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.

[derekja]

Is this what you mean?

Are you talking about a leak on the wheel side (like I have) or on the engine side?

[gmctd]

Inner (differential) side - you have a multiple-ruptured boot on the outer wheel-end, and the makings of one on the inner end

How's the passenger-side?

[derekja]

no evidence of the wheel side boot or the differential side boot leaking on the passenger side of the truck. I presume that this means that I should definately replace the driver's side wheel seal and that maybe I can get away with tightening the differential side for a while but that it will need addressing before too much longer. Sound reasonable?

The GM service manual says to use J-36605 steering knuckle seal installer, but the Chilton manual says nothing about this and says to use a flat plate to install the seal flush to the hub. I presume the use of the special tool is optional?

Thanks!

[gmctd]

Looks to me like you just need the two boots - outer and inner - and when you pull the half-shaft, you'll also need the inner hub-seal.

JohnC is referring to the differential side-seal, to the left of the inner joint in your pic - doesn't look to me like it is leaking, as the joint is dry, but check it anyway.

[ronniejoe]

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

The suspension travel is compensated for with the CV joints outboard of the flange. There is no more radial load on the left outer bearing than on the right. By the way, there are differences in configuration between the 1500 and 2500 front diff's, but they work in similar fashion.

[DA BIG ONE]

If c-clip that retains stub axle to carrier is worn (not holding) the stub axle can slide in and out of carrier then wobble, vibrate and at extreme angles come completely out (especially when tq bar key is overtightened for x-tra lift) of frt/diff resulting in major failure of steering/braking control.

[gmctd]

Sorta suspected that, ronniej - do hope this is all helpful to JohnC

Derekja, you can probably use a hammer and pine drift to install the seals - would not be a confidence-instilling sight in the service bay, tho.

[JohnC]

-do hope this is all helpful to JohnC

Not really - you guys are telling me I need a new differential carrier after 65000 miles! Oh, well, president's day sales are on this weekend... (Oh, btw, the ABS speed sensors started up again today!)

I don't think it has anything to do with oil levels. I know it wasn't low until the leak started. Same with my '95.

After thinking about it, when the front axle and 4WD are disconnected, the speed differential between the axle shaft and the carrier could be quite high. Sounds like another GM excellent design. If only there was a bearing there...

I assumed it was the bearing in the housing that the axle rides in that was the problem, but I can see how if the side gear is providing the other locating point, it could fail that way.

[gmctd]

Not really, dude - I'm suggesting you pull it and check it out - best case, make the adjustment, new seals, and you're good to go.

If you disassemble the outer stub axles from the half-shafts, reinstall 'em, and torque 'em in, you can drive the truck while you fix the drive assembly

That's the same problem AMC had with their part-time awd, with the vacuum-disconnect front axle

[ronniejoe]

I'm curious what adjustment you think will fix this problem? When I had mine apart to repair it, I saw no provision for any such adjustment.

[gmctd]

'Nother words - I'm suggesting repair, not replacement of the front-drive axle.

But, you're right - the K10-20 series has output-shaft bushings in a removable but non-adjustable casting.

The K30 series has real bearings and adjusters.

[ronniejoe]

I'm talking about the K3 (according to manual terminology) unit that is in the HD Suburbans. It's the same unit as the K3500's. The screw adjusters that you're thinking of won't help here.

The only adjustment available is side to side locatoin of the carrier assembly to set pinion to ring gear backlash along with side bearing end play. This adjustment will have no effect at all on the problem we're discussing.

If his problem could be remedied by making these adjustments, there would be other, larger issues to deal with... Namely, replacement of the pinion and ring gear. The mesh would be so bad at this point that teeth would be breaking.

[gmctd]

Draining the oil would indicate if it's that far along, but possibly the 1500 unit is a throw-away - difficult to imagine bushings on an axle shaft that not only rotates any time the vehicle is in motion, but takes heavy radial thrust loading any time the suspension moves

The drive-shaft yoke rides in a bushing, but no radial loading.

[ronniejoe]

What are you talking about?????