Brand New Incredibly Strong One-Piece Transmission Input Shaft!!

[Nicholas R]

One of the first questions I always get when people see my car with the engine swap is "what about the transmission"?

The truth is, ever since I first started thinking about doing an LS1 swap, I've had concerns about the original shaft design. I've always hated the 2 piece design. From the beginning, I installed Toby Peterson's Bullet Proof Shaft coupler. It's really nice, and certainly does help with some of the issues, but there are still a lot more problems on the table. There is no coupler anyone could make that is going to fix all the issues with the design. The shaft has many reductions and neck downs to allow for all of the original splines to be rolled. This includes the splines at the coupler, which neck the shaft down to 17mm diameter (.66in). I never liked the idea of putting a lot of power through that small of a cross section. Even now, I do certainly push my car pretty hard, but I cannot honestly say that I've ever gone all out on it. Shown here is the original 2-piece shaft design:
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In addition to the shaft reductions, the splines themselves can simply wear out within the original coupler. With no lubrication, fretting corrosion takes place, slop builds up in the splines, and eventually they tear themselves apart. That is what happened to this shaft here, from a stock DeLorean with no modifications:
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For reference, this is what the stock shaft normally looks like (the splined end isn't broken):
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Sure there are single piece shafts out there made by GTO Racing/Quaife, as well as the now defunct Holloway Performance, but the price was never something I could justify. The exchange rate fluctuates but it pretty much always hangs around $5,000 for that gear shaft. At the end of the day, $5,000 was more than my engine swap cost, so I just couldn't do it. In addition, I never liked the idea about changing all the gear ratios. The GTO Shaft lowers 1st and 2nd to make them longer, primarily for the Lotus Esprit, and other UN1 boxes. The Lotus Esprit and the majority of other boxes have a 3.89:1 (some are even 4:11) differential instead of 3.44:1 like what the DeLorean has. Given that we already have the lower differential, changing the gear ratios to be even lower always seemed unnecessary to me (and gave up some actual wheel torque).

Last April when Car Fix asked me to be on their TV show to increase the power, and they started saying things like "500hp at the crank shaft," I started getting really really nervous. They even talk about it in the show. Thats why on the dyno, Jared the host said that we weren't going to push it to try and get that big number, because of the concerns about the transmission. Once I knew the episode, along with those performance upgrades were happening, I knew I had to do something. That's when I started modeling, and eventually drawing :reading:...
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I decided that since there was no shaft out there that fit my needs and my budget, I'd design my own. It took almost 8 months to design, find a shop that could do the work, get the tooling, and have the first one fabricated. There is a whole hell of a lot to learn when it comes to gears, especially when it comes to metric helical gears. There were a lot of times where I really wasn't sure if it was going to happen. Still, against the odds, earlier this week my first shaft was delivered!! I spared no expense or engineering opportunity when it came to material used, machining process, heat treatment, and post processing. The end result came out better than I could have imagined. Simply from the look of it, the strength increase is obvious. Shown here is the cross section of my new input shaft, compared to what the stock setup looks like:
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Here are the pictures of the first shaft, along with my huge book of transmission research (assembled over the last 3 years or so), some of the tools (24" vernier and vernier protractor not shown), as well as some of the rapid prototypes I had made to test my gear profiles:
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The shaft is a single piece, designed and machined to be a direct drop into the Renault 369-08 transmission that is in the DeLorean (a hand full of very early cars had the 369-03 which had the different input shaft spline pattern, though this shaft would work if you simply use the standard clutch). No extra specialty tools or modifications are required to install this shaft into a DeLorean manual transmission. The gears are all designed to mesh with the existing DeLorean gears. I did my first test fit of all of the parts and gears assembled on the shaft and everything lines up perfectly! All the gears mesh very well and everything fits just as planned!!
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My goal is to get this shaft installed into my car (unfortunately it probably wont be until after the new year) and then begin testing. By testing, I mean I'm going to drive very very fast, with wide open throttle :biggrin: :burnout: I've been collecting transmissions and now have about 2-3/4 extra transmissions to play around with so I'm not afraid to push it as hard as I can.

