Another I can do it cheaper project. I noticed these Lotus Elan CV Diff Output Shafts on Ebay that were listed for a very long time, so I decided to ping the seller to ask what they were all about. Apparently he manufactures these CV Axles for various distributors and these were his old stock. He had redesigned the kit and says the new kit is stronger, but also said he couldn't get the old design VW Beetle Type 1 CV shafts any longer which may have been the real reason. He also told me that he had a few outboard adapters as well that he was willing to sell me. The only thing he wouldn't supply was the axles, but was very helpful in letting me know what I needed to do. Basically, all I had to do was find some 1970's VW Beetle axles and cut them down and weld them together to make a shorter 12" axle.
Now I could have just made the two adapters on both sides of the axle to attach them to the OEM diff output shaft and outboard stub axle, but the 3 prong diff output shaft has a tendency to break, and with the additional load I didn't want to take the chance. Plus why re-invent the wheel. The seller offered the two output shafts and the two adapters for $388 shipped. Both items were very well made. So back to ebay in search of a pair of Beetle CV Shafts.
The differences in the original version of the shafts and the ones available today was a circlip that held the CV joint on to the axle. Seems that on the Beetle, this was not necessary and it was ok for the CV joint to side back and forth on the shaft, so that feature was removed. Found a ratty but complete pair on ebay for $60 shipped.
Disassembly of CV shafts has to be one of the dirtiest, grimiest, jobs you can ever do. But everything came apart and the splines were in good shape.
First step was to cut the shafts down to 6" lengths to achieve a 12" OVL. But what didn't expect, was that the shafts are made from hardened steel. I had used my cut off band saw to no avail. It barely put a scratch on the surface. Once I realized what I was working with, I had to resort to my die grinder with a cut off wheel. I jigged the shaft on my lathe and slowly carved away the shaft with the die grinder. Lots of sparks and cut off wheels later, I had the shaft in two equal 6" lengths. I had spoken to several people who had successfully butt welded these shafts together, but I was concerned with keeping the shafts true and didn't trust my Tig welding skills to rely on just a Butt weld. So I came up with an idea of a sleeve that was friction fitted to the two shaft halves. The OEM shaft was about 25mm in diameter, or 0.982", and since I didn't have any large metric drills, I had to make the sleeve with my 15/16" drill or 0.9375", which meant I had to mill the hardened shafts down by 0.040", easier said than done, especially when the hardening is hardest on the surface. Finally turned the shafts down to the correct size, but I had to mill down the boot stops, as the sleeve I was making was 4" long. Concerned that the boot would not fit over the sleeve, I milled the 1.375" diameter sleeve down on both sides to around 1.15" which still gave me about an 0.20" wall thickness at the thinnest point in order for the boot to stretch over. But now, if I just welded at both ends, the milled sections may act as stress risers and could easily shear at those points. So directly 0.5" off center on both sides, I drilled 6 3/8" holes and counter sunk them for plug welds. Perhaps over kill, but I do not want to make these things again.
There has been a lot of discussion on how to weld hardened steel, from using Stainless steel wire, to special pre heating and cooling methods, but very little on how to fuse mild steel with hardened. While there was no one consensus of welding hardened steel, the one thing everyone agreed on was the use of a lot of heat and Tig was the preferred method. So the best method we came up with was to directly tig the shaft and then move on to the mild steel as so we did not melt it. I plug or rose welded each axle half in three spots and welded around the sleeve ends. I think this will be more than adequate for what I am using it for. My friend Holgar Ahl has butt welded these shafts on Formula Ford and B cars with no issues. Another spin on the lathe to insure that the shafts were still true and we are good to go.
A nice coat of paint will prevent future rusting, although only the middle 2" will be exposed to the elements. Green was handy.
The CV Joints and boots on the used shafts may have been good enough, but again, I didn't want to repeat this job. I found a new kit of Genuine Lobro GKN CV joints, boots, bolts, and washers, all made in Germany for $60 on ebay, so I bought 4 new kits. Plus shipping, all in cost was $262.00. I also found an EMPI set at half the cost, and others even cheaper, but decided not to cheap out. And this is the reason why. The original CV's was most likely over engineered for the 60 hp Bug, perhaps by over 200%, but when you start trying to economize to get to a much lower target price, you have to cut corners. And with only 60 hp to contend with, you can cut down a lot. Plus some manufacturers has lowered the bar so much, that reports have indicated some failures within a year on a 60 hp Beetle. Plus, if you see the the kit GKN provides, it has everything you need. Specifically the snap rings and washers. The snap ring on the left is the OEM type and the concave washer on the right with the serrated edges is OEM as well. The second set of snap rings and washers that came with the kit is what you want to use. The OEM stuff requires a special press in order to squeeze down the CV in order to get the thick snap ring on. The second set allows you to just slip on the parts and assemble it without the aggravation.
As you can see, the OEM washer sits on the splines whereas the second washer supplied sits on the shaft base. This is about 1/8" difference. Even with the new washer, the circlip supplied is about half the thickness of the OEM and just barely fits in place.
Another reason for getting the GKN kit was the boots. The boots supplied are thick high quality rubber. I had to use two screw drivers to wrestle the boots over the sleeve with lots of WD40. The boots stretched into place perfectly. Overall, a fun project. Outside of the mess for disassembling the used axles, everything else was straight forward. Some thinking and planning was involved, and the hardened steel threw me for a few minutes, but I believe the solution I came up with was adequate if not over engineered for a 135 HP car. Cost for the project was $388 for the diff output shafts and adapters, $60 for the used shafts, $262 for the CV's, and $15 for the steel bar stock used for the sleeves. Total cost is $725 compared with the going rate of $1,600 for the set. Over a 50% savings plus all the fun building them.