Adapting Transmission Input Shaft

superman22x · Dec 18, 2019

I am looking for some advice from anyone who has some here. I am working on a project to adapt an engine and transmission together. Of course the "easy" answer is a custom flywheel/clutch combo. But I would like to use the dual mass flywheel and clutch that originally came with the engine. Let's ignore the bellhousing portion of this project and assume that's figured out already.

My input shaft is a 1" 23 spline. My clutch side is a 1.125" 26 spline. Is there a way to adapt the input shaft to match the clutch? My thoughts are two options (not sure if either is even remotely reasonable). Usually, it would be as simple as taking the flywheel pressure plate from the engine, and a clutch that matches the input shaft. Because this is a twin plate clutch and a dual mass flywheel, it's not as simple.

Option 1: Adapt the input shaft to the clutch. Machine off the old splines, fit a bushing with the new splines already on it (core out an input shaft with those splines?), then weld the bushing. The whole assembly would then of course require re-heat treating, at least in the welded area. Liberty Gears has done something similar to this for me before.

Option 2: Adapt the clutch to the input shaft. Bore out the clutch hub, press fit a clutch hub matching the 23 spline shaft. Pin the two together? Welding these two would not be an option I think, as re-heat treating would destroy the clutch material. I ran a couple online calculators, steel on steel, a 0.05mm (~0.002") interference would be around 800NM of torque capacity. Assuming the inner clutch hub OD is 40mm. Of course, a little more safety factor would be nice, which is where the pins would come in.

This is the 26 spline clutch that matches the engine: The hub has splines that mate to the second clutch plate. This is what makes it more difficult than just replacing the friction disc.

And the clutch and input shaft on the transmission side:

For anyone interested, transmission is Porsche, engine is GM Gen V 6.2L, around 460ft-lbs.

Again, I'm not sure if there is any possibility these things can be adapted in this way, I just thought it wouldn't hurt to ask those that know more.

Illinoyance · Dec 18, 2019

Can you get a different clutch plate with the correct spline?

thermite · Dec 18, 2019

superman22x said:
I am looking for some advice from anyone who has some here. I am working on a project to adapt an engine and transmission together. Of course the "easy" answer is a custom flywheel/clutch combo. But I would like to use the dual mass flywheel and clutch that originally came with the engine. Let's ignore the bellhousing portion of this project and assume that's figured out already.

My input shaft is a 1" 23 spline. My clutch side is a 1.125" 26 spline. Is there a way to adapt the input shaft to match the clutch? My thoughts are two options (not sure if either is even remotely reasonable). Usually, it would be as simple as taking the flywheel pressure plate from the engine, and a clutch that matches the input shaft. Because this is a twin plate clutch and a dual mass flywheel, it's not as simple.

Option 1: Adapt the input shaft to the clutch. Machine off the old splines, fit a bushing with the new splines already on it (core out an input shaft with those splines?), then weld the bushing. The whole assembly would then of course require re-heat treating, at least in the welded area. Liberty Gears has done something similar to this for me before.

Option 2: Adapt the clutch to the input shaft. Bore out the clutch hub, press fit a clutch hub matching the 23 spline shaft. Pin the two together? Welding these two would not be an option I think, as re-heat treating would destroy the clutch material. I ran a couple online calculators, steel on steel, a 0.05mm (~0.002") interference would be around 800NM of torque capacity. Assuming the inner clutch hub OD is 40mm. Of course, a little more safety factor would be nice, which is where the pins would come in.

This is the 26 spline clutch that matches the engine: The hub has splines that mate to the second clutch plate. This is what makes it more difficult than just replacing the friction disc.
View attachment 272921
View attachment 272922

And the clutch and input shaft on the transmission side:
View attachment 272923
View attachment 272924

For anyone interested, transmission is Porsche, engine is GM Gen V 6.2L, around 460ft-lbs.

Again, I'm not sure if there is any possibility these things can be adapted in this way, I just thought it wouldn't hurt to ask those that know more.

"School answer" is probably greater delving of part-bins. Maybe some riveting-fu.

Clutch gurus make up whatever is needed, center spline and such every week of the year. They ain't limited to growing 'em only from the egg of a single sacred print. It can be lower-cost than custom shafts and splines.

