Chevy Trailblazer SS Forum banner

1 - 6 of 6 Posts

·
Registered
2007 Black 3SS AWD
Joined
·
10 Posts
Discussion Starter #1
Hey guys, I usually handle all of my own diagnose/repair work, but I'm completely lost and thought I'd ask for help after searching and not finding anything similar. I hope nobody else has had this, but odds are that someone might have.

I was driving home from work, 65 on the highway, and felt what seemed like an expansion joint - slight thump with a slight wiggle of the truck. It caught my attention but wasn't anything otherwise remarkable. A couple minutes later it happened again. Then another minute later. And another. Then less than a minute later. At that point the rpms started climbing like the trans was slipping, so I popped it into neutral and coasted to the shoulder. As road noise decreased I heard grinding, lots of it. I stopped, and all seemed normal, so it's not engine related.

It's lowered so I couldn't crawl under it, but there was no fluid and nothing hanging. Idled just fine, put it into gear and severe grinding noise. Got a tow, dropped it off at the shop I've been going to for over 25 years for state inspections and work I don't have time/tools/room for. They called the next day after pulling it into the shop and numerous test drives - it ran fine for them. In disbelief I drove to the shop, drove it around, and they're right - drives fine.

I'm lost. My guess is that a tooth broke somewhere and the broken tooth is no longer in the way - but that also means that more issues are coming. What I'm hoping someone can help with is...what broke? I know people have issues with both the 4L70 and also the intermediate shaft splines on the front diff. I've never experienced either. I'm not sure if the stabilitrac kick on if the IM shaft fails, or if the TCM will throw any codes due to part failure (I'm new to electronic trannies) but I've got nothing except the sound of mechanical failure which has now "disappeared". I looked through the "tranny symptoms/failures" sticky post and nothing fit. I've never dealt with failed splines on a diff, so I have no idea what that sounds/feels like.

I suppose the next step is to pull the trans pan and look for metal, but I thought I'd ask here before ordering that new trans, as I don't have that $ laying around. BTW the truck is bone stock (aside from belltech drop) with 130k miles. I've owned it for 2 years (2nd owner) and have never even launched it - it's my DD and I need it for my business.

Any thoughts/recommendations? Thanks in advance!
Aaron
 

·
Premium Member
2008 TrailblazerSS
Joined
·
12,861 Posts
A simple check of the engine oil and trans fluid from the dipstick should tell you if there is metal. The engine oil, maybe not so much. I'd take it and thrash it around a little to see if you can get it to do it again. Sounds like drive train issues.

~Aerodynamics are for people who can't build engines~
 

·
Registered
2007 Black 3SS AWD
Joined
·
10 Posts
Discussion Starter #4
I had the truck idling along the side of the road so the 4-ways wouldn't kill the battery while waiting for AAA, it's definitely not engine. Only seemed to lose power when the rpm's climbed, felt like slippage. (Whether it was gear slippage or band slippage remains to be seen.) That was when I made the quick departure from the passing lane to the shoulder.

I'll be ripping the trans pan off tomorrow and looking for pieces. If nothing else, a new filter/fluid can't hurt. Just thought I'd see if anyone else had a "it's broken, no wait it's fine" scenario, trying to eliminate driveline components to tear apart.

Thanks guys.
-AA
 

·
TT AWD TBSS Jeep
TT AWD SS Pwrd Jeep
Joined
·
5,825 Posts
If your hearing grinding, there has to be metal somewhere. If it siunded like the front, Id drain oil from front diff and check it very carefully. My wifew Envoy did the same thing, and its only usable in 2wd now. But if yours goes, your stuck as the SS is AWD. It will put all the power to the front and you wont go anywhere.
 

·
Registered
2007 Black 3SS AWD
Joined
·
10 Posts
Discussion Starter #6
Just to update, I finally got time (my soon-to-be-former shop wouldn't touch it) to pull the front carrier and IM shaft, and they're both stripped out. I ordered replacement parts (as listed on other posts) and at this point I'm hoping that's all it is. I actually drove it from the shop to my house, about 5 miles, with no issues before tearing into it myself. I am concerned that it could be a larger issue, but for now I'll have to take my chances as I need it back on the road. I plan on taking it to the local driveshaft/axle shop to have them tear into the front diff in the very near future. At 130k it's not a bad idea to have it looked at regardless. I do have some minor leaking where the diff meets the left side of the oil pan, so I want to make sure that's taken care of before taking a trip next month. If I/they find more damage I'll be sure to pass it along.
 
1 - 6 of 6 Posts
Top