Joining the rear diff club

[Crispy]

Not to highjack this thread but I think the point is important. Forums condense problems. I sold my 2007 Cayman (2.7 with the dreaded IMS bearing) with 225,000 miles and no problems. Our TourX is fine now and I’m going to keep servicing the diff regularly. We have a steep driveway with two hairpin turns in snow country so it gets a workout.
The results of @2018 TourX in Texas’ test with LS treatment will be interesting. We all have to do our best and share the info. C.

 

[adam728]

This diff issue is turning into the Porsche IMS bearing lunacy.

What's funny is - search for failures, noise, groaning, etc on Vauxall, Opel, or Holden groups. Rear diff issues are a purely US problem. Makes me wonder if the AWD calibration here is the culprit. There was something published long ago (I'll have to hunt) that the cars got different stability and driving dynamic calibrations depending what region they were for. Does the Buick "smooth at all costs" philosophy glaze clutch plates and lead to the groaning?

Even the Focus RS guys don't really fail the GKN Twinster, they just overheat them doing track and rally games.

 

[94cruiser]

I did see a video (I think in Sweden) while driving on a snow covered closed circuit, they were able to let the rear end loose in sport mode.

 

[quakerj]

What's funny is - search for failures, noise, groaning, etc on Vauxall, Opel, or Holden groups. Rear diff issues are a purely US problem. Makes me wonder if the AWD calibration here is the culprit. There was something published long ago (I'll have to hunt) that the cars got different stability and driving dynamic calibrations depending what region they were for. Does the Buick "smooth at all costs" philosophy glaze clutch plates and lead to the groaning?

Even the Focus RS guys don't really fail the GKN Twinster, they just overheat them doing track and rally games.

There is a new calibration via GM Techline Connect / SPS for the rear differential module. My car didn't have the new version when I updated all the modules in early 2023. The notes mentioned something about driveline noise. To this day I still wonder if that new version might help prevent failures to the unit, but I honestly have no idea.

 

[94cruiser]

What would be the cost at the dealer to update the programming? Is it availalbe for early 2018 aka red needle?

 

[quakerj]

What would be the cost at the dealer to update the programming? Is it availalbe for early 2018 aka red needle?

Dealer is about $250 to program a module.

Or find someone with an MDI clone and do it for the cost of the VIN subscription, about $45 and you can update every module in the car.

My car is early '18 red-needle and the differential module updated just fine to the newest calibration.

 

[Jack GS]

What's funny is - search for failures, noise, groaning, etc on Vauxall, Opel, or Holden groups. Rear diff issues are a purely US problem. Makes me wonder if the AWD calibration here is the culprit. There was something published long ago (I'll have to hunt) that the cars got different stability and driving dynamic calibrations depending what region they were for. Does the Buick "smooth at all costs" philosophy glaze clutch plates and lead to the groaning?

Even the Focus RS guys don't really fail the GKN Twinster, they just overheat them doing track and rally games.

They don't have the rear diff. issues but my goodness do they have transmission issues. Seems like it's the most common failure for them whereas I've heard of no one having trans issues here in the States.

 

[2018 TourX in Texas]

Not to highjack this thread but I think the point is important. Forums condense problems. I sold my 2007 Cayman (2.7 with the dreaded IMS bearing) with 225,000 miles and no problems. Our TourX is fine now and I’m going to keep servicing the diff regularly. We have a steep driveway with two hairpin turns in snow country so it gets a workout.
The results of @2018 TourX in Texas’ test with LS treatment will be interesting. We all have to do our best and share the info. C.

Ok small update here:

I went to add the 4oz GM Friction Modifier, but diff lube level was full (no room).

So I reasoned: drain out the .74 qt, mix in the 4oz LS additive thoroughly & then refill.

So I drained it out totally into a clear graduated pitcher.

(Keep in mind, this is the actual GM LS Differential 75w/90 Gear Lube they specify, bought at my local Buick dealer -with low miles on this gear lube - maybe 5,000 miles est / 3 months).

Behold the N A S T I E S T looking gear fluid I've E V E R seen in my 50 years of fluid changes - including my year of being a "stealership tech" comes out - full of dark material & visible contamination.

(Yet no external leaks or seepage)

I'm baffled - how on earth 🌎 could this be the case ?