Order a spare driven-plate when yah do that and yer set.

"It's the American Way".

moonlight machine · Dec 18, 2019

superman22x said:
I am looking for some advice from anyone who has some here. I am working on a project to adapt an engine and transmission together. Of course the "easy" answer is a custom flywheel/clutch combo. But I would like to use the dual mass flywheel and clutch that originally came with the engine. Let's ignore the bellhousing portion of this project and assume that's figured out already.

My input shaft is a 1" 23 spline. My clutch side is a 1.125" 26 spline. Is there a way to adapt the input shaft to match the clutch? My thoughts are two options (not sure if either is even remotely reasonable). Usually, it would be as simple as taking the flywheel pressure plate from the engine, and a clutch that matches the input shaft. Because this is a twin plate clutch and a dual mass flywheel, it's not as simple.

Option 1: Adapt the input shaft to the clutch. Machine off the old splines, fit a bushing with the new splines already on it (core out an input shaft with those splines?), then weld the bushing. The whole assembly would then of course require re-heat treating, at least in the welded area. Liberty Gears has done something similar to this for me before.

Option 2: Adapt the clutch to the input shaft. Bore out the clutch hub, press fit a clutch hub matching the 23 spline shaft. Pin the two together? Welding these two would not be an option I think, as re-heat treating would destroy the clutch material. I ran a couple online calculators, steel on steel, a 0.05mm (~0.002") interference would be around 800NM of torque capacity. Assuming the inner clutch hub OD is 40mm. Of course, a little more safety factor would be nice, which is where the pins would come in.

This is the 26 spline clutch that matches the engine: The hub has splines that mate to the second clutch plate. This is what makes it more difficult than just replacing the friction disc.
View attachment 272921
View attachment 272922

And the clutch and input shaft on the transmission side:
View attachment 272923
View attachment 272924

For anyone interested, transmission is Porsche, engine is GM Gen V 6.2L, around 460ft-lbs.

Again, I'm not sure if there is any possibility these things can be adapted in this way, I just thought it wouldn't hurt to ask those that know more.

Make a new input shaft. Run small tires so it doesn't get much traction as that engine has enough torque to destroy that puny little gearbox.

DDoug · Dec 18, 2019

Now that we know what engine & xmission, the beeg question is ….

"WHY" ?

:skep:

thermite · Dec 18, 2019

moonlight machine said:
Make a new input shaft. Run small tires so it doesn't get much traction as that engine has enough torque to destroy that puny little gearbox.

Well.. unless he adds a shear-pin?

NOW you've gone and taken all the FUN outta "Deutschland über alles Rechnungs!" (Rechnung or "reckoning" = Invoice).

For repair parts!

thermite · Dec 18, 2019

digger doug said:
Now that we know what engine & xmission, the beeg question is ….

"WHY" ?

He gets shut of a Porsche ENGINE.

Same as a mate long ago who put his Ferrari's V-12 into a ski boat run only a few times a year on some lake out West, commuted in Metro DC traffic with an anvil-reliable 327 Chev in its place as didn't go all contrarian in traffic.

Car was still more than fast enough to break yer neck or land yah in jail, attracted high-grade wimmin - or so they thought they were. So no great loss.

How hard was THAT?

Mind.. make even MORE sense to shed the rest of the glorified Vee dubbyah...

I've heard of Porshe's in Police Pursuit duty. Even SAW one - a white whale-tail coupe - Nederlands or Belgium - doing a U-turn at their border.

Wouldn't want the upkeep cost vs a Ford, Chev, or MOPAR Pleece cruiser.

superman22x · Dec 18, 2019

thermite said:
"School answer" is probably greater delving of part-bins. Maybe some riveting-fu.

Clutch gurus make up whatever is needed, center spline and such every week of the year. They ain't limited to growing 'em only from the egg of a single sacred print. It can be lower-cost than custom shafts and splines.

Order a spare driven-plate when yah do that and yer set.

"It's the American Way".

