1995 Suburban 4WD Problem

Greetings all. I just found this forum, and look forward to contributing.

I have a 95 K2500 Suburban with the 7.4l, purchased last month, and had the need to try the 4wd last night. Houston, we have a problem...

The front diff will not engage. This is the old school lever to engage setup, and the light in the console will not light up. I checked the bulb in the console, and it's fine. Further, there's a reference to fuse #2 (transfer case) in the owner's manual, but there's no fuse there, and there are no wires leading to fuse location #2, so maybe that was optional? Can someone tell me the sequence of checks to determine what's wrong with this? I crawled under it this morning, in the snow no less, and found the actuator, which appears to have two two-wire connectors going to it. I can't tell whether this is the original or the updated version of the actuator.

Thanks in advance!
Joe

Joe: Welcome to AF. 1st thing to check is for 12v at the front actuator. Pull the plug on the actuator and with the key in the "run" position put the selector in 4WD (hi or low) and check each of the 2 wires for 12v. If you have 12v on one and a good ground on the other, it's most likely the actuator. I believe the updated ones are 3 wire.

Let us know what you found.

Joe: Welcome to AF. 1st thing to check is for 12v at the front actuator. Pull the plug on the actuator and with the key in the "run" position put the selector in 4WD (hi or low) and check each of the 2 wires for 12v. If you have 12v on one and a good ground on the other, it's most likely the actuator. I believe the updated ones are 3 wire.

Let us know what you found.

Do you know what the other connector is for? I printed out some stuff from AllData this morning, and will check it out this evening. I appreciate your input and will let you know what I find.
Thanks!

Is your actuator all metal or the newer plastic change over one?

Look at the wires again the old metal one only has two wires into it.

If the newer change over plastic actuator get you dealer to print out a wiring diagram on it.

Is your actuator all metal or the newer plastic change over one?

Look at the wires again the old metal one only has two wires into it.

If the newer change over plastic actuator get you dealer to print out a wiring diagram on it.

Would this new changeover unit have an extra connector on it? I'm on my way home now to look at it, and I'll report what I find. Thanks, guys!

Is your actuator all metal or the newer plastic change over one?

Look at the wires again the old metal one only has two wires into it.

If the newer change over plastic actuator get you dealer to print out a wiring diagram on it.

OK, I got to checking this out, and the 4WD fuse (location 24) was blown. I disconnected both connectors down at the actuator and then replaced the fuse. Sure enough, I had power down at both connectors. No surprise, the fuse blew the moment I plugged the actuator in. As for the connectors, one goes into the end of the actuator, and is a black two-wire side-by-side connector. The other goes into the middle of the actuator and is a white two-wire square quad plug (two diagonal holes in the plug are empty). Would this imply that it's the updated version? I've read on this forum that guys have replaced this part more than once, including the updated version.

Thoughts?

You need to replace the actuator.

The two wire one is old style.
They are bad about shorting out.
But not hard or expensive to replace

The all plastic updated one gives a faster 4W in and out axel lock in shift.
But needs a expensive wiring change over to install it.
Your dealer has you change over plastic one with wiring [depending on year make and model and engine and transmission] for new type if you want to change over.
Usually around 300 -350 USA $
Good luck

I got the updated plastic unit ordered today, and should be at my house tomorrow. Hopefully I can get it swapped out before it decides to snow again.
Thanks for all the input guys. I look forward to checking back and contributing when I can. I used to make my living as a heavy line tech for Chevrolet, but have been out of the game for a number of years (I tried to catch a transmission falling out of a cradle - I don't recommend it, even if it means a payroll deduction. I work an office job now).

I got the updated plastic unit ordered today, and should be at my house tomorrow. Hopefully I can get it swapped out before it decides to snow again.
Thanks for all the input guys. I look forward to checking back and contributing when I can. I used to make my living as a heavy line tech for Chevrolet, but have been out of the game for a number of years (I tried to catch a transmission falling out of a cradle - I don't recommend it, even if it means a payroll deduction. I work an office job now).

You are welcome.
Make sure you get the wiring change over kit with it.
They have to be rewired to use the updated pastic one.
Good luck
LET US KNOW HOW IT GOES.

You are welcome.
Make sure you get the wiring change over kit with it.
They have to be rewired to use the updated pastic one.
Good luck
LET US KNOW HOW IT GOES.

Yes, I did order the harness kit as well. I'm looking forward to getting it swapped out, and I'll let you know how it went. I might even snap a picture or two, if you think it would be helpful for anyone else considering this repair.

