Broken CV axles got you down?

Broken CV axles got you down?

Nov 23, 2022Tyler Mason
Broken CV axle? Broken Front differential (FDU) front drive unit! You might be wondering now that the BroncBuster team has had such great success in solving the broken steering issues on the 6 Gen Bronco: what’s next? What is my next most vulnerable failure on the Bronco? 

As I started to write this Blog post to announce the rollout of some exciting new parts that BroncBuster is offering for the 6 Gen Bronco, I received the following question and picture on Facebook messenger last night. Keep in mind, some days my life revolves around these sort of questions and I love the interaction.  

Question: “Y'all have any plans to fix this weak link on the m210”

I responded with this picture. 

I then asked: "what led to this failure?" I, of course, have had our experiences rock crawling and breaking. 

His response: 

“I went thru a shallow mud hole that wasn't shallow after all. And I beat on it pretty hard to get out. Went through a smaller hole and it all exploded.”

Picture that followed 

 He then went on to explain: 

“I bet the ear broke first. The passenger axle cup broke the side out. Like it was a binding failure. The driver side cup exploded.”

Months ago as we were on our 4th broken differential (FDU) “front drive unit”, we said "So ok, this is our next critical weak link and something that needs addressing". Unfortunately as we started designing this new billet piece we found the cost of material, specialty tooling, and machine time would put this cost close to that of a whole new FDU. So we put this project on the back burner and continued our persistent pursuit of Dana Spicer and the upgraded Ultimate Dana 44 Advantek FDU, and Spicer extreme 1/2 shafts. 

In this post it’s my hope to save you all from hassles and very costly repairs we’ve encountered over the last year of testing the Bronco Platform and I’ll do this in a way that gives you good, better, and best options in our opinion. 

# 1 Good option: do everything you can to minimize stress on your CV axles. Ok what does this mean? First let me say- everyone on the forums likes to talk about correcting “Geometry” and thus many falsely teach or believe this is done by simply replacing upper control arms. This simply is not true! The only ways to fix Geometry issues are as follows! 

  • Install body lift! This allows bigger tires without changing CV angle.
  • Install limiting straps.  Almost all failures happen when at full droop and a little wheel speed is involved.
  • Do a differential drop kit. Dropping the diff gets the angle back to or close to stock geometry. However this is very labor intensive and you loose clearance.
  • Install coil-overs in place of puck lift or perch collars lift. Coil-overs help to minimize the down pressure at full droop.
  • And of course don’t drive it like you stole it!- "you hop you stop!"  

#2 Better option. While all the above are good options they alone can’t guarantee success all the time. Let’s face it, the stock axles and outboard tube on the diff are known to be weak. So, in addition to the "good" options listed above, here are some better ones: 

  • Upgrade CV axles. Yes the CV’s are a weak point and in some cases breaking a CV can take out your FDU. There are two options on the market: Spicer extreme 1/2 shaft and RCV. I have experience with both and I’ve only had success with one of the two. Not to say that issues won’t be worked out with the other option but in my belief they are not there yet.
  • Upgrade tube. This is not an option yet, but as I mentioned earlier, we're starting work on it. However for those that are running upgraded 29 spline either from Spicer or from RCV, once we get a custom billet piece worked out, this could very well prove to be the best option. 

#3 Now for the Best option! We are excited, to bring to you the new Dana 44 FDU! (available at right now!!). As I said, there are some good and better options and with a good set of coil- overs, minimizing stress is always good. But for the long term this is what we would recommend:

  • Upgrade your FDU. Cost on the FDU is $3,800 and this not only gives you a greatly reinforced tube and housing, but also allows for re-gearing to the desired ratio. This in turn reduces stress on components when your gearing is reduced to match tire size. You now also increase to a 32 spline. 
  • With the upgraded FDU you will now need the 32 spline Spicer extreme half shaft. Cost about $2,700.

  • Soon there will be an option to replace the rear axle with the Dana 60. Cost on this has not been released but my guess is somewhere around $6,000-$7000, however there are options to match the front gearing by keeping your rear Dana 44 and installing new gearing. This cost is approximately $600 plus labor. 

As is the BroncBuster tradition, we have found that next weak spot on the 6 Gen Bronco that needs to be fixed so you spend way more time crawling than in recovery! Take a look at the options above and see which is right for you, and as always, if you have any questions or comments let us know!

OK with that here is a little technical data provided from Dana Spicer.




More articles

Comments (0)

There are no comments for this article. Be the first one to leave a message!

Leave a comment

Please note: comments must be approved before they are published