Spec makes a "super twin" clutch that has dial disc. Both spline directly to the input shaft rather than one riding off the other plate. Maybe this would be the way, using two of the Porsche clutch discs.

moonlight machine said:
Make a new input shaft. Run small tires so it doesn't get much traction as that engine has enough torque to destroy that puny little gearbox.

That's a Getrag unit from a Turbo S 911. Factory AWD and 500ft-lbs. Also used in the GT2 911. Handling the torque is not the issue.

DDoug · Dec 18, 2019

superman22x said:
Spec makes a "super twin" clutch that has dial disc. Both spline directly to the input shaft rather than one riding off the other plate. Maybe this would be the way, using two of the Porsche clutch discs.

That's a Getrag unit from a Turbo S 911. Factory AWD and 500ft-lbs. Also used in the GT2 911. Handling the torque is not the issue.

Yes, that's all well and good.

But what is wrong with the engine OEM xmission choice ?

superman22x · Dec 18, 2019

digger doug said:
Yes, that's all well and good.

But what is wrong with the engine OEM xmission choice ?

911 rollers are cheap, I like them, their engines are not cheap. No GM trans is setup for rear engine.

thermite · Dec 18, 2019

superman22x said:
Spec makes a "super twin" clutch that has dial disc. Both spline directly to the input shaft rather than one riding off the other plate. Maybe this would be the way, using two of the Porsche clutch discs.

That's a Getrag unit from a Turbo S 911. Factory AWD and 500ft-lbs. Also used in the GT2 911. Handling the torque is not the issue.

Time will tell.

Got more respect for Getrag than ZF. As do truck makers. But still.

A Pont a Mouson or Packard gearbox as could survive the old BIG torque'y MOPAR Hemi's it is not.

WTH ... the Bosch-brain-(dead) ZF 6-speed slush box in the XJ8-L with a vanilla Ford four-duece 295 BHP V8 "cooking wine" mill is rated 600 lbs ft and doesn't always cope all that well. Wiser and newer for the supercharged ones ISTR is around 700 Ft Lb?

Yew-Ass motor-makers are married to far wider BANDS of torque that DE, y'see.

And then they understate it. Housewives, rednecks, off-roaders, trailer-tow'ers, and generally abusive tall-tire acre and a half of rubber contact-patch coupled with sheer take-for-granted laziness thing.

"Brain box" can protect a trans. Clutches and other "triggers"? Not so much.

"Assimilated" my a**.

"We are the Borg.. warn'er. Prepare to drop a cluster!"

Then drop-trou when yah get the bill!

john.k · Dec 18, 2019

Millenials have a need to tell everyone about their latest efforts ...anyone over 50 just does it in 15 minutes ,and gets on to the next job.

superman22x · Dec 18, 2019

john.k said:
Millenials have a need to tell everyone about their latest efforts ...anyone over 50 just does it in 15 minutes ,and gets on to the next job.

And how would anyone over 50 go about it?

GregSY · Dec 18, 2019

I'd talk to a clutch maker. Chances are good they can come up with a disc(s) with the proper hub. Or even change out your hubs. That's gonna be the easiest way.

It's interesting the trans uses a spline Mopar has used since the 60's....

Garwood · Dec 18, 2019

superman22x said:
911 rollers are cheap, I like them, their engines are not cheap. No GM trans is setup for rear engine.

Bullshit.

Drop in an LS4. Just put it in the rear, not the front. Or fuck, put one in the front and one in the back and really get after things. If you roast the 4t65E then buy a deville/seville for $200 and use the 4T80E. Or you could use the whole Northstar enchilada, but I think most would agree the 4.6 DOHC is a boat anchor compared to an LS.

As for your clutch the biggest problem I run into with clutch business is the hydraulics not being compatible.

I have done a shitload of adapting of this and that and OEM clutch hydraulics rarely work with a different make of pressure plate.

I would make damn sure the porsche hydraulics will play nice with the GM pressure plate before you go down that rabbit hole.

How much is a 911 turbo clutch? If one is reasonable I'd make a new flywheel for your 6.2 from 1045 with the GM ring gear and all the features for the Porsche clutch and pilot bearing.

Garwood · Dec 18, 2019

GregSY said:
I'd talk to a clutch maker. Chances are good they can come up with a disc(s) with the proper hub. Or even change out your hubs. That's gonna be the easiest way.