I swear if it wasn't for bad luck...

I was all set to swap out the actuator Saturday morning, and while I was at it, figure out why it wouldn't start Friday morning (likely fuel pump related). The actuator went in fine, but when I went to lay in the new harness, I discovered that the plug supposed to take the factory actuator plug was wrong. Without cutting and splicing, I was dead in the water. :banghead:

I just talked to my GM parts man, and he's looking into it for me. I'll hopefully either have a correct harness sent to me or splice in the old connector to the new harness.

It's always gotta be somethin'!!!

Greetings, all! I was able to make headway yesterday afternoon. My parts guy told me that the harness I was sent was the only harness for this repair, so I ended up clipping the plug off of the old actuator and splicing it in to make everything connect. Unfortunately, I got the two wires crossed and found out only after I'd put it all together to test. Thank god for connector tools!! I was able to swap the two wires and all is well now. In fact, as I was crawling out from underneath, the snow started! Crazy timing...
Anyway, we tested the 4WD out this morning, and everything works as intended.

Thank you all for the input. I'm sorry I wasn't able to get photos snapped, but I had to beat the snow. Next time!! :smooch:

Greetings, all! I was able to make headway yesterday afternoon. My parts guy told me that the harness I was sent was the only harness for this repair, so I ended up clipping the plug off of the old actuator and splicing it in to make everything connect. Unfortunately, I got the two wires crossed and found out only after I'd put it all together to test. Thank god for connector tools!! I was able to swap the two wires and all is well now. In fact, as I was crawling out from underneath, the snow started! Crazy timing...
Anyway, we tested the 4WD out this morning, and everything works as intended.

Thank you all for the input. I'm sorry I wasn't able to get photos snapped, but I had to beat the snow. Next time!! :smooch:

I have been following your progress and I thank you for letting us know how this all worked out positively for you.

I'm sure in the future others will find this info useful..

I have been following your progress and I thank you for letting us know how this all worked out positively for you.

I'm sure in the future others will find this info useful..


I'm a newbie. Can anyone please tell me how to post a question on a suburban? thanks.

Actually, there are 2 different harnesses in the GM parts system for the 1500/2500 models (there are also 2 additional harnesses for the 3500 models for a total of 4 different harnesses). One harness has flat pins in the 2 pin connector and the other has round pins in the 2 pin connector. If needed, you can take the pigtail off your old actuator to modify the new harness.

Here is a link to give you an idea of what is involved in this conversion/upgrade:

http://www.getdieselpower.com/misc_auto/actuator_upgrade/GM_TRUCK_4X4_ACTUATOR_UPGRADE.html


For those that would like to see the complete TSB:

SLOW OR NO ENGAGEMENT OF FRT. AXLE WHEN 4WD IS SELECTED

TSB#76-43-01A - (09/18/1998)
REVISION: 09/17/98 DIVS INVL 1 5 7

THIS BULLETIN IS BEING REVISED TO ADD INFORMATION TO THE SERVICE PROCEDURE, ADD A NEW PART NUMBER, AND INCLUDE SCHEMATICS. PLEASE DISCARD CORPORATE BULLETIN NUMBER 76-43-01 (SECTION 4 - DRIVE AXLE). __________________________________________________ ____________________

SUBJECT: SLOW OR NO ENGAGEMENT OF FRONT AXLE WHEN 4WD IS SELECTED (REPLACE FRONT AXLE ACTUATOR)

MODELS: 1988-97 CHEVROLET AND GMC K MODELS EXCLUDING 1988-93 MODELS OVER 8500# GVW

CONDITION:

SOME OWNERS MAY COMMENT THAT THE COLDER THE OUTSIDE TEMPERATURE IS, THE LONGER IT TAKES FOR THE FRONT AXLE TO ENGAGE WHEN 4 WHEEL DRIVE IS SELECTED, OR THE FRONT AXLE DOES NOT ENGAGE.

CAUSE:

THE FRONT AXLE ENGAGEMENT ACTUATOR IS A THERMALLY ACTIVATED COMPONENT. BECAUSE OF THIS CHARACTERISTIC, THE TIME REQUIRED FOR THE ACTUATOR TO COMPLETE 4 WHEEL DRIVE ENGAGEMENT IS EXTENDED AS THE TEMPERATURE DROPS.

