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Posted: 10/22/2004 3:44:58 AM EST
My '93 Suburban has been a faithful and trusty vehicle so far, and has never left me stranded. Just yesterday, when trying to shift into 4WD-hi, I noticed that the 4WD light did not come on, and I did not feel the front axle engage. Sure enough, when I pulled a u-turn I did not feel the lockers engage and I knew for sure that 4WD was not working. The truck seems to be driving normal except for that. I checked the 4WD fuze, and that looks ok.

I have no idea what the hell else to look for- any Chevy truck guys out there... h---e---l---p! I'm hoping this isn't the beginning of the end for my old girl
Link Posted: 10/22/2004 3:46:02 AM EST
Chevy doesn't make trucks....they make pick-ups.


SGtar15
Link Posted: 10/22/2004 3:46:57 AM EST
Time to switch to manual hubs!
Link Posted: 10/22/2004 3:50:20 AM EST
The help so far has been outstanding, with a break-out performance by PVTAR15...
Link Posted: 10/22/2004 3:54:26 AM EST
... Did you try popping it in 4WD as you idled in reverse and/or while shifting forward?
I used to have a '93 truck and sometimes it took a little finesse to engage
Link Posted: 10/22/2004 3:56:27 AM EST
Wait for reply from Boomer, or IM him.

You've pretty much diagnosed the problem as a defective locking system. As I understand things, the auto locker is a thermal unit which is why it's temperature sensitive. Apparently, a replacement mechanical locker is cheap and easy.

Link Posted: 10/22/2004 3:58:19 AM EST

Originally Posted By Winston_Wolf:
... Did you try popping it in 4WD as you idled in reverse and/or while shifting forward?
I used to have a '93 truck and sometimes it took a little finesse to engage


I haven't tried it yet, but I suspect that something in my transfer case is screwed- I wonder what the most common breakages are for a 4WD system that has worked 100% up until now. I'm hoping it's just a clutch pad or something cheap in the transfer case. I really don't want to sink any big money into this truck right now...
Link Posted: 10/22/2004 3:59:17 AM EST

Originally Posted By DriftPunch:
Wait for reply from Boomer, or IM him.

You've pretty much diagnosed the problem as a defective locking system. As I understand things, the auto locker is a thermal unit which is why it's temperature sensitive. Apparently, a replacement mechanical locker is cheap and easy.




It's not just the lockers, the FRONT AXLE just does NOT engage at all. I wish it was just the lockers!
Link Posted: 10/22/2004 4:01:00 AM EST
[Last Edit: 10/22/2004 4:06:34 AM EST by Railgun]
There is a chamber in the front differential and when you switch to 4X4 it closes a circuit which heats an element and this element heats a gas charge and the gas charge expands and locked the front wheels in. On really cold days it takes longer to engage.

or...

There is an electronic actuator on the front differential you have to rely on. If you've got push button 4x4 you also have to rely on sensors and servos on the transfercase also.

Manual Locking Hubs!

Railgun....


ETA: You mention a fuse....did you check for voltage on the wire leading to the heater? Broken wire perhaps?
Link Posted: 10/22/2004 4:08:22 AM EST

Originally Posted By Railgun:
There is a chamber in the front differential and when you switch to 4X4 it closes a circuit which heats an element and this element heats a gas charge and the gas charge expands and locked the front wheels in. On really cold days it takes longer to engage.
Railgun....




+1 Not that bad of a job to replace.
Link Posted: 10/22/2004 4:08:36 AM EST

Originally Posted By dissipator556:

Originally Posted By DriftPunch:
Wait for reply from Boomer, or IM him.

You've pretty much diagnosed the problem as a defective locking system. As I understand things, the auto locker is a thermal unit which is why it's temperature sensitive. Apparently, a replacement mechanical locker is cheap and easy.




It's not just the lockers, the FRONT AXLE just does NOT engage at all. I wish it was just the lockers!



How can you tell while driving? The only way you could tell that is on a lift, and the transfer case would pretty obviously be malfunctioning.

The front diff could be receiveing power nicely from the transfer case, and if that element failed to lock the front axle, you'd still have no power to the CV shafts.
Link Posted: 10/22/2004 4:11:26 AM EST

Originally Posted By DriftPunch:

Originally Posted By dissipator556:

Originally Posted By DriftPunch:
Wait for reply from Boomer, or IM him.

You've pretty much diagnosed the problem as a defective locking system. As I understand things, the auto locker is a thermal unit which is why it's temperature sensitive. Apparently, a replacement mechanical locker is cheap and easy.




It's not just the lockers, the FRONT AXLE just does NOT engage at all. I wish it was just the lockers!



How can you tell while driving? The only way you could tell that is on a lift, and the transfer case would pretty obviously be malfunctioning.

