Best CV joint grease and boots

[shoebear]

I will be building new axles for my 2003 Jetta in the next couple of weeks with GKN inner joints and Metelli (boxed as Meyle) outer joints. I'd like these axles to last as long as possible, so I'm wondering if I can do better than the grease, boots, and clamps provided with the bearing kits.

GREASE

I'm thinking of using Redline CV-2 grease instead of the black molybdenum disulfide grease that comes with the joints.

According to Redline marketing info, "Red Line CV-2 Grease is designed to withstand the extreme temperatures and pressures which occur in high-performance wheel bearings and CV-joints." and "The exceptional extreme-pressure performance and the fluidity of the synthetic oil allows increases in bearing life of 200% to 800%. Red Line CV-2 Grease contains a red moly compound which is a superior lubricant to black moly disulfide lubricants."

Here's a video showing testing of synthetic greases -- CV-2 against Royal Purple. RP is not a moly grease, so I wouldn't consider that, but the test results for CV-2 are interesting. Bottom line: CV-2 beat RP as long as water was not involved.

BOOTS & CLAMPS

The best joint and grease will fail quickly if the boot fails. I have seen several boot failures where a crack developed at the inner edge of the small clamp, and others that develop in the folds of the boot. So maybe there's a better boot material that resists these problems, and maybe there's a better small clamp that's easier on the boot. Or maybe I should just go easy when I crimp the small clamp.

In addition to rubber boots, there are plastic, silicone, and even Kevlar ones. There are boots which can be stretched over the entire CV joint so the boot can be replaced without removing the joint. I did that with a Flexx-Boot FB3001 on my right outer joint about a year ago. Today the joint is bad, but the boot looks like new -- so the joint was probably already bad when I installed the boot.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At this point, I'm inclined to use CV-2 grease with stretch-type boots and just go easy when I crimp on the small clamp. But I'd like to hear what has worked for others.

 

[shoebear]

Bump

 

[P2B]

You might be overthinking this, most of us just buy GKN joints and use the boots and grease supplied.

 

[shoebear]

You might be overthinking this, most of us just buy GKN joints and use the boots and grease supplied.

Yes, I may be. I just want to build an axle that will last a very long time, and the boots and grease are part of the equation. Better grease should protect the bearing surfaces, and better boots should protect the grease. At least, that's the theory.

I've done some more boot research and found a couple of alternatives for outer boots, but only one for inner boots. That may be OK, though -- I think the outer boots flex more and tend to crack much sooner than inner. So I'm probably willing to use conventional Neoprene rubber inner boots.

The diameter of the axle where the outer boot clamps on is about 28mm on the left axle. I'm not sure about the right, but it's at least 28mm and may be up to 32mm. I don't have a bare right shaft to measure, though. The outer race boot clamp area diameter is about 85mm.

I ordered a pair of GKN thermoplastic outer boots (GKN 306693) from RockAuto for evaluation.

I have seen online praise for Rockford Duraboots, but their boot catalog goes only up to 1997 VW Jetta. I bet my 2003 is the same, though.

Volkswagen Bootkits

They have no online store and no retail reps in Colorado. I can order by phone; but the outer boot (335-21) is discontinued, and the inner boot (335-24) is out of stock for 4-6 weeks (he had a guy order several hundred 30 minutes before I called).

The correct outer Flexx Boot is FB3001, which is what I installed on my right outer joint about a year ago. The Flexx Boot has two places to clamp to the outer race, 67mm & 85mm. For my right axle, I cut the 85mm section off and used the 67mm clamp location, because the boot would have been too bunched up otherwise. Since the boot is stretchy, this worked OK. The Flexx Boots are thin, soft, and stretchy - they almost feel like silicone rubber. I think these qualities would make them resist cracking under normal use, but they also look easy to tear from road debris.

https://www.amazon.com/Flexx-Boot-FB3001-Blue-Universal/dp/B00C2M795I

I will update this thread after I evaluate the GKN 306693, and maybe get Rockford inner boots.

 

[Steve Addy]

You want a CV that lasts don't use a universal boot or a two-piece boot, get a boot that is designed to fit the CV joint you're working on.

The standard grease pack is fine for CVs, just load the joint properly, sort of like you would packing a tapered roller bearing and you'll be fine.

Steve

 

[tgray]

Regular grease will separate out in time. The new synthetics are way better for long term. You may check with the grease companies themselves. They often will put in certain additives for specific applications like CV joints. Years ago I worked in an auto repair shop and I was warned not to use regular grease in the CV joints for a rebuild. They even didn't want us to use regular solvent when cleaning the old grease out but never heard a good reason why not. I always bought the stuff they sold at the auto parts stores for this purpose. They sell pouches that are pre measured out for each joint.