CORRECTION:

REPLACE THE FRONT AXLE ACTUATOR AND INCLUDE THE APPLICABLE WIRING HARNESS KIT. REFER TO THE PARTS INFORMATION IN ORDER TO DETERMINE WHICH WIRING HARNESS KIT IS NEEDED.

1996 MODEL TRUCKS WITH A BUILD DATE ON OR AFTER JANUARY 2, 1996 ARE CONSIDERED AS "96I". IF THE BUILD DATE OF THE TRUCK IS UNKNOWN, VERIFY THE 3 CHARACTER "AXLE CODE" ON THE FRONT AXLE LABEL IN ORDER TO DETERMINE WHICH WIRE HARNESS TO ORDER.

THIS NEW ACTUATOR USES A MOTOR TO ENGAGE THE FRONT AXLE AND IS NOT AFFECTED BY TEMPERATURE. ON 1988-93 MODELS WITH A GVW RATING OVER 8500#, THE NEW ACTUATOR CANNOT BE INSTALLED AND THE THERMAL ACTUATOR WILL REMAIN THE SERVICE PART.

SERVICE PROCEDURE

1. REMOVE THE FRONT DIFFERENTIAL CARRIER SHIELD, IF EQUIPPED.
2. IF NECESSARY, CLEAN THE AXLE HOUSING IN THE AREA AROUND THE EXISTING ACTUATOR. DISCONNECT THE ACTUATOR'S ELECTRICAL CONNECTION AT THE FRONT AXLE HOUSING.

3. REMOVE THE FRONT AXLE ACTUATOR BY UNTHREADING THE ACTUATOR FROM THE AXLE HOUSING.

4. INSTALL THE SPACER FROM THE WIRING KIT INTO THE AXLE TUBE WITH THE FLAT SIDE SEATED AGAINST THE SHIFT FORK.

5. INSTALL THE ACTUATOR MOTOR AND TIGHTEN UNTIL THE SHOULDER OF THE ACTUATOR SEATS AGAINST THE AXLE TUBE.

IMPORTANT: IF BINDING OCCURS BEFORE THE ACTUATOR IS SEATED, REMOVE THE ACTUATOR AND RESEAT THE SPACER BY PUSHING ON THE SPACER WITH A SCREWDRIVER. THEN REINSTALL THE ACTUATOR.

ON K3 MODELS WITH THE CAST IRON AXLE TUBE, THERE MAY BE A CASTING BURR WHICH MAY CONTACT THE EDGE OF THE ACTUATOR. THIS SHOULD NOT CREATE A CONCERN AND THE ACTUATOR SHOULD SEAT AGAINST THE AXLE TUBE. IF THIS CONTACT REMAINS A CONCERN, USE A DIE GRINDER IN ORDER TO REMOVE THE BURR.

6. CONNECT THE SERVICE HARNESS CONNECTOR TO THE ACTUATOR AND CONNECT THE 2-PIN CONNECTOR TO THE MATING CONNECTOR AT THE AXLE. FOR 1994 TO CURRENT MODELS, IN THE CASE OF A COMPLETE AXLE REPLACEMENT, REFER TO FIGURE 1.

7. ROUTE THE WIRING HARNESS ALONG THE EXISTING HARNESS ON THE RIGHT SIDE OF THE VEHICLE. ROUTE CKT 241 (BRN) OVER THE TOP AND TO THE LEFT OF THE TRANSMISSION. SECURE THE HARNESS USING PLASTIC TIES.

8. FOR 1995-97 INTERIM VEHICLES, LOCATE THE 4-WIRE CONNECTOR (C120) ON THE LEFT SIDE OF THE TRANSMISSION. SPLICE THE BRN WIRE OF THE ACTUATOR HARNESS INTO CAVITY D OF CKT 241 (BRN) ON THE ENGINE SIDE OF CONNECTOR C120. FOLLOW THE SPLICING PROCEDURE DESCRIBED IN SECTION 8A (ELECTRICAL DIAGNOSIS REPAIR PROCEDURES) OF THE APPLICABLE SERVICE MANUAL.

IMPORTANT: THE NEW FAST AXLE ACTUATOR REQUIRES ONLY 1 SPLICE. - FOR 1993 AND PRIOR VEHICLES, SPLICE INTO CKT 50 (BRN) BETWEEN CONNECTOR C152 AND GT101 (FIGURES 2,3,4). - FOR 1994 VEHICLES, SPLICE INTO CKT 50 (BRN) BETWEEN CONNECTOR C152 AND P101 (FIGURES 5,6). - FOR 1995-97 VEHICLES, SPLICE INTO CKT 241 (BRN) BETWEEN CONNECTORS C120 AND C100 (FIGURE 7).

