- 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.