortlessly turns
for comfy chill cruising and carving, but on a
normal skateboard like this, the bushings are often a bit harder, which means you can't
really carve as much, but it is much more stable for landing big sick, nasty tricks. So what do you want in your car? Soft and comfortable or hard
and performance oriented? (low to high pitched sound) So today we're gonna install a set of polyurethane diff
bushings in the Miata. And along the way, we'll talk about what kinda compromises you make when you go from a rubber bushing to a polyurethane bushing. We'll get a look at how to install them and we'll even, hopefully get a good look at how much of a difference
these things actually make so we can figure out whether or not they're worth it. I'm Zach, and this is Money Pit. Time to get stiff. (thunder and upbeat music) So today we're gonna
be installing a set... (engine revving) Oh my god, that has got to be Humphrey. (upbeat dance music) - Big thanks to Hyundai
in the 2021 Veloster N for sponsoring this week's
episode of Money Pit. (upbeat dance music continues) - We really liked the Veloster N. It looks great, it's super fun to drive and it makes all the right noises. One of the cool features is N-Grin Shift, which is the Veloster's overtake mode. Here's how it works. Now for an overtake in a manual car, you can just pull out to the passing lane and just put your foot down, and that will get the job done eventually. But high gears are better for cruising than they are for accelerating. Now, what you wanna do is change down to a lower gear. The lower the gear you're in, the more torque you can deliver and the faster you can accelerate. You could shift all the way down to fourth or even third if the conditions are right, but nobody and I mean nobody can downshift faster than this. (sneeze sound) Now not only is the DCT gonna shift faster but the N-Grin Shift that drop a gear and disappear move, well
it's done automatically. Turn it on and the transmission
gets ready to shift down. Turbo opens up to let more exhaust gas in and the ECU green lights max power then just by flooring it, the trans shifts all the way from eighth down to third, instantly
the turbo releases and the revs match,
instantly from max torque your butt goes through the seat. (explosion rocket sound) Now, the N-Grin Shift can only be used for a maximum of 20
seconds, at which point it has a cool-down timer of three minutes, but here's the thing. Any other car wouldn't even
give you that 20 seconds. The transmission and turbo are generating so much heat on over boost, that the ECU wouldn't even be able to make that available normally, but Hyundai, they said
what like 20 seconds, we'll give them 20 seconds. And so they did, it's awesome. This thing is kinda like a race car. It's kinda like DRS and F1. Thanks Joe. - Anytime man. (upbeat dance music) (crickets chirping) (upbeat retro music) - Hey everybody, don't worry, it's just me again, working on some stuff. All right, before we go yanking
these diff bushings out, I figured we should talk about what a bushing even is, real quick. A bushing's basically just an interface between a part that stays stationary and a part that needs to move. So a bushing allows for that movement. Like in the case of our
automotive suspension, our control arms have
bushings at both ends because the control arms
need to move up and down. And most OEM bushings
are made out of rubber, which is pretty good at its job. It's really soft, so it
absorbs a lot of road noise and vibrations and bumps in the road and things you run over with your car. And that is super comfortable, it's quiet, it's comfy cruising down the road, but it's not very good
for doing big sick tricks down the side of a canyon. So we're gonna be looking
for some more performance out of our new polyurethane diff mounts. But before we go installing them, I wanted to drive around one last time with the stock mounts and really catalog in my brain, how they feel. When I really get on this
thing and load it up, hit the gas pedal, shift
hard, anything aggressive, it feels like there's a big, full diaper in the rear end of this thing. So hopefully with our new poly mounts, that'll lock things down and really tighten up the way the rear of this car feels. We'll drive it again after we're done to see if it's a, an
obnoxious amount of noise, vibration or harshness,
but hopefully it won't be. Now, the only thing we have left to do is go remove the stock stuff so we can put in our new mounts. (upbeat retro music) All right, so the diff is
about ready to come out. All I gotta do is pull two bolts out and then she'll come down. So I've got my jack under it, got it nice and supported. This is kind of the most
dangerous part of this thing. These things can weigh a lot and you don't want it to fall on you. So go about it as safely as you need to. In the case of the Miata,
I think this will be fine. I'll keep a hand on it, we should be good. But if you have any
concerns, get a friend, ratchet strap it to your jack, get a transmission jack, do it as safely as you need to. Feel it out, you know? I feel like this is gonna be fine. Watch me drop it on my legs now. (drilling loose) And the power plant frame is gonna be a little bit in the way. Ow! Dang, that thing just stuck me. Where did it go? (laughing) (upbeat retro music continues) Hey, we picked a pumpkin. Okay, so now we got the diff out. Now we just gotta figure out how to get these bushings out. And there's more than
one way to skin that cat. (cat meows) (slow tempo Blues music intro) Okay, so now that we have the diff out and before I destroy these bushings, let's take a look at them. These are the stock bushings
and to my knowledge, they're the original ones to the car. So they are from 1994. They're made out of rubber and they're honestly in pretty good shape. They're not falling apart. I don't really see any cracking, but even if they were brand new, they're really soft. You can see, look how much
movement that allows for. So these are the only two points that the diff actually
mounts to the chassis and they both moved pretty easy. You can see there are
