grease coming out hole in rear axle

[ericinboca]

I have a 2004 986S that is a dedicated track car. It is driven very hard with R compound tires. The car has solid aluminum coilover mounts, bushings and spherical bearings.

Following two days of a DE this past weekend on the Sebring short course, there was a little bit of grease coming out of the hole on the end of the rear axle (you have to remove the center cap to see the outside end of the axle). It was not much - if you scraped it all up, I would say it is barely a half teaspoon.

It is the drivers side only, although I do recall the passenger side did the same thing briefly right after a rear wheel bearing change. I figured that bit of grease was related to the wheel bearing change - I cleaned it up, and did not have the issue again.

I do not know enough about the axle to to be able to figure out where it is coming from. Does this hole extend the length of the shaft and open into the inner CV joint? If so, could it just be grease migrating down under the g load? Other possibilities?

The CV boots, both inside and outside, are tight and whole, with no grease making its way past the CV clamps. I do not hear any noise that would make me think I have a bad CV joint (or bearing).

Any ideas?

[topmech0]

I have a 2004 986S that is a dedicated track car. It is driven very hard with R compound tires. The car has solid aluminum coilover mounts, bushings and spherical bearings.

Following two days of a DE this past weekend on the Sebring short course, there was a little bit of grease coming out of the hole on the end of the rear axle (you have to remove the center cap to see the outside end of the axle). It was not much - if you scraped it all up, I would say it is barely a half teaspoon.

It is the drivers side only, although I do recall the passenger side did the same thing briefly right after a rear wheel bearing change. I figured that bit of grease was related to the wheel bearing change - I cleaned it up, and did not have the issue again.

I do not know enough about the axle to to be able to figure out where it is coming from. Does this hole extend the length of the shaft and open into the inner CV joint? If so, could it just be grease migrating down under the g load? Other possibilities?

The CV boots, both inside and outside, are tight and whole, with no grease making its way past the CV clamps. I do not hear any noise that would make me think I have a bad CV joint (or bearing).

Any ideas?

if we are both thinking of the same hole (in the end of driveshaft/axle) then this is a breather hole and the grease is the grease for the cv joint. due to the use on the track it is getting hot and becomes thinner and being forced out the hole with temp and pressure. my advice would be once your done with a few track days simply peel back the rubber boots,both inner and outer and regrease the joints just to be safe and prolong their lives.

[Steve Danielson]

To bump up this older thread, I just noticed the same thing earlier this week when I took my wheels off to clean them and do a brake bleed and noticed some grease on my wheel behind the center cap.

 

Interestingly, the wheel with the grease was from the passenger side of the car, but the grease on the end of the axle was on the driver side. That wheel was bone dry, as was the rear wheels from the 2 other sets of wheels I run from time to time.

 

The wheel that had the grease got moved to the passenger side after a track weekend last October at Roebling Road when I flipped my Hankook R-S3 tires on the rim and moved them to the other side. So if the grease was ejected from the axle, it appeared to have happened before I moved the wheels, presumably at that track day?

Factors that may have caused that wheel area to heat up more than normal could be that I picked up a fair amount of speed since my last time there, running laps in the 1:29.x range which was 2 seconds faster than my previous best, and I also had a huge spin that weekend that may have caused things to heat up?

 

https://www.youtube.com/watch?v=5ZVgcA7ui7c

 

I also have TC on my Boxster (2000 S) and I wonder if the TC was going off and braking that left rear wheel and heating it up?

 

Any follow up on this issue - Eric was your car OK and /or did this issue happen again?

Thanks,

Steve

Edit: I have not crawled under there to see if there is any grease coming out of the back side - I will do it this weekend and inspect the CV Boot and see if I can determine whether it is low on grease and needs some added.

[JFP in PA]

The outer CV joint can get pretty hot during track days, and cause some excess grease to vent out.  The hotter the day, and sticky tires often accelerate this.  It isn't really a problem as the amount of grease is typically quite small, but after a lot of track time, it might be a good maintenance item to repack the CV's.

[Steve Danielson]

Thank you for the follow up JFP. It happened again at Sebring this past weekend - the amount of grease was quite small. I am replacing my rear wheel bearings so while I have the axle off I will repack the joints and install new boots. I am thinking of using the Redline CV-2 grease.

 

Thanks!

 

Steve