So I've finally done it. I've completed a VW conversion of my drive train. As far as I know, I'm the only person to have completed one. So why would anyone do such a thing?
Firstly, I think the stock stub axles are the weakest parts of a Europa. They were originally designed for a 50 hp family sedan that competed with the 1100 cc Mini Cooper. They were used on some small formula cars but they are not hardened and so I think they are merely adequate for a Europa. I've heard of people driving down the road only to see a rear wheel pass them by. I wouldn't say it at all common but it's not unheard of. I've had the experience where one of my stock stub axles had a groove worn into it by the inner race of the outer bearing. I suspect that my wider tires (205/50-15) may have been an aggravating factor.
I've already said some of what I'll post here in other threads but I think/hope that constructing a narrative from start to finish will be more useful to those contemplating their own conversion. So let's get started.
Upper link or twin link mod
This conversion, or any CV joint related mod and twin link rear suspension mods go hand in hand so the first step is to implement a twin link rear suspension. There are a couple of threads that spell that out how to do that and there is a twin link kit for those who are a bit less adventurous. Those are referenced below. This has to be done first because you'll need to measure clearances for the rest of the conversion.
The drive flange
Starting from the tranny, you'll need a drive flange that fits the splines on the tranny output shafts. You'll have to fabricate the flange from some splines which are available from inner u-joint yokes or a Renault CV joint from a Fuego, for example. Those splines will have to be welded to a flange drilled for the CV joints you are using (attached pictures: drive flange back, drive flange depth, drive flange face, and drive flange with CV joint show my drive flange as an example). The mounting surface should allow the axle and inner race of the CV joint (sometimes called a “cross”) to “plunge.” Picture drive flange depth shows the depth of the drive flange. The EMPI catalog lists transmission drive flanges. They can be modified by welding Renault splines on them. This is tempting but I believe that they are deeper than they need to be for our purposes and thus would require the use of a shorter half shaft and given the width of a Europa, you'll probably need one of the shortest half shafts you can buy off the shelf so a deep drive flange may require a half shaft shorter than commonly available. That is just conjecture. I don't want to dissuade anyone from investigating their feasibility. More about half shafts later. I should note that in Andy's thread (referenced below), he shows a picture of a drive flange (he calls it a “CV adapter) that he got from Banks (now Lotus Supplies) That flange is not listed on the Lotus Supplies website. I believe it was a one-off that Richard machined for Andy and so it is probably not something to count on. I also understand it was pretty expensive but it might be worth inquiring about them.
CV Joints
I was unable to find any information on the torque capacity of different CV joints. Since I have no concrete torque capacity data I'll list some data points I came across in my investigations.
A fellow at Blind Chicken Racing (a link is provided below) suggested the VW Type 1 CV joints were good for about 100 hp. SwiftDB4 sent me a pair of used CV joints which were the same size as the Type 1 joints (94mm OD) and probably came off his old Formula Atlantic race car (their engines are generally good for about 240hp). He also showed me a vendor who listed the 94mm CV joint as appropriate for “FT”. We both agreed that referred to Hewland FT200 transaxles which is what is used on Formula Atlantic cars. Another listing on Pegasus Auto Racing Supplies (
https://www.pegasusautoracing.com/productselection.asp?Product=1471) suggests they are appropriate for Hewland Mk 8 and 9 transaxles (commonly used for low hp Pinto engine race cars. eg. Formula Ford or Sports 2000) but also for use in Formula Mazda (their motors produce around 180hp). I would say the Type 1 sized CV joints (94mm OD; sometimes called 90mm joints) are surely good for most engines most of us would likely put in a Europa (excepting kram350kram, of course!). As usual, another consideration is quality. Probably the best brand is Lobro/GKN. I suspect they probably outperform other brands (eg. EMPI), but I have to guess. I should also point out that Lobro/GKN CV joints are provided by Pegasus in two versions (Standard and Heavy Duty which they claim has a higher torque rating). There are lightened and lapped joints that would probably not be of interest to us. Having said all that, it is likely that available space will determine the size of your CV joint. With the design of my twin link rear suspension, I could not use an outer CV joint any bigger than 94mm in diameter.
Lastly, another thing to consider is failure mode so you (I) can be on the lookout for CV joints failing (possibly at an accelerated pace due to lower torque resistance). Investigating on the Internet, things to be watching for are: a humming sound – even at lower speeds, the mild bouncing at high and low speed and feels like a worn-out or imbalanced tire, and a knocking sound from the area of the CV joints. It is unlikely that they will explode or otherwise come apart which is a very comforting thought to me as I should be warned long before a potential catastrophic failure.
If you have a stock TC or similar motor, you should easily get away with a VW Type 1 CV joint from most suppliers. If your engine produces more torque, you might want to consider larger CV joints to be safe if there is room for them. If there isn't room for larger joints, you might want to go up in quality and maybe get them from a racing products supplier as they are likely to take more torque than a similar sized street CV joint. Dimensional information on various CV joints sizes is available from Blind Chicken Racing (see link below).
The mounting bolts for CV joints come in a few different sizes depending on the flange they are mounted on. In general, the mounting bolts screw into the flange on your stub axle. In the case of my drive flange, a 5/16” bolt and a nut are used. For the Type 1 stub axle flange, they require M8x1.25 48mm long bolts. They should be used with what is called a “torque distribution” or “torque thrust” washers.
