Help With 4x4

[dkolewaski]

Hey there guys I tried enguaging my 4x4 today in some real muck and all it did was flash the 4x4 high and low lights and did not enguage.. Any idea's? I tried it a few days ago and it worked fine.. Possibly just something electrical? Any help would be appreciated.

Darryl

 

[ajr2000]

Search for shift motor on this forum.

 

[dkolewaski]

Ok new problem.. Now my 4x4 comes on and it says it does but does not enguage the transfer case.. Any ideas?

 

[ajr2000]

How do you know the transfter case is not engaging? can you see the front drive shaft moving?

 

[dkolewaski]

no but its cause i was in mud spinning and the front tires were not turning but it said it was in 4x4

 

[gijoecam]

Search for shift motor on this forum.

For the love of all things celestial, there's no shift motor involved in the 2/4auto/4high shift on the second-gens. It's likely one of the axle shaft speed sensors is bad, but without pulling the GEM codes there's no way to know for sure. If the lights are blinking, the system has detected a problem, and needs to be scanned. The blinking lights do not indicate a specific code (unfortunately). That code is stored in the GEM not the PCM, so AutoZone won't be able to scan it.

Sorry to be the bearer of bad news.

Now, if the light comes on, but the 4wd does not work (i.e. the front wheels don't drive) on a 95 or 96 model year, now we need to look at the transfer case and center-axle disconnect.

-Joe

 

[dkolewaski]

umm i am not an expert but I know what i see and when i was under the truck i saw a shift motor there. problem is now its saying its in 4x4 but the front tires are not turning. Anyone else have any ideas?

 

[gijoecam]

umm i am not an expert but I know what i see and when i was under the truck i saw a shift motor there. problem is now its saying its in 4x4 but the front tires are not turning. Anyone else have any ideas?

I'm not an expert, but I know how the system works. The transfer case shift motor is ONLY used for the high range/low range shift on a second gen. The transfer case locks the front and read driveshafts via the GEM controlling the Torque On Demand Relay, which sends a pulse-width modulated signal to the transfer case clutch coil. The shift motor does not move when locking the transfer case.

There's a halfway decent explanation of the way the system works at the beginning of the Comprehensive Brown Wire Mod thread. Even if you don't do the mod, there's a pretty decent explanation of how the system works.

The problem is that even though the light is on, there's no guarantee that the transfer case has locked. The other problem on a 95 or 96 is that even if the transfer case is locked, if the center-axle disconnect fails to engage (which is vacuum-controlled by a pair of vacuum solenoids which are also controlled by the GEM) the 4wd still won't put any power to the front wheels.

It's not a complicated system, and it's not difficult to troubleshoot it. It only takes about 20 minutes to pin the problem down to one of four things: The transfer case, the center axle disconnect, the vacuum actuation system for the CAD, or an electrical gremlin.

So, with that in mind, you said that the light comes on, but there is no power to the front wheels, correct?

-Joe

 

[dkolewaski]

this is true. but yet when i turn hard one way or the other I can feel hopping like its in 4x4 but its actually not.

 

[ajr2000]

I forgot this was a second gen.

 

[dkolewaski]

so i was right then its prob the shift motor

 

[gijoecam]

so i was right then its prob the shift motor

No, it's not. For the third time, the shift motor has absolutely nothing to do with the transfer case locking. Forget about the shift motor. It's not your problem.

this is true. but yet when i turn hard one way or the other I can feel hopping like its in 4x4 but its actually not.

Now I'm confused. If it wasn't locked in 4wd, it wouldn't hop. Are you flipping it to 4auto or 4high? You should have 2wd, 4auto, and 4low on your switch, correct?

 

[dkolewaski]

this is correct.. 2wd, 4 high, 4 low.. then i am not understanding the point of the shift motor

 

[gijoecam]

Already been covered.

I'm not an expert, but I know how the system works. The transfer case shift motor is ONLY used for the high range/low range shift on a second gen. The transfer case locks the front and rear driveshafts via the GEM controlling the Torque On Demand Relay, which sends a pulse-width modulated signal to the transfer case clutch coil. The shift motor does not move when locking the transfer case. ....{snip}

Maybe I wasn't clear?

The motor engages or disengages the low range planetary gear set. On the on the second generation Control-Trac systems, the low range gear-set is independent of transfer case lock-up. The motor positions the gear. The motor does not lock the front and rear driveshafts together.

 

[dkolewaski]

ok then enough about all this.. now what might my problems be? 4x4 light goes on but no 4wd works..

 

[gijoecam]

OK, Jack the front end up in teh air and support it on jack stands. With the engine idling in park, and the switch set to 2wd, you should be able to turn the front driveshaft. Now, flip the switch to 4high, and you should no longer be able to spin the driveshaft. If you can, the problem is with the transfer case clutch coil, TOD relay, or something in the wiring. If the shaft is locked, we can eliminate the transfer case at this point.

Now, give one front wheel a spin. If the other wheel spins the opposite direction, then everything is engaged and locked just as it should be. I suspect it won't. At that point, we'll need to look at the center-axle disconnect, the vacuum lines that connect to it, and the solenoids that control it.

Report back and we'll see where to go from there.

 

[ARTURPOLAND]

hi, One of my friends suggests to try to lock up 4x4 driving on reverse gear at speed 10-15 mph. I do not know will it works or not. GIJOECAM - please verify this idea before our friend destroy the transfer case.

By the way, My X is clunking very hard while turning on the dry surface with 4x4 the clunk comes from front differential or halfaxes. When I drive in the mud id doesn,t clunk. Is it normal (the klunk is like the differential is blowing)

 

[gijoecam]

hi, One of my friends suggests to try to lock up 4x4 driving on reverse gear at speed 10-15 mph. I do not know will it works or not. GIJOECAM - please verify this idea before our friend destroy the transfer case.

By the way, My X is clunking very hard while turning on the dry surface with 4x4 the clunk comes from front differential or halfaxes. When I drive in the mud id doesn,t clunk. Is it normal (the klunk is like the differential is blowing)

You should not be using the 4wd on dry pavement. Doing so causes the driveline to bind as the front wheels try to roll farther than the rear wheels. Driveline bind-up puts extreme stresses on the driveline components. When turning on dry pavement, you should have it set to 4 auto, not 4high.

Driving in reverse won't hurt anything, but it won't help his problem either.

-Joe

 

[coombs]

wont enguage

i have a 97 xlt 4.0 sohc that wont enguage the 4x4 when i turn the switch i hear the transfer case sounds like to me its enguaging but it doesent any ideas where to start with this prolbem any help would be great p.s the truck has the auto 4high 4low setting thanks

 

[gijoecam]

i have a 97 xlt 4.0 sohc that wont enguage the 4x4 when i turn the switch i hear the transfer case sounds like to me its enguaging but it doesent any ideas where to start with this prolbem any help would be great p.s the truck has the auto 4high 4low setting thanks

Second Gen Troubleshooting How-To