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Based off of your measurements (181mm for the housing), it almost makes sense to go with the Ford TKX does it not? It's already 183mm from flange to tip, which gives you more room to add the adapter plate.
Based off of your measurements (181mm for the housing), it almost makes sense to go with the Ford TKX does it not? It's already 183mm from flange to tip, which gives you more room to add the adapter plate.
Possibly yes but not exactly. At this point the way i was going to do it isnt going to be worth it, Just going to try and have someone mill off some of the housing and get a plate and center it and weld it on.. It really all depends where that extra length on the ford transmission comes from, if its just longer at the end(pilot bearing smooth part) then it wont make any different and actually hurt you in this case. As it stands currently with the auto housing sitting there and with the method of welding 4 mouting blocks to it like was going to do, the shaft is basically the same length as the 5 speed when measuring from the front of the bellhousing but its the splines that dont reach as far, you would need more detailed drawings before i could say for sure if it would be better or not.
Possibly yes but not exactly. At this point the way i was going to do it isnt going to be worth it, Just going to try and have someone mill off some of the housing and get a plate and center it and weld it on.. It really all depends where that extra length on the ford transmission comes from, if its just longer at the end(pilot bearing smooth part) then it wont make any different and actually hurt you in this case. As it stands currently with the auto housing sitting there and with the method of welding 4 mouting blocks to it like was going to do, the shaft is basically the same length as the 5 speed when measuring from the front of the bellhousing but its the splines that dont reach as far, you would need more detailed drawings before i could say for sure if it would be better or not.
The way that I read it was that the distance for the ford vs gm would just be the length of the input shaft. So this would mean the input shaft would stick out of the auto bellhousing by ~2mm. So then you just make the adapter plate the thickness needed to pull the input shaft back into the housing. I don't have the ford to base this off of, but it does tell me I need to measure how far inward the tip of the input shaft needs to be from the face that mates to the motor
The way that I read it was that the distance for the ford vs gm would just be the length of the input shaft. So this would mean the input shaft would stick out of the auto bellhousing by ~2mm. So then you just make the adapter plate the thickness needed to pull the input shaft back into the housing. I don't have the ford to base this off of, but it does tell me I need to measure how far inward the tip of the input shaft needs to be from the face that mates to the motor
the tldr of it with it just sitting there comes up roughly that much short. The tips of the shaft is only .37mm shorter than the 5 speed but thats not what matters. You dont want just half the splines contacting your clutch disk. The extra 2mm is assuming the splines actually reach further and its not just the pilot bearing shaft on the end sticking out further. Either way the more i think of it now im pretty sure i was just overthinking it and confused more people at this point, and building it from just welding a big plate onto it and center it is going to be way easier if it works out like i think it will. Soon im going to be finding someone to actually start milling it and ill be getting alot more detailed info and pictures soon. Im also going to be starting on working on putting an 8.8 in but trying to build some of my own mounts for it to save a few bucks and a different design over the ones currently out there, Can document that here too i suppose. Worst part about that whole deal is axle costs are insane and are like 85% of the whole swap.
I had wanted to make an adapter plate that could be fixed to the auto housing, but the problem is that with the GM, there isn't enough meat on the housing for a 3/8" plate.
Math shows bell housing lengths to be:
Input shaft length + original 6spd tip to flange - adapter plate thickness = total bell housing length
6.71" + 0.410" - 0.375" = 6.745" for GM
7.21" + 0.410" - 0.375" = 7.245" for Ford
My auto housing measured out to 7.0600".
So math says 7.0600" - 6.745" = 0.315" milled off the housing for the GM
Ford is easier because of the extra 0.5" input shaft, so you can actually just make the adapter thicker by... 7.0600" - 7.245" = 0.185"
Problem is, there really isn't 0.315" to mill off of the auto housing. The material has to come off the transmission side unless there is more clearance on the inside for the starter/flywheel/clutch.
Seems like welding tabs onto the side of the auto housing is really the only way to go. Math says you do that then mill off 0.06" to get the ideal 6.745" housing length
I had wanted to make an adapter plate that could be fixed to the auto housing, but the problem is that with the GM, there isn't enough meat on the housing for a 3/8" plate.
Math shows bell housing lengths to be:
Input shaft length + original 6spd tip to flange - adapter plate thickness = total bell housing length
6.71" + 0.410" - 0.375" = 6.745" for GM
7.21" + 0.410" - 0.375" = 7.245" for Ford
My auto housing measured out to 7.0600".
So math says 7.0600" - 6.745" = 0.315" milled off the housing for the GM
Ford is easier because of the extra 0.5" input shaft, so you can actually just make the adapter thicker by... 7.0600" - 7.245" = 0.185"
Problem is, there really isn't 0.315" to mill off of the auto housing. The material has to come off the transmission side unless there is more clearance on the inside for the starter/flywheel/clutch.
