Tremec TKX Swap behind a BP/B6
 

Figured its worth documenting my swap to a Tremec tkx behind a b6 then soon into a more properly built 1.8L Since i dont really see any other in depth info on this swap anywhere.
My Initial plans were to use the quicktime bell housing but they are all on a several month back order which for all i know might keep getting pushed out and so i decided to attempt to make my own and 1600$ in the process.
The exact transmission i went with was the TCET17722 with the .81 5th and 2.87 1st, It seemed the closest match to the 5 speed gearing minus 1st gear being a little bit longer which im hoping to not be too much of an issue and I didnt want 5th to be too tall and wanted it still usable. Im still in the very early stages of the swap and don't really have too many parts other than the transmission in hand, currently waiting my clutch to arrive before i really get to working on this bell housing. My current plan was to use a Semi Custom billet single disk from Spec with a tilton adjustable hydraulic throwout bearing with a 13/16 wildwood master cylinder(hoping it gives me enough throw if not will have to go to a 7/8).


Current findings with the automatic bell housing is with it stuck onto the front of the tkx without any modification the very tip of the input shaft lands 0.37mm shorter than what the input shaft did on the 5 speed which is very close, but the splines do not go quite as far so will have to mill a bit off the automatic housing to get the distance correct depending on the flywheel used, this is assuming your using a stock miata sized/spec'ed flywheel also worth noting the TKX uses the same pilot bearing size as the miata. The TKX uses the center input shaft cover to center everything up vs using Dowels and bell housing runout seems to be very important here with these transmissions, so far the automatic housing was .005" out which is the max allowed by tremec. My plan was to turn down a disk with the bellhousing id and inputshaft cover OD on the lathe and tack it in to use to center the transmission in the bell housing(maybe offset it .005 if i can with the disk) and weld on blocks to use as mounts accordingly vs using an adapter plate. Just raising it up into the tunnel behind the bell housing it seems like its going to clear, if it doesnt its close enough that a hammer should fix it. The shifter is about 4-6 inches too short. Sikky just came out with a 6" shifter relocation that seems to be the only option out right now.
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Will definitely be following this as I just blew up my 3rd 6 speed this year and am considering all other options. I've got a bunch of questions:

Are these compatible with Miata flywheels?
What are your plans for driveshaft and rear diff?
Is there still space for a full 3" exhaust to fit next to it?

still to be determined on the flywheel thing but I believe if you use the QuickTime adapter then I believe yes you can use stock spec’ed flywheels and just the clutch disk resplined for the tkx, if my adapter housing ends up working as it should it would also use stock flywheels. Last night I did more measuring and it seems the auto bell housing is a bit thicker/longer than I previously thought. I believe the input shaft will reach the pilot bearing just fine but the splines start a bit shorter and I’m not sure if they will go all the way through the clutch splines without milling off a bunch of the auto housing which would move the transmission closer, before I go and weld on my mounts, If I have to mill off too much and get rid of that circle on the back side of the housing that I’m using to center everything then there’s no point in keeping going with it the way I am.

For the moment my plan was just to get a custom driveshaft for the torsen I have mainly for cost reasons just for the short term but plan on swapping it sometime in the future kinda depends when it breaks. I’d imagine you can still fit a 3” exhaust in there but no way to know till I get it all in the car and crossmember built, I’ll make sure to keep the thread up to date.

I spoke a bit with Holley on the Quick Time adapter and just general design and he was a huge help overall. It sounds like it may be more trouble than is worth to get the auto to work, but it does sound like it would be fun to make it work.

What are your plans for mounting it to the car? Just fab up a generic mount similar to what kmiata does for the ZF swap?

I just pulled the motor/trans today and am fairly confident that a TKX is the path I want to go down as well

nope, more or less machine a ring for the middle of the bell housing to center it to the bell housing, then weld aluminum blocks to the outisde and tap those to hold the trans, and brace accordingly with thick plate or just however i see fit at the time. And if your talking about the crossmember yeah probably something like that but want to make it detachable from the car to make it easy to drop without having to undo nuts and bolts on the inside of the car, Did they say anything on stock availability of the QuickTime? The site says 1/16/24 and id probably just wait and order it if i knew it would show up around that date and not be pushed back a month at a time.

When I spoke to him, he said that date seemed accurate. Non-surprisingly, they only sell a few of them a year, so that probably plays into the date if they are taking a bunch of orders and making them all at once. I still need to put my order in for one, but I also don't need the car to be running until March 1st.

I just put in my order for one last night, ran into a snag building this, part I needed to make doesn’t fit on my lathe, still might slowly work on it but and if it works out in time can always cancel but I don’t see that happening, with the right tools this auto housing could totally be done.

Yep, I'm sure you'd be able to figure it all out. When are you trying to get the car ready by?

no real date but as soon as I could, not for any real reason I just hate having it down for too long. Might chunk it back together with a 5 speed and be easier on it since it’ll be few months. Had the transmission out just measuring stuff.

I hear ya on that. I just pulled my motor/trans last weekend. Putting together the rebuild plan and then researching cost/feasibility for the TKX swap.

It's so hard to be mechanically sympathetic to these Mazda 5/6 speeds

Just ordered a TKX from SST. Should be here later this week. I'm waiting on the bell house too.

curious what ratio one you went with, I went with the 2.87 1st and .81 5th one and I’m still on the fence on the decision but it’s too late it’s already sitting in my floor lol mainly didn’t want my 5th to just be lugging st 65 down the highway and if I did ever need 5th in the 1/4 it wouldn’t be a huge drop

I was probably going to run a stock 4.10 for a bit but I believe I’m going to pick up a ford 8.8 later this evening but I doubt I’ll do that swap for a little while. Just about any ratio and diff type out there for them. Hopefully the more people that order the QuickTime housing the more likely they are to hit their time estimate but who knows.

I also ordered mine from Holley and am hoping they stick to their 1/16/24 date. I've called so many shops and no one has it.

I'm still debating which ratios I'll go with for the TKX. The car is full track so I only care about how it feels out there.

I've got a Fuji 3.63 in now and am waiting for OSGiken to come in from supermiata. My plan was to stick with that and just weld the stock carrier

Also got this in the other day from Sikky, they just came out with their TKX relocation, so just in time. They only have a 6" one which i think is a little bit too long but got a 2" offset to maybe fine tune it a little more.

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That shifter looks sick. Interested to see how it feels and also how well the 2" offset lines up

f
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did anyone else just get their order canceled and says its "Obsolete"??? ordered from holley and i no longer can find that item on the site either... hopefully some error

It's not, they did the same for the ecotec bell housing we wanted, but said they still have all the drawings, you'll just have to email them to get a "custom" one made. Supposedly won't be too expensive since they have all the drawings, but it won't be as cheap as what they listed.

Email them, mention you could maybe sell ~10-20 of them, and as long as they don't make you buy all of them, they might offer you a discount.

that sounds like a pretty shitty way to do business considering I already had it ordered for weeks and talked to people at Holley before ordering. At this point I’ll do whatever I can to build it and not give them money if this is how they are going to be. Should atleast fulfill what orders they had or atleast not keep me waiting a month before just canceling it randomly, it was already 1600$ no way in hell I’m paying more than that in this situation.