OK so I have had this issues for a while. When I am in the sand (or anywhere offroad) 03 F150 5.4l into either 4hi or 4lo, as soon as I get on the throttle the driver's side CV axle comes apart and the axle tube of the front differential cracks open. The CV axle was replaced with a new one from ORielys back in 2015. Since then I have used the lifetime warranty on the CV axle no less than 25 times.

Today we replaced the front differential thinking that was the cause of all this. After getting it all put together I took it out to test it and the same thing happened again!

Now I am thinking the CV axle I purchased may be the problem, but I am not too sure. What are your thoughts?

 

Doing some more research on this. The brand i purchased from O'Reillys was actually Precision. According to the specs on this model the compressed length is 19 and 11/16 inches. The Duralast model from Autozone measures 20 and 1/4 inches. That is more than half an inch in difference. Would this impact anything

 

Soooo... this needs a deeper explanation. "Comes apart" how? "Cracks open" how? Do you have pics of this?

If your diff is cracked open, how are you sealing it back up, and why are you reusing it?

 

Sorry for not being more descriptive. Unfortunately I don't have any pics, cut the CV axle joint seperates completely on the driver's side where it mounts to the differential. The entire shift, bearings and all, comes out of the "cup".

As for the axle tube, this cracks where it mounts to the differential as well. There is a flange with 4 bolts that secure it to the differential. That flange breaks completely off. I do not reuse the axle tube. I have been locating replacements for it from the salvage yard.

I have a suspicion that the length of the CV axle may have something to do with it. What are your thoughts?

 

That's about 9/16" difference. I can't honestly say if the compressed length really is going to come in to play there or not. I am more inclined to think something in your differential is jacked though.

If I'm in your shoes, here's what I'd do. Hopefully you have the original CV? I would get it rebuilt, if so. Then you know the length is correct. And next, I would replace the entire diff instead of just the tube.

 

Thanks for the advice! I actually replaced the whole differential yesterday, along with the axle tube. Unfortunately I don't have the original CV axle. I think the fact that it happens with both the old differential and the new differential points to the CV axle as the problem, since it is the only other variable. I am wondering if the extra length of the longer CV axle means it is less likely to slip out of the cup. I am thinking the CV axle slips out of the cup, which then puts unnecessary and sudden force on the passenger side, thus cracking that tube.

 

It's possible... I tried to see if the Motorcraft shaft listed the length, but came up empty. Outside of getting the OEM CV rebuilt by a reputable shop, I would personally go with a Motorcraft. I went through 6 or 7 Duralast Gold (Brand New) CV Axles on my Escape before I finally just got the original rebuilt, and it's been fine for several years now. I don't trust Chinese made CV's. And their boots are complete junk, just like hard plastic after a couple months of use, then spit all of the grease out.... and made a HUGE mess. These pics were the last straw... You can see evidence of it happening before on the control arm. So yeah, don't think the Autozone shaft will be better.

 

One more thing... I kept losing this bushing in the trans when I had that Autozone shaft in there. It has not leaked since I last replaced it, and put the original shaft back in. Something tells me that their input shaft is not the correct diameter.... I know that part is not applicable on these trucks, but I tell you that to demonstrate that I believe they are not made correctly.

 

Thanks for the feedback and advice! Looks like I will be waiting to purchase the Motorcraft CV axle. It is only $126 on Rockauto, so not too expensive.