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Discussion Starter #1
I just picked up my TBSS from the shop after they installed a used front diff. From a standstill, with anything more than moderately light acceleration, there is an obvious coarseness accompanied by some noise. Straight, to the left, and to the right. Any thoughts about what would cause that? The repair has a warranty, but I'd I'd like to be able to talk about it intelligently. Thanks.
 

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Bring it back, sounds like they put a bad "used" unit in. Then the obvious wheel bearings and such but if it was good when it went in, its what they did.

Sent from my boujea ass phone
 

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2008 TrailblazerSS
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Bring it back, bring it back, bring it back


2008 TBSS Super Charged
 

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Lighter-than-you
TrailblazerSS
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the only way shop couldve known it was bad was if they took it out of said vehicle that they knew had a bad front diff.. Aside from that, they probably just picked up a diff from the cheapest place they could get one and hoped for the best. Doesn't make sense to me that any repair shop would warranty a used part.. especially a front diff in a TB which involves a good bit of labor to take out/put in.
 

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07 tbss awd
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Either bad used unit or they didn’t put fluid in it. Bring it back, that sucks because it’s a big repair to have to do twice and for you to have to wait for.

As far as talking about it intelligently, sounds like maybe the pinion bearings or carrier bearings are shot. Also possible that it has to much backlash and not enough preload because of worn out carrier bearings. That would be my best guess.
 

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Discussion Starter #6
Thanks for all the replies. I was already going to take it back. I wanted to be prepared to discuss the issue as knowledgeably as possible. I wanted them to get a rebuilt unit to install, but they convinced me a used diff from another TBSS would be a better route to go. I almost never agree to used parts. In this case the Mrs and I were 1800 miles away burying her parents. The cost of the trip, plus the emotions at the time, kept me from standing my ground. I guess it's back for round two!
 

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Discussion Starter #7
Also, it's a new noise associated with this diff. The front end has otherwise been totally rebuilt within the past year, including new axle assemblies, and OEM hubs.
 

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Lighter-than-you
TrailblazerSS
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Thanks for all the replies. I was already going to take it back. I wanted to be prepared to discuss the issue as knowledgeably as possible. I wanted them to get a rebuilt unit to install, but they convinced me a used diff from another TBSS would be a better route to go. I almost never agree to used parts. In this case the Mrs and I were 1800 miles away burying her parents. The cost of the trip, plus the emotions at the time, kept me from standing my ground. I guess it's back for round two!
Ahh, it's making more sense now.. they had to have already had that sitting around somewhere.. Still can't explain why they would've warranted something that they either 1) knew was bad or 2) didn't know for certain that it was good. I hope they stand behind it for your sake. If it were me, I don't know if I would even want these jokers installing a rebuilt diff. I would try to just get them to give me my money back and go to a legit shop. Best of luck bud and let us know how it turns out!
 

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Discussion Starter #9
So far the shop has been pretty good about my concerns. The mechanic who did the install rode with me Monday, and agreed he could hear the problem I was describing. He deferred to the shop owner, who rode with me today. He also agreed that my concern warranted further investigation. The SS is scheduled back in this Friday when he'll have more time to take a closer look.

In the meantime I noticed that the engine is about 2" off center to the passenger side. I know the engine has to be pulled over to get the diff out/back in. I would expect the centerline of the crank to be inline with the centerline of the frame. Is it possible that drivetrain misalignment could be causing the coarseness I'm experiencing? I have been able to pinpoint it to the 20-35 mph speed range.
 

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Lighter-than-you
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1.4" off center from the factory, looks weird but thats what GM saw fit to do.. I guess its to offset the weight of usually just having the driver as only occupant:unsure:
 

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GM was trying to fix the Chevy lean. Lol


2008 TBSS Super Charged
 

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So far the shop has been pretty good about my concerns. The mechanic who did the install rode with me Monday, and agreed he could hear the problem I was describing. He deferred to the shop owner, who rode with me today. He also agreed that my concern warranted further investigation. The SS is scheduled back in this Friday when he'll have more time to take a closer look.

In the meantime I noticed that the engine is about 2" off center to the passenger side. I know the engine has to be pulled over to get the diff out/back in. I would expect the centerline of the crank to be inline with the centerline of the frame. Is it possible that drivetrain misalignment could be causing the coarseness I'm experiencing? I have been able to pinpoint it to the 20-35 mph speed range.
You really need a rebuilt one put in, too much pain in the ass to remove again and again. Even if all the internal were in good nik (which sounds like they are definitely not) you still have all the seals to worry about.. the axle seals are especially prone to leaking with age. Just the fact alone that they didnt suggest a rebuilt unit going in should make you run... Get your money back!
If you paid with credit card, then get them to reverse charges. This joker shop doesn't have a leg to stand on to come after you.
 
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