soft diff bushes?

[venturaII]

I'd think the subframe bushings would be additionally appealing because it not only helps with driveline rubber banding, but also helps lock down rear suspension movement. The only downside really being the addition of some road NVH (versus just driveline NVH).

I suspect the differential carrier bushings would be better at stopping just the rubber banding part of things though, since you'd be tying the diff more rigidly to the subframe, which has it's mounting points spread out over a much larger area, and more bushing surface area. It would additionally add to the perceived weight of the carrier, which might dampen some movement a bit more, too.

The reality though, is likely the first change you make is always the most noticeable, and as such, additional changes are reduced in effectiveness by the preceding improvements.

[wparsons]

Subframe bushings won't do anything to stop diff movement, and since the entire rear suspension is bolted to the subframe it doesn't do anything for keeping geometry consistent. It will keep the subframe more square to the rest of the car though, so it'll drive more predictably under cornering loads.

[venturaII]

Originally Posted by wparsons

S since the entire rear suspension is bolted to the subframe it doesn't do anything for keeping geometry consistent. It will keep the subframe more square to the rest of the car though, so it'll drive more predictably under cornering loads.

Ahh - I thought the upper arms were attached to the body and only the bottom to the subframe. My bad.

[wparsons]

Originally Posted by venturaII

Ahh - I thought the upper arms were attached to the body and only the bottom to the subframe. My bad.

[venturaII]

Well there you go.

[Ultramaroon]

Originally Posted by venturaII

Well there you go.

That pic is a perfect illustration to help explain why the diff mounts contribute more to windup than the subframe mounts do.

Drawing lines from the subframe mounts to the center of the diff, and doing the same from the diff mounts, it's easy to see how, without using big techy words, the diff mounts are to the subframe mounts like a nut driver is to a spanner.

The same goes for the engine mounts. They're really close to the axis of rotation.


I love the Miata differential.

[JazzleSAURUS]

Originally Posted by strat61caster

I really liked the subframe bushings, I liked the diff bushings less, ymmv, maybe if I'd done them in the opposite order I'd feel that the diff bushings were better idfk. There's a balance to stiffening it up, a little stiffer seems to sync the car up to itself, too much and you're back to feeling drivetrain lash imho.

Curious if you remove the subframe bushings which you end up preferring individually. I went with the subframe bushings and am 100% satisfied for my goals, (making the BRZ that could of been if cars didn't have to be so comfortable for the masses.)

[strat61caster]

Originally Posted by JazzleSAURUS

Curious if you remove the subframe bushings which you end up preferring individually. I went with the subframe bushings and am 100% satisfied for my goals, (making the BRZ that could of been if cars didn't have to be so comfortable for the masses.)

If anything I'll probably remove a few of the diff bushings, there's a bit of gear whine that comes through now that supposedly gets reduced by removing the front half the kit.

I agree the subframe bushings on their own are great.

[notout86]

I asked Whiteline by email
"We have a 2013 Toyota GTS86 auto with torsen diff. I experience driveline lash sometimes and would like to reduce it without introducing harshness or increasing noise (or at least only slightly.) I do not compete. I am thinking of replacing just one pair of diff bushes rather than all four which seems simple but would like your advice.
ONLY WITH YOUR PERMISSION I will be posting your reply on forums. "



Here's their great reply
"If you are looking for a compromise between reduced driveline lash without too much added stiffness, our differential bushing inserts are a good choice. Part number KDT925 includes polyurethane inserts that fill the voiding of the factory rubber. The kit contains inserts to stiffen the outrigger bushings and the cradle mounted differential bushings. An added benefit to this kit is that it is a somewhat easier install and is a more affordable alternative to complete polyurethane replacements. If you would rather use full polyurethane replacement bushings, the outrigger bushings (KDT923) would most likely be the first to deteriorate and would therefore be the best to immediately replace. They are also the easier to install of the two bushings. If you are looking to do any work on the car’s differential bushings, we recommend replacing the cradle bushings (KDT924) as well if the car is already going to be taken apart and worked on. Feel free to share this information and please reach out if you have any other questions!"

[JazzleSAURUS]

Originally Posted by strat61caster

If anything I'll probably remove a few of the diff bushings, there's a bit of gear whine that comes through now that supposedly gets reduced by removing the front half the kit.

I agree the subframe bushings on their own are great.

Interesting! I appreciate the feedback.

I experienced a small amount of added gear whine when I did the transmission void insert and was so happy by how the car felt immediately declared that I was done with bushings before I went too far. (That's usually what happens.)

[StraightOuttaCanadaEh]

How many hours of labour is it to have these inserts installed?

[JazzleSAURUS]

Originally Posted by StraightOuttaCanadaEh

How many hours of labour is it to have these inserts installed?

I did my diff and trans fluid, subframe inserts and trans insert in about 2.5 hours on stands in my garage taking my time. Hopefully that's helpful.

[Aluma007]

do the diff bushing inserts work on the automatics too? for that matter, the trans mount and the subframe ones? I did a long trip and experienced that lash for the first time as I came to a stop light after several hours of highspeed corners and undulating roads...thought I'd broken the car.

[new2subaru]

Originally Posted by StraightOuttaCanadaEh

How many hours of labour is it to have these inserts installed?

Jazzle was a bit quicker than me. I'd say both took around 3 hours. I've read some have had trouble with the rear subframe inserts though.

I'm yanking the two carrier bushings tomorrow and will see how that feels