GSP 280zxt CV Axles with Milkfab Engineering Adapters

[FJOVA]

I purchased a set of GSP CV axles (for 1981 to 1983 280zx turbo) and the Milkfab Engineering adapters to convert my 78 280z (R200 Diff).  I am having a very difficult time getting the axles to fully seat (working on passenger side at the moment).  The axles are in the differential but there is a gap between the rim of the CV axle and the differential of about 1 inch (see pictures).  I have pushed as hard as I can to seat them to no avail.   The car is still on jack stand as I am afraid to load the weight of the car on the suspension for fear of binding the axles and destroying them if they are not first seated properly. 

 

Note that the GSP axles are brand new and are identical for the left and right side of the diff.   I understand that is the case with these aftermarket axles unlike the OEM 280zxt axles.

 

Has anyone done this conversion and do you have any suggestions?

 

Please note that I was able to remove the original stub axles from the diff with no issues and they look to be in great shape.

Edited November 15, 2021 by FJOVA

[NewZed]

4 hours ago, FJOVA said:

GSP CV axles (for 1981 to 1983 280zx turbo)

 

4 hours ago, FJOVA said:

78 280z (R200 Dif

 

4 hours ago, FJOVA said:

able to remove the original stub axles from the diff with no issues and they look to be in great shape

 

Have you set the two splined ends of the different axles side-by-side and compared?  Might be a clue there.  Kind of sounds like the taper that lets the axle slip through the locking circlip is too perpendicular.  Might have to grind the corners down a bit.

 

p.s. if you find that that is the problem, check the edges of the groove that the circlip drops in to also.  I have a vague memory of aftermarket shafts getting stuck in a diff because the ramp was too steep to let the circlip slide over it.

Edited November 15, 2021 by NewZed

[G-Tech]

im curious to what you find comparing the old stubs length to the new ones. i converted mine to 300zxt cv joints and i have OEM in the car now and my new rockauto ones have the longer stubs. i didnt have the courage to try them since my OEM's are fine. if you run into a problem, i have OEM 280zxt cv-joints for sale on this site (i have donated to the site).  

[FJOVA]

Thanks to everyone for the comments.

 

So, I had a chance to measure and inspect the GSP CV shaft and I found the following:

1. Both right and left GSP axles are identical in length -- which I wanted to double check;
2. The OEM stub axle is the same length on the passenger side as the GSP axle measuring from the collar to the end of the chamfer end.  I have not taken the driver side stub axle out yet but this will certainly be different;
3. The chamfer end of the GSP axle is very rough compared to the OEM stub axle  -- see the two pictures below of the GSP axle.  I also noted the splines at the end of the GSP axle do not appear to be as consistent in thickness.  Specifically, the splines appear "fatter" near the chamfer end of the shaft.  Maybe I am seeing things but you decide from the photos below;
4. I also measured the diameter of both the OEM stub axle and the the GSP axle and they are nearly identical at ~29.8mm. 

That said, I wanted to see if, perhaps, the problem I was having seating the new axle was something wrong in the differential (damaged circlip, etc).  So I removed the unseated axle  and tried to replace the OEM stub axle into the diff.   Long story short is that I was able to push the stub axle back in place with three or four firm hits with the base of my rubber mallet.   Now, I would expect the new axles to be a bit tighter as they are new but I pushed and hit the new axles as hard as I could to no avail in seating them.  I am not comfortable hitting them harder or loading the suspension with the axle unseated -- they may never come out.   

 

So, the issue here is probably the roughness of the chamfer end and, I believe, the irregular or inconsistent spline thickness at the chamfer end.  

 

At this point I intend to send the GSP axles back to RockAuto.  While I could try to file and smooth the ends I am concerned that once I get them in I may never get them out short of a diff rebuild.

 

G-Tech I am interested in purchasing the OEM 280zxt axles you have for sale.  Please tell me about the condition, price, and terms / shipping?  Or point me to where I can find them and how to complete the transaction with you.  

[G-Tech]

i msg'd you

[FJOVA]

I wanted to provide an update regarding this adventure.   

 

I returned the GSP half shafts without incident.  Ultimately I could not get them to seat properly and the lack of left and right splined ends of the correct length, I believe, could be an issue long term.