Once I'm comfortable with the design, I'm considering making more if there is interest shown. I'll have to really gauge it though since some people are interested in actually buying, where others are just interested in having it available and on the market. I'm not someone that is okay with taking money for pre-orders because of how hairy that can get when it comes to delays, problems, etc. If I'm able to do a run of them, it will be based on what I can afford to have made. Anyway, all that logistical stuff can come later. For now I'm just excited to have the one!!!

For those curious, the shaft is AISI-4340 that is through hardened and tempered with some post machining after heat treat. All of the gears are machined by hobbing. The splines for the clutch and the splines for the 5th gear dog teeth were also machined by hobbing. The 3rd/4th splines are milled and indexed. Both helical gears (1st and 2nd) had their roots and faces shot peened for additional strength. I am also considering having the shaft cryogenically treated for added uniformity and strength.

[Farrar]

:worship:

[David T]

:worship:

It isn't just about going fast. A lot of it is about shock loading. For instance dropping the clutch, spinning the wheels and when they grab the whole system must absorb the shock loading. Because of the length of the input shaft it must be able to twist and not break. You need the right combination of materiel and heat treat to make it ductile enough to twist but strong enough not to break. It is not all about cross-sectional area but as you pointed out that is important too. Every transition becomes a stress concentration point so the "trick" is to make them as gradual as possible. Then there is the logic of having a "fuse" or weak link somewhere in the system by design. Hopefully a part that is easily and cheaply replaceable and it's failure won't cause a cascade failure of other parts. Modeling can only get you so far, after that you must do testing. You are now doing what Legend Industries was up to when they increased the HP of the motor with twin turbos and found they were wrecking input shafts. As you also noted the same input shaft is used in the Lotus. My suggestion is to increase the available market and offer a drop-in replacement to the Lotus community also. I wish you luck but this can be a very expensive endevour.
David Teitelbaum

[Nicholas R]

It isn't just about going fast. A lot of it is about shock loading. For instance dropping the clutch, spinning the wheels and when they grab the whole system must absorb the shock loading. Because of the length of the input shaft it must be able to twist and not break. You need the right combination of materiel and heat treat to make it ductile enough to twist but strong enough not to break.


I agree about shock loading. Thsi was the logic behind going with the 4340. I went back and forth between 8620 and 4340 but 8620 is really good for gears because of it's ability to case harden, but 4340 is higher strength, and is better for shafts. In this case, I had more faith in the design of the gears (they're already a pretty robust design) than I did the shaft. Dont get me wrong, the 4340 is also great for the gears, but it is excellent for the shaft. I found an excellent balance between the strength and izod curve on the 4340 hardening graph that I believe will give excellent results.



It is not all about cross-sectional area but as you pointed out that is important too. Every transition becomes a stress concentration point so the "trick" is to make them as gradual as possible.


I agree, avoiding any kind of neck downs or notches was really important to me. I tried to keep the shaft as consistent as possible without adding any features that would add a "notch factor". The lowest cross sectional area is about 23mm where the first snap ring goes, as opposed to 17mm on the original shaft.



Then there is the logic of having a "fuse" or weak link somewhere in the system by design. Hopefully a part that is easily and cheaply replaceable and it's failure won't cause a cascade failure of other parts. Modeling can only get you so far, after that you must do testing.


