4th Gen Poly-Urethane Body Mounts
- Thread starter BlackWorksInc
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fourwd1
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Yes, a softer material is more absorbive.
BlackWorksInc
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Anyone happen to know or have an idea of what the factory durameter is for the Body Mounts?
Most factory rubber bushings are in the 50-60 A range give or take. Pretty soft. The problem with urethane that soft is it has a tendency to creep (or cold flow) under sustained load. I've seen this happen pretty severely to subframe and control arm bushings that are soft. They can flow so much the joint can develop play.
The other question is if the stock mounts are liquid filled. This is pretty common on larger factory bushings, as it gives them compliance and a lot of damping, which just rubber has little of. Think of it as a shock to the "spring" of the rubber, to help control its motion.
Do these things ever leak? Or are they solid rubber.
Rough idea on when they "wear out?" I'm just over 100k in my 4Runner. Mine look fine, but you never know on some compressed bushings.
The other question is if the stock mounts are liquid filled. This is pretty common on larger factory bushings, as it gives them compliance and a lot of damping, which just rubber has little of. Think of it as a shock to the "spring" of the rubber, to help control its motion.
Do these things ever leak? Or are they solid rubber.
Rough idea on when they "wear out?" I'm just over 100k in my 4Runner. Mine look fine, but you never know on some compressed bushings.
BlackWorksInc
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They are solid rubber pieces. I was thinking about just getting some 60A PolyUrethane and making replacement bushings for the 4Runner. I am curious if a lot of the people complaining about harsher vibration when they switched is due to the fact that the bushings are not as degraded and sloppy as their factory ones (mainly coming from the 3rd gen guys who have mentioned it.) I remember last night I saw a few mentions that the 3rd gen kits are 60~65A, though I don't know how strict the scale is (i.e. how much harder 60A is to 65A.)
The only other thing that makes me slightly curious is that the factory bushings have a scalloped design vs. solid bushings in the aftermarket kits. The only thing I could think of is that they allow a bit more flex than a solid rubber piece. That shouldn't be too hard to accomplish anyways, granted machining 60A is not easy; but it is doable and tolerances will probably not be a big deal for those relief portions, freezing should be enough to create them on a lathe.
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BlackWorksInc
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Any ideas on whether or not the reliefs shown in the picture above would be worth replicating?
Do you have a picture of what everything looks like uncompressed? I'm curious how difficult these would be to make.
BlackWorksInc
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Nope...
But they do look the same as the parts diagram.
I'm starting to wonder if I should try and make my own.
Post Note-
#5 in that picture only applies if you have a 3rd Row seat (wonder why its different?)
Nope...
But they do look the same as the parts diagram.
I'm starting to wonder if I should try and make my own.
Post Note-
#5 in that picture only applies if you have a 3rd Row seat (wonder why its different?)
Those don't look too hard to make, the biggest challenge will be the 60a polyurethane because it's a pain to machine. When you freeze the polyurethane, just know that it thaws extremely quick unless you have some way to cool the cutting tool/piece. In the past I've used water based coolant at 25 F to cool the part so I could machine it longer, although that was a giant pain to setup.
Looks like Mcmaster-Carr has a decent selection of Polyurethane Rod/Tube
McMaster-Carr
BlackWorksInc
New member
The real question is whether or not you really even need to machine the reliefs in. Most of all the Poly-Urethane Body Mount kits are lightly shaped (i.e. the small shoulders for where it fits through a hole) and lack the reliefs that the factory ones do. If that's the case, I would imagine you could probably cut them with a saw and then machine the shoulders pretty easy on a lathe without freezing and drill the center hole.
I could be completely wrong here but it looks like this part is available on Rockauto.
It's listed as a Dorman 924266 Subframe Bushing and the picture looks identical. Is it not the part that you are looking for and only Toyota sells for a stupid-high peremium?
More Information for DORMAN 924266
It's listed as a Dorman 924266 Subframe Bushing and the picture looks identical. Is it not the part that you are looking for and only Toyota sells for a stupid-high peremium?
More Information for DORMAN 924266
BlackWorksInc
New member
Those are only for the two mounts by the radiator, I need all 8 pairs.
having fun
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I haven't search and going on a thought here, but, maybe going with a lower number like 40+/- to get a softer/flex action out of them, but, would be more durable than rubber?
Just saw this. With how I remember the bushing working, yes, if you want anywhere near stock stiffness/compliance, you'd need to have approximately the same void area/geometry.
A solid block of PU is going to be pretty stiff in compression. You also have to watch for not having steel sleeves going through the entire bushing to where it's essentially metal on metal.
BlackWorksInc
New member
I'm not entirely sure I follow that? The way the bushings are designed, the sleeve goes the entire length of the bushings and physically stops the washers from crushing the bushing too much when you tighten. One end is firmly attached to the body while the bolt/washer on the other end float with the bushing separating the sleeve from the frame.
Then it should be easy to make a PU replacement if one end is floating. In some bushings that have the sleeve captured, but portions of the bushing decouple it, it's harder to design a PU bushing that won't have most the load going into the hard steel sleeve.
This is a 240SX subframe bushing (stock design of course):
The whole bushing is captured in a steel holder on the bottom, and the raised rubber portions up top help keep the vertical stiffness from being that of the steel sleeve. It really needs a bonded sleeve design to do this, which PU bushings don't have.
I wasn't sure if the stock bushings had something fancy to keep vertical compliance.
This is a 240SX subframe bushing (stock design of course):
The whole bushing is captured in a steel holder on the bottom, and the raised rubber portions up top help keep the vertical stiffness from being that of the steel sleeve. It really needs a bonded sleeve design to do this, which PU bushings don't have.
I wasn't sure if the stock bushings had something fancy to keep vertical compliance.
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