Hey yall. been a while.



Broke 4th in my stock 6 speed at the end of last season on track. 400hp car that made alot of cold weather boost that day.

Worked on/working on a ZF6 speed swap. Installed KPOWER kit, noticed high RPM vibrate on jack stands, took the car for an exhaust to get made and finally drove it. And yep, right at 60 the car shakes itself apart.







Ive read every thread/seen every post on these, did everything to prepare/prevent. Just today shipped driveshaft off to Kpower for them to look at. Pinion angles are spot on, side to side alignment great. Replaced axle shafts, ran car with wheels of on quick jacks etc.

There are spots in the slip joint of the driveshaft that were 30thou plus out. most of the shaft was good. Who knows how the balance is.
https://photos.app.goo.gl/j4Zi3cqWqHV4U91W8

A few questions for those that have gone down this journey before.

1. Has anyone actually got this to work without a getrag diff? lul
2. In your kit, is the adpater plate on the diff side or trans? mine is on trans. My trans mount crossmember has a round cut out (seen above).
3. Getrag diff- is it the same driveshaft with a second adpater on diff side? I assume getrag diff the driveshaft is in extended position more so?
4. My driveshaft is juuuusttt barely fitting between diff face and trans adapter face. Had to shave down the ZF6 alignment pin. Is this ok? seems like room for movement would be ideal?
and lastly
5. After focusing on the driveshaft vibration I noticed this decel noise. I went with Spec stage 3+ clutch. Car was previously tuned with bp lightweight flywheel. When rpms dip this rattle can be heard in the trans/bellhousing/or vice versa drag in trans is causing rpm dip. Sometimes killing the car. This is with car in neutral. Clutch out. Clutch engaged, no noise. Seems odd, trans had good history. Im leaning on tune needs adjusting but cant figure out what is actually happening here.
https://photos.app.goo.gl/ViLCnhExCqM3PR2a6


thanks guys..

 

This is insane that these issues are still happening.

99% sure my vibration was an imbalance/runout in one or both of the driveshaft adapters. Mine got marginally better after loosening the driveshaft and adapters and adjusting them by hand. My components weren't perfectly self-centering and each had more than a few thou of slop that could be manipulated/adjusted by hand.

 

Hey man, yeah i think that was your thread I spent way too much time reading haha.

Only one adapter on my setup and it very good in terms of runout.

 

I tried to include it for posterity haha.

Are you on the high HP miata Facebook group as well? There's a couple posts about it on there too. I made one myself and another guy said his adapter came out of balance from KP. Might be worth checking out as well.

 

That's awful!

They should stop selling those until they can Test/verify quality of components before they ship parts out.

If a Georgia cracker such as myself can redneck together a ford transmission, torque converter, 8.8 differential and custom axle setup that doesn't shake itself to pieces it is inexcusable that kpower cannot.

 

Sounding alot like the slip joint of the driveshaft could be the source of alot of high speed problems.


anyone with insight on this sound?

5. After focusing on the driveshaft vibration I noticed this decel noise. I went with Spec stage 3+ clutch. Car was previously tuned with bp lightweight flywheel. When rpms dip this rattle can be heard in the trans/bellhousing/or vice versa drag in trans is causing rpm dip. Sometimes killing the car. This is with car in neutral. Clutch out. Clutch engaged, no noise. Seems odd, trans had good history. Im leaning on tune needs adjusting but cant figure out what is actually happening here.
https://photos.app.goo.gl/ViLCnhExCqM3PR2a6

 

My original driveshaft from KP has a little bit of play in the slip joint, even before install, which I thought might've contributed to the vibration. The second driveshaft that I had built locally didn't have any play. Don't think it made a difference in the vibration, but obviously it could be a different story if yours has excessive play.

I can't be of any help on the decel noise. I remember having a lot of decel chatter with my 9lb Miata flywheel, and a decent amount with the 12lb KP ZF flywheel, but nothing rattling like that. Have you had a buddy duplicate it while you got under the car to listen for the exact location?

 

Yeah, I was able to have a friend help out and get under the car and listen. Its definitely dead center of the transmission. Not up near the bellhousing/clutch etc..

KPower had me send the driveshaft back to Indy Rack and Axle, they built a new driveshaft to a "new design" and have confidence in this new shaft. Should be here this week to test out.

I did buy a second ZF6 and will also swap that in, 1. to be able to check on pilot bearing etc.. and 2. just to see if this one is any better or not in terms of rattle. Talking to a e46 guy i bought it off, switching to a single mass flywheel really contributes to ZF6 rattle compared to the stock dual mass.

 

Nice man. Keep the thread posted with what you find next! Hopefully that shaft takes care of you.

 

Also interested to hear if you have any luck.

I've been busy with other stuff, but never really got mine right.

It still has a bad vibe at high shaft speeds, and is crazy loud/noisy on decel. I do not think the two things are related- but I am really not happy with the swap.

My adapter has zero runout- but I have never had it checked for balance. it's something to check, but my local shop is going to upcharge me on labor because they will have to machine an adapter plate to get the whole assembly in their rig.

It is insane to think they are still selling this kit. KPower will keep feeding you parts (and wasting your time/money) to hope to bandaid a flawed setup IMO

I bet the getrag diff guys have the same problem at higher shaft speeds, but most/all of them are regeared so it does not show up until you're going quite fast- at that point it may blend?

