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2009 Cadillac sts v8
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25 Posts
Discussion Starter #1
Hey i have a RWD 4.6L and It’s making a like rapid clicking sound underneath the car when you get on the throttle from a stop. it sounds like it’s Coming from underneath the center console. Already changed the differential fluid with the recommended new stuff. Changed the rear right cv axle. Still no improvement. Wondering if anyone’s had this same problem before and has any tips what it might be? Pretty sure it’s the u-joint and if so anyone have any tips on replacing it? Apparently it’s non serviceable
 

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2006 STS V8 AWD, '95 Ford Ranger
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29,054 Posts
There are no u-joints in the drive shaft.It has flexible couplings and a support bearing in the center. Get the car on a lift and start poking around. The flexible couplings are known to come apart and the center bearings wear out. A deteriorated transmission mount can put unwanted pressures on the coupling at the transmission.
 

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2009 Cadillac sts v8
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25 Posts
Discussion Starter #3
There are no u-joints in the drive shaft.It has flexible couplings and a support bearing in the center. Get the car on a lift and start poking around. The flexible couplings are known to come apart and the center bearings wear out. A deteriorated transmission mount can put unwanted pressures on the coupling at the transmission.
I appreciate youre response man! Also I replaced the coupling closest to the rear differential about 5000 miles ago and the center support bearing AND the rear differential bushing about 10000 miles ago. I suppose it could still be one of those, or as you said the coupling closest to the transmission. The coupler connecting the transmission to the driveshaft however didn’t look too bad when I replaced the rest. I bet its the transmission mounts, considering the car does have a noticeable not exactly lurch? Or jerk? I don’t know but you definitely feel when it shifts? Again I appreciate any responses this cars been a mechanical nightmare in every since of the word since I bought it☠ Any more input anyone?
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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479 Posts
If it were not RWD but was AWD, my guess would be the chain inside the transfer case. Since it is RWD I will suggest checking the exhaust baffles and thermal covers on the exhaust system. Good Luck.
 

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2009 Cadillac sts v8
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25 Posts
Discussion Starter #5
If it were not RWD but was AWD, my guess would be the chain inside the transfer case. Since it is RWD I will suggest checking the exhaust baffles and thermal covers on the exhaust system. Good Luck.
Thanks for your response firstly sir. Also so you’re saying it could be a noise from the exhaust making contact somewhere it shouldn’t? I don’t knoooow lol the sound reaaally sounds like a bad cv axle or u joint like it’s a really bad rapid clunking noise coming from (sounds like) the driveshaft or somewhere along the drivetrain. Ughhh. The struggle of owning a luxury car on a non luxury budget lol
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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As cars progressed and things got added, the space between things got less and less. Throw in a worn out engine mount or transmission mount that lets the engine and transmission move around more than they are supposed to. This results in things making contact that should not. Put the car up on a lift that supports the frame with someone in the car to start and put in drive. CAREFUL - make sure the vehicle is solidly supported but not by the wheels. Stand at the rear of the car and look along driveshaft. Look for abnormal vibrations or contact as the car is accelerated gently. Be very careful because the car can fall off the lift with fatal or expensive results. Good Luck.
 

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'08 Cadillac STS Northstar 4.6 RWD
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20 Posts
Pretty sure there is a U joint on these driveshafts, right near the support bearing and slip yoke. I don't think its serviceable though.
 

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2009 Cadillac sts v8
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Discussion Starter #8 (Edited)
Dealership did confirm that there is a u-joint, you are correct. And the dealer also confirmed it is unserviceable, you are also correct there. I would have to buy the whole driveshaft just for the u-joint LOL. Haven’t had a chance to get under there like CWB said and check out the drive train for any oddities (although i sure can hear them when just kinda shifting back and forth at a stop, between reverse and drive there’s at least a couple of clunks lol☠).Hopefully I will either today or tomorrow and I’ll let you guys know if I find anything. worst case scenario I have a diagnosis appointment with the dealership for this Friday so I will find out for sure what it is then.

