2002 Trailblazer won't move in 4Hi

Icekolde

Original poster
Member
Dec 11, 2012
8
Ok, long story, and I'm pretty sure a few people's story goes this way.

Bought this truck about a year ago, knew absolutely nothing about the clutch in the T-case, or that the fluid needs to be changed. Recently noticed that the 4wd stopped engaging - back wheels spin out, front wheels don't bind at all, and this accompanied by a hot oil smell. Did some searching and messaged the Roadie. Tried changing my fluid to see if I there was any luck in my corner, Tcase seemed to be engaging at low speeds aka take off from stop. Today I tried putting my truck into 4Hi while at a stop sign ( I could see big drifts of snow ahead). When I stepped on the gas it was like the back of the truck was trying to go, but something was holding it. Wouldn't move at all, I didn't try too hard. I shifted it back to 2hi, and the truck still wouldn't move. I had to back up about 10-15 feet, then go, and the truck drove home fine after that.

I'm guessing my T-case is shot, I'm really just here so someone can confirm that...
 

dave_stumph

Member
Dec 5, 2011
25
It might be the splined dissconnect? From the sounds of it you were going a good speed while changing from 2hi to 4hi or awd?
Edit: re read your thread. Seems you changed 4x4 at a stop....... Sorry :sadcry:
Still could be the dissconnect?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
A bad disconnect can't cause those symptoms. A diff or transfer case full of broken bits can.
 

Icekolde

Original poster
Member
Dec 11, 2012
8
the roadie said:
A bad disconnect can't cause those symptoms. A diff or transfer case full of broken bits can.

That is what I am expecting. The truck seems to have some resistance now, I don't know how to explain it. Watching the RPMs it doesn't seem to be acting weird, but it feels heavy, sluggish? It doesn't feel like it's did before this happend.

After reading a bunch threads on the forums, I am now looking for a 2006 transfer case. There is one advertised on kijiji as a rebuilt, but they want $650. I would really need to vet the guy to be comfortable giving that much money.

And then there is the no garage problem, although it wouldn't be the first time I've done major repairs in the snow in my parents driveway...lol
 

seanpooh

Member
Jan 24, 2012
461
I think I know what you mean about the "resistance/sluggishness" you're feeling. I had some 4x4 problems; switching from 4wd to 2wd i would be stuck in a state of "neutral" but the tranny is in drive. Happened multiple times last year. The front disconnect was swapped along with both CV joints since so I know those were not a cause. To get out of the neutral state, I would have to turn the switch back to 4wd and when it engaged, immediately I flipped back to 2wd and BANG, it could be heard underneath every time. But the Envoy still drove.

Happened about 10 times, but this last time I have a feeling that something more is permanently damaged.

I have this sluggishness that new plugs, both upstream and down stream 02 sensors, new catalytic convertor from Magnaflow didn't improve. Something is causing resistance and it is killing my MPG too. On the hwy I get 12mpg doing 70mph... 65mph I get 14-16 mpg. Only if I'm going 55mph and less I get decent mpg.

You probably seen the thread about 0-60mph time, mine is 14-15 seconds which is sad. So I'm also assuming the TC is attributing to sad 0-60 time.

Fluids are constantly changed every 25K-45K miles. Front diff and rear diff are drained and filled with Amsoil Severe Gear and TC with blue fluid. Never found chunks or anything odd that seems like metal. Maybe it's too big to pass through the drain hole :eek:

I haven't used 4x4 this whole Michigan winter, I'm just taking it slow and careful. Transfercase repair is in the near future. I don't know what the charge of dropping my TC and rebuilding would cost. I know I couldn't do it myself. But for $650... that's like paying someone to do it.

Next thing you know, all the snow will be gone and I'll forget out the TC. Then I'll remember my gas bill...
 

Icekolde

Original poster
Member
Dec 11, 2012
8
Update:

Picked up a t-case from a 2006 trailblazer with 176,000 on it for $200. Trailblazer was rolled and wrecked for parts.

That is the good news.... the bad news on the trip to pick up the t-case, the CEL comes on and the truck started running hot. Keeping the heater on full blast kept the temp gauge at in the normal range. Tried to check the codes while at the sellers house, there were 2 codes, PO420 and something else, but couldn't get his code reader to display the second code.

So now I am investigating this problem. Any thoughts, please chime in or direct me to threads.