 

[shoebear]

Regular grease will separate out in time. The new synthetics are way better for long term. You may check with the grease companies themselves. They often will put in certain additives for specific applications like CV joints.

Thanks, tgray.

That's why I like Red Line CV-2. It's synthetic grease made specifically for CV joints.

From Red Line...

Red Line CV-2 Grease is designed to withstand the extreme temperatures and pressures which occur in high-performance wheel bearings and CV-joints.

The excellent high temperature stability, extreme-pressure protection and water resistance enables it to out-perform even the best conventional or synthetic greases.

Red Line CV-2 Grease can be used in a wide range of applications at temperatures ranging between -100°F to 500°F and provides good oxidation and corrosion resistance, low evaporation and oil separation, and has a minimum effect on rubber seals.

The exceptional extreme-pressure performance and the fluidity of the synthetic oil allows increases in bearing life of 200% to 800%.

Red Line CV-2 Grease contains a red moly compound which is a superior lubricant to black moly disulfide lubricants.

 

[JordanTr]

Ball in cage CVs should use a moly disulphide grease.

 

[shoebear]

Two subjects: Red Line CV-2 grease availability and an update on boot material.
_______________________________________

FYI for anyone trying to get Red Line CV-2 grease, I had a conversation with their Customer Service earlier today.

Red Line moved their manufacturing and packaging from California to Tennessee early this year. When setting up everything in Tennessee, they found that the packaging machinery for CV-2 was damaged and inoperable. They expect replacement machinery to be back up and running by year end, but in the meantime, there is no CV-2 available anywhere (at normal prices, that is). The rep promised to send me an e-mail when they start shipping to distributors (I have a backorder from Jegs). I have about half a grease gun tube left -- probably enough to do one axle. But my axle rebuilds can wait until next year -- no rush.

I found out that CV-2 uses a calcium sulfonate thickener. This adds to the EP protection provided by the red moly EP compound and is compatible with many other greases.

_______________________________________

I purchased GKN thermoplastic outer boots along with a pair of Flexx Boot FB3001's. The GKN polymer boots are flexible, but less so than either the regular neoprene boots. However, they are tougher, smooth and have less friction, so two bellows rubbing against each other would be less likely to damage each other. They are also longer than the regular boots, so they might be pretty cramped on the right axle where the hollow shaft limits how far the small opening of the boot can go.

The Flexx Boots are very flexible, thinner than the neoprene boots, and probably about as thick as the thermoplastic. They feel like silicone rubber., and they are somewhat tacky, as is typical. They are also extra long, but they are made so they can be trimmed shorter.

I think there are three failure vectors to consider: cracking due to repeated flexing, friction from bellows rubbing against each other, and tearing from contact with road debris. Here's my guess on how susceptible each boot type will be to each vector. Low is good and High is bad.

• Neoprene: flexing: medium; friction: medium; tearing: medium
• Thermoplastic: flexing: medium; friction: low; tearing: low
• Flexx Boot: flexing: low; friction: medium; tearing: high

When CV-2 grease is available again, I think I will build one axle with a Flexx Boot and the other with a thermoplastic one. Then I'll inspect every oil change and see which one lasts longer.

 

[shoebear]

Outer CV joint options
L-R: Standard GKN 300426 neoprene rubber, GKN 306693 thermoplastic, Flexx Boot CVBOOTLG untrimmed, Flexx Boot CVBOOTLG trimmed

Outer CV joint options w/boxes
L-R: Standard GKN 300426 neoprene rubber, GKN 306693 thermoplastic, Flexx Boot CVBOOTLG trimmed

The Flexx Boots are made with two possible diameters for the large end. The larger diameter is a bit too big for our CV joints, and the smaller diameter is a bit too small. However these boots are extremely stretchy, so the smaller diameter works fine. Also, trimming the boot to the smaller diameter makes the boot shorter, which is helpful especially on the right hollow axle where there is a limited length of solid axle before the diameter increases for the hollow part.

 

[PakProtector]

I like the NAPA CV joint grease. Nice and gooey, and has a fair loading of Moly-disulfide in it. Easy to get too.

For the inners, put the inboard seal on first when everything is clean. It is waaaay troublesome to try once there is grease everywhere...LOL

GKN goodies( boots, clamps, and of course the joints ) serve well for me. About 50% more grease than comes in a single packet also seems to help. IOW, buy 3 for two joints.

Douglas