Rear diff bushes who runs what

[mx589]

Have googled around and some people say a full bush (Polyurethane style) top and bottom for the diff mounting in a street car brings 2 much nvh into the car.

Has anyone just ran this super pro kit before on their car ?

SPF2875K
https://www.superpro.com.au/show-produc ... n-SPF2875K

[The American]

I don't mind the full poly version - if you're needing upgraded diff bushings, then NVH is probably not the main consideration anymore. The original rubber is probably fine for most use

[ManiacLachy]

I run the Energy Suspension full upper and lower poly kit. When I switched over I noticed a very slight increase in NVH, really minor. But, my car is already moderately high in NVH, so it might be masked a little bit. The feeling in response was good though.

If you're concerned at all about NVH, then use poly absolutely nowhere and stick to rubber only! I'd go with the Mazda Comp rubber bushings.
https://www.mx5mania.com.au/Genuine-MAZDASPEED-Competition-Differential-Mount-Upgrade-NA/NB-1989-2004

[mx589]

Thanks for the info guys
Both you guys running them on street cars or they 100% track cars ?

[RS2000]

I run the SPF2875K bushes which stiffen the existing factory bushing.
I haven't noticed any increase in NVH, but my NB is 100% track. Certainly reduced axle tramp for hillclimb launches, & easy to fit too!

[ManiacLachy]

Thanks for the info guys
Both you guys running them on street cars or they 100% track cars ?

I'm 100% street and daily dríven (meant to be some track in there, but that never happens). The NVH is starting to get to me TBH, I think it's time for a dedicated daily.

[mx589]

rs2000 thanks for the info
By the look of the bushes do you have to remove the lower mounting plate and burn off remove the old rubber before sliding these in place ?

Kinda like this picture below

[RS2000]

NO! That plate has to be removed & the rear cradle dropped down a fair way, but no original rubber is removed.
The poly bushes fill the voids in the rubber, both top & bottom. The fitting instructions are on the link in your 1st post.
The tapered lower section of the lower poly bush fits into the valley of the rubber on that lower plate. Cheers

[mx589]

ok ok i see now rs2000
yeah i saw the little circle bush bit goes at the top and the larger one at the bottom

[hks_kansei]

NO! That plate has to be removed & the rear cradle dropped down a fair way, but no original rubber is removed.
The poly bushes fill the voids in the rubber, both top & bottom. The fitting instructions are on the link in your 1st post.
The tapered lower section of the lower poly bush fits into the valley of the rubber on that lower plate. Cheers

Actually depends on the brand of bush.

Some brands (Energy suspension from memory being one) do in fact require you to cut off the original rubber there.
The full superpro kit may be the same.



Also worth noting, the Superpro item listed above isn't actually a bush kit, it's their "void filler" kit, which is essentially a kit that leaves most (all?) of the OEM bush intact and simply uses poly parts to fill in the holes the OEM ones have.

Void fillers:
https://www.superpro.com.au/find/superp ... 00704/vid-

fulll bush:
https://www.superpro.com.au/find/superp ... 00704/vid-

[RS2000]

I was only talking about the void filling kit, because that's what the OP asked about.
I used it because it's much easier to install than a full kit, & seems to do the job.