EDIT: I was at work and did this with speech to text. Autocorrects a b****
 

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2006 STS V8 AWD, '95 Ford Ranger
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29,054 Posts
RWD has a U-joint near the center bearing. AWD has flexible couplings all the way front and rear. Some owners report they were able to locate U-joint parts and a replacement center bearing after market from a bearing supply house.
 

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2009 Cadillac sts v8
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25 Posts
Discussion Starter #10
I already replaced the center bearing (unnecessarily it turns out the problem I was attempting to fix by replacing this, was actually resolved by replacing the rear differential bushing) however Ive found a u joint on CARID.com, only place I’ve found one. And it says it’s only for their brand driveshaft...ughhhhh. The dealer said the u-joint is... I guess I should quote here those idiots... “non serviceable”. I’m really appreciating everybody’s feedback and for keeping this thread alive LOL. Do you have any idea how they were able to “service” the u-joint? Or in other words how did they get it apart? since I don’t think there are any handy clips holding it in considering they say it’s again I’ll quote “unserviceable”... get a Cadillac they said! It will be so fun they said!😐 I want to be as humble as possible, a lot of you seem like experienced owners and most are owners of multiple cars. I’m a young inexperienced diy’er, with this ‘09 as my daily and just trying to save some money from cadillacs outrageous repair costs.
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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Something you said indicates another problem. The clunk from drive to reverse and/or back is a symptom of a differential bushing also being bad. Nearly impossible to see it but you can test by having the car on a lift and pushing up on the front "nose" of the differential. Any more than slight upward movement indicates a need to replace the bushing on the top front of the differential. It can be done by DIY but have to remove driveshaft and probably exhaust which you probably have to remove to fix the other problems anyway. Do it while you are in there.

Oops, just read more carefully and you may have already done that bushing.
 

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2009 Cadillac sts v8
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25 Posts
Discussion Starter #12
Something you said indicates another problem. The clunk from drive to reverse and/or back is a symptom of a differential bushing also being bad. Nearly impossible to see it but you can test by having the car on a lift and pushing up on the front "nose" of the differential. Any more than slight upward movement indicates a need to replace the bushing on the top front of the differential. It can be done by DIY but have to remove driveshaft and probably exhaust which you probably have to remove to fix the other problems anyway. Do it while you are in there.

Oops, just read more carefully and you may have already done that bushing.
Well it’s not so much of a clunk really, at least not compared to before I replaced the rear diff. I do however gentlemen have a confession to make lol. The tool I rented from a local bearing shop to install the bushing snapped while I was torquing the rear differential bushing to I believe it was like 140lbs or something like that. Anyway I never did get the torque wrench to actually click and signify the desired torque had been achieved...cuz the bolt for the tool snapped lol. Turns out after I took the tool back, it wasn’t clear in the directions but I was supposed to torque the bolt that goes back into the bushing once you’re done installing it.... and so in other words the rear diff was never fully torqued and it kinda looked funny because a little bit If the bushing was still sticking out. It wasn’t flush. So it’s loose maybe? I’ll commit to Getting under it tomorrow And checking it out it’s just been so hot lately LOL. Again I appreciate everybody for trying to help. I hope somebody else finds this thread useful as well.
 

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'08 Cadillac STS Northstar 4.6 RWD
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20 Posts
I think the U joint on the RWD shaft is not considered serviceable because they don't use traditional clips to hold the joint caps in, they just mash a little divot in the ear of the shaft to hold the cap in. Hopefully that makes sense. It would probably be a huge pain to try replacing just the u joint. You should have been able to tell if it was bad when doing the center support bearing though. Another thought, the center support can be a bitch to get seated perfectly, and don't last long if theyre not installed right.
If it does come down to a new shaft, rockauto has an AC Delco for the best price I could find, use a 5% off code and it might cover shipping.
 
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