Joining the rear diff club

[Displayhawk]

As an update, my original rear differential had to be replaced at approximately 50k under warranty about a year ago. The service advisor told me that the new rear differential was from a different vendor than the original. I am wanting to replace the "break in" gear oil in the new unit, but I am trying to decide between the AC Delco OEM gear oil or try the Triax 75w90 gear oil. The Triax shows that it greatly exceeds the OEM specs.

 

[fredzy]

As an update, my original rear differential had to be replaced at approximately 50k under warranty about a year ago. The service advisor told me that the new rear differential was from a different vendor than the original. I am wanting to replace the "break in" gear oil in the new unit, but I am trying to decide between the AC Delco OEM gear oil or try the Triax 75w90 gear oil. The Triax shows that it greatly exceeds the OEM specs.

That’s interesting. The rear diff is supposed to be a GKN twinster which can only come from GKN. If true it would be very interesting to hear what it is. Maybe it’s the assembly of the twinster into the whole diff sub-asm that can come from different vendors.

If it is still a twinster then you definitely do not want to put anything besides the OEM stuff in there. There is a long trail of dead diffs from people putting fluid other than the OEM stuff into them.

 

[Buckjoe]

As far as differential lube, I just tried the Valvoline equivalent. Now I know what people are talking about with the moaning. Also, very harsh going from throttle to coast to throttle. Put the nice clean 6k GM product back in before work next morning. All better. I guess it’s worth what it costs. I don’t know what additive pack GM uses….now I’m wondering if the Delco lube is masking an issue the Valvoline exposed, or if the Valvoline just doesn’t cut it. Hoping the former.

Update….started getting a slight low frequency moan with right turns, after replacing the Valvoline product. I bought fresh GM lube AND a 4oz bottle of GM friction modifier. Drained diff. Lube was a hair darker, but still looked good. Magnet looked like somebody colored it with a black Sharpie. I added 1-1.5 Oz. modifier (eyeball method) to the lube and filled the diff. 250-300 miles later, super quiet. I’ll update when anything changes. BTW, I did a little research on extra friction modifier…..too much will reduce the posi effect. I’m hoping the little bit I added is good.

 

[farbinator]

Chalk up another one!

2019 With 41,500 miles. Started to notice the classic low groaning at low speed when turning right. The local dealer is servicing the Rear Differential and PTU fluids which hopefully will fix it. Also having them take car of the transmission fluid given I'm close enough to 45,000 miles.

According to the technician, no signs of any leakage so that's good. I'll provide an edit update in a bit with the result.

Edit: All is well after the fluid change, no more noise.

 

[stevie123]

2018 TourX. 99K miles. I get a slight groan when turning right that I thought was the power steering pump (then discover its electrical..) Read this entire thread. I will have the car on a hoist soon. Brought the AC Delco fluid (88862624). Question:
Based on the photo in post ~228 above, are those the drain and fill plugs? I guess its as straight forward as draining from the bottom, then filling (with a tube?) from the side plug hole until it won't take anymore. Then tighten plug back on?

Side question: Nobody seems to be talking about transfer case (PTU?) failures... should I bother changing out that fluid? Is it the same AC Delco LS oil? or something else? Similar question for DIY - is it easy/straight forward? Or do I need to cycle the gears, warm the car, etc.?

 

[FavaBean]

Side question: Nobody seems to be talking about transfer case (PTU?) failures...

I had a PTU failure at about 95k miles.
Thankfully I bought an extended warranty with $0 deductible which saved my butt. Replacement cost would have been around $5500. I was without a car for 2 months waiting for the part to be imported as it was out of stock nationwide.

 

[fredzy]

2018 TourX. 99K miles. I get a slight groan when turning right that I thought was the power steering pump (then discover its electrical..) Read this entire thread. I will have the car on a hoist soon. Brought the AC Delco fluid (88862624). Question:
Based on the photo in post ~228 above, are those the drain and fill plugs? I guess its as straight forward as draining from the bottom, then filling (with a tube?) from the side plug hole until it won't take anymore. Then tighten plug back on?

Side question: Nobody seems to be talking about transfer case (PTU?) failures... should I bother changing out that fluid? Is it the same AC Delco LS oil? or something else? Similar question for DIY - is it easy/straight forward? Or do I need to cycle the gears, warm the car, etc.?

Yes those are drain (bottom) and fill (back) plugs, it's like a normal diff in that way. I use a pump that threads onto the oil bottle for such fills. The fill plug on this one is a pain due to sway bar blocking tool access, I grab it with vice grips to remove and tighten lol

I have not seen/heard of frequent transfer case failures, but it wouldn't hurt to change the fluid, no. Just be sure to use the exact spec fluid.