 

Rich, good to hear from you! Although not so good to hear the situation never changed...

I don't think we spoke after I did my Getrag swap, did we? My vibration didn't change after. Got a bad driveshaft from their other supplier (buncha runout), got my own shaft made locally again, then still had the vibration and found out the shaft and adapters weren't perfectly self-centering. Went from a 3.6 miata diff to a 3.73 Getrag. Good point, the higher geared diffs probably up the speed that the resonant frequency occurs at.

 

Yeah man! I don’t think we spoke but I have been following your thread updates.

I bought a focus ST on a whim and have been enjoying that car a ton! Though I am picking it up from the dealer today with a new transmission. It was replaced by the PO under warranty and has been replaced again. The PO sold it to me with a few hundred miles post trans replacement. Felt a little weird but I figured fwd, new car to me. Started making some noise, again thought maybe I’m just getting used to the car.

it stayed the same for some time, and one morning I started it up and could hear the input shaft spinning down when I depressed the clutch.

went to check the fluid and…there was none. They did not fill the transmission (no leaks, would have been pretty obvious if it dumped 2qts). Both fill/drain plugs were just past hand tight. Guess we know that assembly lube will last 2-3k of light driving! Ford techs, am I right ??

anyways yeah my luck has not improved on the vehicle front.

back on topic: Are you saying that the bolt holes are not drilled concentrically with the center point of the adapter?

ie- even if you nudge the adapter around to get zero runout, you will have some problems with the flange of the driveshaft being off center?

I have like 1-2 thousands runout on the adapter, minimal. I’ll have to look but I don’t recall really having another place to check runout just downstream of the adapter that would yield useful data (maybe a machined surface on the yoke somewhere, but then you’re past the u joint so idk.

If folks are having to balance the steel adapters, KPower should absolutely be doing that step before sending them to customers.

i still think that there is more to the story (some resonance with the stock diff) and chasing perfect balance with each component are damping it to some degree.

 

Ha, no way! Bummer about the transmission. I won't lie, I've seen a couple wild mishaps done by other shops since I've been at the dealership. Multiple rags left behind timing covers after cam phaser replacements, etc... Don't think I've ever seen a transmission leave the shop without fluid in it though wild but glad it was covered under warranty. You must've done something in your past life to anger the drivetrain gods. Stoked for you, though. Those ST's are kick *** cars. Maybe one day when I'm older and more sensible I'll pick up one of those or an RS even and stop buying upgrades for my car every other paycheck.

I'm going to have a hard time conveying this properly over text, but what I found was that each of my adapters and each of my driveline flanges had more than a few thou of "adjustment" if the bolts were loosened. I.E. the trans to driveshaft adapter could be moved around a bit before the bolts were tightened, same for the driveshaft flanges, diff adapter, etc. I found runout in each component and junction that could be adjusted out by hand via finding the low point with a dial indicator. So I had runout in basically every part of the system at first. By adjusting each component by hand, and removing the resulting runout, I got the vibration speed to raise from about 65mph to 100mph, with much less violent resonance.

I still had a tiny bit of visible runout in the driveshaft to diff adapter and think I could've all but eliminated the vibration by getting that dialed in perfectly. Unfortunately I bent a couple intake valves the week I was going to tackle that task and ended up getting pissed and parting out the car lol

 

Right, I had the same experience. My last adapter was the “tightest” with only a little adjustment.

I don’t have one on the desk to measure, but I think the point that I’m making is that you can remove all the runout in the adapter, and while it might run true itself- you may be putting the actual bolt center off axis, so you’d end up with a driveshaft flange that runs off center when you snug it all up. So you remove one vibe (the heavy *** steel adapter) and add it back with the offset driveshaft.

But really, it’s pretty wild there is such a fine margin with alignment- which speaks in my mind to an under-researched/tested product. Most OEM driveline components are rated to .005” (or much higher) runout.

KPower claims up they haven’t had issues (we know this is not true) or pushes the blame to the vendors (prob somewhat true) but the onus is on them to implement some sort of QC program for these parts, not to mention the appropriate engineering/testing to make sure the combos they offer will work.

Their “perfect to 170mph” kswap car uses a carbon shaft, lower gear getrag, k24 etc. so it’s not really a good point of comparison.

 

Ahh ok ok I'm on the same page as you now with the driveshaft offset concern.

Yeah, at any rate it's crazy we've all been getting the same reaction from KP. All the way back from Craig Yeeters' issue (which was in 2018ish?) to the present day. What a PITA.

 

im by no means a driveshaft specialist but pinion angle in relation to output shaft on the gearbox is correct?

 

The "it doesn't happen on our shop cars" answer is so classically KP it would make a great meme, if it weren't so frustrating and expensive. I hope never to buy another part from them again.

 

Just saw this:
Looks like even ole Preg Geters was still having vibration issues on his car and recommends a 2 pc driveshaft with a center support bearing. Interesting.

 

New driveshaft just got here.

Looks nice.....slip joint is different.





However, it's worse then the last one.. didn't change a thing with setup. Just swapped driveshaft. Didnt even measure runout yet, made me too pissed for the night. Shook the car worse then ever on the quick jacks.

https://photos.app.goo.gl/pkUraMHcPgqt6dS89

 

Yuuuuup