Change diff fluid in 13 GS M6, prepping for upcoming track weekend. I have since drove about 60 miles and checked again for correct fluid level after the change. When I removed the fill plug to check the level (it was good, ran out a little bit) I heard a short burst of air, don't know if it was going in or coming out. Is there a rear diff vent somewhere?

 

Did you follow the fill procedure, for differentials with oil coolers. fill lift car 2 nd gear at 2000 rpm for 60 seconds and refill?

 

Yes, sir, followed the tutorial found here on forum. Actually ran it for 2 minutes at 10 MPH in 2nd gear,then checked again. Added about a 1/4 quart after the 2 minutes. It may be nothing, just wanted to see if anyone had similar experience.
Thanks for the reply.

 

Oh good! I did also have the very same experience. Few months later i wanted to check to see the level was still ok, when i pulled the plug i heard the slight whoosh, but since i was not ready for it i do not know if it over pressure blowing out or suction. I will pay attention to it next time i am checking levels. That makes me believe that it does not have a pressure relief valve anywhere in the differential.

 

Thanks for the info, glad I am not the only one to hear it. Previously I have changed the rear diff on a GS A6 before and didn't notice the slight 'whoosh'. The A6 doesn't have a cooler so that may be the difference.

 

Yes the G/S has a breather too.

Hey all seems normal for GM to make these cars with a spring loaded breather I have the rear out rite now when I removed the plug did too find it was pressurized I really don't like the idea just that GM trusts their seals I guess.

I for one never leave well enough along so I removed the cap on the breather and there's a spring loaded up against a black round robber seal, the spring is like I'm guessing 3/4 inch long, the spring presses the seal down against the breather tube, this allows pressure to build till it overcomes the spring resistance then over pressure is released, I feel is a little much for my tolerance so I cut two coils off the spring thereby reducing the pressure it can allow thereby allowing relieve at a lower pressure.

I will advise against removing the spring all together cause the spring closes the breather to keep out water and dust.

There's only about a 1/4 inch hosing distance for the spring so by cutting off ruffly one third still have a 1/4 inch compression against the seal still closing contaminants out while the pressure against the diff seals get a brake.

There's also anther side to this story I should share with you the pressure allows the diff oil pump to be more efficient circulating the thick oil so It may circulate at a lower pace if you take too much pressure off the spring by over cutting it.

I have an after market cooler instead of the factory heat exchanger which is highly efficient.

And finally yes is a grand sport with a zr1 diff which is why I have the cooler instead. xboostx.

 

Thanks xboostx! Good to know. You got my curiosity peaked, mine is also a GS but stock differential with MN6. I am going to pull the shop manual tomorrow to research this subject.

 

XB, thanks for all that good info on rear diff!