Cadillac Owners Forum banner

1 - 20 of 23 Posts

·
Registered
2015 ATS AWD 2.0T Luxury, and 2017 XT5 AWD Luxury
Joined
·
9 Posts
Discussion Starter #1
Hello,

I just thought I'd chime in and mention that I discovered I had a failed rear differential on my 2015 ATS 2.0T AWD. I discovered the differential problem at about 77,000km and at 3 years + 11 months - just prior to the end of the lease (I ended up buying out the car).

The end of the lease was approaching (September 2019) and I had been keeping my options open regarding handing the car back or buying it out. Finally I decided to purchase the car...so I was driving to a tire shop to buy NON-run-flat tires (so much better). I decided to shut off the radio and air conditioning so I could compare the road noise between the old run flats and the new summer tires. That's when I heard the differential sound. Anyway, I had a good experience with my dealer, Roy Foss. It was during the labour disruption so the replacement differential parts were on a long back-order. Eventually, they came in and they took care of it on warranty.

I'm posting this message because I observe here that there are many who seem to think that ATSs have more than their share of differential failures...so I figured I'd make it known that it happened to my ATS, too.

At the end of the lease I bought an extended warranty that will last until 140,000km or four extra years. I get peace of mind from that. I'm still enjoying my ATS.
 

·
Registered
2014 ATS 2.0T Luxury
Joined
·
34 Posts
77K is pretty low for a diff failure. What are the symptoms/sounds of one that's on the way out?
 

·
Registered
2015 ATS AWD 2.0T Luxury, and 2017 XT5 AWD Luxury
Joined
·
9 Posts
Discussion Starter #3 (Edited)
It was a grinding sound. I could hear the sound beginning around 40 km/h and it got louder, the faster I drove. It reminded me a bit of the sound a bad wheel bearing makes. I agree - 77,000 kilometers (48,000 miles) is wayyyy too early for this type of failure.
 

·
Registered
2013 ATS 3.6 Premium RWD
Joined
·
360 Posts
Did you ever check the rear diff pumpkin for fluid leaking on it? Usually a diff failure occurs on the ATS due to the rear axle seals leaking enough that fluid gets low enough to cause damage. Consensus on the forum is that the leaky seals are related to the diff vent not working properly (pressure builds up and doesn't vent, pushes fluid past the seals). I would find out if the vent was replaced or reused when they replaced the vent - it is a cheap part, so change that if they haven't.
 

·
Registered
2015 ATS AWD 2.0T Luxury, and 2017 XT5 AWD Luxury
Joined
·
9 Posts
Discussion Starter #5
Thanks for this tip. I will ask about this.
 

·
Registered
Joined
·
69 Posts
I’m at 83,000kms and so far I’ve had a trouble free experience with my ATS, only issue was the Cue failure just outside of the 4YR/80KM Warranty. Deep down I feel like I’m due for something to give, that’s why I’ve left my engine and tune completely factory in case there’s a dispute with the dealer.
 

·
2016 ATS Premium 6-spd MT
Joined
·
14,059 Posts
Did you ever check the rear diff pumpkin for fluid leaking on it? Usually a diff failure occurs on the ATS due to the rear axle seals leaking enough that fluid gets low enough to cause damage. Consensus on the forum is that the leaky seals are related to the diff vent not working properly (pressure builds up and doesn't vent, pushes fluid past the seals). I would find out if the vent was replaced or reused when they replaced the vent - it is a cheap part, so change that if they haven't.
Had my seals replaced about six weeks ago, and they said the vent was okay even though the seals were clearly leaking which would seem to point to another cause (bad seals, bad design, bad previous fix, etc). I change my oil every 3k miles (5k km), so I'll be checking my diff each and every time I do that from here on out. I will report back.
 

