Synthetics causing a leaky rear end?

[ferr1s]

Replaced the fluids in the hoe a number of months back, then noticed that sometime later my rear axle seal was leaking abit. I replaced seals at the end of December on both sides, since I had to take the rear end apart. (I used Moog parts) Now I'm smelling gear oil every now and again. I don't see any leaks though. The shafts looked great when I took them out, no burrs or knicks, but I find it a bit crazy that I'm having this problem again on a hoe with only 40k on it. Anybody else ever face this issue?

I had one guy tell me the synthetics were too slick! I had to laugh a bit =-)

- Ferris

 

[jomulk56]

Synthetic will leak easier than conventional. It's not exactly "slicker" but it flows better and could be thinner than conventional.

 

[Jay]

Synthetic motor oil particles are smaller and more spherical in shape than regular oil. So they will find their ways through older seals that regular oils won't.

With new seals there shouldn't be any leaks unless the corresponding mating surface isn't completely smooth.

 

[91RS]

Synthetic does not leak more than regular, that is an old wives tale. Besides, the rear differential comes from the factory with synthetic lube and requires it.

 

[ferr1s]

Chevrolet puts synthetics in the diff from the factory? I figured with all the cost cutting automakers do that we'd be sporting old honey or bad maple syrup back there!

I checked the surface of the new seals, coated them with oil, and then checked the surface of the axle and didn't find anything out of the ordinary. The axle didn't have any wear or grooves that would suggest a problem anyway.

It's weird that I didn't notice the leak the first time until about a month or two after I changed the fluids to AMSOIL (engine, tranny, and rear diff.) Changed the seals on BOTH axles and the same side that leaked the 1st time, began to leak again a month or so later. Though I'm leaking very little now versus what I was leaking originally. I thought maybe it was somehow overfilled the 1st time and caused the seal to leak, but the second time there is no way that is the case.

If it leaks less every time I change it, then eventually it will stop if I change it enough, right!?!

 

[Jay]

It's not an old wives tale. I've owned a sizable fleet of trucks over a few decades and experienced this first hand a few times. Switching to synthetics at higher mileage... talking 100k+... in vehicles that only had regular lube will usually reveal leaks until you switch back or replace the offending seals. At 40k it shouldn't be an issue though.

The only advice I can give the OP is to drive the truck until you smell oil then stop and check everything to verify there is a leak. Check all lubed systems bumper to bumper (engine, axles, etc). Put on a glove and feel in the areas around the new bearings to see if one is running too hot. This could be an install issue or a faulty bearing if you are sure it's from the recent work.

 

[greenhornet]

I have been using Amsoil for 21 years in everything I own Lawnmowers to my old 1976 Chev C10 454 auto.2wd.I have never found any extra leaks that they never had befor Synthetics are th only way to go.