4x4 Generic Electronic Module

smileyr8a · #1 10-26-2009, 04:07 PM

I have a 97 f150 with a 4.6 engine ,auto trans ,manual shift 4x4. I started having problems with my 4x4 light lighting up on the dash without me manually shifting the truck into 4 wheel drive,the transfer case grinds because the truck is not shifted yet. I was told it was likely to be the GEM,after changing the very expensive part i was suprised to have the same problem days later. Is there another fix that can be done or should i just go buy a new truck.Any info would be nice.

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chiefFX4 · #2 10-26-2009, 09:40 PM

i would check your 4x4 solenoids and the hoses that are connected to them.

you can find them on the firewall to the left of the engine compartment. should be two right next to each other with little green caps on them.

smileyr8a · #3 10-31-2009, 09:03 AM

I was told today that there may be water in the front diff that is causing some sort of electronic shift problem...does this sound possible..also i don't see the 2 solenoids that you spoke of.

masseyman · #4 10-31-2009, 02:22 PM

Do you have lockout hubs? ie The ones where you have to go to each front wheel and turn them to lock or free.

kingfish51 · #5 10-31-2009, 03:07 PM

Quote:

Originally Posted by masseyman

Do you have lockout hubs? ie The ones where you have to go to each front wheel and turn them to lock or free.

A 97 does not have hubs.

masseyman · #6 10-31-2009, 03:32 PM

Quote:

Originally Posted by kingfish51

A 97 does not have hubs.

Are you sure??? My son has a '97 F150 and I'm pretty sure it has lockout hubs.

kingfish51 · #7 10-31-2009, 05:29 PM

Quote:

Originally Posted by masseyman

Are you sure??? My son has a '97 F150 and I'm pretty sure it has lockout hubs.

No hubs, it locks and unlocks at the diff. Locks and unlocks by the solenoids sending vacuum to a vacuum motor which moves a shift fork in the diff to engage or disengage the front diff.

smileyr8a · #8 11-01-2009, 12:07 AM

how do i test the solenoids to see if this is what is making my truck want to go into 4 wheel drive all on its own.

smileyr8a · #9 11-01-2009, 12:08 AM

kingfish51 · #10 11-01-2009, 07:59 AM

The solenoids will not cause you to shift into 4x4. All they do is lock or unlock the front diff. If you are getting grinding from the transfer case, then it is either the switch, GEM module, or transfer case itself.

kingfish51 · #11 11-01-2009, 08:54 AM

Only other possibility is that the front diff is partially locking in. Make sure that the vacuum lines are not crossed, ie disengage solenoid hooked to the engage side of vacuum motor and vice versa. Have never heard of this happening, but is a possibility.

smileyr8a · #12 11-01-2009, 09:12 AM

what noise might it make if the front diffs are trying to lock up without the transfer case being lockrd in,the grinding is not in the transfer case but in the front end and stops when i finally put the transfer case into 4 wheel drive.what would make thefront hubs want to lock up before they are being asked to.

kingfish51 · #13 11-01-2009, 10:02 AM

First, you do not have hubs. All locking is done at the diff. The grinding might be the diff partially engaging. From the diff out you have half shafts to a CV joint and regular bearings, which turn at all times, whether in 4x2 or 4x4.

smileyr8a · #14 11-01-2009, 12:30 PM

So what would be causing the diff to try to lock up,I have never touched the solenoids or vac lines on my truck so can not see how they would get crossed. Someone said if water gets in the front diff it could cause the problem but don't see how.Sorry for so may questions but am trying to understand what is happening.I may need a complete description of what happens in a 4x4 frtom start to finish when you put the manual shifter from 2 wheel into 4 wheel to when the front wheel are in 4 wheel drive. Maybe this would help me see the light.

kingfish51 · #15 11-01-2009, 01:50 PM

Until you find out for sure it is the diff, there is no way to say exactly what the problem is. Put the vehicle on a lift, and in 2wd. Try turning the wheels, and if the driveshaft turns, then the diff is not unlocking. whether because of the shift fork, vacuum motor, disengage solenoid, or vacuum lines being broke or some other reason. Water in the diff could cause corrosion which would cause the diff to not work properly, especially the engage/disengage process.

As far as what happens, when you put the vehicle in 4x4, the front driveshaft spins up, a signal is sent to the engage solenoid to send vacuum to the vacuum motor, which moves a shift fork in the diff to engage the diff, allowing it to turn the axles, which should already be turning at the same speed. The reverse happens when you go to 2wd, except that it is the disengage solenoid, which sends vacuum to the vacuum motor that disengages the diff.
Do a search, as there has been some diagrams showing all the parts posted before.