·
Registered
2013 ATS 3.6 Premium RWD
Joined
·
360 Posts
Had my seals replaced about six weeks ago, and they said the vent was okay even though the seals were clearly leaking which would seem to point to another cause (bad seals, bad design, bad previous fix, etc). I change my oil every 3k miles (5k km), so I'll be checking my diff each and every time I do that from here on out. I will report back.
A new vent was $17 shipped from RockAuto, so it wouldn't be a cost-prohibitive "preventative maintenance" item to do every year or so (assuming that helps with the issue). Mine is still waiting to get swapped (have to do it at work, and wouldn't you know it when I'm done with the day I really want to leave), but I have been quick crawling under the car and tapping the vent a few times once or twice a week. Very likely psychosomatic, but I swear it seems to help some weird vibes I was feeling (kind of a light windup type of feeling) the latter half of this summer. Might be worth doing, might not, but for 15 seconds and a dirty finger as my investment I'll keep at it.
 

·
Registered
2013 Luxury ATS 2.0T Manual
Joined
·
861 Posts
I gotta say, I'm pretty satisfied with the amount of actual leaking my seals have been doing. Basically, my seals and the pumpkin itself are always wet with oil, so it's pretty consistently leaking. That said, in March I drained and replaced the diff oil and gave the vent a good cleaning. Yesterday I removed the vent and it was fine and when I went to top it off, pretty much as soon as I started adding the fluid, it started streaming out. So, even though everything is always wet and I get regular drips in my garage, it really isn't losing much at all. I think I'll just jiggle the vent on oil changes now and top off the fluid once a year going forward.

Of course other's experiences may be different and all that, don't go by my diff as a baseline, do your own testing. Also, I see people mention two different wrench sizes for the vent on the forum. I can say, absolutely, on my diff (I have the LSD), my vent is 9/16". It could very well be that the non-LSD is 16mm (which is a little bigger than 5/8'', so way to big for my vent), but I know mine is 9/16".
 

·
2016 ATS Premium 6-spd MT
Joined
·
14,059 Posts
I gotta say, I'm pretty satisfied with the amount of actual leaking my seals have been doing. Basically, my seals and the pumpkin itself are always wet with oil, so it's pretty consistently leaking. That said, in March I drained and replaced the diff oil and gave the vent a good cleaning. Yesterday I removed the vent and it was fine and when I went to top it off, pretty much as soon as I started adding the fluid, it started streaming out. So, even though everything is always wet and I get regular drips in my garage, it really isn't losing much at all. I think I'll just jiggle the vent on oil changes now and top off the fluid once a year going forward.

Of course other's experiences may be different and all that, don't go by my diff as a baseline, do your own testing. Also, I see people mention two different wrench sizes for the vent on the forum. I can say, absolutely, on my diff (I have the LSD), my vent is 9/16". It could very well be that the non-LSD is 16mm (which is a little bigger than 5/8'', so way to big for my vent), but I know mine is 9/16".
Interesting about your fluid level staying good. Also good to know about the wrench size.

When you guys "jiggle" the vent, do you ever hear escaping pressure as if you're releasing some buildup?
 

·
Registered
2013 Luxury ATS 2.0T Manual
Joined
·
861 Posts
Interesting about your fluid level staying good. Also good to know about the wrench size.

When you guys "jiggle" the vent, do you ever hear escaping pressure as if you're releasing some buildup?
I didn't. I did get a long, low hiss when I was removing the vent, but I'm pretty sure it was inhaling since I was able to move the seal so easily with a toothpick from the inside. My vent appears to be working properly at least most of the time, I guess.
 

·
Registered
2013 ATS 3.6 Premium RWD
Joined
·
360 Posts
Interesting about your fluid level staying good. Also good to know about the wrench size.

When you guys "jiggle" the vent, do you ever hear escaping pressure as if you're releasing some buildup?
Haven't heard anything - I've usually been doing it after everything has cooled down, which should reduce any pressure differentials. I'll try to do it sometime after running the highway and try to listen for any noises.

Edit - did not hear any hissing or other noises when I jiggled it yesterday evening after a 15+ mile drive; this would jive with my inclination that it has been working as late. I also haven't seen any fresh fluid on the pumpkin, although I should really get some brake clean and a rag to get a clean canvas to leak on.
 