I have to be honest, I disagree somewhat with this. It has only ever been on this forum where I've heard people talk about the coupler being a "mechanical fuse". Never on the Lotus, Renault, or GT40 forums have I ever heard someone speak as though the coupler was needed. I agree that in theory this isn't necessarily a bad idea (in some cases), but I dont believe that this is the purpose of this coupler. Truthfully I think the coupler is there for 3 easy reasons:
1. Ease of machining - It's a lot easier to machine two 12" shafts than it is to machine one 24" shaft, espeically when one shaft is simply 2 sets of rolled splines.
2. Ease of assembly - It's easier to assemble the entire gear train on a 12" shaft then it is on a 24" shaft, especially when you're trying to do it at a production rate.
3. Versatility - The Renault UN1 and 369's are both decendants of the 367, which was used in different vehicles that required different length clutch shafts. The 2 piece design easily allows for different length clutch shafts installed. The line also includes the UN5 which has a different clutch shaft than the UN1. Not sure about the UN7, haven't done much research on that.

Plus, look at the picture I posted above of the failed input shaft. It failed because the teeth inside the coupler stripped out, but look at what broke; it wasn't the coupler but instead it was the main gear shaft. The splines failed, so the entire load was going through the roll pin, which simply sheared off the end of the main shaft. Like you said, it was a cascade of failures. That transmission is essentially useless now unless that main shaft is replaced. In my opinion, the coupler in this transmission serves no valuable purpose.



You are now doing what Legend Industries was up to when they increased the HP of the motor with twin turbos and found they were wrecking input shafts. As you also noted the same input shaft is used in the Lotus. My suggestion is to increase the available market and offer a drop-in replacement to the Lotus community also. I wish you luck but this can be a very expensive endevour.
David Teitelbaum

I've thought about trying to expand the market. The difficulty is that the shaft will only work in gearboxes that have the same gear ratios as the DeLoreans (the Renault 369-08). First gear has to be 3.36:1 and second gear has to be 2.06:1. The good thing is that there are a lot of other UN1 and 369 boxes that share those ratios so hopefully it will be possible. It will just be up to the customer and myself to ensure that they have the ratios they think they have. Thanks for the luck!! I've already discovered how expense this can be....

[Josh]

Amazing work Nick.

[BABIS]

awesome work! now you need just a new LSD ;)

[ccurzio]

Very, very nice work.

If this were to become a production item, do you have ANY guess as to what an individual unit would cost?

[David T]

Very, very nice work.

If this were to become a production item, do you have ANY guess as to what an individual unit would cost?


I agree the coupler was never designed to be the fuse. It may just have worked out that way and was a convienient way to modify the transaxle to couple to the PRV. Snap ring grooves are a very high stress concentrator and should be avoided whenever possible. So are holes. Too bad things like this are unavoidable.

[Nicholas R]

awesome work! now you need just a new LSD ;)

It's definitely on my list!! My goal is to eventually create the ultimate DeLorean manual transmission using the single piece shaft, a Quaife Limited Slip Differential, an new clutch from either Centerforce or AP Racing, and a transmission cooler (that I'm also slowly working on).



Very, very nice work.

If this were to become a production item, do you have ANY guess as to what an individual unit would cost?

Tough to say. The tooling and process development for this first one has been pretty expensive. I can't imagine I'll be able to afford more than runs of 3-5 shafts at a time (and even that could be pushing it). At least for now. If I can bring these to the Delorean market, my goal would be to try to get the price to be at least half the cost of the existing shafts that are available (essentially shooting for the $2000-25000 range.) I know that's not cheap but it's better than $5000. I wish I could say that this machining was cheap but it's not; at least not at the quality I'm looking for. Especially when you add all the heat treatment and post processing.

Time will tell. I'll start with small runs so that if there ends up being no interest, hopefully I won't be out too much.

[Nicholas R]

If I can bring these to the Delorean market, my goal would be to try to get the price to be at least half the cost of the existing shafts that are available (essentially shooting for the $2000-25000 range.)

I meant for that to be $2000-$2500 not $25000, haha. Hopefully I'll have a better idea in the next few weeks/months, right now it's way to soon to say.

[Dangermouse]

Very impressive work Nick.

Even though I am fortunate to own an auto and am a member of the "more than 130HP in a sports car is crazy talk" club, ( :angry_whip: ) I am constantly amazed by the stuff you do

[Nicholas R]

I installed the shaft into a transmission to ensure that everything lined up, meshed well, and that all of the splines worked well. The clutch is a stock clutch to prove that the splines are correct. The idler pulley bearing in the photo also has the same dimensions as a DeLorean pilot bearing.

Thus far everything still looks great. Also made a quick video showing the shaft in the box with the differential.

Unfortunately because of my schedule right now, it's unlikely I'll get a chance to install the new shaft into my car until after the new year so no testing until then.

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https://www.youtube.com/watch?v=QNTqEuTY5ZI

[tommyrich]

Nick, that is truly amazing! You were just talking about your idea of building a one pice shaft at DCS in June. Very nice work.. As usual.
Tom

[Shuttleman]

This is really impressive! You can add me to your customer list. Thanks for taking time to share your work with us.

[Mark D]

Great job Nick, your work here is really impressive. I wish I could say I was interested in buying one but my car is bone stock and I doubt I'll be in need anytime soon. Hopefully you find enough interest to at least do a small run and make a few bucks for all your hard work.

[Nicholas R]

Nick, that is truly amazing! You were just talking about your idea of building a one pice shaft at DCS in June. Very nice work.. As usual.
Tom

Thanks Tom! That means a lot!! After I got home from DCS I really started digging in on refining the design. I bought a couple gear books and with every chapter I would read, the drawing would change, haha.

[Buntedii]

Hello sir,

Did you ever finish this single.piece shaft?

Frank

[Henrik]

Hello sir,

Did you ever finish this single.piece shaft?

Frank

I don't want to speak for Nick but his favorite machine shop is closing so he may not take his one-piece input shaft into production:

http://dmctalk.org/showthread.php?12119-One-Time-Opportunity-Upgraded-(“bulletproof”)-transmission-coupler-order&p=188966&viewfull=1#post188966

[Nicholas R]

I don't want to speak for Nick but his favorite machine shop is closing so he may not take his one-piece input shaft into production:

http://dmctalk.org/showthread.php?12119-One-Time-Opportunity-Upgraded-(“bulletproof”)-transmission-coupler-order&p=188966&viewfull=1#post188966

Henrik is correct. At the moment, I do not have a timeline on when the shafts would be complete, or if the will be complete, as I no longer have a shop to work with.

I should be back in the country in early March and am hoping to get the shafts that were in process; they are about 95% complete. As of now, all of the gears have only been hobbed, meaning the gears are rough, and potentially slightly distorted by the heat treatment. It is customary to finish the gears by either grinding or shaving, to ensure the correct profile, and ensure that they run quietly. Unfortunately this is one of the most difficult and precise processes, that is made more difficult by the fact that the shaft is so long. The shop did not have the ability to finish grind a shaft of this length in house, and we were going to work to try to find someone that could do the finishing process.

The shaft that is installed in my car, was hobbed, heat treated, shot-peened, and hand finished and polished by me, and you can still hear some slight whine in first and second gear (more so during engine braking than under acceleration). It's similar to how a Muncie M22 "rock crusher" transmission sounds, though not nearly as loud. It doesn't bother me to run with it; in fact I feel like it makes the car even more "mine," but unless I can finish the gears to where they run as quiet as stock, I don't think I'd be comfortable selling one. This all being said, I am sure though that it is no where near as loud as the GTO Racing or Holloway Shaft is in first gear, as the first gear on those is straight cut. If you think of the whine the transmission makes while in reverse, that's what it will sound like to run a straight cut gear set (reverse is straight cut in almost all transmissions).

Thanks for the interest, I'll post updates if/when they occur.

[Drive Stainless]

Is this available?


Sent from my iPhone using Tapatalk

[Josh]

Is this available?