The front diff could be receiveing power nicely from the transfer case, and if that element failed to lock the front axle, you'd still have no power to the CV shafts.


Obviously a man that knows way more about my truck than I do, thank you- I stand corrected.
Link Posted: 10/22/2004 4:15:11 AM EST
[Last Edit: 10/22/2004 8:39:05 AM EST by GunLvrPHD]
Ask over at forums.vmag.com/suvsuburban0103.

Link corrected.
Link Posted: 10/22/2004 4:19:05 AM EST
You might want to check out ColoradoK5, a wealth of info there.

I found this reply to a similar problem with a '93 Z71 that wouldn't go into 4wd and also no light:

"Probably the junky thermal actuator in the axle. Check to be sure the connection is good.If it is unscrew the switch and put in 4WD,it should extend in 30sec or so. Prob needs replaced."
Link Posted: 10/22/2004 4:20:51 AM EST
The easiest fix for this unless it is a fuse/fuseable link or a loose wire is going to be installing manual locking hubs on the front axel.
This unfortunately means that you will have to get out and turn the little dial to get 4X4.

My K5 would not come out of 4X4 so I went this rout.
It was this or start messing with electrical.
I figured this way I would know for sure.
Link Posted: 10/22/2004 4:24:16 AM EST
I was just discussing something like this with a guy at work last night. Do you have the push button 4WD on the dash? Or do you have a manual shift handle on the floor?

The reason I ask is that last night I was told that trucks having the push button system have a fuse somewhere under the hood that can blow thus disabling the 4WD engage.

Probably not much help, but I tried. Good luck.
Link Posted: 10/22/2004 4:27:13 AM EST

Originally Posted By sonofbp:
The easiest fix for this unless it is a fuse/fuseable link or a loose wire is going to be installing manual locking hubs on the front axel.
This unfortunately means that you will have to get out and turn the little dial to get 4X4.

My K5 would not come out of 4X4 so I went this rout.
It was this or start messing with electrical.
I figured this way I would know for sure.



This is an IRS system that locks upwind of the CV assemblies. It is not the older solid front.
Link Posted: 10/22/2004 7:26:55 AM EST

Originally Posted By sgtar15:
Chevy doesn't make trucks....they make pick-ups.


SGtar15



My dad says the same thing.
Link Posted: 10/22/2004 7:32:00 AM EST
A friend has a 2002 trailblazer and has the same problem. We were in his truck, drove onto a muddy dirt road, he switched to 4WD and nothing happened, no light, no 4WD. He is taking it back to the dealer as it's still under warranty.
Link Posted: 10/22/2004 7:35:16 AM EST
We have an 86 Jimmy s-15 that wouldn't go into 4x4, we traced it down to a broken vacuum line. I don't if your truck's 4x4 is vacuum actuated or not but you might want to look for broken or rotted vacuum lines. Just a thought.
Link Posted: 10/22/2004 7:38:43 AM EST

Originally Posted By Combat_Jack:

Originally Posted By sgtar15:
Chevy doesn't make trucks....they make pick-ups.


SGtar15



My dad says the same thing.



Well my daddy says Chevy doesn't make trucks... they make junk I kid I kid
Link Posted: 10/22/2004 7:43:37 AM EST

Originally Posted By dissipator556:
I'm hoping it's just a clutch pad or something cheap in the transfer case. I really don't want to sink any big money into this truck right now...




That's the problem with these newer transfer cases electronicall actuated..clutches etc...the older NP203 was all gears, a chain and a manual lever....

Have you tried all modes, give low a try 4wd Hi might need a kick in the pants...check the signal into the transfer case w/ a multimeter....
Link Posted: 10/22/2004 7:57:05 AM EST

Originally Posted By Daytona955i:

Originally Posted By Combat_Jack:

Originally Posted By sgtar15:
Chevy doesn't make trucks....they make pick-ups.


SGtar15



My dad says the same thing.



Well my daddy says Chevy doesn't make trucks... they make junk I kid I kid



Should you and he ever end up at, say, Gunstock talking about something, don't mention Chevy diesel engines. He hates them with a passion. 6.5 and 6.2 that is, Chevy didn't have a decent diesel until they went to Isuzu.
Link Posted: 10/22/2004 8:11:55 AM EST
You need to replace the actuator in the front diff. & probably the wiring harness also.

There is a GM bulletin on this issue. #76-43-01a(sept 18, 1998)
Covers 88-97 model year Chev & GMC trucks under 8500gvw

Looks like the actuator lists for $128.38 & the harness for $28.11 to give you an idea on price.

HTH
Flaco
Link Posted: 10/22/2004 1:04:49 PM EST

Originally Posted By Flaco:
You need to replace the actuator in the front diff. & probably the wiring harness also.

