Repacking OEM axle CV boots?
 

My 2018 BRZ with 40,000 miles started leaking grease from the inner axle CV boots (worse on the right side, but also on the left). The boots themselves look great, and the leak is from under the small clamp in both sides.

Car is driven fairly aggressively on the street and I do 2-3 HPDE days a year running endurance 200TW tires. Drivetrain is stock and car is on RCE Yellows.

Reading about axles I know they are a weak point in the Twins, but I think that specifically for grease leaking out it's due to the OEM grease liquifying and not due to lowering or boot problems.

That got me thinking if I can just undo the clamps, slide the boots off, wipe as much of the grease as I can and repack with high temp grease (like Redline CV-2). At the very least this will save me the effort of pulling the axles out and the cost of new boots and clamps.

Question is, can the OEM clamps be reused this way? Looks like carefully bending the locking tabs and opening the hinged part should work, but it might be wistful thinking.

Or should I just bite the bullet, get the rebuild kit (Subaru 28497FE021) and drop the diff to pull the axles?

For what it's worth, back in ~2012 when I bought my 2004 WRX, the front boot near the downpipe was seeping just like this. I put a worm clamp over top of the existing clamp and cleaned things up. It never leaked after that until the boot itself finally tore about a month ago from age... 12 more years later. During the time, the car was autocrossed extensively doing about 20 events per season for 4-5 years.

When it tore recently, I personally ended up using a Red Hippo split boot kit and repacking it with grease. The car's 20 years old and I feared removing the axle would cause more issues. I'm not sure I'd recommend a split boot kit for track use, even a good $45 one like this one I used, but it worked and has been holding well. Car only sees about 1k miles per year now.

But I digress. Given the boot is fine here and it's just seeping, I'd probably unclamp it from that leaking end and use a proper CV boot clamp (aftermarket or OEM... they should be damn similar). I wouldn't bother with regreasing as you'll likely introduce dirt. You're then also unclamping the other side too.

It's highly unlikely any debris or water is in the boot. I doubt you lost enough grease to cause any issues. The OEM clamps can't be reused. They're also a bit of a bitch to cut off without harming the boot, so just be aware of that. I'd have a boot on hand and be ready to pull the axle in case you damage the boot itself.

Doing the rear axles on these car's (or any Subaru that I'm aware of) doesn't require dropping the diff. They'll slide right out with 2-3 bolts being disconnected on the hub. Check Youtube for the process. This is the proper and best way to do it. The problem is, you're removing the axle, cutting the boot off, literally taking the axle apart at that end to get the new OEM boot back on, regreasing and clamping... and reinstalling. It's a lot and why a lot of people just get new axles at that point.

Really appreciate this suggestion, I think this is what I'll try first. Can all CV boot clamps go over the axle? It looked to me like the Subaru ones are a closed loop that need to be slipped on (which makes sense when replacing the boot as well).

I see both methods used fairly frequently, and just looking at the instructions I feel dropping the diff is more comfortable for me. But I'm open to being convinced that unbolting part of the suspension is simpler (my main concern is the hassle of retorquing at ride height and potential alignment changes (I have a good string setup to do alignment, but I hate the rear toe adjustment with a passion)).

Yeah, this is actually my bigger concern (not just the potential unneeded expense of the boot kit) - having to disassemble the CV joint completely to get the new boot on.

Unbolting the rear hub to get the axle out should minimally affect your alignment and ride height (IIRC it was just one or two bolts, and the hub hinges out of the way) since the mounting points are well relatively constrained (I think it was the main LCA bolt, and the traction arm main bolt).

You don't have to disassemble the entire CV joint to replace the diff-end boot. You just need to unclip and remove the bearing cage on the diff-end. It's not that involved if it's the diff-end only.

You do have to disassemble both sides for the hub-end boot (since it slides off-and-on from the diff-end).

New axles are way expensive compared to new boots. My strategy is having one spare OEM axle from a part-out rebuilt and ready to go, then swapping it out when time comes. I rebuild the boots on the removed axle when I have more time, and repeat when necessary.



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Also the OEM boot clamp is a closed loop; the loop size is specific to the small and large ends. If you wanted to replace it with a new OEM one, the axle has to come off of the diff.

Thanks for confirming. Some of the aftermarket/generic clamps do appear to be able to open up. I'll take some measurements and hit up my local stores to see if anything suitable turns out.

Maybe just a matter of terminology - this video shows the process and for me it basically "disassemble the CV joint" (relevant portion starting at 6:10):

https://youtu.be/TkKEFYvhnsk?t=370

If all you're doing is seeking to replace the diff-side boot, your job ends at 10:00 in the video as far as disassembly.

I ended up deciding to replace the boots and repack with Redline CV-2 to hopefully prevent future issues. Before removing the axles I'll try removing the current clamps and see if it can be done in-situ, but otherwise I'll remove the axles and do it properly.

Reporting back - redid the axle grease today, together with changing the diff fluid.
It turned out to be pretty easy to undo the Subaru clamps on the boots - bend back the two ears that hold it closed with a flat head screwdriver, then the clamp pops open mostly on its own. On the small clamps I had to pry them open more to get them off the boot, but the big clamps opened up enough on their own.
The original grease turned to syrup or thick oil - just came pouring out of the boot after I removed it (no problem catching that on the right side, but on the left side it poured on the exhaust pipe, making a bigger mess). I then wiped away all the grease syrup I could from the axle and boot, but that's obviously not as thorough as taking it apart.
Packed the area with CV-2 grease and closed the clamps. No issues there, they closed up just fine and seem to be as snug as before.

I still have the OEM boot kits and plenty of leftover CV-2 if this doesn't work out well and I do have to remove the axles and do a proper replacement. I'll keep an eye on the boots and update here.

I recommend using new clamps, I tried to reuse the originals and they always fail losing some CV-2 grease, especially the big one.

Very well might be, but the point of the exercise was to see if I can repack with higher temp grease (that wouldn't liquify like the OEM grease) without taking off the axles. This necessitates reusing the clamps (or putting new clamps that can be fully opened to go over the axle).

As I said, I have two boot and clamps kits, so I'm covered if this hack doesn't work.

I use new clamps that open completely, at least the long one, which is where the grease always comes out.

Did you try reusing the stock clamps? Might be that the aftermarket clamps that can open all the way don't work well.

Regardless, I'll be sure to keep a close eye on both sides of the boot to see if any more grease leaks out. Thanks for sharing that the big clamp can also leak (as originally I only had issue on the small clamp side).

Try to reuse the original clamps without success 3 times, in 3 different driveshafts, only the normal open clamps have worked for me.

I think the problem is in the boot, it deforms slightly over time and needs more strength to stay without leaks.

Cool, thanks for sharing. Fingers crossed it works better for me, and if not I'll bite the bullet and get the axles out and do the proper job.

Yeah, I think that's the case. Comparing the small side of the boot between the diff side (that was leaking) to the wheel side (which does not leak), it looks like it doesn't seal as well.
Still, I can't decide if the problem is the boot, the liquefied grease or both together, though.