NOTICE: CONNECTIONS MUST BE WATER TIGHT IN ORDER TO PREVENT WATER FROM ENTERING THE CIRCUIT AND CAUSING DAMAGE TO THE COMPONENTS.

9. ON K3 MODELS, INSTALL THE DELAY RELAY, INCLUDED AS PART OF THE WIRING HARNESS KIT, AT THE ENGINE SIDE OF THE BULKHEAD, ADJACENT TO THE EXISTING RELAY. MOUNT THE NEW RELAY WITH SELF-DRILLING FASTENER, P/N 22510339. ROUTE AND SECURE THE RELAY WIRE HARNESS BEHIND THE RIGHT OXYGEN SENSOR HEAT SHIELD.

10. VERIFY SYSTEM OPERATION. WHEN SHIFTING THE TRANSFER CASE, YOU SHOULD HEAR THE ACTUATOR MOTOR OPERATE.

IMPORTANT: THIS RELAY INCORPORATES A 5 SECOND DELAY FOR THE FRONT AXLE TO ENGAGE IN ORDER TO ALLOW THE TRANSFER CASE SYNCHRONIZER TO ENERGIZE.

FOR 88-93 VEHICLES, IF THE AXLE HAS TO BE REPLACED, USE JUMPER HARNESS P/N 15313272. CKT 1695 (BLK/WHT) FITS INTO CAVITY A OF THE FAST ACTUATOR. THE CIRCUIT INCLUDES THE CABLE SEAL AND THE TERMINAL PIN. THIS CIRCUIT PLUGS INTO THE 5-PIN AXLE ACTUATOR CONNECTOR.

11. DO THE FOLLOWING STEPS IN ORDER TO INSTALL JUMPER HARNESS P/N 15313272:

1. LOCATE THE AXLE ACTUATOR 5-PIN CONNECTOR ON THE SERVICE ACTUATOR WIRING HARNESS AND REMOVE THE TPA. 2. REMOVE AND DISCARD THE CAVITY PLUG FROM CAVITY A. 3. INSTALL CKT 1695 LEAD (BLK/WHT) FROM THE JUMPER HARNESS THAT HAS THE CABLE SEAL AND TERMINAL INTO AXLE ACTUATOR CONNECTOR CAVITY A. 4. REINSTALL THE TPA ON THE 5-PIN CONNECTOR. 5. INSTALL THE SERVICE ACTUATOR HARNESS 5-PIN CONNECTOR INTO THE AXLE ACTUATOR. 6. CONNECT JUMPER HARNESS 2X2 CONNECTOR INTO THE EXISTING VEHICLE 4WD MATING CONNECTOR. 7. STRAP THE JUMPER HARNESS AND THE SERVICE HARNESS TO THE TAB ON THE AXLE TUBE.

PARTS INFORMATION:

P/N DESCRIPTION QTY --- ----------- ---

26060073 ACTUATOR ASM, FRT DRIVE AXLE 1 22510339 FASTENER 1 15313272 HARNESS, JUMPER (Z SPLICE)(88-93 K1-3) 1

AXLE CODE 12376316 KIT, ACTUATOR WIRING HARNESS (88-96I K1,2) ZLS, ZLT, ZLW ZLX, ZLY 12376317 KIT, ACTUATOR WIRING HARNESS (96I-97 K1,2) ZWA, ZWB, ZWD ZWF, ZWG 12376318 KIT, ACTUATOR WIRING HARNESS (94-96I K3) ZLX, ZLY, ZLZ 12376319 KIT, ACTUATOR WIRING HARNESS (96I-97 K3) ZWF, ZWG, ZWH

PARTS, EXCEPT P/N 15313272, ARE CURRENTLY AVAILABLE FROM GMSPO. P/N 15313272 IS EXPECTED TO BE AVAILABLE 9-21-98.


12376316 KIT, ACTUATOR WIRING HARNESS (88-96I K1,2) ZLS, ZLT, ZLW ZLX, ZLY


12376317 KIT, ACTUATOR WIRING HARNESS (96I-97 K1,2) ZWA, ZWB, ZWD ZWF, ZWG


12376318 KIT, ACTUATOR WIRING HARNESS (94-96I K3) ZLX, ZLY, ZLZ


12376319 KIT, ACTUATOR WIRING HARNESS (96I-97 K3) ZWF, ZWG, ZWH