FC 8.8 Service Bulletin

[Bowtie7]

It6 sure would be good to know what kind of date range the inferior axles fell under. I am building a no expense spared new car for Russ at this time with the kit that we've been running for a season and would hate to have an issue pop up now. I am in a tight time crunch so teardown and return is not a realistic option. Doesnt the supplier know when the problem axles were built? It would be pretty easy to figure out whether axles bought match up to time of manufacture, right?

[PapioGXL]

You can still use the center link to adjust camber, but you should set camber before welding the front mount tab. Maybe even add a shim so you can go lower with the pinion/raise the rear of the subframe later if need be.

[largeorangefont]

When doing my kit I mocked up and tack welded to set my pinion angle, then final welded. The stock camber link was not the correct length at that point, so I used an adjustable sublink.

That said I run solid bushings and mounts everywhere, so there is no camber adjustment to be made.

[frijolee]

It sure would be good to know what kind of date range the inferior axles fell under. I am building a no expense spared new car for Russ at this time with the kit that we've been running for a season and would hate to have an issue pop up now. I am in a tight time crunch so teardown and return is not a realistic option. Doesnt the supplier know when the problem axles were built? It would be pretty easy to figure out whether axles bought match up to time of manufacture, right?

New Option for Validating Axle Material

I finally got an answer I've been asking for for some time.  It's one which I had to pry out of my supplier as I'm guessing this was borderline proprietary info: hardenss data.  The incorrect shaft material will measure mid 30s on a Rockwell C hardness scale.  The correct parts are designed to target 50-54 Rockwell C. 

If you're concerned about your axles (which of course any race effort would be) this means you can take any axle to a material testing house and have a hardness test done locally.   There's likely to be a bit of variation but hopefully the numbers above are a large enough window between good and bad to give folks a thumbs up/thumbs down response.  Note, the one thing to be careful of is that the hardness test will give you a tint dent in the axle which will act as a stress riser.  Testing the end of the shaft would be ideal if you have access but at a minimum the test should be done on one of the CV boot bulges where the diameter is larger (and stress lower).  If you have to, it's worth cutting one of the boot bands and sliding the boot down to expose more of the bulge to gain access.  I strongly recommend users not put this dent in the shaft's "minor diameter".

Unfortunately specific dates aren't available.  Without serialization (added cost and headache) we aren't set up to track which boxes we pack from which batch of axles we order and we always reorder before we run out.  Best I can tell you orders from about a year prior are unaffected (that we know of).  We've done our best to notify folks and be transparent as to the issue.  However, most of these cars are already running triple the horsepower Mazda intended so the fact we can offer a lifetime warranty on axles is pretty damn good considering what folks put these through...

[Bowtie7]

Very helpful. Thank you sir!!

[frijolee]

Another new FC 8.8 topic.  Fatigue inspection recommended!

Greetings norotors,

A heads up for users of our FC 8.8 kit.  One of our earliest testers recently reported a fatigue crack starting to form on the top of the passenger side box tube.  Wanted to request folks check for this.



As to why: the load path from the diff has to travel up the two shaped side plates and transition into this box section. The input load of the driveshaft results in a load attempting rotate the diff counter clockwise.  As passenger side of diff tries to lift the top of the box tube sees tension.  However the reacting load to the shaped plates is offset from the box tube in our design (driven by packaging under the car).  This means the assembly racks ever so slightly and the fatigue crack starts at the extreme forward corner on the top of the passenger side weld as shown.

If you see this issue our recommendation on a repair is as follows.  1) fully grind out the top weld until you're sure the crack is gone.  2) Re-weld.  3) Add an 1/8" double plate over the weld (bent in the middle).  Weld that all around (fillet welds on the ends and groove welds on the sides, a few plug welds in the middle) and you should be good to go.  The new doubler will share the tensile load and should move us out of the fatigue range.



As far as a more permanent solution on our end, we're in process of building the next batch of cradles and we've upsized the wall thickness of the box tubes so we can put a bigger weld there.  We'll likely add the doubler plate as well but I may run some analysis to check if it's needed.  We presently have only a few pre-built cradles in stock which still have the former tubing wall size and we're adding the doublers to those prior to shipping.

Apologies for any headaches this causes, but wanted folks to know.

Regards,
Joel "continuous improvement" Payne

[Bowtie7]

That looks like drivers side to me?

[frijolee]

That looks like drivers side to me?

I think the perspective is throwing you.  It's passenger.  The housing interface plates are offset to the rear of the diff so the above picture would be looking aft if it was taken from the car's perspective.  Similar view during a trial assembly from way back when (but less from above).




The twist of the driveline tries to pick up the left front and right rear.  However under acceleration "picking up the right" rear shows up as that side of the car squatting.  Drag cars tend to show this well because the forces are so extreme.




In our case this means that the top of the passenger tube is in tension (lifting) while the top of the driver tube is in compression (trying to yank the stud out of the car).  It doesn't hurt to gusset both if desired, but only tensile stress tends to give fatigue problems. 

Here's the doubler welded in (pre-emptively in this case):




We know it's not our weld quality.  I just have to stare at this stuff for a while every time I pick up a batch.   

[mech-head]

Nice welds.  That reminds me of this.


These are from a mountain bike company called Ventana.  The owner says that a great weld is better than sex.

Well Joel, I don't know if the Ronin welds are better than sex, but they are probably better than sex with me...

Keep making awesome products.

[PapioGXL]

Rick, you can check out the welds in person when Brown Santa delivers them to me tomorrow. 

[atli126]

I know this is old but if I was planning on doing this rear in the future are the new setups sorted now? 

[frijolee]

I know this is old but if I was planning on doing this rear in the future are the new setups sorted now? 

Missed this some time back, but we've been adding the gussets for you since we first discovered it could be an issue.

[onefastrx7turbo]

hi Joel, is this something I should be concerned with? I haven't dynoed but I'm guessing I'm 500hp/500tq. Do I need to reinforce those areas?

[frijolee]

hi Joel, is this something I should be concerned with? I haven't dynoed but I'm guessing I'm 500hp/500tq. Do I need to reinforce those areas?

It seems to be more about fatigue than straight power but yes I'd recommend reinforcement.  A diamond shaped gusset witha few extra plug welds works well (slightly different than the sketch shown above).

[onefastrx7turbo]

Roger that, thanks!