There is a GM bulletin on this issue. #76-43-01a(sept 18, 1998)
Covers 88-97 model year Chev & GMC trucks under 8500gvw

Looks like the actuator lists for $128.38 & the harness for $28.11 to give you an idea on price.

HTH
Flaco


How hard is it to remove the actuator from the front diff (special tools, gasket kits, etc. required?), and how hard would it be to replace the wiring harness?
Link Posted: 10/22/2004 1:32:59 PM EST
Actuator is easy, harness I don't know.

Had many of them go bad in those models of pickups at work, vdot.

Danny
Link Posted: 10/22/2004 1:39:01 PM EST

Originally Posted By Combat_Jack:

Should you and he ever end up at, say, Gunstock talking about something, don't mention Chevy diesel engines. He hates them with a passion. 6.5 and 6.2 that is, Chevy didn't have a decent diesel until they went to Isuzu.



Thats just silly... The 6.2 and 6.5 were designed by Detroit Diesel and are a VERY stout motor for the HP rating. I love getting the Powerstroke people all riled up by telling them that their 7.3 and 6.9 diesels were gas conversion motors
Link Posted: 10/22/2004 1:49:16 PM EST
7.3 IS NOT a gas conversion. It was a diesel from the start. I know little of the 6.9.

The 6.2 sucks ass. Starters fail a lot, alternators, etc. Lots of money to fix them. The 6.5 was better, but still a POS.
Link Posted: 10/22/2004 1:53:08 PM EST

Originally Posted By Flaco:
You need to replace the actuator in the front diff. & probably the wiring harness also.

There is a GM bulletin on this issue. #76-43-01a(sept 18, 1998)
Covers 88-97 model year Chev & GMC trucks under 8500gvw

Looks like the actuator lists for $128.38 & the harness for $28.11 to give you an idea on price.

HTH
Flaco



Call 4 Wheel Parts or maybe Jegs before you go back with an original part. They have a manual actuator that will lock you up reliably. Both my best friends and my sisters truck had the same problem. Intermittent engagement and disengagment. Sucks to deal with it when your in a bad situation. Also maybe post on "pavement sucks.com" for step by step info.
Link Posted: 10/22/2004 2:29:13 PM EST
[Last Edit: 10/22/2004 2:29:48 PM EST by Minuteman419]

Originally Posted By Combat_Jack:
7.3 IS NOT a gas conversion. It was a diesel from the start. I know little of the 6.9.

The 6.2 sucks ass. Starters fail a lot, alternators, etc. Lots of money to fix them. The 6.5 was better, but still a POS.



We (vdot) just surplused 6.2's with over 200k on them. Automatic trannys were their downfall in our models. Alternators on both the 6.2 and 6.5 are the same, may last a year. Starters not a problem. Best thing about the 6.5 is the turbo which ain't much IMO.

My new Powerstroke 6.0 (International) and the 6.6 Duramax (Izusu) seem pretty much equal to me at the moment, not enough miles to tell yet. Both are strong. The Allison transmission behind the Duramax is impressive.

Danny
Link Posted: 10/22/2004 2:58:34 PM EST
The more I hear about Chevy and Ford 4wd systems the more I like my Tacoma and Jeep.
Sure, I've got to get out of the truck but its 100% worth it. Besides, seems like I always have to piss before doing any off roading anyway.
Link Posted: 10/22/2004 3:09:05 PM EST
Is the trucks 4wd activated by little buttons on the dash or by a lever sticking through the floor? if its on the dash yuo may need to replace that bank of switches. if its a floor shift check the linkage to the t-case to make sure its good.
Link Posted: 10/22/2004 5:09:55 PM EST

Originally Posted By Combat_Jack:
7.3 IS NOT a gas conversion. It was a diesel from the start. I know little of the 6.9.

The 6.2 sucks ass. Starters fail a lot, alternators, etc. Lots of money to fix them. The 6.5 was better, but still a POS.



Actually, the 6.9 and the 7.3 IDI are the exact same engine (barring a bore and stroke change) and they are an International block/gas conversion. The Powerstroke 7.3 is based on the same block (also a gas conversion). There is nothing wrong with it, its just the way it is.

My 6.2 has run nearly 300K, I've had 1 starter die and 2 alternators. Turbo'd, the 6.2 and NA 6.5 can produce nearly the same power levels as your stock 7.3 TD, all while maintaining 20 + MPG. Any diesel costs a lot to fix, its the nature of the game. The 6.2 and the 6.5 again are almost identical.
Link Posted: 10/22/2004 5:18:36 PM EST
i was gonna post, but i think yall got it.

<­BR>


but i posted anyway.
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