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Rear diff problem - sierra
http://auszookers.com/forum/viewtopic.php?f=5&t=9655		 Page 1 of 1
Author:  acc1 [ Thu Feb 04, 2010 10:35 pm ]
Post subject:  Rear diff problem - sierra
Need some friendly advice /opinions for my tonka; :)

Pissed most the oil out last time It was driving from around the flange, at 110kph about a week ago. Thought it might just be the seal, was going to do it at home today, Just about to start unbolting to replace seal and the shaft has got a good amount of play in it, compared to the front which has none, Thinking a bearing or 2 has gone.. Or worse :( ?

Any idea on prices/ recommended place to get the diff looked at in case its a serious problem?

Or attempt to do the seal and tighten it back up and see if problem still exists?

I think it might be worth getting checked just to be sure, tho im not looking forward to the bill. (best place to get it done? - Newcastle area)

1991 sierra.

Have no diff experience. Just have a few pdf manuals that have been looking at and think the seal might be as far as Id be willing to go.

What to do?

Thanks.
Author:  Rusho [ Thu Feb 04, 2010 10:48 pm ]
Post subject:  Re: Rear diff problem - sierra
Shaft play, would possibly be the uni's. If you are confident and have a manual there give the seal replacement a go. You won't learn if you don't. There would be plenty of experienced guys on here that can give you some extra info ant tips if you run into trouble.
Author:  31zook [ Thu Feb 04, 2010 10:52 pm ]
Post subject:  Re: Rear diff problem - sierra
weaves sell's bearing, $50 the lot, mcwilly paid $600 a diff to get them rebuilt, but try newcastle gear box and diff shop, should be cheaper then $600 tho...
Author:  acc1 [ Fri Feb 05, 2010 12:14 am ]
Post subject:  Re: Rear diff problem - sierra
k, had a play with it, looks like it tightens up the play when the pinion nut? is tightened a little, trying to replace seal now, bitch of a thing to get in lol will try get it in then bolt up n see how it feels, put some oil in tomorrow and give it a drive to see how it runs.

Anyone recommend any oils other then whats recommended in the driver manual?
Author:  Rusho [ Fri Feb 05, 2010 12:16 am ]
Post subject:  Re: Rear diff problem - sierra
Castrol 80w-90, can't go wrong
Author:  acc1 [ Fri Feb 05, 2010 1:28 am ]
Post subject:  Re: Rear diff problem - sierra
okie dokie, seal in and bolted up, much better now did about an extra quarter turn and slack is all gone.

manual says 80w-90, 75w-80 and "recommends" 75w-90

Either way Ill get one of them tomorrow fill it up, then test drive.

Should be good as new.

Now that is done I can go onto contemplating if I want to get 6.5-1 transfer gears.. And if I do it, or get someone else to do it. lol
Author:  Gwagensteve [ Fri Feb 05, 2010 2:15 am ]
Post subject:  Re: Rear diff problem - sierra
acc1, I don't want to be the bearer of bad tidings, but your diff is pretty much toast.

A) Tightening the pinion nut might remove some play, but the seal is likely already damaged and so, potentially, is the seal area on the pinion.

B)Preload on the pinion bearings is critical. You need to know why is went slack. Were the peened sections of the pinion nut still sitting in the slots on the pinion shaft? If so, nothing loosened off, what's happened is that the crush sleeve has collapsed a bit. This is common under high load. I've had discussions with diff specialists about if it's feasible to just "crank it up" once this has happened, and it's not at all clear that it will work. (and that's even assuming the seal, gears and bearings are OK.

C) Play in the pinion shaft means the pinion can start thrusting backwards and forwards. That creates rapid wear on the gears and results in a gearset than can never achieve a proper pattern ever again.

D) Odds are, if the car has done any offroad use since the seal was leaking, you've pulled dust and possibly mud/grit past the seal. That's never going to be a good thing.

I've learned all this the hard way. You might get away with it for a short time, but be aware it will get noisy, probably continue to weep oil and that when you take this diff to a specialist, be prepared for them to say the gears and bearings are junk.

Steve.
Author:  royce [ Fri Feb 05, 2010 2:29 am ]
Post subject:  Re: Rear diff problem - sierra
While I agree a bearing has died and the diff needs rebuilding

Gwagensteve wrote:
what's happened is that the crush sleeve has collapsed a bit. This is common under high load. I've had discussions with diff specialists about if it's feasible to just "crank it up" once this has happened, and it's not at all clear that it will work. (and that's even assuming the seal, gears and bearings are OK.



is stupid, how does this make sense? for the sleeve to crush and the bearings go loose there must of been freeplay in there already and the spacer to be longer than the seated distance between the 2 bearings but then it wold make no difference anyway as the freeplay will be the same as its set but eh 2 extremes of the pinion and the nut
go google around on this, the sole reason solid spacers are used in high hp applications is ease of setting up and not having to buy new crush sleeve every time
Author:  Gwagensteve [ Fri Feb 05, 2010 2:52 am ]
Post subject:  Re: Rear diff problem - sierra
As per the other thread Royce. Excessive torque = thrust loads that defeat the preload applied to the bearings by the crush sleeve and accelerate failure.

Steve.
Author:  acc1 [ Fri Feb 05, 2010 4:25 am ]
Post subject:  Re: Rear diff problem - sierra
Gwagensteve wrote:
acc1, I don't want to be the bearer of bad tidings, but your diff is pretty much toast.

A) Tightening the pinion nut might remove some play, but the seal is likely already damaged and so, potentially, is the seal area on the pinion.

B)Preload on the pinion bearings is critical. You need to know why is went slack. Were the peened sections of the pinion nut still sitting in the slots on the pinion shaft? If so, nothing loosened off, what's happened is that the crush sleeve has collapsed a bit. This is common under high load. I've had discussions with diff specialists about if it's feasible to just "crank it up" once this has happened, and it's not at all clear that it will work. (and that's even assuming the seal, gears and bearings are OK.

C) Play in the pinion shaft means the pinion can start thrusting backwards and forwards. That creates rapid wear on the gears and results in a gearset than can never achieve a proper pattern ever again.

D) Odds are, if the car has done any offroad use since the seal was leaking, you've pulled dust and possibly mud/grit past the seal. That's never going to be a good thing.

I've learned all this the hard way. You might get away with it for a short time, but be aware it will get noisy, probably continue to weep oil and that when you take this diff to a specialist, be prepared for them to say the gears and bearings are junk.

Steve.


Well hopefully its not going to be the end of the world any time soon lol.

It doesn't get many klms on it at all, it would be lucky to see more then 3k per year.

If it does shit its self then Ill get it checked out / repaired and probably get a locker in at the same time.

What would be an estimate to get it completely rebuilt if it does shit its self?
Author:  v.w.dave [ Fri Feb 05, 2010 5:14 am ]
Post subject:  Re: Rear diff problem - sierra
Or you could find a mate on here that has a backyard full of parts and or other mates that have more.... Aint that right 31zook :) I think at last count I had 3 complete diffs and about 5 taken apart in boxes. My roomate has a few too.
Your not too far away let me know if I can help.
Author:  acc1 [ Wed Feb 10, 2010 9:52 pm ]
Post subject:  Re: Rear diff problem - sierra
lol ok, its running ok so far no problems. Will keep an eye on it to see if it goes poop again anytime soon.
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