It's interesting the trans uses a spline Mopar has used since the 60's....

There aren't that many different clutch discs and pressure plates out there. There's more than a few, but nowhere near as many as there are different vehicles.

superman22x · Dec 18, 2019

Garwood said:
Bullshit.

Drop in an LS4. Just put it in the rear, not the front. Or fuck, put one in the front and one in the back and really get after things. If you roast the 4t65E then buy a deville/seville for $200 and use the 4T80E. Or you could use the whole Northstar enchilada, but I think most would agree the 4.6 DOHC is a boat anchor compared to an LS.

As for your clutch the biggest problem I run into with clutch business is the hydraulics not being compatible.

I have done a shitload of adapting of this and that and OEM clutch hydraulics rarely work with a different make of pressure plate.

I would make damn sure the porsche hydraulics will play nice with the GM pressure plate before you go down that rabbit hole.

How much is a 911 turbo clutch? If one is reasonable I'd make a new flywheel for your 6.2 from 1045 with the GM ring gear and all the features for the Porsche clutch and pilot bearing.

Good thought on the hydraulics, that's all part of what I will have to figure out in addition when the time comes.

A customer flywheel with the turbo clutch would be the last option, they are reasonably priced. It would mean ditching the dual mass flywheel from the LT1 engine unfortunately. Not a huge loss, but they do make for nice drivability.

Garwood said:
There aren't that many different clutch discs and pressure plates out there. There's more than a few, but nowhere near as many as there are different vehicles.

Funny thing is, a Mopar clutch is what some people have used in the LS1 944 swaps. It's extremely close, but the Porsche is ever so slightly different (25mm vs 1"?). There are a few people who have sheared the splines off the shaft. The Spec clutch fits tighter on the splines.

thermite · Dec 18, 2019

superman22x said:
Good thought on the hydraulics, that's all part of what I will have to figure out in addition when the time comes.

A customer flywheel with the turbo clutch would be the last option, they are reasonably priced. It would mean ditching the dual mass flywheel from the LT1 engine unfortunately. Not a huge loss, but they do make for nice drivability.

Funny thing is, a Mopar clutch is what some people have used in the LS1 944 swaps. It's extremely close, but the Porsche is ever so slightly different (25mm vs 1"?). There are a few people who have sheared the splines off the shaft. The Spec clutch fits tighter on the splines.

C'mon. 25 mm to 25.4 mm / one inch, under nine thou on the radius. IF MOPAR AKA Daimler-Chrysler, AKA FIAT-Chrysler, is even still using the "inch".

Lotta stuff far more critical, this ain't one of them that leads to shorn splines. Dumped the clutch when yah shuddna' done is more likely.

Buy shoes with less slippery soles or check yer HEADSPACE, and yer good.

EmGo · Dec 18, 2019

Just make a new shaft. Welding little parts together to make a big one is maybe not a good idea in this case.

It's a pretty simple lathe / mill job, no big deal. You probably want to use something fairly strong, find a heat treater with a brain, straighten, maybe have to adjust size because it will likely grow, then viola, on to the next part of the project.

A few people here are capable of doing it if you don't feel up to the task yourself, but it's elementary lathe and mill work. Nicer if you have a hobber and the correct tools but feasible without for a one-off.

If there's a demand, make three and sell two. I have had three or four people start small businesses that way.

superman22x · Dec 18, 2019

EmanuelGoldstein said:
Just make a new shaft. Welding little parts together to make a big one is maybe not a good idea in this case.

It's a pretty simple lathe / mill job, no big deal. You probably want to use something fairly strong, find a heat treater with a brain, straighten, maybe have to adjust size because it will likely grow, then viola, on to the next part of the project.

A few people here are capable of doing it if you don't feel up to the task yourself, but it's elementary lathe and mill work. Nicer if you have a hobber and the correct tools but feasible without for a one-off.

If there's a demand, make three and sell two. I have had three or four people start small businesses that way.

It's hard to see in that picture, but first and second gear are a part of the input shaft in this transmission. Makes building a one off shaft quite a bit trickier I think.

Adapting Transmission Input Shaft

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