Damn. You’re going through the same nonsense the rest of us have.

funny, a friend and I were talking about replicating the BMW driveshaft setup today. No adapters, no bullshit, oem design. Sounds like Greg got there first and it worked out.

 

Just finished watching Gregs new video. Yeah... He had to go to a 2 piece due to the dogbox needing a guibo. And a guibo has to have a straight line output from trans.

But i agree, sounds like he is/was still fighting driveline shake issues all along still.

 

I got the impression from the video that he had driven his oem ZF5 with the 2 piece. I want to try the same thing, last ditch effort to save this setup. I’ll shoot him a message to verify

I don’t really have the cash at the moment to throw (getting married is expensive!) at the car.

Also, I have had a dog box in a street car before, it gets old pretty quick. They do not like to be driven lazy, you need fast engagement to keep the wear on the dogs down. Not so nice unless you’re railing on it all the time.

 

After being initially frustrated i went back to the shop. measured runout on the new driveshaft.
Adapter up at the transmission is fine just as before. As you progress down the driveshaft runout gets progressively worse.
Measuring runout at the slip joint is where it gets interesting. Now seeing over 70thou.

What method did you all use to ensure side to side pinion angle to output flange of trans? Up/down is dialed in 100% perfect.

I am going to double check that when looking from above/below both flanges are parallel. I originally setup the car with a laser down the middle, but want to put a laser on each flange pointing down with a straight line. Then marking on concrete with tape, and measuring between the two like checking toe angles if that makes sense.

However there really isnt a ton of movement on either side to side if this truely is off. Which I doubt, but ill double check.

 

Yeah im not interested in throwing cash around either (and congrats!). Please let me know what you find out from Greg. This really points me back to DSS saying a slip joint wont work on a u joint long high speed shaft like this. Needs CV joint with no slip.

 

thanks!! Wild times.

anyways

For side to side, I used a telescoping rod to take a comparative measurement. two pieces of stiff welding rod zip tied together can work well enough.

sharpen a point at each end, mark your measuring points with a sharpie, fix one end (I did diff side) and slide the rods apart until they make contact. It’s a little tricky, but works well once you get the hang of it.

work N/S/E/W to determine parallelism

adjust trans side/side & up/down until your “measurement” is the same. This is the lowest error method I could come up with.

used that method for years when making bicycle frames, the mitering/joinery had to be water tight before welding, so precise measurement was super important. this was an excellent way to transfer actual distances from the frame jig to the tubing, and typically could nail it down to .25mm or so.

 

Great idea.. will be trying to replicate. will try lasers as well. Do you recall if ZF6 to miata diff is able to achieve 0 degree offset side to side? or will the trans be pointing slightly driver side, and diff pointing slightly passenger side in offset like north south pinion angle?

 

That was my experience. Engine and Trans biased towards driver (off the centerline of the car) diff flange biased towards passenger. I also did the laser method, nothing wrong with doing it like that, just easier to get some error. The measurement doesn’t matter as much as the parallelism of the flanges, but I also never got my car to run smooth so take it with a grain.

I might reach out to my drive shaft shop for a quote. Having a car sitting around that is not right is a burden I’m tired of carrying!

 

My ZF6/Miata diff setup had a bit of lateral offset. Diff was about 1/2" port compared to the transmission if I remember right. Measured with a laser as well

 

70 thou runout is just awful for a driveshaft.

I'm curious on that adapter they made if the two faces of it are perfectly parallel. I know you measured runout, however if the faces aren't also perfectly parallel that can create a runout condition in the driveshaft too.

Also you may be able to take that driveshaft to a local to you shop that builds driveshafts and have them check for trueness of the shaft. if the part of the slip yoke that welds into the driveshaft was not welded true they should be able to heat straighten it. Will have to be re-balanced after that though.

 

from greg:

"Yes I tried it with the OEM ZF as well, even though I had sorted most of the vibration issues out, it was still noticeably smoother."

 

Ok good to know. thanks!

I did chat with Kpower last night and they seem receptive on making this right, and its not up to their standard. Will report back once i hear more.

I spent time triple checking face runout, all is well there. Spent time quadruple checking pinion angle as well.

Im 99% sure driveshaft is to blame.

 

good luck. It’s my feeling they do not have a solution for this problem. They should figure out the two piece shaft and carrier bracket.

 

I've heard that before. Keep us posted, I really want to see this issue figured out.

 

In the meantime, solutions like the NEAT's proposed upgrade of the Aisin box look increasingly attractive. It's still vapourware, and isn't going to hold insane power if/when it arrives, but it should avoid issues associated with transplants.

 

Sent my 2nd driveshaft back to their vendor today. Kpower spoke directly with them. Will be sending me a 3rd shaft to try.
Asked to have the shaft shortened 3/4" myself along with others have mentioned the slip yoke being bottomed out isnt a good thing. Reiterated the runout and out of balance, esp where the slip yoke is welded to shaft.

If this 3rd one still has issues, will look into more serious fix attempts.

 

If that next one doesn't work, I might hit up the shop that made Greg's 2-piece shaft. I was honestly kinda surprised to find that he was able to have one made locally. I briefly talked to a couple shops/guys about doing a two-piece driveshaft for my car and nobody seemed to have any interest in attempting it.

But at any rate, I'll cross my fingers for a magical fix for you with this next shaft.

 

3rd shaft was better runout but not great, was shortened a bit as well.

Car still shook like hell.

Looky at link kpower sent today.

https://kpower.industries/products/3...nsmission-kits

 

Dawg that's the same type of driveshaft they sent with my Getrag kit that also had a bunch of runout. I showed them a video of said driveshaft and after a couple weeks KP told me the supplier would reimburse me if I sent it back to them on my own dime.

Absolutely f*cked.

 

The new 3.5" aluminum driveshaft I linked also had issues for you as well?