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2005 saab trailblazer_lt
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5 Posts
Discussion Starter #1
2005 Saab 9-7X; 4.2L, AWD; 83,400 miles.

This thing has never leaked seriously. Never.

I change-out the front diff. fluid a couple of weekends ago and the thing leaks clean fluid routinely now.

I’ve buttoned up the drain and fill plugs and have confirmed these are not the loss locations.

I can’t imagine that it’s been over-filled as only almost exactly one quart of new fluid went in as this volume was all it would take.

Anyone have insight into my WTF?
 

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2005 saab trailblazer_lt
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5 Posts
Discussion Starter #3
So can you see where is it leaking?
No question I’m gonna have to get underneath again.

However, when I was looking for the source previously there was no obvious origin on the differential itself. Just a wet rear-ward cross-member exhibiting drips.

I honestly thought perhaps I’d spilled fluid into the hollow portions of a support member and the fluid was eventually finding its way out. However, that theory is losing support.

Thought maybe someone had some quick “yep, been there done that” insight.
 

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2004 GMC Envoy SLT 4.2
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175 Posts
You might consider pressure washing the differential . Once dry , it should be fairly easy to see the origin of the leak .
Obviously , you'll have to keep a close eye on it until that happens .
 

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2004 buick rainier
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80 Posts
2005 Saab 9-7X; 4.2L, AWD; 83,400 miles.

This thing has never leaked seriously. Never.

I change-out the front diff. fluid a couple of weekends ago and the thing leaks clean fluid routinely now.

I’ve buttoned up the drain and fill plugs and have confirmed these are not the loss locations.

I can’t imagine that it’s been over-filled as only almost exactly one quart of new fluid went in as this volume was all it would take.

Anyone have insight into my WTF?
After a front-differential fluid change, I spent a year replacing seals to stop leaks on my 2004 Buick Rainier. Turns out, I was overfilling! I was filling to just where the lube would ooze out of the fill hole, then replace the plug. When driving, I think the lube warms up, expands, then finds a way out -- even if the vent tube is clear and unkinked and the seals are good.

My solution was to lower the lube level so it's about 1/4-inch below the fill hole. No more leaks since I did that. I've got more than 220,000 on my Rainier, and the front diff remains dry as a bone.
 

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2007 gmc envoy_denali
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1 Posts
2005 Saab 9-7X; 4.2L, AWD; 83,400 miles.

This thing has never leaked seriously. Never.

I change-out the front diff. fluid a couple of weekends ago and the thing leaks clean fluid routinely now.

I’ve buttoned up the drain and fill plugs and have confirmed these are not the loss locations.

I can’t imagine that it’s been over-filled as only almost exactly one quart of new fluid went in as this volume was all it would take.

Anyone have insight into my WTF?
Make sure the diff vent is clear. A plugged vent builds pressure, causing leaks everywhere.
 

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Drop the oil level to about 1/8 of an inch below the fill plug and all problems should stop all of your problems as the oil does expand with heat and it will find areas to come out even though the seals are good, the oil will seep around them. It does not ruin the seal it is that you have too much oil in the diff.
 

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2008 chevy trailblazer_lt
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68 Posts
It probably won't apply at all, but I found that my rear diff on our 2008 4.2L leaked at a weld for holding the tube to the center section. I ended up cleaning it with brake cleaner and then adding a dab of RTV to it, and so far, so good. Manufacturing defect, if you ask me. Perhaps fronts may have some similar issue.

Rob in AZ
 

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2005 saab trailblazer_lt
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5 Posts
Discussion Starter #9
Much obliged for the input men ...

Differential area cleanup (again) and vent tube check/maintenance is on my agenda for today.

The fluid level observations and recommendations make sense based on vehicle’s absolutely leak-free history.

As a matter of fact, I thought it quite odd (and was a bit concerned) when I only recovered a little more than 1/2 quart of fluid when I did the drain and refill as the previous differential service (at about 40K miles) was done by our now deceased Saab dealership.

If this fluid volume thing is accurate, it’s troubling that the information available related to differential fluid capacity is down-right wrong.
 
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