As part of my Restomod Project I purchased a couple of the best quality Polyurethane bushings for my build.
The poly bushings came as part of an assembly and I was told by the vendor and manufacturer that they never had a failure reported to them regarding the poly bushings.
Last week I installed the first poly bushing which consisted of a poly top bushing and Delrin cushion to mount the front differential snubber bracket to the frame bracket.
I installed it pursuant to the instructions and torqued it to the required 70 ft lbs torque.
Two days later I went out to the garage to install my strut bracket and immediately noticed the new poly bushing crumbled.
At first I was told the only way that bushing could fail was if “I” over torqued it, Nope, torqued to spec.
Next came the accusation that I installed it in a bind, Nope, the differential was supported by a transmission jack, there was nothing in a bind and the mating pieces slid together before the bolt was tightened then torqued.
I am being sent a new poly bushing and Delrin cushion in the mail, no charge.
I wasn’t going to post this but, this is the first and only poly bushing I have installed in my project and it lasted two days.
That’s a 100% failure rate in my calculations, so I decided to start a thread letting my fellow hobbyists know.
I have a new Moog rubber snubber bushing that’s been stored in its original packaging, up on my shelf for the past six years and I might toss the poly and go with a six year old rubber bushing instead.
One thing I did notice is that the Moog rubber cushion is 1” thick and the Delrin cushion is only 1/2” thick.
That is a big difference.
What do you guys think?
Do you see anything wrong in the way the bushing was assembled in the pictures?

 

Ditch the poly.

 

If i used poly.. i would only use usa made ones like energy suspension..

rubber seems like the way to go here.my new rubber seemed larger too..
I torqued to 50 ft pounds.

https://www.corvetteforum.com/forums...hing-79-a.html

 

Every one of the poly or delrin bushings I received for VB&P were crap and disintegrated after zero miles but 8 years sitting in the shop. Course no VB&P to bitch to. Last ones to replace are the front & rear roll bars, I just need to mic the size so I order the correct replacements.

 

And I just replaced all my energy suspension front A arm bushings, after about 10 years, well, just because I was covering absolutely everything trying to nail down a shake in my car. The energy suspension bushings were fine. It was a waste of time and money.
I have a energy suspension bushing in my diff snubber now for well over 20 years. I was looking at it last night. Looks fine.

 

I agree. Poly bushings seem to "bind" the suspension.

I have to ask, why are you using Poly? Is there something the car was not doing that you wanted it to do? Were you were told Poly was better?
If your going to track the car, consider offset solid bushings for your front control arm. It will allow more caster.
I have a metal bushing on my diff. I miss Guldstrand.

 

My $.02
Poly is ok for things that turn (like control arm bushings) but not things that twist/flex like T/A fronts or lower struts type of thing
HOWEVER
It seems that there's been a decade or so long history of poly just failing when not even being used... just sitting under pressure.

I don't follow it enough to see that there's a brand that's ok and one that isn't (energy was where I bought the handful of pieces I do have and so far as yet none have fallen apart but they were all bought back 10-15 years ago, and again I can't say they are ok because they are Energy or because they were made a long time ago.
I'm certainly leery of buying ANY poly anything today, Spacers, bushings, mounts doesn't seem to matter how they move. Cheap and expensive doesn't seem to matter. Country of origin doesn't seem to matter. It really seems to be hit and miss and although I do lots of things more than once I really hate doing things again because something I spent good $$$ literally fell apart

Some of the rubber isn't great but a lot of the poly seems to be terrible

Anyway, rant over, moving on
M

 

Clearly either the vendor lied to you or started working this morning when he said that he had never had a complaint about poly. This forum is full of posts about them. Regarding the differential mount, you are correct, they are too thin. I put one in and the U joints hit the tunnel with a passenger in the car on turns and over rough roads. I switched back to rubber and all is well many years later. I also put poly in the trailing arms in my 66 and 68 coupes. They turned to glass and crumbled. Back to rubber. Beautiful frame and under carriage by the way. Jerry

 

Greg,
I highly recommend you do not use poly, especially a poly snubber. My opinion is that they are junk, no offense to those selling them every day without a care. The snubber poly I have seen were too large and caused a change in the driveshaft length. correction- meant to say driveshaft angle.
Next, as mentioned a lot of the poly used the past 15 years has broken down and fallen out. I had a new set of offset TA shipped to me last year the owner bought 20 years ago from a well-known vendor. They sat on his shelf until he sent me the arms, the ploy bushings were crumbling when I checked them.
The rubber snubber is what you need, for those who push the car hard go to a solid mount like Tom's or machine up your own.

 

I don’t understand why people believe poly is superior to rubber.

 

I think I will go with a rubber bushing and get rid of the poly.
Do you think the six year old one on my shelf, still sealed in its original packaging, is still good to use or should I go with a new one?

 

If there is no cracking in it and it doesn't appear to dried out I would use it. You never know how long they were sitting on a vendor shelf.

 

Thanks Gary!
I’ll use what I have.
The AIM says to torque it between 55ft lbs and 75ft lbs.
I generally torque somewhere in the middle of any specs.
Is it best to torque these rubber snubber bushings toward the lower specs so the bushings aren’t smushed out too much?
Thanks,
Greg

 

Keep in mind you're also slightly affecting the diff angle. Worth having a look at. I had to actually thin out my bushing to help get it to sit "right" without squishing the living crap out of it
M

 

It sounds like the best plan is to leave it alone for now.
Once I set the engine and transmission into the chassis I can install the drive shaft, check drive shaft angles and torque it accordingly.
If needed trim the bottom cushion.

 

My poly bushings were a “quality brand” but failed miserably after sitting for six years. Lessons learned!

 

China

 

Nope, Made in the USA!

 

What brand?

 

The GM engineers decided on rubber, and that's good enough for me.
Man, I wish my C3 was that nice underneath!