 

[stevie123]

Yes those are drain (bottom) and fill (back) plugs, it's like a normal diff in that way. I use a pump that threads onto the oil bottle for such fills. The fill plug on this one is a pain due to sway bar blocking tool access, I grab it with vice grips to remove and tighten lol

I have not seen/heard of frequent transfer case failures, but it wouldn't hurt to change the fluid, no. Just be sure to use the exact spec fluid.

Thank you! What fluid does the transfer case use and how many qt should I buy? Similar 2 plug setup for the drain+fill?

 

[stevie123]

I had a PTU failure at about 95k miles.
Thankfully I bought an extended warranty with $0 deductible which saved my butt. Replacement cost would have been around $5500. I was without a car for 2 months waiting for the part to be imported as it was out of stock nationwide.

Wow! Thats bad luck. What was the symptom? I brought the GM/Buick extended warranty and just ran out (did not use it at all...) My only repair was a squeaky accelerator pedal when new and a battery replacement a few years back. Car actually improved fuel efficiency the last 2-3 years...

 

[FavaBean]

What was the symptom?

It started out as a light humming noise. So with the amount of complaints here, I assumed it was the differential. Noise then became louder, especially at speeds above 40 mph. Eventually, it became less of a consistent hum and more of a pulsating noise, especially under throttle load. (Tough to replicate the noise in words but sort of a loud wa-wa-wa-wa-wa sound which now started at low speed and sped up as I accelerated.)

I was always a bit perplexed by the noise as it seemed that its sound originated in the back but moved forward to the center of the undercarriage as it got louder.

As a side note, I was getting water collecting in the spare area. I realized if I back my car into my inclined driveway my spare tire remained dry. This slanted position allowed my front sunroof drains to remove the excess water instead of the rear ones.

But one day I pulled straight up the driveway. That's when I noticed reddish oil drops on my driveway from my leaking PTU. Evidently, when parking backwards on my inclined driveway, the dripping PTU oil collected on top of the brush guard instead of on my driveway.

 

[fredzy]

Thank you! What fluid does the transfer case use and how many qt should I buy? Similar 2 plug setup for the drain+fill?

Sorry I haven't done the transfer case myself, but @Hunter Mike has a good writeup on that. You might guess why I haven't done it proactively yet myself heh

Thread 'Regal AWD PTU(transfer case) fluid change DIY'

Jan 14, 2020

I took the time today to change the factory fill in the PTU unit. For someone who has a lift this is an easy 15 minute job using minimal tools. I did it on my garage floor using ramps and jacks and it took about an hour. Mileage was 15,400, 90% highway.

The PTU uses a ACDelco specific fluid p/n 19351882. It has a list price of over $90USD/quart! The description shows it's a 75w-90 synthetic gear lube with EP additives. I was tempted to use some 75w-90 gear lube I have in the stash but with a new transfer case price of $1k or more plus install I bought the fluid from the dealer. I...

• Hunter Mike
• Replies: 56
• Forum: 2018+ Buick Regal Sportback and TourX Forum

• 

 

[nstiesi]

I've read through this thread but I'm not sure I noticed if temperature is a factor in diff "groaning"?

I've had my 2018 white needle since august, and i have noticed some noise from the rear while turning, but only in the first few miles of driving. Once I am on the road for 10 mins or so it goes away completely. I assume the fluid gets some friction heat in it and thins out and/or gets more distributed and things quiet down?

Is this a sign that I should do a fluid service? My car has ~54k on it, but only 2k since I bought it. Thanks!

 

[fredzy]

I've read through this thread but I'm not sure I noticed if temperature is a factor in diff "groaning"?

I've had my 2018 white needle since august, and i have noticed some noise from the rear while turning, but only in the first few miles of driving. Once I am on the road for 10 mins or so it goes away completely. I assume the fluid gets some friction heat in it and thins out and/or gets more distributed and things quiet down?

Is this a sign that I should do a fluid service? My car has ~54k on it, but only 2k since I bought it. Thanks!

At minimum I would get under there and check for any signs of weeping or leaking seals on the diff, and then pull the drain plug to check the fluid level. But since you're already noticing a sound, getting it serviced at the dealer or DIY fluid change yourself is highly recommended at this point.

 

[nstiesi]

Just ordered a quart of Dexron. Looks like I know what I am doing this weekend!

 

[nstiesi]

Done! Wasn't too bad. A VERY short test drive revealed the noise to be gone, and it sounded good on the commute this morning. Finger crossed long term.

The old fluid:


Some weeping from the axle shafts:



But I he prop shaft input looks pretty dry: