With 2600 hours on our CV Axles (between transmission output flange and prop shaft thrust bearing) and 8000 miles of travel in the offing, we figured it prudent to have a look at this important gear.Removing these is not easy. They reside in the very tight space between transmission and hull. But with the help of Dave Wyman, and expert suggestions from Tom at Ventura Harbor Boat Yard, we had them sitting in the shop after a couple of hours of grunt work. It will be easier next time as we know the system now.
Here is a partially disassembled unit on the bench. They are actually quite clean, although they don’t look it in this photo.
One of the things were were checking for was the level of grease inside the bearing areas. In theory the grease is a lifetime packing, but you never know for sure as they “spit” grease when initially installed, until the correct level is achieved. These stopped spitting some time ago. As it turns out, the grease level was fine.
Ernie Cruz is cleaning one end of the unit in a bath of diesel. Ernie is an ex-auto-mechanic, and well familiar with CV axles.
Cleaned insides. Note that the ball bearings show no signs of wear, and the sealing surfaces are clean as well. We think those striations on the inner face of the carriers are from machining rather than wear (the other CV unit does not show these and they run counter to the direction the balls run). We tried to check this out with the folks at PYI who sold us these units, but were unable to make contact (maybe they got tired of our phoning for information on the units – the “manual” leaves a lot to be desired).
The consensus of Ernie and Tom is that we’ve probably consumed about 1/4 of the useful life of these CV axles. We are going to rotate them now, so the aft face now goes forward (to even out wear) and we’ll schedule the next look 5000 hours from now.
Posted by Steve Dashew (March 21, 2008)
May 26th, 2012 at 11:33 pm
Those “striations” are normal. I’ve rebuilt a lot of cv axles over the years and have noticed that same pattern on most of them. PS…GREAT website. Love all the detailed info. Please keep up the good work.
November 23rd, 2012 at 8:35 pm
Edit ~ I some how glitched my previous response..
CV joints… Nobody in the car world touches them anymore, they just swap them out. The folks that actually mess with them(he said mess..) are motorsport enthusiasts, wanting to preserve their finely made OEM parts. Being one of those enthusiasts, I may be able to offer some advice that crosses over to the marine CV shaft. They appear to be a direct adaptation of the Rzeppa style CV shaft. I’m going to be forced into making a few assumptions, but certainly they will sort out with a response.
We know nothing is “lifetime” lubricated. Not unless the lifetime is short! I can say with certainty that what is critical on this type of gear is metallurgy; heat treatment. No surprise, real German brands, and a couple Japanese brands are where the quality, long lived joints come from. They have well broached, matched and heat treated parts. When these parts are re-manufactured, really worn, or highly stressed for their rated app, then this surface hardening goes away, and problems start. Usually vibration starts, then excess wear. Breakage usually comes from stress risers in a complexly machined piece. Racers would de-burr, polish, and re-heat treat. Now, you just buy a motorsport piece. But for the rest of us…
Rotating the shaft upon servicing. Yes, good idea. Most of the wear I have found is actually on the splines of the shaft, so sometimes this means you have to actually swap the joints on the shaft, to put the loading on the “coast” side, vs. the “drive” side of the spline Or the CV. Worn Splines can really get by a pair of eyes, and still vibrate or introduce backlash.
Lubrication. The key. Ultra high quality Moly grease will do wonders for longevity. Boutique blenders (such as SWEPCO’s #101) produce grease that really works well, and really holds up to extreme pressure use. While some cold flow is good, drop out is not. Evaporation and “drying” is the main reason to clean and re-pack a CV. Getting rid of wear metals cant hurt, either. Grease is not grease. Don’t put tallow and chalk in your “axle”
A question could come in with corrosion resistance and salt compatibility. Swepco ( or others ) would be happy to help us, but I know that their lubes are anti corrosion, particularly their gear and hyd lubes. Since the shafts dont contain dissimilar metals, I would think this is a step in the right direction for a marine application of this grease. I know that a calcium base grease has its merits with dissimilar metals and or salty applications, but I think typically the EP (extreme Pressure) capacity is lower. Max EP is key in CV and hypoid type gears.
To tie together a few things, spline wear and lube drying go hand in hand. The grease wont work into and around the splines.
In this marine application, unless a lot of angularity is used in the shaft, the CV will be wearing in roughly the same spot, rather than plunging and articulating as they do in a car. This may be of interest.
Lastly, fasteners are a HUGE issue. Fasteners that are not safety wired or retained by a lock (STAGE 8 brand) will likely loosen and then transfer stress to the threaded part of the bolted joint and Break. This is no damn good. In my opinion, having replacement bolts on hand would be wise. That said, those fasteners need to be of very high quality. They are specialized, and so should your tool be for tightening them. At sea, when you depend on that specialty piece, no cheap socket will do. They break and they strip. Corroded bolts should be binned, and plated ones are tough to find. German Zinc plated can be found. Drilling for safety wire is tough due to bolt hardness. Good idea though.
AND (ha) there is more… LockTite. A lifesaver. But you try to get your clean locktited bolts through the greasy joint and flange… You would be better off performing minor joint replacement surgery on yourself. So Torque wrench tighten those bolts and lock em on with the same nice annealed safety wire you keep in your rigging kit. If you have never safety wired something, than learn how, from an expert. Use good grease in the joint.
I know this is wordy. Since we all seem to be concerned with sea worthiness, I felt it would be worthwhile to drone on. I really enjoy this forum. I like that you called it an Axle, Steve.
Josh
November 23rd, 2012 at 11:35 pm
Thanks for the long and thoughtful comments, Josh:
We have had minimum maintenance with the CVs over the years. The 6000 hours so far in these probably equals 300,000 miles on a truck. We pulled them out to check them, not because there was any sign (noise/heat) of wear.