Sent from my iPhone using Tapatalk

I believe Nick never got this to the point where he was comfortable selling it. Not to say the end result was bad, but he has very high standards.
He is using it in his car though.

[BLWNAWY]

It has only ever been on this forum where I've heard people talk about the coupler being a "mechanical fuse".... I don't believe that this is the purpose of this coupler.

As the original designer of Toby's "Bulletproof Coupler" in 2000, necessitated when my supercharged Chevy-powered BLWNAWY tore the splines out of its coupler "accelerating briskly" in 3rd gear, I may be to blame for starting that "fuse" line. I attributed the fact that the stock coupler splines do not go all the way around to being an intended "weak link", which would hopefully prevent damage to more expensive parts as it did in my case. (In my defense I'm an Environmental Engineer, not a Mechanical one.) I don't even know if Toby still sells his couplers, but when I did the cost was minimal, somewhere around $450. I greatly applaud your efforts to come up with a one-piece shaft. I did not have the financial or mechanical resources to try that, although I certainly considered it. At your projected $2,000-$2500 cost I would not hesitate to use your one piece shaft if I were going the high HP route today. Bravo.

[Josh]

As the original designer of Toby's "Bulletproof Coupler" in 2000, necessitated when my supercharged Chevy-powered BLWNAWY tore the splines out of its coupler "accelerating briskly" in 3rd gear, I may be to blame for starting that "fuse" line. I attributed the fact that the stock coupler splines do not go all the way around to being an intended "weak link", which would hopefully prevent damage to more expensive parts as it did in my case. (In my defense I'm an Environmental Engineer, not a Mechanical one.) I don't even know if Toby still sells his couplers, but when I did the cost was minimal, somewhere around $450. I greatly applaud your efforts to come up with a one-piece shaft. I did not have the financial or mechanical resources to try that, although I certainly considered it. At your projected $2,000-$2500 cost I would not hesitate to use your one piece shaft if I were going the high HP route today. Bravo.

Nick also made a run of these couplers in 2016, since they were no longer available. I use them with my LS swap kits with great success.

[Nicholas R]

Is this available?

No it is not.

Outside of use in my own vehicle, it's unlikely I'll be selling any of these. Liability is too high, production cost is too high, and the market is too low.

Also for what it's worth, after the coupler, the next weak point in the transmission is the cast aluminum case. I've got a set of cracked case halves in my garage to prove it.

[MikeWard]

It might be worth checking with GTO Racing in the UK, I believe they sell an uprated input shaft.

https://www.gtoracing.co.uk

[Nicholas R]

It might be worth checking with GTO Racing in the UK, I believe they sell an uprated input shaft.

https://www.gtoracing.co.uk

Indeed they do; if someone has sincere interest, I think they're worth looking into. Just be aware that the kits are primarily designed around the UN1-027 that was installed in the Lotus Esprit V8. With their kit you actually get different output shaft gears as well for 1st and 2nd because 1st is straight cut (so you're going to hear it loudly), and the ratios for both are altered to increase the length of the time in the gear. This is because the UN1-27 has a lower rear end ratio (3.89:1) than the gearbox used in the DeLorean (3.44:1) so 1st and 2nd are even shorter. The other thing to be aware of is that these gearboxes used a different thrust bearing setup on the fifth gear side of the input shaft. Instead of the single double thrust ball bearing, they used two tapered roller bearings (similar to the way the output shaft is setup). This would need to be accounted for if fitting into the DeLorean.

None of this is to say that the shafts aren't usable, just to be sure to ask the right questions when ordering and know what you're getting into.

With all that being said, there are still limits to the strength of the case of the gearbox. I've heard them say 500hp cars run these. Personally, I cracked a case of a DeLorean (Renault 369) gearbox with the power shown in the dyno sheet in my signature. (Granted the case of the UN1-027 box is known to be a bit stronger because of the different thrust bearing configuration).

[BladeBronson]

None of this is to say that the shafts aren't usable, just to be sure to ask the right questions when ordering and know what you're getting into.

