7.5 Axle Shaft End Play

[Redgoat]

So I have almost 150K miles, 4:10 gears with Trac Lock, and at least 3/16 or more in and out axle shaft end play. The rear end seems fine, with no unusual noise and just a small amount of fine metal paste on the magnetic filler plug when checking the lube level. From what I have read here the end play cause seems to be clutch pack wear. Question; Do I need to worry about failure of the differential? As in can the side gears spread apart, and if so, far enough to become a problem? I am not overly concerned about not having positraction because of the wear.
Any thoughts appreciated!

 

[MikeG]

There's a tad bit of end play because there has to be for a c-clip axle/rear end to work.

Whether that is too much or not, someone else will know.

 

[Dirtman]

3/16" is high but unless you see damage to the cross pin I wouldn't be overly concerned.

 

[4x4junkie]

It seems the side gear should eventually bottom out against the carrier before the c-clip can fall out. If it didn't, we probably would hear plenty of horror stories of people's axles coming out on the freeway. You should be fine (it just makes a knocking noise when going over speed bumps and such).

Replacing the clutch stacks in the Traction-Lok differential is normally how to eliminate the play (to within a couple hundredths or so).

 

[MikeG]

Dirtman has it correct. The cross-pin is what keeps the end of the axle shaft from going further into the case. Remove cross pin, push axle IN, then there's enough room to take the c-clip out. Then slide axle out.

The clutch packs are to add friction between the side gear and the carrier, not to change the position of the axle. Since the axle is splined to the side gear, it is free to move in and out - till you put the c-clip in, and the cross pin.

The spring in the middle of the trak-lock adds pressure to the clutch packs, but it doesn't affect the position of the axle. It can't.

 

[4x4junkie]

Um I was talking about WEAR of the clutch packs.

When the clutch packs wear down, they get thinner. This opens up a gap between the cross pin and the end of the axle shaft (the side gear moves away from the cross pin as the clutches wear). Eventually at some point the side gear will bottom out within the carrier, and the clutch pack will no longer have any pressure on it. From that point on, it functions as an open differential.

 

[scotts90ranger]

Given enough time and use, the spider gears can wear out... when I bought my '00 Explorer the main issue I thought was a clicking in the rear axle, this is what I found... conveniently I had a spare set, or I grabbed some from a junkyard, I don't remember anymore since it was 5 years ago...

There was no friction material left so this was steel on aluminum and the C clips stayed in, so there's that

 

[4x4junkie]

Dang, those look just like gears I pulled out of my Traxxas RC car differential one time. lol

I can see how the lesser amount of tooth engagement might cause that (the fix on the RC is infact to shim the gears tighter).

 

[MikeG]

Um I was talking about WEAR of the clutch packs.

When the clutch packs wear down, they get thinner. This opens up a gap between the cross pin and the end of the axle shaft (the side gear moves away from the cross pin as the clutches wear). Eventually at some point the side gear will bottom out within the carrier, and the clutch pack will no longer have any pressure on it. From that point on, it functions as an open differential.

I don't think so. The clutch packs don't keep the axle from moving farther in, the cross pin does. Half (roughly) of the clutches are keyed to the carrier, and the other half to the side gears. The side gear 'floats' on the axle splines. The axle goes all the way through the side gear till the end of the axle stops when it touches the cross pin. Found this pic:

Yes, clutch packs wear for sure, but they don't have anything to do with how far into the carrier the axle goes.

Look at the end of the axle, the only thing that keeps it from coming out of the carrier is the c-clip that fits in the groove. There's nothing to keep the axle from going further into the carrier, except the cross pin, at least till the bearings bottom out on the outer end of the axle where it goes into the rear end tubes.

 

[scotts90ranger]

It's not the axle moving further in, it's the side gears moving out opening up the gap for the C clip... I get what you're saying, but the side gears still move outward as the clutches wear out opening up the gap which is what they're talking about above.

I've never looked at a 7.5 LS but I'm sure it's just a smaller version of the 8.8. I imagine it'd be very difficult for a C clip to fall out with the S spring in there anyway.

 

[MikeG]

Ah OK I see what you are saying now.

 

[Dirtman]

Yea you really can't get enough room for a c-clip to come out unless you have either damaged the cross pin or mangled side gears like whatever the heak Scott did to that poor explorer. Both of which would be blatantly obvious in noise and chunks of metal in the gear oil. The clutches can be worn to nothing and still not give enough room to let the c-clip come out. New clutches and spring will suck up some of the play but it's not something you need to loose sleep over.

 

[Redgoat]

Thanks guys for all of the input and pics. Guess I'm just gonna have to get dirty and pop the cover off, see if I can get an eyeball on the side gears and crosspin to see if there's any unusual looking wear!

 

[Dirtman]

Don't forget to put your tools away!

 

[scotts90ranger]

Don't put too much weight on my picture above as to what "will" happen, it's more of a "could" situation...

I bought the explorer that way, was hoping for a free fix, which that part was, but it turns out the transmission was fubar, I have like $1100 just in PARTS to get it back together... The thing had I think 206k on it when I got it, one key note that I know to look at in the future is the receiver is bent down I'm assuming from towing a lot in the past. How they killed the spider gears in the rear of an AWD 5000lb explorer is beyond me, did they try to do donuts all the time or something? That poor 4R70W was rough...