Whiteline KDT923/924
 

So I had the KDT925 diff bushing inserts and liked them quite a bit. Unfortunately had to take them off cause they were causing my DSS driveshaft to vibrate. Having taken them off, I do miss them quite a bit and actually thinking of sacrificing the driveshaft for them. I still can't find a single review of KDT923/924 bushings anywhere on the internet. All the reviews are just for 925. Has anyone here installed them? Would be even more helpful if you had KDT925 installed before that or ran a 1 piece alu driveshaft in conjunction.

I had the 924 kit at one time. They are a pain in the ass to install. It is much easier to just by a cheap diff brace and run that. Since they are a solid poly bushing they are probably not as forgiving as the 925's. I have never run the 925 kit but from my digging that was my impression.

Motoiq has used them,https://motoiq.com/project-fr-s-more...d-whiteline/2/

Thanks for the link, looks like they had this to say:

What is amazing is that NVH had not changed one bit over stock. Even with urethane and bearings replacing rubber the ride and noise have not degraded at all.

Oh I'd let my mechanic do it. Especially with something this involved, I'd much rather leave it to the professionals

With the right tools it is not as bad. It is still a drop the diff out and prepare to swear a lot job. I'd really not recommend the 924's unless you are doing everything to take up drivetrain lash already. And like I said above, a cheap diff brace is only 10-20 bucks more and a way easier install and more effective.

Forgot, I have had the 923's as well. I didn't really notice much additional NVH from these. I have another set I will be installing in my other diff when it shows up next week.

I have both KDT923 and KDT924. The 923 is fine, the 924 is trash and just failed (rubber separated from metal collar). Will post pictures after the weekend when I am back from the track but this is not the first failure reported on this forum, there is an older thread but the pictures are gone.

I removed my 924’s after hearing about this.


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I'm interested too. I have the STi bushings and I would like to buy a carbon driveshaft, but I don't want any vibration.

Depends on the type of bushings you have. From all the research I've done on this, it seems to be primarily the diff bushings that cause the vibrations. And not just in our cars. Mustangs, BMWs, you name it.

I'm obviously talking of differential bushings...
I'm quite sure that front arm bushings will not affect vibrations with carbon driveshaft. :-D

Anyway, I made a lot of research too: the causes of vibrations for driveshaft are essentially two.
The first one is poorly balancing (and this affects A LOT of known brands, but I'll not name them); the second one is the pinion angle, so the angle between the driveshaft and the gearbox/differential.
The stock two piece driveshaft is made that way to have a near to 0 angle. The best angle is around 0.5 degrees; 1,5 to 2 degrees is acceptable, 3 degrees is too much.
This 2 things will cause vibrations. Stock bushings probably will quiet them down, but stiffer bushings can't.
So, it would be better to have a correct driveshaft, than fixing the issues it causes with bushings.

gpvecchi is spot on. Drive shafts that are out of balance or more commonly, pinion angles that are not set up correctly will cause vibration. The miata uses an adjustable truss to tie the diff and trans together. Few miata owners take the time to adjust it correctly so pinion angles go wack and generate vibration. I have not seen a specific procedure on the 86 but switching to a one piece drive shaft and doing diff bushing/inserts is likely going to require some careful measurement and moving around the components within the slop of the mounting holes to get pinion angles right.

We're adding the 921 subframe along with a DSS aluminum driveshaft to Blub. We'll report back in Blub's build thread once its dialed in. 925 diff mounts already installed.
https://www.ft86club.com/forums/showthread.php?t=131052