Poly bushing on top differential link

[Catmonkey]

Anyone replace the bushing on top of your 8.8 differential with a polyurethane bushing? Since I pulled my rear end to install a Truetrac and a crush sleeve eliminator, I went ahead and burned out my rubber bushing and replaced it with an Energy Suspension bushing. My car is not back together yet, but was wondering what your results were from the change to poly.

 

[Tob]

So we've put 4 or 5 iterations of Rear Upper Control Arms (UCA) in this car and have been happy with none of them. No matter what brand or style we try it always eventually comes loose, then clanks and bangs around on any bump. Very frustrating. The various designs have also taken their toll on the axle-side UCA bushing, that is press-fit into the axle. Our techs noticed that this rubber OEM bushing was cracked and completely shot, so while the axle was being refurb'd they pressed it out and in went a fresh new one. Why not poly, you ask? Well this is one of those "terrible places for a poly bushing"... as it needs to both rotate and twist in 2 axis. Polyurethane rarely has the material properties for this task - it should be rubber or a spherical bushing.

From here.

Terry's right. Poly isn't a better solution than rubber or a steel joint at this location. We'd all like it to be but it isn't.

 

[BMR Tech]

I agree "mostly" with Terry.

That said, I also disagree to an extent, under specific circumstances.

Typically, you have enough articulation with one side, or the other, to handle the minimum angle of articulation (on any axis).

Now, my personal favorite solution is a bearing. As a matter of fact, a Poly UCA with a bearing Diff side.....is one of my favorite combinations.

A bearing/bearing set-up is best.....however, you run into issues of a free moving/articulating UCA System, that does not allow for the bearings to stay indexed. IE; NVH levels out of this world.

At the end of the day, the Poly diff bushing on most cars won't "hurt". Especially considering the fact that they will last longer than your OEM diff bushing, when being abused.

 

[Catmonkey]

What's it take to install a bearing on the differential joint? I'm currently running the BMR UCA with a poly end.

 

[SCGallo2]

Anyone replace the bushing on top of your 8.8 differential with a polyurethane bushing? Since I pulled my rear end to install a Truetrac and a crush sleeve eliminator, I went ahead and burned out my rubber bushing and replaced it with an Energy Suspension bushing. My car is not back together yet, but was wondering what your results were from the change to poly.

Replaced OEM rear suspension with the BMR Level 1 Drag Racing Package, all poly bushings including upper diff. Night and day difference over stock... smooth, quiet, and precise articulation. Fixed my severe wheel hop and plants the power with my Nitto 285 drag radials. Great package for aggressive street and mild strip applications. Torqued everything to factory specs and have had no issues with UCA loosening up. Recently cleaned, inspected, and re-lubed all bushings with AMSOIL NLGI #2 Synthetic grease with no problems noted. Cannot speak directly for improvement of poly diff bushing over stock rubber piece since I replaced everything at the same time. If I replace the entire rear axle with an FRPP 3.55 assembly, I may just install a new OEM rubber bushing since it seems like a durable piece. I won't make the move to a bearing style bushing for my driving style. Overall, I am very pleased with my suspension setup.

 

[Tob]

Now, my personal favorite solution is a bearing. As a matter of fact, a Poly UCA with a bearing Diff side.....is one of my favorite combinations.

At the end of the day, the Poly diff bushing on most cars won't "hurt". Especially considering the fact that they will last longer than your OEM diff bushing, when being abused.

Of all people, you know how I feel about well engineered bearings. I simply limited my response in the context of a rubber vs poly argument, void of NVH concerns, by sharing Terry's road course experiences.

Kelly, I do not prefer a poly bushing at this location simply because of what you are asking it to do. It is small diameter and moving in two axis, as Terry intimated, not good for poly. You're also introducing more bind as you very well know. Do you have any data that supports the assertion that a poly bushing at that location lasts longer than rubber?

If I replace the entire rear axle with an FRPP 3.55 assembly, I may just install a new OEM rubber bushing since it seems like a durable piece. I won't make the move to a bearing style bushing for my driving style.

When I added FRPP's complete 3.73 axle assembly I installed a new factory rubber bushing. It has worked very well in conjunction with a Roush upper and Maximum Motorsports Extreme Duty lower arms complete with sphericals at each end.

 

[BMR Tech]

Awesome feedback SCGallo2! Happy to hear sir.

Catmonkey, you have to remove the entire OEM bushing/sleeve....and install the bearing. The bearings will usually have a two-piece bearing housing, that will install into the OEM diff bushing ring.