One good thing - the prior fluid I had drained - which was of uncertain age / miles but HAD been in roughly 2 years & 15,000 miles bare minimum - it looked SO clean that I had saved it - I will put both side by side tomorrow & shoot pictures or video to document the vast difference & these diff troubles.

My plan is to re-install the prior good clean fluid with half (2 oz) of the new small bottle of LS Friction modifier and see what if any improvement in diff clutch noise occurs.

I'd love any feedback & will be posting visible evidence ASAP, tomorrow if at all possible.

Cheers - David in Texas
.

 

[fredzy]

Guess I haven't been in here for a while. At 18,200 miles I had a pinion leak, dealer replaced the seal under warrenty and changed fluid.

Fast forward, and around 77k the rear diff was making significant groans in slow, tight corners (like intersection, parking, etc). Changed to Valvoline full synthetic fluid with friction modifier, and at the same time ordered the right AC Delco fluid. The ~60k mile fluid that came out did not look bad at all, and only a little slurry of metallic sludge on the magnetic drain plug. New fluid did nothing for quieting up the diff. Put about 1000 miles on in the 2 weeks I was awaiting the factory fluid and free time to change it.

Changed to the AC Delco fluid, instantly quiet. Went from groans you could feel shudder the car in slow lefts to nothing. 4k on it since, zero noise or issues. And I have been testing the AWD often. Car will do some nice, big long drifts with traction and stability control off.....

Fingers crossed as I await noise to return.

Can you confirm that the AC Delco fluid you used that worked to quiet the diff was PN 88862624?

Ok small update here:

I went to add the 4oz GM Friction Modifier, but diff lube level was full (no room).

So I reasoned: drain out the .74 qt, mix in the 4oz LS additive thoroughly & then refill.

So I drained it out totally into a clear graduated pitcher.

(Keep in mind, this is the actual GM LS Differential 75w/90 Gear Lube they specify, bought at my local Buick dealer -with low miles on this gear lube - maybe 5,000 miles est / 3 months).

Behold the N A S T I E S T looking gear fluid I've E V E R seen in my 50 years of fluid changes - including my year of being a "stealership tech" comes out - full of dark material & visible contamination.

(Yet no external leaks or seepage)

I'm baffled - how on earth 🌎 could this be the case ?

One good thing - the prior fluid I had drained - which was of uncertain age / miles but HAD been in roughly 2 years & 15,000 miles bare minimum - it looked SO clean that I had saved it - I will put both side by side tomorrow & shoot pictures or video to document the vast difference & these diff troubles.

My plan is to re-install the prior good clean fluid with half (2 oz) of the new small bottle of LS Friction modifier and see what if any improvement in diff clutch noise occurs.

I'd love any feedback & will be posting visible evidence ASAP, tomorrow if at all possible.

Cheers - David in Texas
.

I had trouble following, but you: 1. had the noise 2. changed out to the PN 88862624 fluid the car calls for 3. still had the noise and then 4. are experimenting with adding more friction modifier to try to quiet it?

My car is quiet now, but was brought in for service by the previous owner back in Aug '24 complaining of the noise, traded it instead and the dealer replaced the fluid - no noise so far. My hunch was that the fluid level was low after 80k miles of seeping through the one axle seal.

 

[quakerj]

Ok small update here:

I went to add the 4oz GM Friction Modifier, but diff lube level was full (no room).

So I reasoned: drain out the .74 qt, mix in the 4oz LS additive thoroughly & then refill.

So I drained it out totally into a clear graduated pitcher.

(Keep in mind, this is the actual GM LS Differential 75w/90 Gear Lube they specify, bought at my local Buick dealer -with low miles on this gear lube - maybe 5,000 miles est / 3 months).

Behold the N A S T I E S T looking gear fluid I've E V E R seen in my 50 years of fluid changes - including my year of being a "stealership tech" comes out - full of dark material & visible contamination.

(Yet no external leaks or seepage)

I'm baffled - how on earth 🌎 could this be the case ?

One good thing - the prior fluid I had drained - which was of uncertain age / miles but HAD been in roughly 2 years & 15,000 miles bare minimum - it looked SO clean that I had saved it - I will put both side by side tomorrow & shoot pictures or video to document the vast difference & these diff troubles.

