R180 CV conversion idea, input needed

[ezzzzzzz]

Here goes... I have the basic components to complete the CV conversion of the NISMO R180 LSD differential in the 240Z. The parts list is as follows.... 280Z stub axles, Ross' billet z31 (4-bolt) companion flanges, 300ZX turbo axles with custom length shafts, R180 differential CV side flanges (6-bolt pattern) from a late 720 4x4. Here's the kicker... I'm thinking that I will cut the short shaft off of the inner fixed CV joint housing and remove the seal dust guard. A companion flange can be machined which friction fits over the lip on the inner joint (where the seal dust guard would have been pressed on) and then welded both sides. On the housing side, the weld would need to be stitched to allow room for the bolt heads. This flange would be stepped (imagine a short top hat) so mounting suface is moved out from the joint housing allowing for the 6 bolts to be inserted for attachment to the differential side flange. Once welded up and cooled down, the CV joint can be reassembled and driven onto the axle shaft. The only pain is if the joint ever wore out the process would need to be repeated entirely with new stepped flanges and inner CV joint housings. I don't see this as a monumental detriment since these joints rarely fail. The original thought was to allow the axle shaft to float between to CV tulips. I don't see this as a viable path since every manufacturer has gone to great length to design their CV shafts with a fixed end. Input?

[260DET]

So you have to use bolt in inner stub axles in the diff, not the clip in type?

 

With the clip in type diff center I was looking at using 280ZX automatic transmission CV axles which seem about the right length and if so would only require an adaptor at the companion flange. Don't know if you had the same setup in the US with the ZX auto.

 

From the sound of it, if you have to use bolt in stubs what you really need are CV axles that are flanged both ends like on some RWD Euro cars, BMW, air cooled VW, etc. Suitable length of course.

[ezzzzzzz]

Yes, the early NISMO R180 uses the bolt retained side flanges. I could swap out to R200 but don't want or need to. I'll have to look into fixed CV joints from other makes as a possible alternative. In the mean time I'll continue pursuing the present path I've chosen. Thanks for the feedback.

[260DET]

About to do something similar but using a Torsen type center in a K case R180 with the 4x4 inner stub axles.

 

By my measurements the diff is 234mm wide at the axle faces and there is 1.054m from companion flange to companion flange, which leaves 410mm for each CV axle including any adaptors. Thats measuring at full suspension droop with 1.5 negative camber gained by extending the track, not at the strut tops.

 

Now to find a suitable CV axle which is short enough.

[ezzzzzzz]

I'm looking at Porsche inner CV joints as a possibility. Custom axles will probably be the only, although expensive, course. I just added a rough drawing of my Z31 CV joint modification to my gallery. This will give viewers an idea of what I'm trying to do. In the drawing I show bolts and nuts retaining the CV to the R180 side flange. I don't think there is room for the bolts head though. In that case, I'd simply install studs and weld them on the backside to prevent movement. Alternately, I'm now thinking of the possibility of having Porsche stub axles machined to minic the R180 side flanges. This would allow a direct bolt-up of the Porsche CV. It would also move the CV further inboard providing for more axle articulation. Again, custom axles would be required.

[ezzzzzzz]

I just purchased a complete set of Porsche 911 axle assemblies, including the diff flanges and stub axles. The idea is the have the Porsche diff flanges machined to mimic the R180 CV side flanges (assuming there is enough material to do so) or machine a simple 1/2" thick spacer to bolt to the R180 side flange and then bolt the Porsche inner CV to the spacer. It's only a matter of having axle shafts machined to match the Porsche splines at one end and the Z31 splines at the other.

[260DET]

Sounds good, probably stronger than what I'm looking at the moment.

 

Which is using 280ZX R180 CV axles but replacing the inner CV joint and stub with another outer CV joint similar to the 280 one. Which will give CV axles that are flanged at both ends, the inner flange matching the 720 4x4 stub flange.

