Put the pitchforks away please. This transmission is swappable into the miata with the kpower adapter plate. It's a big power mod and it's a awesome. But mine has issues. It makes a lot of noise when at cruise. There isn't much load on the shafts and it sounds like they are trying escape the transmission case. I suspect the input shaft bearing is bad. I can hear the whine in neutral. I've searched the googles and haven't found a good document or video except of what not to do. So I will continue with another what not to do so everyone can learn from my fails.


Just going to pop it open


Yep, it's open

 

Do not use a hammer to open the case. Do not use wedges to open the case.

Unscrew everything possible in the bell housing half of the transmission. You need a T50 torx bit and an external torx E10 socket. Some of the torx bolts needed tapped on with a hammer to loosen the sealant and get them to break free.

Remove the input shaft seal by tapping in on one side and hopefully the other side will pop out enough to get it out. You may need to stab it with a pick but beware of the bearing directly behind it. Remove the retaining clip and shim washer.

Fabricate a pressing tool. This is a square tube that bolts across the housing and presses the input shaft through the input bearing. There is a detent and spring that might fall out of the housing so be ready to find it.


Square tube, long bolts, parts of a bearing puller

 

This kills the seal





I should not have taken all of the shift lever keepers out of the end housing at this point. But they needed to come out eventually anyways.

 

Thanks for the laugh, I've done similar stuff. Good info here too, thanks for sharing!

 

I'm still fighting to fix this thing. Getting the shafts out is a battle. I need a press.

 

Yeah trans work is no joke

 

Someone was just telling me that you put a hole in your trans housing. Didn't expect to see it on here. Good luck with the fix, I'll be excited to see that thing rip again next year.

 

Thanks. It will live again. I'm not yet sure this transmission will, but the car will.

 

This. is. nightmare fuel.

 

I had to make many holes in my square tube that would allow me to swap back and forth from the top and bottom shafts. They would move at most 3/16" before I'd swap back to the other.

 

 

I can try to get the bearings out before I weld and hope they go back in. Or I weld it with them in and potentially ruin them.

FYI, all of the screws are T30.

And to top it off, I can't find a bad bearing in there. The only one that I'm not sure about is the one that connects the input shaft to the output shaft. It seems like there is play there but I don't know what is normal.

 

That absolutely sucks that you didn't find anything obvious. Hope assembly happens without too much cursing and bloodshed.

 

It might just be NVH from making everything solid. Engine is K24z3 with no balance shafts, solid clutch disk, hard mounts, solid drive shaft connection.

 

Welded it back together

 

Reassembly

Don't forget to put on the input shaft before everything is pressed together.



The detent needed to come out or the shift arm won't go in.

Trying to keep things in place with string



Detent cover put in with a 12mm wheel stud.

The input shaft must be pulled that last mm.

 

I am currently trying to get a gs6-37bz apart, I’ll document that here too.

so did you replace the bearings?

are you worried about damaging the input shaft bearing there by pulling the shaft in without supporting the inner race?

I have a very similar problem with my 6 speed. (kmiata swap to BP) Shifts great, under throttle it’s normal, but decel in gear, light loads there is a ton of gear noise.

in neutral (with clutch pedal out) it sounds like the transmission is full of rocks. Clutch in (stops input shaft) it quiets down. Figured I had pooched input shaft bearings too! My box def has a little play in the input shaft. It’s hard to tell if it’s normal/excessive because I cannot find any documentation or service manual for these (ZF) transmissions.

I’ve talked to several companies who used to split these for service, and across the board they have told me to just keep buying used boxes until you get a “good” one. I’m on #2 now, so I may at least try to get one apart for science before throwing more cash into the fire.

sad thing is, after buying multiple transmissions and the swap, I could have gotten a bolt in race box (though those come with their own annoyances)

 

I didn't replace any bearings. I couldn't find a bad bearing. I thought for sure I would find a freely spinning bearing on the input or the counter shaft. All of them felt tight and nothing ruff or discolored.

It would be a better tool to push the shaft from center bore of the bearing. Just don't keep turning the nuts when the shaft is seated. It's no different than pressing the shaft out unless you keep going.

After most of this was apart I found a BMW forum post that had some instructions on this transmission. You might try alldata too.

What clutch and drive line and diff do you have? I have an ACT unsprung 6 puck. I just discovered that most of the material has broke off and the clutch hasn't seen that much usage.

Someone on a BMW forum mentioned the noises after they replaced their clutch and put on harder mounts. I'm wondering if it's just a race car thing.

 

 

When BMWs get rid of the dual mass flywheel, they get quite loud without the clutch pressed, and go silent with it pressed. That's very normal. I can try to post a video and see if I can capture it, but I won't be back with one of our race cars until 1/2. Unsure if this phenomenon would transfer to a ZF equipped miata, but thought I'd mention it.