"Hey guys, how’s it going? I have a quick question regarding a CV axle replacement on my 2018 CX-5.

I recently purchased an aftermarket CV axle assembly and installed it with a friend. However, we didn’t replace the output shaft seal at the time, and it’s been leaking transmission fluid ever since. I ordered a genuine OEM seal from Mazda, which was on backorder, but it’s finally ready for pickup today.

A friend suggested that the bearing might also need to be replaced, believing that could be the root cause of the leak. However, Mazda informed me they don't sell that bearing separately and that it’s rarely replaced unless the transmission itself is being rebuilt, Mazda mentioned as well that the problem may be the size of the assembly axle. If any of you have experience with this, I’d appreciate your thoughts. I’m hoping that installing the new OEM seal today finally puts an end to the leak. Any thoughts?

 

Welcome to the forum! Unfortunately, some aftermarket parts are not built to the same specs as the original vehicle's manufacturers parts. If that new shaft is any smaller in diameter than the original shaft was, and you used the old oil seal, then you can definitely end up with a leak there. The older seal has been "worn in" to ride on the older shaft so if there is even a slightly smaller shaft inserted there.....it's going to leak.

As long as the new shaft is only slightly smaller than the original shaft, I think a new oil seal will fix you up, more than likely. If it does not, the metal "finish" on the new shaft may be playing a part in the leaking......or the new aftermarket shaft could be out of round at the seal location. I would try the new oil seal and see how it goes......remember to lube the oil seal rubber 'sealing lip' with some new transmission fluid before sliding the axle shaft in place.

Report back and let us know how it goes!

 

Thx Buddy I really hope that fixes it, a OEM part goes for a lot of money, thank you I will keep you post it on it

 

"Update: It turns out there are two seals, not one. The inner seal "small pic" (transmission oil seal) is actually more important than the outer one "Big pic seal" (Dust and wanter Seal), so we replaced both. Three days later, the leak is officially gone! Just a heads-up to others: verify your part numbers against the diagrams before ordering. My dealer originally gave me the wrong part, causing a week-long delay. Thanks again for the advice!"