big voids in the rubber that allow for that movement. Polyurethane bushings are pretty hard, so things only move a little and you can go one step even crazier. And you can go with solid metal mounts, which allow for no movement whatsoever. But it's the biggest
compromise in terms of noise, vibration and harshness, 'cause those just transmit everything through to the cabin. So poly kind of strikes that nice balance where things are locked down and power is transmitted
straight to the ground, but it still absorbs some vibration. So it's not terrible to live with. So without further ado, let's hog these things outta this thing and replace them with poly. (power tools and upbeat music) All right, so now I've got
this one slit cut here. Basically that'll let the
bushing kinda collapse a bit, so it becomes smaller. And then I should be able
to just hammer it out through the bottom. There's half, and the other half. Not too bad, I did clip the bore right at the bottom, but not too bad. It'll be okay. Think we'll do a little
better on the next one. There she goes. About the same as the other one. I (beep) it a little bit, but not too bad. That'll be just fine. All right, the hard part's over with. The old bushings are out, but luckily poly bushings
are usually easier to install because a lot of times they're
split in half like this. So all we need to do, is
put this one in from the top and then this one we'll
go on from the bottom and it should be quite simple. So before we install these,
we're gonna grease them up. These came with specific
polyurethane grease, that's what I'm gonna use, and that should help these install a little bit
easier, drop into the bore, and will definitely keep
them from squeaking. - [Eddie] I didn't like that very much. - You didn't? - [Eddie] No. - Oh, it was really satisfying to me. You didn't like watching it squish out? (upbeat music) Now we also don't really need to worry about getting these
completely bottomed out in the diff mount right now, by hand, because as we put the thing back in, the bolt will actually
cinch these things together. So even if this isn't completely
bottomed out, that's okay. It'll bottom itself out when I torque down the actual diff bolts. You know? So now these are put into
the, the old diff housing. So that's great, but we're
not out of the woods yet. This is ready to go back in the car, but this is the stock
piece with all these, you know, triangular ridges. And this is the poly piece that is supposed to meet up with it. You can see this kind of metal lump where the bolt goes through, is gonna sit right in there, but you can also see
that I need to get rid of all these rubber triangle pieces, like this, so that our new poly bushings can sit like this, okay? And as you can see, that looks perfect. It looks brand new, it looks great. All we gotta do here, use a little heat and we're gonna torch this a bit, okay and the idea is that
that's just gonna kinda break the bond between the
rubber and the metal here. We gotta burn a little bit of rubber, but hopefully not too much. All right, now that we got all our rubber triangles cut off, these things are ready, which means everything's
ready to go back in. So we're gonna start by putting the diff back up in this thing and then all we gotta do is put everything back together. - [Eddie] Just like that. - No big deal. Queue the montage. (upbeat drumming music) Okay, so now we're on our studs. So basically the diffs ready to go straight up to the chassis, but we need to bolt the power plant frame back to the diff. It's a Miata specific thing, but I'm gonna get that done first. Then we can send the diff
the rest of the way up. And then she's in, with
the new fancy bushings. All right, now we're ready to put our lower piece of poly in with our modified washer and then nut right in the back. (upbeat drumming music continues) Okay, that's it. She's in. This car's ready to go back on the ground. But the problem is, to
put a GoPro under the car you wouldn't be able to see anything 'cause it's night time. So that means we're gonna
have to wait til the morning. See ya then. Okay, it's a new day. The sun is out again, and it's time to drive this thing around and see how our new mounts do. I just strapped up the GoPro, so let's take it for a drive. I think they're gonna feel good. Oh wait, they do. Ah, that already feels
so much better on shifts. Man, it feels so much
tighter in the rear end. You know what I mean. It used to feel like the diff was barely connected to the car. Like if I shifted too
hard or launched too hard, I might leave it behind. But now it feels like that thing is bolted to the car and it feels really good. And also, what's more, it doesn't sound too bad either. So it's gonna be case dependent. You know, some cars will gain a lot of noise from diff mounts, but I can't tell a difference
in the Miata at all, which is awesome. It means I really just get the benefits of having those nice diff
mounts, without really having to deal with any of the compromises. I don't feel any harsher vibrations. There's really no noticeable extra noise. I mean sure, maybe there
is some, but I can't tell. My ears aren't that calibrated. So in the case of the Miata, I think this is a huge win-win situation. It feels way tighter,
the diff feels great. And that makes the car better
at launching, shifting, and just being driven hard overall. And honestly it feels, just like it did. And I think that's a pretty
good modification if you ask me. It really wasn't very
difficult to install. It didn't take that much time. And the parts didn't cost very much. You can get these puppies for
less than a hundred bucks. So I'm calling this a big
fat win for the Miata. It feels great. So thank you guys so much for watching. I hope you had a good time. We had a great time making it. Don't forget to follow
me on Instagram @zachjobe follow Donut @donutmedia, ooh sweet truck. And I'll see you guys next week. Goodbye. Gotta bring you some big news. We made a Money Pit T-shirt. It's so new I don't even have it yet. You gotta look at the pictures. Look at these pictures. It's sweet, it's got everything. It's even got a parrot and we made it in tie-dye. There's so cool, I love it. And they're gonna ship
before the holidays. So get your order in
now at donutmedia.com. Thank you so much. I love you.
