# Tesla Model 3 Driveshaft Adapter



## EV-FAN (May 17, 2021)

In the process of converting my Jeep, I ran into the problem of adapting the Model 3 drive unit to a driveshaft (and eventually to the solid axles. I thought the problem deserved its own thread as it ended up being a challenge and has broader potential interest.

I was [told] that for the Model 3 motor, the only current option is to use the stock driveshaft stumps.


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## EV-FAN (May 17, 2021)

The OEM axle end did not appear to lend itself to adaptation to the solid axle pinion (on the Jeep axle).


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## EV-FAN (May 17, 2021)

I disassembled the outboard end of the OEM axle.


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## EV-FAN (May 17, 2021)

I measured the outboard spline with the hope that it would be a standard cv. The spline measured close to 27mm and has 33 splines. Upon research, I found a cv that happened to have that spline specification. 






Lobro CV Joint, 6 Bolt, 78mm Bolt Circle, 33 Spline - Pegasus Auto Racing Supplies


Our CV joints fit Hewland and Webster Mk 9, Staffs, Formula Mazda, and some LD200 racing gearboxes. Available in Standard or high-torque Heavy-Duty versions.




www.pegasusautoracing.com





I ordered one and tried it out. It did press on with a light press, but the splines did not seem quite right. (Also, some modification would have to be made even if this route was chosen, as the snap ring groove landed within the cv splines.)

Ultimately, I decided this route was not going to work for me as the axle lengths were too far from what I needed anyways (not to mention the questionable spline compatibility).


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## EV-FAN (May 17, 2021)

At this point I decided to make a custom piece that would allow for a 2" driveshaft to be used with the OEM Model 3 tripod joint.


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## EV-FAN (May 17, 2021)

I was able to have a custom adapter made out of hardened 4340 that reuses all the pieces of the factory tripod joint, even the factory cv boot. I plan the preheat the adapter and the driveshaft tube before welding to ensure a good weld. The adapter was made for use with 2" O.D. 0.120" wall driveshaft tubing so that it will work with the 1310 double Cardan joint I have for the other end of the driveshaft.


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## EV-FAN (May 17, 2021)

The factory tripod joint outer housing and bearings are reused.


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## EV-FAN (May 17, 2021)




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## D&VsEVJeep (Dec 9, 2021)

This is great. We almost went with a Model 3 PU like this but choose a more "conventional" solution to ease these types of issues. I assume you swapped the Model 3 gearset and installed a LSD too?


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## EV-FAN (May 17, 2021)

D&VsEVJeep said:


> This is great. We almost went with a Model 3 PU like this but choose a more "conventional" solution to ease these types of issues. I assume you swapped the Model 3 gearset and installed a LSD too?


Thanks! I plan to install a spool once I get the motor working good in the stock configuration. I kept the stock gearing and bought super high axle gears (2.73:1).

Here’s my Jeep build thread:








Jeep Willys Tesla Build


I am converting my grandfather's M38A1 Jeep Willys to electric (as well as restoring the jeep). Some features include: Tesla Model 3 drive unit; narrowed Dana 44 axles from a 1975 Jeep Wagoneer; Jeep YJ leaf spring conversion; Orion 2 BMS 132s; and, a Chevy Volt battery pack. I am just...




www.diyelectriccar.com


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## bronco_zed (Dec 21, 2020)

I'm putting together a similar setup and I contacted The Driveshaft Shop to get a flange adapter made : <[email protected]>

I had to send them the Tesla tripod joint cup and flange that I wanted to use, but they could probably do the same with a CV yoke instead of a flange. Cost about $300 in labor for two of them:


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## Lowcoe (Jul 3, 2020)

I had the cup turned down to just the splined shaft and then had a flange added on that mated to the original Land Rover drive shaft bolt pattern. The machinist said the metal was hardened and very difficult to cut down without a special lathe chisel.


