axles and cv joints

so long story short, i broke the passenger side inner cv joint. already have a solid mount so transaxle movement wasnt the cause. so right now im tossing a parts store axle in the car for the time being and starting to plan on something better.

so my initial plan was to start with a pair of Empi chromoly shafts. now from my understanding the xschop shafts are these with an inner snap ring groove cut in them. im able to cut the groove in them myself, but there seems to be some contradicting info out there weather it needs the inner groove or not. some people say its better to run no inner clip to allow the shaft to slide in the joint to prevent it from binding, however i would think on a car it would be better to hold the joint in place. any thoughts on this?

joints is the next question, seems to be a lot of varying opinions here, and its hard to pick out whats best for a car as most discussion is for buggies. i was looking at the empi high performance/off road type 2 joints, and i read that they are "looser" for higher angle operation. now does that mean looser as in a sloppy joint with a ton of lash in it that will translate to a noisy driveline? i read others prefer to run an empi non race joint, but put a chromoly cage in it, although i cant find specifics of what cage to run, i was under the impression the chromoly cage from the high performance joint wouldnt fit as it had larger balls than a type 2 joint. another option is gnk joints, i read they are a higher quality joint, but cant seem to find how they stack up strength wise against other options.

something else ive come across is the lindsey racing/drive shaft shop 930 conversion, not that i would go with their parts, but it brings up the idea of building axles using 930 joints. i see they are just using adapter plates to convert the outputs and stubs to accept the 108mm joints, and while that does work it adds another possible failure point. i cant seem to find any info on if there is a stub shaft that fits the 944 (85.5+) or trans outputs for the 016 trans that accept a 108mm joint without adapters.

id like to get some input on aftermarket/upgraded axle setups. what are you guys running (thats not stock)?

I am also interested on where this topic lands!

How did you end up breaking yours? I have been putting 400 whp through mine now all summer but next summer I am moving to 525 whp so the driveline is always on my mind.

Thanks

broke it at the dragstrip. after a couple easy runs with terrible 60' times i decided i needed to try and get it off the line a little faster. tried to slide the clutch out and feed it throttle and while doing that the turbo spooled up real quick and it left freaking hard. at the top of first gear is where it let go. the general consensus seems to be that it broke from binding up because it squatted so hard, not from over powering it. the cage is what broke.

that being said, i dont want to rely on stock components in the future. i dont subscribe to the theory that the cv axles should be considered a fuse in the drivetrain.

I agree, if I could get stronger axles that would hold up to just about anything I would! Then somehow get a trans to hold up to more. Side note, I have been following a guy on facebook 944 outlaws page drifting his 944 with 800hp on a turbo trans so far it is holding up.

well, ill give you guys the rundown on what ive sorted out so far

there are 4 types of vw/porsche cv joints that are very common, you can see the breakdown here http://blindchickenracing.com/How_to/CVJoints_Axles/cv_joints_101.htm

type 1 is old vw, its a 94mm joint and is of no use to us, so we wont discuss it. our cars use a type 4 joint, they are very close to a type 2 joint, but a slight bit thicker. also note a type 2 joint is commonly called a bus style joint as they were common on a vw bus. both the type 2 and type 4 joint are 100mm diameter and can be interchanged. vw/buggy guys like to use factory type 4 joints as they give a little more angle than a type 2 joint. the common type 2 and type 4 joints are 33 spline, the 944 up till around 87 used the 33 spline stuff, after that they went to a 25 spline. no real reason i can find for the change aside from its the same joint a bmw used in that era.

the nice thing about our cars using vw stuff here is that the buggy world has lots of aftermarket parts, and some can be used here. Empi is a major brand that makes chromoly axles (im pretty sure the axles XSchop used to sell were these axles with the additional groove cut in them) and high performance joints. below is a link to the empi axles
https://www.dansperformanceparts.com/off-road/off-road-rear-suspension/irs-axles-acc/21-3-8in-axles-33-spline-pr.html

these shafts are the same length give or take a hair as a stock axle at 21 3/8". they are 4340 chromoly, that material is designed to "wind up" so they will absorb some of the shock load. these axles are completely straight, no bumps or grooves for the boot to locate, this eliminates a failure point of the stock axles as any groove or raised part is a stress point. as i mentioned earlier, you can see there is no inner snap ring groove on these shafts, with long travel suspension in a buggy they prefer to let the splines slide on the joint to prevent the joint from being pushed apart. like i mentioned above, not really sure on this for a car, i think id rather the joint not slide around on the axle, so an inner groove needs to be cut by a machine shop.

as for joints, there are a few options. bellow is a GNK/Lobro joint, these are considered a high quality replacement joint
https://www.dansperformanceparts.com/off-road/off-road-rear-suspension/cv-joints-accessories/latest-rage-501331211-cv-joint-bus.html

empi makes a replacement joint as shown
https://www.dansperformanceparts.com/off-road/off-road-rear-suspension/cv-joints-accessories/cv-joint-new-vw-202.html

now we get into the most common "high performance" type 2 joint made by Empi. it uses hardened inner and outer races, larger .750" balls and a chromoly cage. these are also made to give more angle, said to be a max of 25 degrees (opposed to 17 degrees for a type 2 and 22 degrees for a type 4), however ive read this is due to looser tolerances, but cant seem to find out if this joint suffers downsides because of it.
https://www.dansperformanceparts.com/off-road/off-road-rear-suspension/cv-joints-accessories/empi-type-2-cv-joint-ea.html

there isnt a whole lot else i can find in the type 2/4 joints, generally if those are insufficient people step up to a 930 joint in a buggy. the type 2/4 joint and the parts ive shown above can be used to build a complete bolt in axle for 85.5+ 944 cars (i think even a 924s as well), combined with the right boots and snap rings. i think for most people the chromoly axles and a good set of joints will make a strong enough axle where its no longer the weak point, and you need to be more worried about the trans.


