Questions on suspension parts

[RETed]

Originally Posted by infernosg

Are you referring the "mounts" colored purple in the picture below (picture credited to Racing Beat)? If so, then yes, I replaced those with the "Competition" units along with what's colored red and yellow. I made sure the "voids" or gaps in the rubber material were facing forward/aft per the FSM. Only the subframe mounts (not colored) were replaced with delrin units.

Yes, those are the "weak points".
You can literally grab the rear diff and sometimes shake it with your hands and see the entire rear diff swaying under there.
Imagine the amount of torque backlashing through the drivetrain?
It's violent.

I've never seen "solid" aftermarket mounts to replace those "Differential Casing Mount" (PURPLE).
I've seen aluminum ones - TOO stiff.
I've seen stiffer replacement for the "Differential Stop Washer" (RED) underneath - i.e. URAS - that don't really do squat either.
If I could, I would try and play around with a SOLID polyurethane mount.
If I ever get off my lazy ass, I might even try and play around with a brand new set of mounts and injecting some of that "gray weatherstripping RTV" into the voids - it's a trick some racer use for those bushings with voids in them.

Those mounts are the cause of why the rear diff moves around so much.
The other extreme problem (mentioned with the aluminum mounts) is that if those mounts are too stiff, you risk damaging the rear diff casing itself.
Those mounts absorb a lot of the rear diff movement.
Once you start to restict that movement, something else gets stressed.
What happens is that the "ears" of the rear diff housing that those mounts are inserted in tend to crack off.
Remember, the rear diff housing is made out of cast aluminum...
To combat this problem, I've seen custom rear diff frame braces made to minimize the ears cracking.
And now we're back to square 1...

Also, if all of that isn't bad enough, the front diff mount is a stupid design.
That mount resticts movement via a shear force of the mount - WTF???
This is where a pinion snubber comes in and does help...but it can only do so much.
There is still a lot of movement up there.
So what can you do?
Most will tend to crank down (reinforce the front diff mount or solidly mount it) the front diff (pinion) to the rear subframe...
Again, now you risk breaking the rear subframe itself - I've seen this happen also.
And now we're, again, back to square 1...


-Ted