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## EV-FAN (May 17, 2021)

I thought I should update this thread with some photos of the finished driveshafts from over the summer.


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## EV-FAN (May 17, 2021)




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## remy_martian (Feb 4, 2019)

Mixing the cardan and the trilobe from the CV joint may be futile. I don't think you can phase a mix, so they might as well not be there at all if I'm right.

I believe you need the same degrees of movement at each end of a solid shaft. So cardan at both ends, or trilobe at both ends. Maybe I'm wrong, but there's something rotten in Denmark about this setup, imo.

Are you going to weld the spiders or machine a spool for the drive unit? I don't think anyone makes a limited slip diff, or do they?


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## piotrsko (Dec 9, 2007)

I believe Remy is correct that it's going to have some sort of terrific shudder/vibration because of mixed modes.

You can get by with one at the transaxle end if you accept the associated wheel swinging up and down in an arc like a swingaxle VW


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## brian_ (Feb 7, 2017)

EV-FAN said:


> View attachment 133786


I see that's a double Cardan joint at the axle end. Does it need support on each side to stay aligned properly, or does it have a centring device intended to work in this configuration?

For who are concerned about mixing the tripod CV joint with a U-joint (a.k.a. Cardan joint)... this is not just a U-joint, it is a double Cardan joint, which is two Cardan joints appropriately phased, acting as a CV joint.


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## piotrsko (Dec 9, 2007)

brian_ said:


> For who are concerned about mixing the tripod CV joint with a U-joint (a.k.a. Cardan joint)... this is not just a U-joint, it is a double Cardan joint, which is two Cardan joints appropriately phased, acting as a CV joint.


Notice carefully the appropriately phased requirement. My driveshaft machinist didnt.


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## brian_ (Feb 7, 2017)

brian_ said:


> I see that's a double Cardan joint at the axle end. Does it need support on each side to stay aligned properly, or does it have a centring device intended to work in this configuration?
> 
> For who are concerned about mixing the tripod CV joint with a U-joint (a.k.a. Cardan joint)... this is not just a U-joint, it is a double Cardan joint, which is two Cardan joints appropriately phased, acting as a CV joint.


In case this isn't clear, a double Cardan type CV joint has something (typically a spherical joint) in the middle to keep the two sides of the joint (the two Cardan joints) at the same angle... and of course correct phasing is ensured by the one-piece centre section which acts as one yoke for each of the two joints (Spicer calls it the "center yoke"). A example:
Dana Spicer 920648 Double Cardan CV Head

I assume that this is the type of joint being used here, in its intended application in a propeller shaft.


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## EV-FAN (May 17, 2021)

brian_ said:


> In case this isn't clear, a double Cardan type CV joint has something (typically a spherical joint) in the middle to keep the two sides of the joint (the two Cardan joints) at the same angle... and of course correct phasing is ensured by the one-piece centre section which acts as one yoke for each of the two joints (Spicer calls it the "center yoke"). A example:
> Dana Spicer 920648 Double Cardan CV Head
> 
> I assume that this is the type of joint being used here, in its intended application in a propeller shaft.


Yes, exactly!
The version I used is:



https://www.summitracing.com/parts/sdh-923289




I tested the driveshaft--on the car--up to 1,700 rpm driveshaft rpm. The car was up on jack stands for the test. (Maximum driveshaft rpm in my application will be right around 2,000 rpm.) The driveshaft ran really smooth with no abnormal noises or vibrations. Under load: the car has only been driven up to 10 mph, but there were no abnormal noises or vibrations. More testing to follow.

After a lot of searching I discovered that some of the 1995-1997 Jeep Grand Cherokees used a front drive shaft with a double cardan joint on one end and a Rzeppa cv on the other end: 









Crown Automotive 52099260 Front Drive Shaft for 96-98 Jeep Grand Cherokee ZJ with 4.0L Engine & NP249 Transfer Case


33.50" Collapsed Length.




www.quadratec.com


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