I've seen a number of posts on BMO where guys have blown some rear diff fluid during 'very spirited driving.' I'm not sure I'll have the issue, so I didn't want to spend $100+ on something I may or may not need. So as a "trial run" I put together a temporary rear diff overflow setup using a fuel filter on which I capped one end (with a small pinhole to allow some limited breathing)

Everything cost about $15 so if I find after a while I get no overflow, I'll remove and go back to the OEM pressure relief valve. If I see some overflow I'll get a better reservoir and connect the setup up more permanently. Will post once I get some real testing done, but figured I'd share for anyone interested.

Eventually I'll put in better fluid in the rear end as well, but in the meantime this will hopefully prevent any unwanted/unexpected overflow when I really get on the car and get things hot.

 

Wait, so what's the original problem? If you drive your car hard there is some diff fluid that leaks from an overflow valve.. am I understanding correctly? Was it specific to the torsen diff or GT in general?

 

Yeah, fluid will spurt out the PRV all over the axle and possibly brakes/tires (which I would like very much to avoid). The boss guys seem to have it happen at track days. Doubtful there is any issue on the street... I am skeptical I'll have any issue, but I really don't want any fluid coming out when I go push my car hard. There is a kit available that a couple poeple I know have installed.

 

It isn't specific to GT or Boss - if you push any Mustang hard it will push some fluid out of the rattle cap. Happens on my V6 when I take it to the drag strip, so it isn't dependent upon road course situations either.