 

The long end springs will have to go, they take up too much space, and an adaptor to the outer S30 stub axle will be required. Yet to check out the 720 axles though, they might be better than the 280 ones.

[ezzzzzzz]

I've given that setup some serious thought. Initially, I was going to do that very thing. I have four of the outer CV joints for that purpose. The outer CV and associated spring (I assume you're refering to the internal spring that preloads the axle shaft on a 280ZXT axle assembly) can remain if you use Ross' 280ZXT companion flanges. The problem arises that with the spring installed the inner CV joint (original 720 4x4) innards are pushed into the back of the cup and will lump over with every rotation. This joint was not intended ot be used in such a manner. Maybe a nylon button could be inserted in this joint to prevent bottoming out. Otherwise, life expectancy cannot be long in this arrangement. If the spring is removed then the axle can float between the inner and outer CV joints. The same effect takes place within the CV joints as mentioned above but without the preloads. Some have said to have run this arrangement for many years without detrimental effects. My newly thought out conversion has a fixed CV joint at the diff and allows the axle to float within the outer CV joint to account for suspension movement. This is the way all factory CV axle assemblies have been produced (at least, all that I've ever seen). It would be a fluke if I found out the Porsche CV were dimensionally the same as the Nissan pieces but a pleasant surprise none the less. I still suspect I'll be having custom axles machined for this project.

[260DET]

Great minds think alike eh

 

Yeh I agree that some sort of internal spring arrangement is required, although what effect they actually have when the car is in motion is hard to work out. My present solution is to use a different type of spring, which I don't know the name of, the coil type that compresses up within itself. Like the flat top cone shaped coil springs that are used behind internal car window winder and door handles. They should do the job and fit in to the limited space.

 

Apparently the 720 axles are splined into the outer hub so my guess is that they would be too long. So it looks like the 280ZX axles are the go for mine.

[blueovalz]

I just purchased a complete set of Porsche 911 axle assemblies, including the diff flanges and stub axles. The idea is the have the Porsche diff flanges machined to mimic the R180 CV side flanges (assuming there is enough material to do so) or machine a simple 1/2" thick spacer to bolt to the R180 side flange and then bolt the Porsche inner CV to the spacer. It's only a matter of having axle shafts machined to match the Porsche splines at one end and the Z31 splines at the other.

 

It's been a while since I've had the parts in hand, but I've been working (on and off, mostly off) on the Porsche axles for quite a while. The 944 (Turbo) axles are close in length but still too long (there is a difference in length between the manual and the automatic, but whichever ones I did work with, they were the shortest of any Porsche axle made, and they were still about 1/2" too long) when you include the thickness of a 1/2" adapter plate on both ends of each shaft. What I think I've finally narrowed my parts down to was a custom length axle fit between two 930 joints. I chose the 930 joints because of their added strength (BIG!), AND mostly because the bolt pattern is large enough that they do not interfere with the Z stub pattern (the other Porsche joints are smaller and run-through bolts or studs would butt up against the Z stubs), which allows a thinner adapter on both ends. Another option with these parts is that the ZX turbo companion flange is extremely close in size to the OD of the 930 joints. With minor machining of the ZX Turbo companion flange lip, the 930 joint can be made to slip snugly into the lip of the ZX turbo companion flange. This would necessitate drilling a new bolt pattern in the flange for the 930 joints to bolt directly onto the ZX Turbo flange, but this would then eliminate the adapter on the outer joints. Again, I'm working off of memory here being this is kind of a side-bar project that has little priority at this time, but when I finish the interior of the BlueOvalZ, I'm going to complete this set of axles.

[ezzzzzzz]

Very interesting, I haven't got the axles in hand but they are suppose to be appeoximately 3 3/4" across with a bolt pattern on a 3 1/2" diameter. These should still be easily stout enough for my L6 as I don't push the car very hard anyhow. They also have at least 5 (maybe 6) balls in the much heavier joint housing. I've already conceded to custom axles. I'll know more when they are in my hands. Photos and more info will be coming...

