RCV vs JD fab 934 axles

I am considering options for an upcoming long travel build on my GX. I will be running a 4.88 ARB and 37” tires. The GX is V8 powered (4.7 2UZ) and full time AWD. I am leaning toward the RCLT kit for the fabricated knuckle and LC 200 series steering rack.

RCV notes that their inner joint is a double offset CV. From googling that it’s a ball and cage style joint that plunges via the outer housing. So the function is similar to the OEM tripod joint except it uses a 6 ball and cage instead of the 3 bearing OEM tripod/ roller bearing.





Theoretically this should be stronger since it spreads the load across 6 balls instead of 3 posts. The operating angles are going to be similar through travel between the two since the center shaft is a fixed length. The operating angle of the RCV shaft is 22.3 degrees as measured by @Tacoma1192. The stock joint does 21 degrees. The outer joint uses their Dana 60 architecture which I assume is a 6 ball and cage non-plunging joint similar to the OEM outer joint but probably larger.


The JD fab axles use a Porsche 934 inner CV. This is a 6 ball joint that plunges via the center shaft spline. JD fab states 28 degrees of movement for this joint. The kit includes a 300m center shaft with 33 spline at the inner CV but reuses the stock inner stub, outer CV and stub.


RCV pros

Completely new assembly with 300m and 4340 components

35 spline 300m center shaft


RCV cons

Supposedly their boots suck

Slightly more expensive

Less operating angle


JD pros

More operating angle

Plunges at splines means shorter inner cv body so lower cv angles through travel

Slightly less expensive (with core charge refunded)


JD cons

Reuses inner stub

Reuses outer CV and stub

Larger inner CV requires frame notch


So in summary, both options are limited in shaft strength because they use the stock diameter and spline count stub shafts at the differential and wheel hub, however the RCV should be stronger because it uses chromo for these shafts while the JD uses the stock material. The 35 spline RCV and 33 spline JD center shaft won’t be the weak point in either assembly because they both use a 30 spline inner and outer shaft. It seems that many CV failures are of the inner stub and often are caused by CV bind


The JD 934 allows for more travel, the shorter inner CV with plunge at the splines means less angle at the same travel compared to stock or RCV which plunge using the inner CV body. As measured by @Tacoma1192 the limiting factor for droop with the RCLT kit was the RCV maxing out operating angle, theoretically the JD fab axles would allow for more droop.


What considerations am I missing? Other options I should consider? Thoughts or experiences from people who have used either or both of these axles?

 

@SearArtist

 

@81Trekker can give you more technical info about the CV and why they are better than RCV. IMO neither one should ever give you any problems. I went with JD as I’ve heard RCV have many issues with binding at the stock length, as I'm keeping mid travel.

coincidentally i (aka my installer) just installed them on my GX470 with a modified tundra rack. I can tell you it takes some work to make everything fit nicely together. I’m sure the 200LC rack is just as thicc so be prepared to “make things work”. Also the plates that JD provides aren’t enough. There’s still only 2mm of clearance between the frame and the inner. Nothing a BFH won’t take care of though.

See my IG post here:
https://www.instagram.com/p/CrmkTOaNYn3/?igshid=YmMyMTA2M2Y=

 

This is after cutting the frame and welding in the supplied plate. the 120 series frame requires a lot more work than the Tacoma (since they were designed on them)

 

The RCV, while very strong, will wear at at faster rate than a stock type hardened CV joint, especially if you are retaining the AWD in your GX470. I actually converted my old FZJ80 to part time specifically to combat the known wear issues of those CV Joints in a full time drive application.

I have another option in the works that may interest you. It uses UZJ100 Land Cruiser CV parts, everything is 30 spline. The inner joint is a 6 ball double offset plunging, 105mm OD. NTN advertises 30.5 degree operating angle. The outer joint is a a massive 112mm OD that will swing a full 50 degrees. They can be run with drive flanges or manual hubs, either style of which reduces the time to swap a blown axle.

 

Just to clear things up the front crossmember is the same on the Tacoma and 120 series. We have installed 934’s on a bunch of different 120 series frames and the supplied fill plate provides plenty of clearance every time.

It’s always best to test fit the 934 first- mark the frame- make your cut- tack the fill plate in and then refit the 934 to check for clearance before welding it in.

 

This is my DD and I will be keeping AWD. Durability is definitely a big consideration and stories of RCVs splitting boots and puking grease with low miles on them concerns me.

@SearArtist sweet build

@Jowett sounds like an interesting option, where can I find out more.

 

I’ll start a thread shortly… the gist of it, the inner CV is plug and play, and sits roughly between a 930 and 934 CV joint in size. The outer joint has a long stub and has a design/function like the manual hub version of the gen 1 Taco (and converted 2nd or 3rd gen), but everything is larger.

 

Taco tripod vs 6 ball CV. The 100, 200 Land Cruisers and 2nd gen Tundra all utilize this CV size.

 

cut twice, measure once

 

I was under the impression that the 100/200 Tundra used a 32 spline shaft to match the rear. Thats interesting to know those stubs are interchangeable. I have no desire to run locking hubs but totally understand why that’s desirable for a Tacoma.

 

Clarification- the stub shaft splines diameter are different between the 100 series and the 200/Tundra, but the CV joint bell/cage/balls/race is the same size. The 100 = 30 spline, and the 200/Tundra stub is a larger 34 spline.

 

For full time AWD a drive flange can be utilized. Pulling the outer CV is then as simple as a dust cap and C-clip removal, rather than dealing with the large nut.

 

So far I'm stoked with my Rcvs, aint breaking them.
Plenty of broken outer cvs the other week at the Best of the West wheeling event. Seems annoying.
With rcvs the add tube is the weakpoint, so I just carry a spare add tube now

 

suprised you haven’t switched to the fj tube yet.

 

Thanks @Buttskevin21 how many miles do you have on the RCV’s?

the GX doesn’t have ADD so no weak point. What’s the next thing to break after that’s upgraded?

 

Just a 3k mile trip on some used rcvs i picked up, supposedly around 20k miles on them prior.

And the tube is still the weak point, guy down in cali has broke 2-3 non add tubes. Seems its even between that, and the diff arms snapping.

 

The diff needs a fabricated tube and/or a 4th mount, the cast junk needs to go. Maybe the UZJ100 LC tube will be a good piece to base it on… that tube is welded/fabricated, and has the same carrier bearing and shaft seal.

Taco/GX vs UZJ100.