 

I managed to purchase OEM 280zxt CV axles from one the members (G-Tech) and completed a rebuild using kits from Rock Auto (BECK/ARNLEY 1032280 and BECK/ARNLEY 1032282).  Thank you G-Tech.  The kits were about $50 total for the 2 CV axles.  The OEM axles were in good condition where it mattered (splines, tulip cup, and tri-pod ) and the rebuild is not difficult to do.  Upon installing the splined ends into the diff they seated with a firm push and easily connected to the Milkfab Engineering adapters.  The most difficult part of the install was disconnecting the lower control arms to allow enough clearance to fit the axles into the adapter on the companion flange (wheel) side.  Ultimately this was not really difficult, just time consuming.   One other note, if you do this swap be sure to keep all the adapter threads clean for effective bonding with Loctite (I used blue 243 type).

 

I have been running with the install for about 4 weeks and there are no issues and the clunking sounds are gone.  Note, my car is set up with Koni shocks and Eibach progressive rate and lowering springs yet the CV axles do not bind.  I have taken it through the paces and all is good so far.  The car hooks up better and is quiet.  I am happy with the result and the "value for money" (cost me about $500 including all supplies) versus other options.

[Larry]

Great timing on the post - I'm about to tackle the exact same project. 78 280z, 280zxt axles, Eibach springs, etc.

 

I've been debating whether to use the Milkfab adapters or WHP: https://whiteheadperformance.com/product/billet-280zxt-cv-axle-companion-flange-adapters-27-spline-datsun-240z-260z-280z/

Do you (or anyone) know anything about the WHP adapters? My only reservation w/Milkfab is that they list a torque limit of ~400 ft/lbs. Wondering if the WPH adapters are any stronger. They're certainly pricier.

 

 

How difficult was it to remove the stub axle from the diff? Did you have to pry it out? Also, did you disconnect the LCAs from the spindle pin or from the inside? Good to hear that you're not having binding issues. 

 

[NewZed]

It's not certain that the 280ZXT CV axles are stronger than the u-joint halfshafts.  If your main reason is durability.  

 

The two adapters are different designs.  The WP requires replacing the inner flange of the axle.  The Milkfab adapter fits in between the CV axle and the four hole u-joint axle flange.  Milkfab is easier.

 

The diff axles just pop out with applied force.  I've used a lubed chisel between the diff housing and the axle flange if they're tight.  They're held in with a circlip.

 

https://milkfab-engineering.com/shop/ols/products/240z260z280z-cvaxlekit

 

https://whiteheadperformance.com/product/billet-280zxt-cv-axle-companion-flange-adapters-27-spline-datsun-240z-260z-280z/

[lowrider]

The torque limit of the milkfab setup really depend on usage. The adapters themselves were designed to hold more than the ~400lb-ft torque threshold stated on the website. Not taking into account shock loading from hard launches, a static FEA of the adapters showed there was a safety factor of 2.5 at 800lb-ft of torque. Will the axles hold at that? It's yet to be seen and really wasn't the intended market.

 

For context, the milkfab adapters with 280zxt axles have been living behind my ~380lb-ft L28et for the better part of 7 years with no problems besides a torn boot. I had issues with breaking u-joints in the half shafts prior to the upgrade due to drive-line angles and torque. Even the power-force (or was it brute-force) grease nipple less u-joints weren't holding up. The main reason why the stated torque is~400lb-ft on the site is that it has been thoroughly tested at those power levels.

 

 

Edited January 20, 2022 by lowrider

[NewZed]

1 hour ago, lowrider said:

The main reason why the stated torque is~400lb-ft on the site is that it has been thoroughly tested at those power levels.

 

Curious - how do you know this?

[calZ]

Judging by his profile, I would guess that he owns Milkfab

[NewZed]

4 hours ago, calZ said:

Judging by his profile, I would guess that he owns Milkfab

 

Oops. I missed that.  But, ironically, it makes the numbers even more suspect without the verification.  No offense to him, but he is selling parts.  Let's see the dyno sheets or at least a description of how they were tested.  Somebody with an LS swap did some burnouts?  I don't think he's getting 400 ft-lbs from an L26 or L28, even with a turbo.