My plan is to re-install the prior good clean fluid with half (2 oz) of the new small bottle of LS Friction modifier and see what if any improvement in diff clutch noise occurs.

I'd love any feedback & will be posting visible evidence ASAP, tomorrow if at all possible.

Cheers - David in Texas
.

I'm looking forward to your tests/results and images of the old fluid. The more people out of warranty that no longer post "dealer replaced X,Y,Z" and offer good information, the better this thread is going to get (for me).

 

[2018 TourX in Texas]

Ok I have some significant updates.

First a question:

Where does GM say exactly which lube for our TourX Front & Rear Differential ?
I looked in my 2018 Owners Manual - no reference found !

Is it only in the Factory Service Manual ?

I know I read in threads here that it's the GM 75w/90 LS enhanced Fluid - do they make more than one ?

In the video I just made I show which one I used, maybe there's others too - but hard to be sure when owners manual is silent.

I guess they figure it's beyond owners & only Stealerships are qualified to change gear case fluids - lol.

Ok I made a video that gives the overview with shockingly positive result - please watch it fully & let me know any ideas that occurr.

Just know that I test drove the car just after filming this & the groaning noises are G O N E after switching back to the original Gear Lube I had removed from the diff last July - it was the original lube car in when purchased used at 62,000 miles, and I drove on until 77,500.

You won't believe the color of the fluids respectively.

Please post this anywhere it'll get views to help others.

Cheers - David

 

[2018 TourX in Texas]

Fredzy:

Not quite that order.

Car was quiet 100% no drive line noise when purchased August 2022 at 62,000 miles.

Drove it seamlessly to 77,500 by about July 2024.

Got to thinking: Diff & front PTU lube is of unknown age - should probably change it to be sure.

Bought the recommended GM LS 75w/90 - - pn# 88862624 at Buick & put it in Rear Differential. I was shocked at how absolutely new & clear the "Old Fluid" was - so much so I saved it.

I'm SOOOO glad I did - please see & still pictures posted above & watch video for everything.

Today just after shooting that I made numerous 10 to 20 mile test drives & slow speed parking lot circles.

The noise is 100% gone - HALLELUJAH.

Of course I'll monitor to see if it stays quiet.

Cheers - David in Texas

 

[fredzy]

Fredzy:

Not quite that order.

Car was quiet 100% no drive line noise when purchased August 2022 at 62,000 miles.

Drove it seamlessly to 77,500 by about July 2024.

Got to thinking: Diff & front PTU lube is of unknown age - should probably change it to be sure.

Bought the recommended GM LS 75w/90 - - pn# 88862624 at Buick & put it in Rear Differential. I was shocked at how absolutely new & clear the "Old Fluid" was - so much so I saved it.

I'm SOOOO glad I did - please see & still pictures posted above & watch video for everything.

Today just after shooting that I made numerous 10 to 20 mile test drives & slow speed parking lot circles.

The noise is 100% gone - HALLELUJAH.

Of course I'll monitor to see if it stays quiet.

Cheers - David in Texas

Oh wow, OK. Thanks for clarifying. So the clean-looking oil is what you received the car with, and it is a mystery what it is? At least it's working! I will try to check the video tonight.

Judging by the little bit that has dribbled out of my diff when I checked the level, I definitely have the sewage-looking oil haha.

 

[2018 TourX in Texas]

Oh wow, OK. Thanks for clarifying. So the clean-looking oil is what you received the car with, and it is a mystery what it is? At least it's working! I will try to check the video tonight.

Judging by the little bit that has dribbled out of my diff when I checked the level, I definitely have the sewage-looking oil haha.

Precisely my friend.

Also - I re-installed the clear looking "mystery diff lube" back in WITHOUT adding the 4oz bottle of GM LS Friction Additive.

My logic was to just go straight back to the fluid that car came with, worked perfectly & looked clean.

That way it's a "control" not a modification.

(Can always add the Friction Additive later)

I'd assume the lube remove & now re-installed was original 75w/90 LS fluid but admittedly if that is a correct assumption - WHY did my swap out to what I bought at the Buick dealer as PN# 88862624 - which should have been the same fluid fail SO spectacularly as to nearly destroy the diff ?

There's no satisfying, verifiable answer just now.

Obviously I'll monitor this closely for any negative change in operation.

Opinions & reflections are welcomed.