Seems like welding tabs onto the side of the auto housing is really the only way to go. Math says you do that then mill off 0.06" to get the ideal 6.745" housing length
got a new toy to play with yesterday to help with the project, nothing too fancy but hopefully be enough to get me close with it enough that i can use a flat file to get me the rest of the way and get it parallel. I had the same idea in the beginning but honestly milling it off and welding on the plate isnt THAT scary but i guess you have to know how to weld aluminum or know someone close that does, seems to be the hardest part. I have to mill off .726" off the housing, put a .5065" hole in the plate, center it then weld it on, line up and drill and tap holes for the mounts, should be about it.
got a new toy to play with yesterday to help with the project, nothing too fancy but hopefully be enough to get me close with it. I had the same idea in the beginning but honestly milling it off and welding on the plate isnt THAT scary but i guess you have to know how to weld aluminum or know someone close that does, seems to be the hardest part. I have to mill off .726" off the housing, put a .5065" hole in the plate, center it then weld it on, line up and drill and tap holes for the mounts, should be about it.
Why so much off of the housing? Adding thickness somewhere else? Nice tooling and cat, both should help with the final product. I saw some old T5 threads that had good ideas for centering the input shaft with the crank. In my head, you'd center it up there, then tack the plates on and drill
Why so much off of the housing? Adding thickness somewhere else? Nice tooling and cat, both should help with the final product. I saw some old T5 threads that had good ideas for centering the input shaft with the crank. In my head, you'd center it up there, then tack the plates on and drill
have to come off the housing .226" to get the splines back to the stock location and then add the 1/2" plate so have to take off what the plates going to take up.
A normal GM bellhousing is 6.3", I think you should be closer to that, but I am not that familiar with the crank stickout of the Miata engines.
Ima go through and remeasure everything just to be sure but pretty much all I did was put a straight edge on the stock 5 speed bellhousing and measure from that to where the splines start on the input shaft, Then i did the same by just sitting the auto housing on the TKX and measuring the same way(example pic below)
I took my own measurements using the straightedge and caliper on 3 dead 6 speeds I have (0.410", 0.417", 0.425") as well as cross referenced it with aidandj in his thread from 2016
The spline on the miata input shaft from the flange measured to start around 1.2375" end at 2.55". Starting points differed by about 0.004-0.008mm, end was all the same 2.55" or 65mm. I'm counting the end as the point where the bearing retainer starts
I took my own measurements using the straightedge and caliper on 3 dead 6 speeds I have (0.410", 0.417", 0.425") as well as cross referenced it with aidandj in his thread from 2016
The spline on the miata input shaft from the flange measured to start around 1.2375" end at 2.55". Starting points differed by about 0.004-0.008mm, end was all the same 2.55" or 65mm. I'm counting the end as the point where the bearing retainer starts
This is all i was doing to come up with the .226" shorter on the tkx vs the 5 speed measured the same way and that's just the difference not the total measurement from the housing face . The actual distance to the end of the splines is what i think matters the most in this case dont want your clutch only riding on 1/8th inch of splines, the overall tip of the shaft length is fine. I think everyone uses different wording here, i know im for sure not the best at this and all the terminology and what not, first time doing all this.
Got a little bit done tonight, bellhousing is now milled down .726" and with the .5" plate that will bring the transmission .226" closer to the engine. Might take a swing at boring the center hole in the plate tomorrow.
Hi Kanaan,
I've read this and am trying to get up to speed.
When you are referring to auto bell housing, are you referring to a miata auto bell housing, or GM ? And why not use a miata manual bell housing to cut, weld plate, and machine to the specs you need? Thanks
Got a little bit done tonight, bellhousing is now milled down .726" and with the .5" plate that will bring the transmission .226" closer to the engine. Might take a swing at boring the center hole in the plate tomorrow.
adapter is looking good, really looking forward to seeing how well it all fits together. I'm waiting to hear back from my engine builder to see if the machining/welding is something he can do or not. I don't have the tooling for it myself.
If I'm honest, I'm waiting to see how yours turns out before actually buying the transmission at this point haha
Hi Kanaan,
I've read this and am trying to get up to speed.
When you are referring to auto bell housing, are you referring to a miata auto bell housing, or GM ? And why not use a miata manual bell housing to cut, weld plate, and machine to the specs you need? Thanks
This is the adapter from the Miata auto. The manuals do not have a removable bell housing like the autos do
Thank you.
if you were going to modify a auto trans with a plate to get the right distance/mounting point, would there be any advantage of using a manual bell housing to do the same thing? They would at least be more plentiful.
12-13-2023, 02:06 PM
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