Rear Differential Seepage?

[brynamic]

I noticed a line of liquid on my garage floor towards the back of my bronco sport. Turned out to be water but while investigating I noticed the rear differential has a bunch of grease? on it. I thought it was seeping fluid at first but it’s not that. Anyway, is this normal?

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[Major Kong]

Permatex ?

 

[brynamic]

Permatex ?

I took a closer look and it’s something along those lines. Seeped out when they joined the two pieces together. One would expect they would wipe away excess when assembling. At least in this vehicle it’s only seen when one is underneath.

 

[Mark S.]

One would expect they would wipe away excess when assembling. At least in this vehicle it’s only seen when one is underneath.

I found the same thing on mine when investigating another post about a rear diff leak. This is called sealant "squeeze out."

I don't know this for certain, but my guess is the squeeze out on these assemblies is left on purpose. Certain types of sealants must partially cure before joining the parts. The timing is important: Too much time and the seal may become too hard to squeeze into the shape required to seal the space between the parts. Too little time and the sealant between the joined parts may never cure, and the seal may fail the first time it sees any pressure. An appropriate squeeze out of the sealant is evidence of the appropriate cure time, which aids final inspection of the assembly. Peeling away the squeeze out of a partially cured sealant after joining the parts might take part of the sealant between the parts with it, thereby weakening the seal.

 

[brynamic]

I found the same thing on mine when investigating another post about a rear diff leak. This is called sealant "squeeze out."

I don't know this for certain, but my guess is the squeeze out on these assemblies is left on purpose. Certain types of sealants must partially cure before joining the parts. The timing is important: Too much time and the seal may become too hard to squeeze into the shape required to seal the space between the parts. Too little time and the sealant between the joined parts may never cure, and the seal may fail the first time it sees any pressure. An appropriate squeeze out of the sealant is evidence of the appropriate cure time, which aids final inspection of the assembly. Peeling away the squeeze out of a partially cured sealant after joining the parts might take part of the sealant between the parts with it, thereby weakening the seal.

Seems like sound logic. Thanks for the insight!

 

[tburner]

An appropriate squeeze out of the sealant is evidence of the appropriate cure time, which aids final inspection of the assembly. Peeling away the squeeze out of a partially cured sealant after joining the parts might take part of the sealant between the parts with it, thereby weakening the seal.

This, and manufacturing lines are designed to be highly efficient (or "lean"). Performing non-value-added operations, like removing squeeze out from places that won't be normally seen by consumers, is a waste of resources and complicates the flow of product down the line. Orienting the assembly to facilitate sealant removal after the appropriate cure time could be disruptive and may even be prohibited by tooling design.

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