Joining the rear diff club

[2018 TourX in Texas]

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.

Yes the differential costs about $1395 ish
You use the part # for the Cadillac XT6 I'm 90% certain.

Apparently Cadillac sells more by far than the TourX so our diff is same & goes by their part #.

But most GM Buick dealers charges total around $3000 for the job Inc labor & module reprogramming if needed.

Hope that helps.

 

[2018 TourX in Texas]

Yes, AC Delco 10-4034, GM 88862624.

Uh, don't forget that's also the # of the GM fluid that turned very nasty in 5,500 miles in my diff.
Hopefully I got a bad quart from a bad batch of LS 75/90 GM Diff fluid is all.

If others have gotten the same fluid & it quieted the noisy diff, then I suspect that's the case

 

[LeeH]

Has Anyone had a differential go bad AFTER having a new one installed under warranty? I am hearing a moan/drone sound at about 40 MPH when I barely touching the accelerator pedal..let's say just between accelerating and decelerating (but not coasting). the sound goes away when I pop the gearshift to neutral position.

 

[94cruiser]

Has Anyone had a differential go bad AFTER having a new one installed under warranty? I am hearing a moan/drone sound at about 40 MPH when I barely touching the accelerator pedal..let's say just between accelerating and decelerating (but not coasting). the sound goes away when I pop the gearshift to neutral position.

I had mine replaced, and a year later replaced again (the second one was at a different dealer)
I believe first failure was at about 35K.

 

[LeeH]

Mine was first replaced at near 15,000 miles..crazy just before warranty expiration. I hope the noise I am hearing now is not a repeat.

 

[Pacer69]

Rear diff on mine just got a re-do at 95k miles. The Check AWD light started coming on last spring maybe. I asked my dealer tech, he said they'd charge 188 to look at it and maybe not be able to reproduce it, and I'd be out that money. Directed me to wait 'til it stayed on. It started that a few weeks back, and then it felt like the gears were slipping.

Repaired and seems fine now after five days but not much driving. Dealer invoice said control module has internal failure. They replaced that and reprogrammed. Replaced rear pinion and axle seals. Replaced diff fluid and topped clutch fluid. Installed slinger and retainer. Also found left front axle seal leaking transmission fluid. Replaced and topped fluid. Changed transfer case fluid.

He said it was a $2800 job. I had bought in early 2023 an add'l 60k mile/5-year extended warranty at $3k. I was at 57k miles at that time; so...in effect for about another 3 years or about 20k miles. So I guess that gets me about another year or so assuming 15k miles a year. This stuff can get super expensive real quick. Still cheaper than a new car!

 

[fredzy]

Rear diff on mine just got a re-do at 95k miles. The Check AWD light started coming on last spring maybe. I asked my dealer tech, he said they'd charge 188 to look at it and maybe not be able to reproduce it, and I'd be out that money. Directed me to wait 'til it stayed on. It started that a few weeks back, and then it felt like the gears were slipping.

Repaired and seems fine now after five days but not much driving. Dealer invoice said control module has internal failure. They replaced that and reprogrammed. Replaced rear pinion and axle seals. Replaced diff fluid and topped clutch fluid. Installed slinger and retainer. Also found left front axle seal leaking transmission fluid. Replaced and topped fluid. Changed transfer case fluid.

He said it was a $2800 job. I had bought in early 2023 an add'l 60k mile/5-year extended warranty at $3k. I was at 57k miles at that time; so...in effect for about another 3 years or about 20k miles. So I guess that gets me about another year or so assuming 15k miles a year. This stuff can get super expensive real quick. Still cheaper than a new car!

So the diff internals were fine, they just sort of overhauled the thing: new control module, new seals?

One thought I had was: for people whose diff starts making noise, can they just unplug it and have a FWD car? The driveshaft will still be turning the innards of the diff. I bet it would give a fuel economy boost, though 😒

I finally stopped in at my dealer and reviewed the service history with them and they have no record of updating the diff control module. So whatever benefit that might give, I'm not getting. And I wasn't able to get a straight answer for how much it might cost to do the update, which the service person wasn't convinced even existed

 

[quakerj]

So the diff internals were fine, they just sort of overhauled the thing: new control module, new seals?

One thought I had was: for people whose diff starts making noise, can they just unplug it and have a FWD car? The driveshaft will still be turning the innards of the diff. I bet it would give a fuel economy boost, though

Very doubtful as the failure seems mechanical in nature. The clutches shouldn't apply until the diff module commands them to. Given that folks report the noise occurring on deceleration, that would be the least likely scenario that the clutches might engage.

What's interesting to me is I've always read the noise goes away when put into neutral (which shouldn't be all that different from deceleration) so it might be worth a try.

 

[Pacer69]

So the diff internals were fine, they just sort of overhauled the thing: new control module, new seals?

One thought I had was: for people whose diff starts making noise, can they just unplug it and have a FWD car? The driveshaft will still be turning the innards of the diff. I bet it would give a fuel economy boost, though 😒

I finally stopped in at my dealer and reviewed the service history with them and they have no record of updating the diff control module. So whatever benefit that might give, I'm not getting. And I wasn't able to get a straight answer for how much it might cost to do the update, which the service person wasn't convinced even existed

Not sure if they put in a whole new diff, I just basically made my post what I saw written on my invoice. Sorry can't be of more help than that, but next time I'm in there I'll try to remember to ask what exactly they replaced. I'd think it would say an entirely new part if that's what was done, though.