These are the questions I'm going to ask of the guys at gas stations that tell me I "need to LS swap that thing!". You guys are famous. :)

[Holley'dDMC]

No it is not.

Outside of use in my own vehicle, it's unlikely I'll be selling any of these. Liability is too high, production cost is too high, and the market is too low.

Also for what it's worth, after the coupler, the next weak point in the transmission is the cast aluminum case. I've got a set of cracked case halves in my garage to prove it.


If possible, what would it take to get one from you? Ill happily sign a liability waiver. I could pay the machining cost, or whatever...
Im building a big-bore, high compression, high rpm prv thats going to be putting down power. The kit from gto racing is far too questionable to try to use in the 369, yours would be the most ideal.
My coupler broke recently and I really dont want to go back together with the same thing.

[Josh]

If possible, what would it take to get one from you? Ill happily sign a liability waiver. I could pay the machining cost, or whatever...
Im building a big-bore, high compression, high rpm prv thats going to be putting down power. The kit from gto racing is far too questionable to try to use in the 369, yours would be the most ideal.
My coupler broke recently and I really dont want to go back together with the same thing.

I linked this thread to you for reading, Not to try and convince Nick to sell you an input shaft. He has said more than once he is not selling them, and I told you this as well. I do not understand why you think this is an opportunity to purchase.
Like I mentioned in email and this thread i use couplers on my swaps and they are adequate. No need for much more than that especially if you are keeping the PRV.

[MikeWard]

The kit from gto racing is far too questionable to try to use in the 369
:hmm: it has already been used successfully in a 369 by at least one owner in the UK, and having driven his car I know it drives a lot better with the uprated parts. As Nick mentioned though the straight cut 1st and 2nd gears are noisier.

[Helirich]

I linked this thread to you for reading, Not to try and convince Nick to sell you an input shaft. He has said more than once he is not selling them, and I told you this as well. I do not understand why you think this is an opportunity to purchase.

This is a strange response. Why are you concerned with this guy trying to offer Nick money. Nick can give him an unrealistic price or he can tell him to buzz off, but I think that's his option. Maybe this guy is willing to have the shaft completely reengineered, but would like to give Nick a chance to recoup some of his money/time. Maybe they will come to another agreement for just drawings. As far as unrealistic, what's unrealistic to you or me might not be unrealistic to him.

My wife has a bunch of original paintings she has collected over the years displayed in our restaurant. Every once and awhile someone wants to buy one. She says their not for sale. I tell her "set a price that you would be happy to sell at". She says "no one would pay that". I say "well then you won't sell it and that's what you want". She finally gave in and set a price on every painting. You can guess what's next. Three of them sold. She (and I) was flabbergasted.

[Josh]

This is a strange response. Why are you concerned with this guy trying to offer Nick money. Nick can give him an unrealistic price or he can tell him to buzz off, but I think that's his option. Maybe this guy is willing to have the shaft completely reengineered, but would like to give Nick a chance to recoup some of his money/time. Maybe they will come to another agreement for just drawings. As far as unrealistic, what's unrealistic to you or me might not be unrealistic to him.

My wife has a bunch of original paintings she has collected over the years displayed in our restaurant. Every once and awhile someone wants to buy one. She says their not for sale. I tell her "set a price that you would be happy to sell at". She says "no one would pay that". I say "well then you won't sell it and that's what you want". She finally gave in and set a price on every painting. You can guess what's next. Three of them sold. She (and I) was flabbergasted.

That's strange, I did not recall asking your opinion. You are not familiar with this situation so I do not see how you feel qualified to evaluate it and criticize my actions. Not all things are for sale.

Even if this was a sellable item, considering Ezra asked me to quote out $400 worth of parts for him then tell me it was out of his budget, he does not have a bottomless pit of money for a input shaft coupler. I can understand of someone changes directions and does not want to buy something, but please dont BS me.