Diff leaking fluid... what has failed?

[WoGGo]

End of Oct/early Nov I had the diff out for a new driveshaft cv joint and front diff bushing... drove home, all was well.

I've driven it twice since then, and pulled the her out this morning for a wash and noticed a significant amount of diff fluid on the garage floor.
Washed her, then slowly drove her around the block.. all seems fine.

The leak appears to be at the front of the diff - right under where the brace is; the rear diff cover looks perfect.

What has failed here?

[mrgizmo04]

Pinion seal (aka front diff seal) needs replacing. A bit tricky to do, because you dont torque the nut to a specific torque, you must tighten it to the same "position" to properly preload the pinion.

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[jet_dogg]

Perhaps she is on her period?

[WoGGo]

Pinion seal (aka front diff seal) needs replacing. A bit tricky to do, because you dont torque the nut to a specific torque, you must tighten it to the same "position" to properly preload the pinion.

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Any guide, or tips you can share?

I take it this is the part # 33121213949 ?

Is the Pinion Shaft Nut Retainer (33121205138) and Differential Pinion Dust Cover (33137600693) also required?

Is this basically it?

[sapote]

Any guide, or tips you can share?

I take it this is the part # 33121213949 ?

Is the Pinion Shaft Nut Retainer (33121205138) and Differential Pinion Dust Cover (33137600693) also required?

New seal, but the other parts can be reused.
Add marking to the nut position relative to the shaft, then carefully count the number of turns to remove the nut in order to install the nut back exactly at the original position. One turn more or less will cause problem, and don't ever turn the nut CW past the original position or you have to buy a new crushed spacer and more headache to set the torque right.

[mrgizmo04]

Yeah the video is "basically" it, but I would not just use air or a driver like in video to put the nut back on (or take off).

Like sapote said, there is a crush sleeve on the inside of the diff pretensioning the pinion to get proper bearing preload and lash with ring gear. Tightening the nut past where it is set when resistance torque was set on the crush sleeve, will require full disassembly of internals to replace the crush sleeve and properly pretension the resistance of the pinion and potentially readjust the lash with ring gear.

So it is a bit of a delicate procedure. I think the nut is on there with around 50 Nm of torque, but each diff is different. And getting it right matters in terms of how internals wear, how much whine comes from improperly pretensioned bearings and correct gear lash, etc.

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[bigjae46]

Don't put a jaw puller on the pinion shaft to pull the shaft off. You might push the pinion through the outer bearing and then your life will be much more difficult.

The crush sleeve takes the last and applies preload on the inner and out pinion bearing. It doesn't take much to get well beyond the preload spec once the sleeve starts to crush (already crushed). Once the play is taken out of the input flange, the preload will go from 0 in/lbs to 30 in/lbs in about 5 degrees. The spec is 12-23 in/lbs, ideal is 14-16 in/lbs.

I would recommend tightening the pinion nut by hand. Although less important on a higher mileage diff than a fresh rebuild.

[WoGGo]

Don't put a jaw puller on the pinion shaft to pull the shaft off. You might push the pinion through the outer bearing and then your life will be much more difficult.

The crush sleeve takes the last and applies preload on the inner and out pinion bearing. It doesn't take much to get well beyond the preload spec once the sleeve starts to crush (already crushed). Once the play is taken out of the input flange, the preload will go from 0 in/lbs to 30 in/lbs in about 5 degrees. The spec is 12-23 in/lbs, ideal is 14-16 in/lbs.

I would recommend tightening the pinion nut by hand. Although less important on a higher mileage diff than a fresh rebuild.

I'm thinking of giving this job to diff specialist and get him to change all three shaft seals (and lock rings) and adjust preload if need be... this would allow me to sleep better at night.

[bigjae46]

I'm thinking of giving this job to diff specialist and get him to change all three shaft seals (and lock rings) and adjust preload if need be... this would allow me to sleep better at night.

The side seals are much easier to replace.

For this job, you want to get close to the same torque. Doesn't have to be exact. The bearings are worn in and have probably lost some of the preload due to wear. You don't want to start adding preload by over-torquing the pinion nut. You'll accelerate wear on the pinion bearings but it doesn't affect backlash or the pinion and ring gear contact. Its not too bad of a job...the video is spot on as far as the procedure.

If the races and bearings are new then getting the pinion preload correct is a lot more important.

[WoGGo]

The side seals are much easier to replace.

For this job, you want to get close to the same torque. Doesn't have to be exact. The bearings are worn in and have probably lost some of the preload due to wear. You don't want to start adding preload by over-torquing the pinion nut. You'll accelerate wear on the pinion bearings but it doesn't affect backlash or the pinion and ring gear contact. Its not too bad of a job...the video is spot on as far as the procedure.

If the races and bearings are new then getting the pinion preload correct is a lot more important.

If I was only to replace both the input and output shaft seals (and o-rings and lock rings), could this be done without removing the diff from the subframe?

[sapote]

If I was only to replace both the input and output shaft seals (and o-rings and lock rings), could this be done without removing the diff from the subframe?

Yes, no need to be removed.

[ColinGreene]

Mine did this.
Its a good time to replace the diff bushings if you have some miles on the car.
My exeprience doing this leads me to say, probably order the front diff bolt and the front diff bushing to have on hand since someone previously had damaged mine. If you dont need it you can always return it.
Mine also pulled the threads out of the case while i was pulling it up to torque from the damaged bolt.

If you want to get real fancy you can always add a differential at this point but that would add a significant amount of cost.
Read the how to a few times, space for removing the rear diff bolts is tight. and keep in mind the differential its self is really heavy and covered in oil so dont put your face under it at any point when removing it.

[bigjae46]

If I was only to replace both the input and output shaft seals (and o-rings and lock rings), could this be done without removing the diff from the subframe?

Yes. Not too hard to do the seals with the diff in the car. Just need to lock the brakes on so you can get the pinion nut off with hand tools.

Do the input seal first and then remove the rear axles and do the side seals. Hopefully my lesson learned helps you lol


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[WoGGo]

Yes. Not too hard to do the seals with the diff in the car. Just need to lock the brakes on so you can get the pinion nut off with hand tools.

Just the handbrake is enough I assume?

[bigjae46]

Just the handbrake is enough I assume?

Not sure, my car doesn't have the hand brake.