 

[94cruiser]

Here are the stats for the video I posted:
https://www.youtube.com/watch?v=aFhfgxqQUxU

 

[Buicurious]

Has anyone tried to run the fluid spec'd by Ford for the Focus RS in their Buick? It seems odd that the mystery oil in David's wagon would be the factory fill, but presumably when 94cruiser's diff started to groan at 34K mi it was also still filled from the factory.

David, were you just using the quadrasteer bottle because it was easier to transfer the fluid or is that what the dealer gave you? Its interesting because I believe the quadrasteer fluid (pn12378557) which I thought is no longer available, was replaced by the Dexron 75w90 LS (pn88862624). The forum post below from GM Truck Club talks about the change a little. It sounds like the quadrasteer rear differentials were also groaning if they didn't get the correct fluid.

Quadrasteer new GM rear end fluid

So I knew it was inevitable that GM would stop making the Quadrasteer Synthetic fluid #12378557. They now recommend using fluid number #88862624, but that says it has Limited Slip additive in it which if I remember will cause problems with the quadrasteers. I know the old fluid worked well and...

www.gmtruckclub.com

 

[fredzy]

Dealer is about $250 to program a module.

Or find someone with an MDI clone and do it for the cost of the VIN subscription, about $45 and you can update every module in the car.

My car is early '18 red-needle and the differential module updated just fine to the newest calibration.

Do you check versions and apply update through the ODB port? Or have to connect to the unit? Appreciate if you can share if there is a GM PDF or service bulletin on this.

I think my car may have been updated last August when the previous owner brought it in for the noise and they changed the fluids to remedy. I would expect it to pop up as a recommended action when troubleshooting the noise - I have no idea how that system works though.

I had them look up the work order in the fall when I was there for an oil change and I saw the fluid change but wasn't looking for the SW update. I just called, and the service advisor wasn't interested in looking it up on the phone like they did when I was there in person.. they said they would need to do a $135 diagnostic to tell me 😡 though he did say there are "no updates open against it." So I might stop by later and finally get the w/o printed out for my records.

 

[2018 TourX in Texas]

Has anyone tried to run the fluid spec'd by Ford for the Focus RS in their Buick? It seems odd that the mystery oil in David's wagon would be the factory fill, but presumably when 94cruiser's diff started to groan at 34K mi it was also still filled from the factory.

David, were you just using the quadrasteer bottle because it was easier to transfer the fluid or is that what the dealer gave you? Its interesting because I believe the quadrasteer fluid (pn12378557) which I thought is no longer available, was replaced by the Dexron 75w90 LS (pn88862624). The forum post below from GM Truck Club talks about the change a little. It sounds like the quadrasteer rear differentials were also groaning if they didn't get the correct fluid.

Quadrasteer new GM rear end fluid

So I knew it was inevitable that GM would stop making the Quadrasteer Synthetic fluid #12378557. They now recommend using fluid number #88862624, but that says it has Limited Slip additive in it which if I remember will cause problems with the quadrasteers. I know the old fluid worked well and...

www.gmtruckclub.com

It was exactly what the local Buick Dealer brought out when I asked for
Part # 88862624.
Only the bottle didn't just say 75w/90 LS it also said "Quadrasteer" and the bottle looked super old - as pictured.
Also a hand printed label was on it.

I'll look up that other PN #12378557 & see what that shows / looks like in comparison.

Hey, did you notice our TourX Owners Manual doesn't list a Fluid Spec for our Differential or PTU ?

Did you download or print a copy of the TourX Factory Service Manual ?

It should say the exact spec, right ?

Thanks David

 

[Mspaff]

So at 47K, we are on our 2nd rear end transaxel/differential replacement. First at about 23K and the second, Dec 2024. We caught it a month before the 48K drive train warranty ran out. I purchased a good extended warranty early on and when this one goes out at an estimated 70K, and again 90K, We'll sell it! LOVE the 2018 TourX but at 65 and the low miles we drive, well, I probably won't be driving anymore anyway! Was told that yes, this is a problem with the the all wheel drive TourX and Regal. It's a sealed unit. Does anyone know the actual price for part? It looks to be easy to replace.

 

[adam728]

Can you confirm that the AC Delco fluid you used that worked to quiet the diff was PN 88862624?

Yes, AC Delco 10-4034, GM 88862624.