 

[Mordor67]

Gonna reply to this thread as it's relevant. Just dumped my rear diff fluid at about 38000 and it was nasty black, all kinds of metallic stuff on the magnetic drain plug, if you haven't done this on your tourx do it soon.

 

[Chef jpd]

I did a full drive line fluid replacement at 30k miles.
The fluid condition was revolting.

 

[quakerj]

If anyone needs fluids to do this to their vehicle, I recently sold my Tour-X and have the complete set of fluids for this service:

PTU fluid (about $75)
GM Dexron LS (rear diff, about $25)
Pentosin synthetic hydraulic fluid for the rear diff clutch/actuator (forget price but not inexpensive).

These are all genuine GM fluids sourced from the dealer. I'll sell the fluid package for $100 shipped.

If you're interested in oil filters, cabin air filters and other odds & ends that I have, we can probably work out a deal with everything so I can clear some space out of the garage 🙂

 

[kbtuba]

If anyone needs fluids to do this to their vehicle, I recently sold my Tour-X and have the complete set of fluids for this service:

PTU fluid (about $75)
GM Dexron LS (rear diff, about $25)
Pentosin synthetic hydraulic fluid for the rear diff clutch/actuator (forget price but not inexpensive).

These are all genuine GM fluids sourced from the dealer. I'll sell the fluid package for $100 shipped.

If you're interested in oil filters, cabin air filters and other odds & ends that I have, we can probably work out a deal with everything so I can clear some space out of the garage 🙂

what else do you have?

 

[quakerj]

If anyone needs fluids to do this to their vehicle, I recently sold my Tour-X and have the complete set of fluids for this service:

PTU fluid (about $75)
GM Dexron LS (rear diff, about $25)
Pentosin synthetic hydraulic fluid for the rear diff clutch/actuator (forget price but not inexpensive).

These are all genuine GM fluids sourced from the dealer. I'll sell the fluid package for $100 shipped.

If you're interested in oil filters, cabin air filters and other odds & ends that I have, we can probably work out a deal with everything so I can clear some space out of the garage 🙂

No longer have these items for sale, thank you everyone for the interest.

 

[djhellen]

Hello,

I had a 2018 TourX with 55,000 miles before it was totaled when I got rear-ended last week. I'm in the market for a new TourX and have located one at a dealership. However is prepping it for sale, the service they did includes a differential fluid change because the it was noisy. My concern is they should have replaced the differential. what are everyone's thoughts about them just having changed the fluid and not replaced the diff ?

 

[bollox74]

As with all things the diff will go eventually, sometimes sooner sometimes not. 😉
Does the dealer offer an extended service contract on drivetrain?
I'd look for one of those if you want otherwise use it to haggle the price down.

 

[djhellen]

As with all things the diff will go eventually, sometimes sooner sometimes not. 😉
Does the dealer offer an extended service contract on drivetrain?
I'd look for one of those if you want otherwise use it to haggle the price down.

Thanks for the reply.

Just occurred for me to ask. Has anyone here had a noisy diff and had a fluid changed "fix" the situation and not had to replace the diff ? I guess I'm asking, seeing that the diff was noisy, and not not noisy with the fluid change - does anyone think I can get another 50,000 miles out of it ? (the car currently has 55,000 miles)

 

[DrFaustus]

There have been a few people who have reported no issues after a fluid change. It's all going to depend on how long is been an issue. Neither of you have that answer currently.

 

[fredzy]

Thanks for the reply.

Just occurred for me to ask. Has anyone here had a noisy diff and had a fluid changed "fix" the situation and not had to replace the diff ? I guess I'm asking, seeing that the diff was noisy, and not not noisy with the fluid change - does anyone think I can get another 50,000 miles out of it ? (the car currently has 55,000 miles)

This was my case exactly. The previous owner brought the car to the Buick dealer in Aug 2024 at 75k miles reporting "noise from rear" and it was diagnosed as the diff. It had the original diff. So the owner then traded it in 😆 and the dealer changed the diff fluids, among many other services. I bought it a week or two later and am over 90k miles now and haven't had any trouble.

My guess is the dealer scared them into trading it in by saying it will cost $4000 to fix, but that is just me being cynical. The car needed a fair bit of service so it might have just been good timing for the previous owner. My theory is that the diff fluid level dropped too low after years of very slowly weeping out of the one half-shaft seal (as evidenced by tons of slightly oil damp dirt all over the diff on one side) until it finally started making noise. Fortunately changing the fluid addressed it for now and the fluid level hasn't changed in ~1 year. Still drips out when I pop the fill plug to check.

As bollox says, I would use this to haggle the price down. I wish I would have known the same when I bought mine! I would also ask them to do the software update for the rear diff control unit/module. GM might have updated it in a way that might help prolong the life of the diff, per the @quakerj post here: Joining the rear diff club

 

[adam728]

Thanks for the reply.

Just occurred for me to ask. Has anyone here had a noisy diff and had a fluid changed "fix" the situation and not had to replace the diff ? I guess I'm asking, seeing that the diff was noisy, and not not noisy with the fluid change - does anyone think I can get another 50,000 miles out of it ? (the car currently has 55,000 miles)

Just crossed 10,000 miles since fluid change on mine. Diff was groaning in left hand turns, similar sound to a clutch-type limited slip on the wrong fluid. Not a peep since changing, but not that many miles since changing either.