Ok ladies an gentleman. I need opinions on the issue I am having with my 4x4. I have a 2002 ZR2 Blazer. 125000 miles. I bought it 3 years ago and everything on it has worked great up until now.


3 weeks ago when it snowed, (Im in VA) I put it in 4 hi to go to the store. It ran fine for about 5 miles. Then I started hearing a slight clanking and grinding noise coming from under the vehicle. All of a sudden the truck seemed to slam on the brakes all by itself. It seemed like the transfer case had locked the front wheels up or something. I put it back in 2 wheel drive and it drove fine. Once I got it near my house, I tried 4 hi again and it worked but it still had a clanking/grinding noise. last week when it snowed again, I put it in 4 hi and low and it is not engaging. The 4x4 lights light up on 4 hi and lo but it is not going into 4 wheel drive. I have driven it a few hundred miles in 2 wheel drive since then and it seems to run fine. To me it seems like it could be the transfer case. Has anyone ever heard of these failing like this or has anyone had a similar problem.


Anyone have any suggestions on how to diagnose it?


Thanks in advance for your help.

 

May have to just pull it and tear it apart, or just gat one from the junkyard/boneyard and swap em. afternoon job

 

I would change the fluid in the front differential and the transfer case and look for metal chunks or particles.

 

Ok so I finally found time to drain the fluid in the front differential and t-case. The front Differential had NO FLUID at all in it. I am assuming that is my problem. Lovely!!! The t-case fluid looked alright. I just drained and put new fluid in it. As far as the front differential, what are my options, go to a junk yard and get a new front dif? I read about doing a Bravada axle swap and I am interested in that instead of dealing with the vacuum actuator. Mine is a ZR2 Blazer so does it matter what front dif I get? I know the ratios have to match but anything else I should be aware of? I will try to start tracking down an entire bravada front axle assembly. Do I even have to replace the entire assembly or can I just swap parts from the bravada into mine?

 

The other thing is the wheel mounting surface (WMS) measurement. I think the bravada may be narrower than your ZR2. The ZR2 rear differential is wider and heavier duty than a non-ZR2. Hopefully it's just your ring & pinion gears. It may be cheaper to rebuild yours with better parts and new seals than getting a weaker, high mileage one from a junkyard. As for changing your push button t-case over to an Oldsmobile smarttrak. That would be the t-case and transfer case control module (tccm) and maybe reprogramming and additional wiring. It also may be weaker than your ZR2.

 

OK so I had a chance to mess with the blazer this past weekend. I refilled the front differential with gear lube. I then decided to drive it down to my parents for the weekend (about 250 miles round trip.) I have AAA so if it broke down no worries. I made it about 15 minutes from my house and it started making the same grinding/clanking noise in the front end. It made that noise for about 30 minutes then it went away and ran fine. On the way back Sunday, it started making the same grinding noise for about 30 miles then it went away again. What could it be in the differential that makes noise intermittently? I really do not want to swap out a new differential if I do not have to. I'm going to pull the battery and disconnect the cable on the vacuum actuator just to see if somehow that is trying to engage while driving. Any thoughts?

 

Verify that the front differential is still full of gear lube. Look at the pinion and cv shaft seals to find out where the old gear lube leaked out from. It sounds like it was the front differential that locked up your front tires. If it were mine I would jack all 4 tires off the ground and do some diagnosis on why the 4 wheel drive is not engaging. There are many good threads here for that. You didn't mention if it was grinding/clanking 2 wheel drive now. I'm concerned about the tires locking up and causing damage to you, your blazer, or someone behind you because your truck suddenly stopped in front of them. Generally, the longer you drive while it's grinding/clanking, the more expensive it's going to be to repair. There are also threads here about a posi-lok kit. It replaces the vacuum system for a cable system to engage 4wd plus it allows for low range 2wd. I don't think you'll need to replace your entire front differential if you can find the problem before it scatters apart.

 

Ok Thanks. I will check all of that this week. It is just weird how it makes noise at first but then both times it has went away. Weird. I will put it on jack stands and put it in 4 wheel drive and try to replicate the grinding noise just to see exactly where it is coming from. It does still make the noise when it is in 2 wheel drive. I will try to get a video of the noise this week sometime. Ill check all of the gaskets and find the leak. Thanks again.

 

sounds like the chain in the transfer case let loose.

 

the other thing to look at might be the ring gear bolts in the front diff..... I had a friend that had an AWD Caliber, and ran on a donut spare for about a month (duh!).... needless to say, she f'ed up the entire driveline.... after replacing the transfer case and front diff assembly, I thought I had it licked.... but after a month of driving the rear axle locked up, because the bolts holding the ring gear in backed up and caught the housing, ripping a nice hole in it. It destroyed the rear axle, because that's where the donut was run.... Given that you say that it makes the noise for a while and stops (i'm assuming the noise is coming from the front end, and not the tailstock of the tranny (transfer case) it might be a good place to look