now ill touch on the 930 joints a little. these are not a bolt in option for our cars. the 930 joint is 108mm diameter. these are a very strong joint and has a huge amount of aftermarket behind them as they are very popular for sand rails, along with high performance cars. these joints use a larger axle with 28 splines and have a max angle of 25 degrees for a stock style joint. the top level lindsey racing axles for our cars use 930 joints, and they use an adapter bolted to the stub shaft and trans output to allow the larger joint. changing the stub shafts would be a better option, im trying to sort out if using a 911 stub shaft is possible, or if any of the aftermarket "micro stubs" will fit the 944 hub, im having a lot of difficulty finding the dimensions i need for our stock parts so i can compare (just need to take my car apart and do some measuring). im fairly sure there is no 930 style output available for the 016 style trans so an adapter would be needed. really the 930 joint is overkill for most 944 builds, but it is possible, but if i were to do it id like to not use adapters on both ends and rather have a proper stub shaft if at all possible.

How much squat does your car have? Fix that first.

Xschop makes the 930 adapters. They are top quality. I have purchased a set for my stub axle location. I then purchased a set of new stub units that fit my Z06 trans that are 930. I did purchase the empi 930 cvs complete kit. Now it will be rob to make the axles. Should be as close to bullet proof at this point.

robstah wrote:How much squat does your car have? Fix that first.

obviously too much lol. i have a set of vw bump stops on the way that ill be putting on it.

i was hoping to avoid running adapter plates at both ends, if i could find a stub shaft that fits the late 944 that runs a 930 cv i would go the 930 route. i think any extra angle the 930 joint gives would be negated by the axle being 1-2" shorter. im sure the hardened type 2 joints with the chromoly axle will be strong enough, but i figured if im going this far anyways, may as well look at the 930 route. also, for some reason i can see myself ending up with a corvette transaxle in the future, and if thats the case it would be nice to already be using 930 joints.

what empi cv joints did you get? are they the factory style replacements, or the hardened "off road/performance" style?

i purchaced the chromemoly units. They have the larger balls and all hardened units. more angle and good with shock load. My adapters for the Z06 trans are very well made. They came from a company that does the vette trans swaps for the 928.

Robs adapters are on page 20 of my build.

930 off road hardened CV from Emphi

My cv adapters for the vette trans.

Robs 930 adapter

I purchased a set of chromoly axle shafts without the inner c clip notch from XSchop.. They work well and the CV joints will never slide to far inward once bolted to their flange. I would probably try the shafts from EMPI next time.. mine came bare, not chromed as I thought and they were more expensive. I haven't seen an axle shaft break personally, I have found my CV joint is the weak spot. (Hopefully not anymore)
I used the EMPI chromoly type 2 joints and redline CV-2 CV grease.
They are all working well for me so far although i haven't beat on them that hard. (LS3, 430rwhp, 430rwtq)
I do have a bad driveline slack problem though.. not sure the cause yet... it was the same before I changed engine mounts, transaxle (now with lsd), clutch, motor mounts, trans mount, axle shafts..

i ended up going with the empi axle parts. i got the offroad/race joints, steel boot flanges and the chromoly axle shafts. i decided to try and cut the inner groove, using a hss parting tool i was able to cut the groove quite easily. i used spirolox snap rings as well. they are now ready to go into the car, just need the weather to cooperate so i can put them in and test them.

Nice. They look good. Should do the trick.

so i got them in the other day and so far so good. driveline slack was a concern of mine initially with the offroad joints, on the bench i wasnt able to feel any slack in the joints, however once i put them in the car and i had some leverage (trans in gear and moving the tire while the car is in the air) it is clear these joints have a little slack in them. the slack is not noticeable at all when driving, there is no noises, no vibration, feels just like it did with the stock axles. im hoping with time they wont gain slack.

one thing i should mention is i noticed while building the axles that these joints at 0 degrees angle you can actually see light between the tracks and the balls in certain spots. when you start adding angle these channels seem to tighten up and the gaps go away. seeing as these cars dont run the axles flat and there is always some driveline angle this may be why on jackstands i feel the slack but on the road there is none.

sharkey wrote:so i got them in the other day and so far so good. driveline slack was a concern of mine initially with the offroad joints, on the bench i wasnt able to feel any slack in the joints, however once i put them in the car and i had some leverage (trans in gear and moving the tire while the car is in the air) it is clear these joints have a little slack in them. the slack is not noticeable at all when driving, there is no noises, no vibration, feels just like it did with the stock axles. im hoping with time they wont gain slack.

one thing i should mention is i noticed while building the axles that these joints at 0 degrees angle you can actually see light between the tracks and the balls in certain spots. when you start adding angle these channels seem to tighten up and the gaps go away. seeing as these cars dont run the axles flat and there is always some driveline angle this may be why on jackstands i feel the slack but on the road there is none.

I’m looking at a similar setup. How did this work out? Did the joints hold up?