[260DET]

To complete the record, the conversion is proceeding as previously outlined using 280ZX CV axle half shafts with the inner CV removed and replaced with an outer. In other words, the otherwise stock 280ZX R180 CV half shafts will be used but using two outer CV joints.

 

Some work will have to be done on coming up with a satisfactory modification of the stock internal spring tensioning and buffer arrangement. Fiddly but doable.

 

An adaptor will be made up so that the outer CV flange can be bolted to the hub of the outer stub axles. That adaptor will be welded to the hub.

 

Finally an observation. These tripod type CV joints would appear to be significantly stronger than the stock S30 axle half shaft universal joints. Its estimated that on my setup there will be ~20mm end float in the CV joints.

[ezzzzzzz]

Sounds great. I just got my Porsche axles. These CV joints are super strong. I now plan to have a 1/2" thick adapter machined to nestle between the R180 CV side flange and the Porsche CV joint. On the outer side, I am still considering using Ross' billet pieces and Z31 CV joints. Alternately, I could use the Porsche CV joints and another adapter plate between it and the 280Z stub axle flange. It would be much cheaper!! The upside would be identical CV's that are readily available if needed.

[JMortensen]

That's pretty much what they did on the BRE 510 back in the day. VW (Porsche) CV's with a short little shaft, and adapters to go between the diff and the CV and the stub and the CV.

 

I don't think you need to worry about the button or spring under the CV's. IIRC all of the Porsche CV's have the "tracks" for the balls at angles, 3 one way and 3 the other way. What that does is move the balls to the center, while allowing them to move either direction when necessary. If you pull one of your joints apart you'll see that the tracks look like this: / / /

 

If you pick up a Porsche magazine you'll find that there are many shops that do custom axles for Porsches. I remember one where you could get gun drilled chromoly axles in any length you wanted. Probably $$$, but you should also be able to find one that isn't so expensive.

[260DET]

That should be excellent ez, it won't break in a hurry.

 

This thread has turned out to be the R180 CV conversion bible just about. To celebrate here is a pic of my bank busting Torsen type center compared with the stock four pinion non LSD K case one

 

[ezzzzzzz]

Sweet... I hope to soon have some basic drawings for the adapters for all to see. I don't have any fancy software so I have to do it the old fashioned way with pencil, ruller and compass. I'll be heading out to a few machine shops with hopes of finding someone willing to make these without emptying my bank account.

[260DET]

Here is a pic to update progress, incidentially it was found that the basic 280ZX CV axle was the same for the R180 and R200 diffs, one of each is being used.

 

The ex 4WD R180 diff stub axle is shown on the left, followed by the CV axle components, on the right is the stock companion flange modified to adapt to the six bolt CV flange. That modification involved making up the six holed circular plate you can see and welding it to the stock companion flange. Actually a blank plate was welded to the comp flange first followed by the machining, to take care of any distortion caused by the welding.

 

Incidential parts such as the spring loaded internal buffers and their retainers are not shown.

 

I just hope to hell that my measurements were right and it will all fit in

 

[ezzzzzzz]

That's great. Will you just let the axle float between the CV joints? That was my intention too initally. Now I consider that a problem because no manufacturer does that. Every CV axle assembly has a fixed CV end. How much did your modified outside flanges cost you to get made?

[260DET]

All finished, this is what went in, double end modified 280ZX half shafts with modified internal springs at each end to keep the axle firmly centered. You can see the modified spring retaining plate at the end nearest the camera, the other end didn't have such a plate, it bolted straight up to the diff stub axle flange.

 

 

This is it all installed. Axle end float is ~25mm which is plenty, no axle shortening required. Hope it all drives OK

 

[260DET]

Went for a run around the block a few times, seems to be smooth as. See how she goes at the sprints next Saturday