The vent really should lose that cap and run a hose up...somewhere. Maybe someone familiar with the nooks and crannies of the rear end could tackle this and somehow have a hose run up into a fender or even the trunk (and do a nice write up for the rest of us).

 

I don't know that much about differential vents but assuming heat builds up, with it pressure and then the relief just has to release at a lower pressure than the seals? Not following why it would need a high pressure rating on the relief and would have thought it's only goal is to let air in and out but not water and dirt? With diffs around since the beginning of the car why is this an issue now? Seems like GM could have perfected this decades ago.

 

I have a rear Dana axle in my motorhome, something really heavy duty. The vent is a simple rubber tube that runs about 2 feet+ and then points down, I assume to keep water out. Very simple! With the Cadillac I would run a hose just like this and make the last foot point down. Maybe put a filter at the end. Total cost might be $10.

 

I don't know whether GM specified the vent design or if it was specified by AAM who builds the axle assembly. It was probably done for simplicity and cost as opposed to using the traditional hose type vent. An easy change that should be more robust and provides better filtering is the type using a sintered bronze filter element. These excel at keeping dirt out and screw in without needing an added hose but the downside is they potentially can clog although failure is FAR less likely than the stock rattle top design. Height is about the same as a stock unit so clearance shouldn't be an issue but I would plan to check/clean it every 2 to 3 years.

You could easily add a fitting with a hose barb on it. AAM traces it history back to both GM and Mopar and I suspect you can probably find the near identical axle with a vent tube in a FCA product if not in a GM model so you wouldn't have to do any engineering. The hose type is definitely the simplest in function and the only time I have seen a failure problem with those was with the GM HD pickup platform in the early 2000s; AAM required synthetic lubricant in the rear axle of the HD pickups but with 4WD applications the vent tube connector specified by GM for the front axle would disintegrate in a few months after exposure to synthetic so you either had to use different versions of the same weight fluid between front and rear or replace the front breather like I did. GM did some goofy stuff during that time period, my 2001 GMC had the differential vent issue and my 2006 came with the then new Dexron VI fluid but the Allison transmission had seals not compatible with Dex VI during that time so I quickly changed to the far superior Transynd fluid used by Allison as the factory fill for every application but GM.

If you are still in the powertrain warranty (6/70K) I would leave it stock but probably check/clean it at oil changes.

Rodger

 

snip
GM did some goofy stuff during that time period, my 2001 GMC had the differential vent issue and my 2006 came with the then new Dexron VI fluid but the Allison transmission had seals not compatible with Dex VI during that time so I quickly changed to the far superior Transynd fluid used by Allison as the factory fill for every application but GM.
snip

I have spoken to the Allison engineer (Tom Johson, retired) that spec'd Transynd 295 and it is compatible with all GM Dexron versions all the way back to Dex III. I put it in my RV (Allison1000) and my 83 Monte Carlo SS (350 Hydro) and never had an issue. But, if you make the switch you need to do a double change to get to the 99% Transynd fill.

 

Removed my differential vent last week and it was perfectly clean. I too noticed it took a relatively high amount of pressure to vent, so I took it apart and made the spring a little lighter. Now it still works as designed but starts releasing pressure a little sooner.. There's a reason the spring cap is there vs. the open vent with a hose like on my Silverado (solid axle, old school), I just don't know those details.

 

When I last checked my vent, the top bobbled very easily and loosely, doesn't seem like it take much pressure to me. Unless the cap movement is not the same as the spring up/down movement? This is my first RWD car so I am still learning.

I have looked at parts diagrams for the diff but not seeing the vent as a separate part number. Those who have bought a diff vent, do you have a part number for it to share?



What do you mean "made the spring a little lighter? Did you swap a different spring into it or alter the factory one?

 

What model years And trim are affected?

 

Pretty safe to say all model years and all trim levels.

 

Anybody have a photo or two to post?