I plan on upgrading the diff on my Z and I'll be replacing the subframe bushings when I do it. I'm looking for help deciding on poly or solid mounts. I've wanted solid mounts because I want the performance and what I've read about NVH isn't terrible, but I've read a few places it increases the risk of causing cracks in the subframe. This is a totally street driven car but I do a lot of traveling and miles with it and dont want any cracking going on. I've had Whiteline differential bushings for a few years now and really like the difference they made. I'm trying to decide on switching out the diff bushings with solid ones when I upgrade it as well. Any advice is appreciated!

 

If it's not a race car just save yourself a lot of work and headaches get the Z1 collar kit.

 

I was considering that at first but since the subframe will be completely out anyway I wanted to put new bushings, just trying to decide solid or poly.

 

Do you track the car

 

My point was you don't have to drop the subframe to do a diff, I don't see a point to remove it ever unless it's damaged.

 

Nope only street driving

Oh gotcha, thats true but I want to replace them anyway when doing the rest of the rear end.

 

No point in solid, and it transfers bumps and vibration into the car more

 

As Trav said no point on a street car, I have a set of poly bushings collecting dust in the basement. Why cause they are an absolute b!tch to do and they have windows in them like OEM...the collar kit effectively removes the windows making the stock ones better than the poly ones. For a street driven car they give you 99%of the benefits for about 10% of the work, I just don't see how someone go out of their way for 1% unless it's a race only car.

 

the Whiteline Poly made a high difference, then the swap from Whiteline poly to solid has hardly noticeable. Forget those collars, the rubber on the stock ones is way soft. It’s about 4 hours in the driveway for me to do a set of the bushings, not bad, and well worth it.

 

Yet I don't see the rubber compressing all that much when it's filled with metal. I bought both, collars won me over and still are easier and effective for a street car.

 

Thanks for the advice, thats really all I was looking for and I'll be going with poly for the subframe when I do the differential. I agree the collars are probably very similar and seem good, but I'm putting the extra work into this car wherever I can with upgrades and maintenance and all bushings will be replaced eventually. I plan on getting a brace for the diff anyway so I'll keep the whitelines in there when I upgrade it and have all poly.