·
Registered
2014 ATS 2.0T Luxury
Joined
·
34 Posts
Do dealership shops look for leaking seals or other issues when the car is in for service? I have an oil change coming up soon and I'd like to look into the condition of the seals, etc., and replace the vent as I'm not sure when last it was done - if ever. I got the car at 68K km and it now has 132k km.
 

·
Registered
2013 Luxury ATS 2.0T Manual
Joined
·
861 Posts
Do dealership shops look for leaking seals or other issues when the car is in for service? I have an oil change coming up soon and I'd like to look into the condition of the seals, etc., and replace the vent as I'm not sure when last it was done - if ever. I got the car at 68K km and it now has 132k km.
My dealership always pointed out leaking seals when I would go in for an oil change and they would then replace them under warranty (when it was still under warranty). I think it's a high price repair so it was/is in their best to point it out, especially when it's under warranty.
 

·
Registered
2015 ATS Sedan / 2.0T / RWD / 6-AT
Joined
·
138 Posts
Ever changed the diff oil? If it is the LSD it should have been changed at 75.000 km due to GM service sheet.
 

·
Registered
2013 3.6 RWD Premium - 2006 BMW Z4M
Joined
·
1,566 Posts
Do dealership shops look for leaking seals or other issues when the car is in for service? I have an oil change coming up soon and I'd like to look into the condition of the seals, etc., and replace the vent as I'm not sure when last it was done - if ever. I got the car at 68K km and it now has 132k km.
If you want them to do something you are better off just asking them to do it over hoping they check everything. No harm in asking.
 

·
Registered
2014 ATS 3.6 Premium RWD, 2016 Corvette Z06, 2018 GMC Sierra Denali 2500HD Diesel
Joined
·
2,864 Posts
Haven't heard anything - I've usually been doing it after everything has cooled down, which should reduce any pressure differentials. I'll try to do it sometime after running the highway and try to listen for any noises.

Edit - did not hear any hissing or other noises when I jiggled it yesterday evening after a 15+ mile drive; this would jive with my inclination that it has been working as late. I also haven't seen any fresh fluid on the pumpkin, although I should really get some brake clean and a rag to get a clean canvas to leak on.
The failure mode is odd and seemingly somewhat random and I wonder if that vent is getting jammed up when the differential is hot enough due to thermal expansion/warping that only affects some of the valve/vent assemblies? The differential can get extremely hot under high load conditions which is also the time that it would be venting air or fluid via the seals if it can't vent air. It shouldn't have that issue but there has to be some logical reason why these leakage events and subsequent lack of lubrication failures are occurring.

My 2014 ATS has been fine but if I do end up with a CT4V, if it has the same vent system I will probably change the valve to a fitting and tube like other axles have successfully used for decades without problem. I don't use the dealership for oil changes, tire rotations, etc. so if needed I could easily put the original part back in for dealer visits.

Rodger
 

·
Registered
Cadillac ATS Coupe 3.6 Performance AWD
Joined
·
138 Posts
Add another case file to the 'ATS rear differential leaking output seals' box of trial evidence. Spotted at 79,000 km, and they'll both be replaced on Cadillac's dime this Monday.
Of course will first thought was 'They better fail again before my 110,000 km powertrain warranty expires, because it's obviously a crap part and I'll be damned if I eventually have to pay for it myself."
 

·
Registered
Joined
·
25 Posts
My 2013 had an axle seal replaced before 40,000km, that was before I owned it, then at 100,000kms all the seals were leaking, and the diff was howling very loud. It was all replaced under warranty.
 

·
Registered
Joined
·
25 Posts
Speak of the devil, just drove about 700kms this weekend and noticed little oil spots all over the back of the car. I looked under Neath and seen a soaking wet rear diff and actually watched it drip. Greeaaat...
 
1 - 20 of 23 Posts
Top