 

You can find a lot of posts from the past making fun of the 800 HP claims for various axle options.  Seemed picked from thin air.

[lowrider]

13 hours ago, NewZed said:

 

Oops. I missed that.  But, ironically, it makes the numbers even more suspect without the verification.  No offense to him, but he is selling parts.  Let's see the dyno sheets or at least a description of how they were tested.  Somebody with an LS swap did some burnouts?  I don't think he's getting 400 ft-lbs from an L26 or L28, even with a turbo.

 

You can find a lot of posts from the past making fun of the 800 HP claims for various axle options.  Seemed picked from thin air.

That's correct, I am the owner of milkfab engineering.

 

I can understand your skepticism and welcome it! By no means am I making claims of this axle setup living behind 800hp or even the 800lb-ft of torque that the FEA (finite element analysis) for this adapter design was performed at. Most aren't interested in or don't understand the technical details, but I am more than happy to provide them. Below is a screenshot of the FEA that was performed in Solidworks when designing the parts. A 5000N load was applied tangent to the center axis to each of the 6 axle mounting holes, which are radially 40mm away from the center axis. The mounting holes that attach the adapter to the stub flange were held as a fixture point. Granted in a properly clamped configuration, the mounting holes are not going to be seeing the entire load like modeled.

 

5000 N x 6 (mounting holes) = 30,000 N

30,000 N x 40 mm = 1,200,000 N-mm

1 N-mm = 0.00074 lb-ft

1,200,000 N-mm x (0.00074 lb-ft / 1 N-mm) = 888 lb-ft

 

As you can see from the screenshot below the FOS (factor of safety) is 2.59.

 

As for the axle testing I have done no formal lab testing. I just have my word and the testimonials of several customers.

I have had the setup on my personal car for the better part of 7 years like I said above. Within that time it's been subjected to numerous hard launches, burn outs, and a few runs down the local drag strip on street tires. I have not found the breaking point of the axles yet, but we all know that usage is the determining factor. If I were taking to car to the drag strip every weekend on radials they are more likely to break than if I am launching on a street tire on an unprepared surface.

 

As for the power claims of the old worn out L28et in my 260z I recently had the car dynoed this past spring on a local dyno dynamics dyno. Going into the session the shop made it clear that the dyno was a "heart breaker" and read similarly to a mustang dyno. I am not a huge fan of using the dyno to produce quantitative results when compared to other dynos, but according to varying sources the dyno dynamics dynos read on average 10-14% lower (take that with a grain of salt) than the more common dynojet that most use as a baseline.

 

The car made 317.3 hp / 351.8 lb-ft in 86.5F weather. Approximate a 12% lower rating than a dynojet and you're left with roughly 394 lb-ft of torque if the car had been ran on a dyno jet. That is why the website mentions ~400 lb-ft. There are also other customers that are in/around that same power area and running without issues, a simple Facebook (I hate refering people there) search in any of the large Datsun groups with pull up the posts.

 

Here is the dyno sheet for your reference as well.

 

I apologize for being so long winded. I try my best to be as transparent as possible when it comes to the development of the products I provide. FWIW, these adapters/axle setup were designed for my personal use with no intention of being sold. It wasn't until there was interest some 5 years or so later that I considered making them to sell.

Edited January 21, 2022 by lowrider

[Larry]

This is great info, and the level of detail is much appreciated. I'm willing to give these adapters a shot.

My main concern is angularity as well. I don't have the original (and perhaps stronger) Nissan u-joints on my half shafts anymore, and I've heard of these failing w/lowered V8 Z's. Even the JTR manual warns against using greaseable u-joints in a lowered swap, so I feel this might be a better setup.

[FJOVA]

FWIW, I am using the adaptors and they are doing very well.  I am running a bored and stroked l28 -- Rebello setup.  While I am not making the kind of torque and HP of a V8 I have run the adaptors hard.  The only watch out I would offer anyone is to be sure when using loctite/threadlocker (or equivalent)  on the bolts make certain all surfaces are clean of contaminants.  I used the Permatex® High Strength Removable Threadlocker Orange with great results so far.