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:
Old Shaft.jpg
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:
Broken 4.jpgBroken 1.jpgBroken 2.jpgBroken 3.jpg
For reference, this is what the stock shaft normally looks like (the splined end isn't broken):
103056.JPG
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 ...
New Shaft.jpg
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:
Original Shaft Assembly Cross Section.jpgNew Shaft Cross Section.jpg
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:
Shaft 1.jpgShaft 3.jpgShaft 2.jpg
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!!
Shaft 5.jpgShaft 4.jpg
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 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.