IFS Oil leak Driver's side

[JohnC]

I asked this question a few years back and didn't like the answer I got. It's reared its ugly head again, so I'll ask again.

First time around I asked about slop in the CV stub axle on the driver's side of my '95. I could move the outer end of the stub up and down about 1/8" and the seal was leaking profusely. I was told that play there was normal. (That's the part I didn't like). I crawled under the '99 at that time and that axle was rock solid. I kept adding oil and eventually sold the truck.

Well, today I noticed an oil stain on the ground under the '99. I crawled under there and the driver's side of the axle is dripping wet and the axle has about 1/8" up and down play. Don't tell me it's supposed to be that way!

Why are these things failing (for me, at least) and how difficult is it to fix? Can I do it without special GM tools?

[ronniejoe]

When you say "stub axle", do you mean the flanged shaft that comes out of the front differential? If so, then you must be talking about gear oil from the front diff leaking?

This can only mean a failed bearing and subsequent seal failure.

[gmctd]

Assuming the 1500's are constructed similar to the 2500\3500 -

The differential side-adjusters can be tightened after removing the stub shaft - pull the half shaft, use a slide-hammer on the stub shaft.

Should really be done with the diff on the bench, so you can get the proper backlash pattern - adjust it up, replace the seals, and you're good to go

[JohnC]

I can't believe I'm the only one having this problem, and I'm 2 for 2 after 60,000 miles.

JD: I doubt if it's a carrier bearing issue. The '96 went another 80,000 miles with frequent oil additions. (This one seems to be leaking more earlier in its life ).

AFAIKT, there's some sort of bearing that supports the stub axle (This is a European front wheel drive term. It refers to the thing that splines into the side gear and has the cup for the inner CV joint. I think you're right, RJ, that the cup is separate on the GM version.) And yes, it's gear oil leaking out of the front differential carrier.

So, what stresses the bearing and why isn't it up to the task? If the CV joints are working well there shouldn't be much stress there!

Last time I looked into it, it appeared that the bearing was the first thing to go in and the whole axle was assembled into the housing on top of it. Passenger's side, on the other hand, looked like a 10 minute job...

Anyone have any info on this?
TSB #3340 -- LEFT FRONT AXLE SHAFT DIFFICULT TO REMOVE. AXLE DIFFERENTIAL LEAK SEAL SHAFT. *KB (NHTSA ID #10020874, SEPTEMBER 23 2006)

[ronniejoe]

I had a problem on my Suburban back in 2004. The bearings themselves were OK, but the side gear had worn the carrier badly allowing the inner end of the axle shaft to slop around quite a lot.

What happened is that the oil level had become low and I didn't realize it. I was actually pretty careless about checking it because I figured it wasn't run down the highway in 4wd much.

However, these diffs with the central axle disconnect have spinning parts all the time and need to maintain proper oil level. When not in 4wd, the left axle is still directly connected to the left front wheel so it will turn. The disonnect takes place on the right axle output shaft with a sliding shift fork and collar. Therefore, the left axle drives into the differential, through the spider gears and out to the right axle output shaft, which is turning backwards as you go down the road. The outer axle shaft and CV joints are connected to the right front wheel, so they are spinning forward. When 4wd is engaged, the front drive shaft will begin to turn the pinion which turns the carrier. As the carrier speed reaches the same speed as the left axle shaft, the spider gears will slow to a stop and the right axle output shaft will spin forward at the same speed as the right outer axle. The shift fork then slides the shift collar over to engage the front differential.

The differential side gears sit in a precision machined bore in the carrier with no rolling bearing. There is sliding contact between the gear and carrier when 4wd is disengaged. If the oil level gets low, over time the gear will wear the cast iron carrier and open up clearance between the gear and the bore. When this happens, the output shaft can flop around and wipe out the seal.

This may be what has happened.

To fix it, you must replace the carrier. I also replaced the differential gears (spider gears).

[gmctd]

Good explanation, rj - the left half-shaft is always spinning and is too short for the available suspension travel.

All that extra radial thrust takes out the bearing assy on that side - the passenger-side has the long split disconnect shaft between the half shaft, so the carrier assy gets none of the same type wear.

You can tighten it up and seal it, but if you're keeping the truck, it'd be better to R&R the diff assy, imo.