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Greeko

Bushings: Which Rubber and Which Poly to maximize comfort and performance

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Greeko    1

Well, that was the impetus for the RT design so you're on the right track.  Your angles might be the determining factor in how you proceed.  If you need a higher nose, maybe a shimmed stock mount and a snubber on top.  If you need a lower nose, maybe the GM mount on top with or without a snubber on the bottom.  The basic RT design has a lot of flexibility in how it's used.

 

The mustache bar ends are pretty loosely held so urethane makes it less floppy in general.  I solved my diff noise transmission problem by using washers on the ends of the sleeves to create a small air gap.  Basically created a longer inner sleeve).  The way that they're designed with their inner sleeve. the urethane gets compressed when installed and transmits more noise.  My theory.

 

 

I ordered the RT Mount with a new lower diff isolation mount to start. We will see if i need to go for the GM mount if my alignment is off.

 

So you feel the rubber doesn't hold the diff firmly enough?   I am trying to envision the washers on the end of sleeves....

 

Thanks so much for the great feedback everyone!...

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Given what we found out in this thread, I would make sure you get the taller mount so you can shim down. Granted I don't know too many people that make the RT style mount other then RT himself or Technoversions, so I imagine you got a Technoversions kit.

 

The rubber piece on the the front diff mount is acting in the wrong direction which is the main fault. The diff pulls up as you go forward, eventually it will pull the mount apart, it should have a mount on top to fight the diff from moving up and another mount to support the diff when it is not under load. That is what the snubber does is it fights that motion of the diff pulling up and prevents the diff from pulling the bottom mount apart. This was done with a strap early on, but those deteriorate and fall apart very quickly on the underside of the car.

 

What newzed means if I read it correctly is that he added very small washers that are the same size as the inner sleeve of the poly bushing to space the actual poly bushing away from the subframe that way the contact area for the bushing is much less. I imagine it had to be a series or at least two different size washers to keep the top bushing from being pulled towards the top. That would isolate noise with the trade off being that the mustache bar bolt is now encountering an axial load through the bolt more directly. Honestly with the size of the bolt that would be a very minor concern.

 

I want to say there was a better example, but 

was one of the reasons I wanted to run all poly instead of rubber. Solid would be better to prevent movement, but would most likely propagate cracking somewhere down the line especially in our cars. Edited by seattlejester

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Greeko    1

Given what we found out in this thread, I would make sure you get the taller mount so you can shim down. Granted I don't know too many people that make the RT style mount other then RT himself or Technoversions, so I imagine you got a Technoversions kit.

 

The rubber piece on the the front diff mount is acting in the wrong direction which is the main fault. The diff pulls up as you go forward, eventually it will pull the mount apart, it should have a mount on top to fight the diff from moving up and another mount to support the diff when it is not under load. That is what the snubber does is it fights that motion of the diff pulling up and prevents the diff from pulling the bottom mount apart. This was done with a strap early on, but those deteriorate and fall apart very quickly on the underside of the car.

 

What newzed means if I read it correctly is that he added very small washers that are the same size as the inner sleeve of the poly bushing to space the actual poly bushing away from the subframe that way the contact area for the bushing is much less. I imagine it had to be a series or at least two different size washers to keep the top bushing from being pulled towards the top. That would isolate noise with the trade off being that the mustache bar bolt is now encountering an axial load through the bolt more directly. Honestly with the size of the bolt that would be a very minor concern.

 

I want to say there was a better example, but 

was one of the reasons I wanted to run all poly instead of rubber. Solid would be better to prevent movement, but would most likely propagate cracking somewhere down the line especially in our cars.

Very cool man,

I totally get it. I am going to play around a bit.

 

I ordered the technoversion RT mount.

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ZHoob2004    1

Since we're talking about the RT mount here anyway, what is the recommended mount configuration for a nearly stock l28? I'm experiencing some clunking and if I find it's the mount, would it be a mistake to simply add a RT snubber on top of it?

 

Essentially, keeping the stretched factory isolator and adding poly above.

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If the mount has failed then it would be best to replace the lower mount before adding on the RT mount if you plan on running a factory style rubber mount on the bottom.

 

The snubber setup will be fine as it basically replaces the limiter strap.

 

Keep in mind clunking can come from other sources, so inspecting your mustache bar, axles etc would be a good idea. One source of a clunk that is missed fairly often are the control arms in the rear. If the bolts become loose that retain the bushing on power on or braking the entire control arm can shift forward or rear ward.

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ZHoob2004    1

Yeah I'm going to investigate further tomorrow (need to pull the driveshaft for an output shaft seal). Everything else should be be good since I just replaced all bushings. It's either the mount or a part of the driveline.

 

Any comments on vibration with your setup?

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Greeko    1

If the mount has failed then it would be best to replace the lower mount before adding on the RT mount if you plan on running a factory style rubber mount on the bottom.

 

The snubber setup will be fine as it basically replaces the limiter strap.

 

Keep in mind clunking can come from other sources, so inspecting your mustache bar, axles etc would be a good idea. One source of a clunk that is missed fairly often are the control arms in the rear. If the bolts become loose that retain the bushing on power on or braking the entire control arm can shift forward or rear ward.

 

Great suggestions! 

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