 

[BMR Tech]

Kelly, I do not prefer a poly bushing at this location simply because of what you are asking it to do. It is small diameter and moving in two axis, as Terry intimated, not good for poly. You're also introducing more bind as you very well know. Do you have any data that supports the assertion that a poly bushing at that location lasts longer than rubber?

Tob, but - if thousands of people purchase and install a component....with nothing but great things to say, does theory or paper data really matter? That is kinda what I am getting at in my post. Sure, I do agree that you are asking a lot of the poly in that configuration. You are also asking a lot from a bonded rubber bushing, that is notorious for ripping.

The majority of my data within my posts comes from being the "go to" person at BMR, for Suspension tech, offering, design, etc.

Here is some data from that direction. To my knowledge, I only know of (2) occurrences of "failure" with our EN001 Diff Bushing (same as Energy)

As for the OEM Rubber bushing, I bet that I sell an EN001 bushing to a customer atleast once a week - because when they were installing their other components (UCA/Mount) they noticed a ripped OEM Diff Bushing. I mean, it's constant, it happens all the time.

To bring up another point, the dreaded clunk. I cannot tell you how many times I have spent an extreme amount of time with a customer to pinpoint a "clunk" after installing their rear suspension pieces.....only to find out, the OEM bushing (failed) was the culprit.

Again, on paper and theory, I am right there with Terry (and you). In the real world, I'll rock a poly diff bushing all day long over a bonded rubber piece.

It takes two to tango. Or, rather, two pivot points to aide in stability and articulation. If the chassis side mount was delrin, or solid metal - my thoughts would change 150%.

 

[BMR Tech]

Tob, have you closely examined the design of said Poly diff bushing?

It is a 4-piece, dual durometer design. You cannot compare it to say, a traditional 2-piece design found in most poly bushed pivot point designs.

I really like the design. It has a higher durometer center, with lower durometer outer inserts.

IMO, it is one of the better designed poly pivot point pieces.

 

[Catmonkey]

Catmonkey, you have to remove the entire OEM bushing/sleeve....and install the bearing. The bearings will usually have a two-piece bearing housing, that will install into the OEM diff bushing ring.

Does BMR make such a bearing? If not, do you know a source? I'm going to "rock" the poly and see how it works out. The OEM bushing deflected way too easy with just a punch inserted into the sleeve and me applying pressure by hand. I could see how it wouldn't take too much abuse before it fails. Looks to me like the bonded portion of the rubber is not the length of the bushing either allowing it to deflect way easier then the weight and forces subjected to it would require. The poly doesn't deflect much given similar treatment, but I'm sure the weight of the chassis can exert far greater persuasion than my hand.

 

[BMR Tech]

We do not offer a bearing for the diff.

I typically recommend the Steeda piece (555-4104)

Yes, I send business to my competitors. lol

 

[Catmonkey]

I appreciate all the info.

 

[69b302]

I have been running a the diff poly bushing for several years. I have the Steeda competition UCA, which has a Chrome moly rod end on the body side of the UCA, so articulation is not an issue.

 

[Robert M]

Tob, have you closely examined the design of said Poly diff bushing?

It is a 4-piece, dual durometer design. You cannot compare it to say, a traditional 2-piece design found in most poly bushed pivot point designs.

I really like the design. It has a higher durometer center, with lower durometer outer inserts.

IMO, it is one of the better designed poly pivot point pieces.

Hi Kelly,

Who makes/sells the 4pc. diff. bushing you have shown above?


Thanks, Roebrt

 

[masterman]

Hi Kelly,

Who makes/sells the 4pc. diff. bushing you have shown above?


Thanks, Roebrt

He does. That's the BMR diff. bushing kit.

Here you go
http://www.bmrsuspension.com/?page=products&productid=178&superpro=0

 

[Robert M]

He does. That's the BMR diff. bushing kit.

Here you go
http://www.bmrsuspension.com/?page=products&productid=178&superpro=0

Thanks.

I wonder if it is available in Black?



R

 

[Tob]

Tob, have you closely examined the design of said Poly diff bushing?

It is a 4-piece, dual durometer design. You cannot compare it to say, a traditional 2-piece design found in most poly bushed pivot point designs.

I really like the design. It has a higher durometer center, with lower durometer outer inserts.

IMO, it is one of the better designed poly pivot point pieces.

Interesting piece. In theory D) that piece should perform far better than the typical two piece poly bushing at that location - I wouldn't argue that.

Had I the time and resources, I'd set up a test rig and counter that pounded that bushing both fore and aft for X number of cycles but also axial/angular for X number of cycles. I'd be interested to see how it fails when it does fail. Same tests with a stock bushing. That's some data I'd love to see...