Back to the T-case, is there any maintenance items I should do before installing, seals / gaskets? I've read that it is much easier to change the fluid while it is out.
 

seanpooh

Member
Jan 24, 2012
461
I just changed out my tcase which solved all my problems above. Mine had a little less than 70K miles on it. Yeah, draining it off the vehicle helps but you want to fill it when it's bolted on the tranny. Also, I didn't have to change any seals or bearings. If I had to spend money on a overhaul kit, you might as well buy a reman tcase.

You will need the gasket between the tcase and tcase adapter on the tranny and about 1 quart of tranny fluid. You could also change ujoints while doing this job since you're dropping both drive shafts.
 

Icekolde

Original poster
Member
Dec 11, 2012
8
seanpooh said:
I just changed out my tcase which solved all my problems above. Mine had a little less than 70K miles on it. Yeah, draining it off the vehicle helps but you want to fill it when it's bolted on the tranny. Also, I didn't have to change any seals or bearings. If I had to spend money on a overhaul kit, you might as well buy a reman tcase.

You will need the gasket between the tcase and tcase adapter on the tranny and about 1 quart of tranny fluid. You could also change ujoints while doing this job since you're dropping both drive shafts.

I've read the threads about these driveshafts and having to heat them to melt the plastic retainer. I'm pretty handy but I've always had problems with getting u-joints in and out. Should I take this to a shop, just to be safe?

Also, how hard is it to separate the front driveshaft from the t-case? The one I bought came with the shaft still in it....
 

Icekolde

Original poster
Member
Dec 11, 2012
8
Icekolde said:
I've read the threads about these driveshafts and having to heat them to melt the plastic retainer. I'm pretty handy but I've always had problems with getting u-joints in and out. Should I take this to a shop, just to be safe?

Also, how hard is it to separate the front driveshaft from the t-case? The one I bought came with the shaft still in it....

Good news everybody!!

It wasn't the transfer case at all, YAY!

Unfortunately it IS the front differential. I am 100% sure the problem is in there and 99% sure it is lunched. The front driveshaft cannot be turned, by hand or by putting it into 4wd. Also horrible sounds were coming from the diff where the driver's side driveaxle is. I confirmed this by jacking up the wheels and turning. No noise from the passenger side, horrible grinding clunking sound from the driver's side. Wisely I decided to stop driving this beast until I could remedy the problem.

Since I don't have another vehicle, I decided to pull the driver's driveaxle out, so I can drive until I find a replacement diff. I separated the cv shaft at the pot, then re-assembled everything. For now I am fine, I sprayed white lithium grease into the hub to keep the splines from rusting, and I packed the pot with paper towel to stop the grease from dripping out too bad.

So, next question, and I've searched high and lo to no avail - what years/vehicles can I get a front diff from?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Icekolde said:
what years/vehicles can I get a front diff from?
Sorry to hear, but at least you now know what's up. All years and 4WD/AWD are interchangeable. Ignore anybody who asks if you have a certain number of "yoke bolts". All diffs are the same mounting. Just make sure you get one with a matching gear ratio.
 

Denali n DOO

Member
May 22, 2012
5,596
I think it's listed in your glove box. Here's the codes.

GU6 = 3.42
GT4 = 3.73
GT5 = 4.10
 

Icekolde

Original poster
Member
Dec 11, 2012
8
Denali n DOO said:
I think it's listed in your glove box. Here's the codes.

GU6 = 3.42
GT4 = 3.73
GT5 = 4.10

Thanks, is there any way to tell if the unit is already removed from the vehicle?
 

fletch09

Member
Nov 20, 2011
1,982
don't know if there is a way to tell. quickest way is to open glove box, look @ the black & white sticker that should be on the glove box door.
those are your build codes. look for any one of the 3 codes that Denali n Doo listed, that should tell you what the gearing is.
unless you kow gearing has been changed prior. go w/ what the code says. :twocents:
 

gmcman

Member
Dec 12, 2011
4,656
Icekolde, In addition to what has been stated already, what tires do you currently have, sizes, and treadwear? Please be as specific as possible especially with the treadwear.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Icekolde said:
Thanks, is there any way to tell if the unit is already removed from the vehicle?
Assuming you're talking about the junkyard unit, the yard should know. If not, then you have to just rotate the input shaft and count revolutions of the outputs. Make sure they're both rotating. If only one rotates, the number of rotations will be off by half. Gear ratio is just the number of times you have to rotate the driveshaft to get the outputs to rotate once.
 

Icekolde

Original poster
Member
Dec 11, 2012
8
Ok, just an update here.

Still looking for a replacement front diff. I'm trying to find the disconnect as well so I can prep everything ahead and just do a re & re.
 

Forum Statistics

Threads
23,321
Posts
637,914
Members
18,526
Latest member
GODSBROOKS

Members Online