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4 wheel low not engaging


Tallpaul

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I've had my BII for a few years now and it's never had a front drive shaft in it. The other day I cut one down and put one in. It will go into 4x4 high with no problems, but when I try to put it in 4low the light just flashes and it never engages. I pressed the test button on the side of the TCCM and the red light comes on but will not flash. I replaced the TCCM and the push button switch with ones out of the junkyard. The test light in the "new" TCCM stays on too. When I try to put it 4 low now the light won't even flash, but still goes in and out of 4high. I took off the shift motor and then pressed the button same thing on the motor. It goes to the 4high position but never tries to go to 4 low. I manually turn the knob on the back of the transfer case to see if 4low worked when engages and it did perfectly. So I just put it back in 2h til I can figure something else out.

A while back I did swap out the A4ld for a fm146 and used a 5spd computer from a 2 wheel drive and wiring harness to the tranny. ( didn't know if that could be my trouble) I've tried every trick to get it in 4 low; clutch pressed, e brake on, out of gear, in 1st gear, in reverse, and combinations of all. Does anyone think that the "new" TCCM is bad too? Isn't the test light supposed to flash if working properly? Any other suggestions and help would be appreciated.
 


wildbill23c

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If its going in and out of 4hi it has nothing to do with swapping the transmission and computer. Does your shift motor make any noises when you try and engage 4Lo?

Also, it may sound pretty dumb but are you shifting the transmission into neutral, or clutch pushed in on a manual transmission before trying to shift into 4lo? Seen many people have issues with their 4WD systems and they simply didn't have the transmission in neutral or clutch pushed in.

Other than that I'm not really sure, don't have an electronic 4x4 system in my B2.
 

Tallpaul

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If its going in and out of 4hi it has nothing to do with swapping the transmission and computer. Does your shift motor make any noises when you try and engage 4Lo?

Also, it may sound pretty dumb but are you shifting the transmission into neutral, or clutch pushed in on a manual transmission before trying to shift into 4lo? Seen many people have issues with their 4WD systems and they simply didn't have the transmission in neutral or clutch pushed in.

Other than that I'm not really sure, don't have an electronic 4x4 system in my B2.

No it doesn't make a noise at all when trying to go into 4low. The shift motor won't even move to the 4lo position when it is taken off the transfer case. Yes I have tried all of those; in neutral, brake on, clutch in, e brake on, everything like that. Still have no idea.
 

dirtcowboy

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No it doesn't make a noise at all when trying to go into 4low. The shift motor won't even move to the 4lo position when it is taken off the transfer case. Yes I have tried all of those; in neutral, brake on, clutch in, e brake on, everything like that. Still have no idea.
The shift motor won't go into 4 low even when off the transfer case? Mebbee you need a new shift motor? Or mebbee a SHIFTSTER?? blatant plug I love mine:D
 

Tallpaul

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The shift motor won't go into 4 low even when off the transfer case? Mebbee you need a new shift motor? Or mebbee a SHIFTSTER?? blatant plug I love mine:D
Nope the shift motor won't move past 4h, never even tries to go into 4lo when it's not bolted to the transfer case. I haven't heard of the shiftster. I'll have to look into that. Thanks for the info. If someone else has anything, please feel free to chime in.
 

vwa1

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Open wire from control module to transfer case maybe? Had an f150 do something similar years back and that's what it was.
 

Tallpaul

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Ok thanks ill give that a look tomorrow. Thanks for the info.
 

Tallpaul

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Ok so I returned the TCCM that I got from a junkyard and tried 2 other TCCMs but they all do the same thing. What's funny is that my original TCCM is the only only that causes the 4low light to flash. All of the other tccms, nothing happens when the 4low button is pressed, not even the 4low light flashing. Any suggestions? Could a magnet be knocked loose in the shift motor that will let the motor shift into 4high but not 4low? Thanks for the replies
 

bfiakas

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Check the wiring harness at 4x4 module. The 7 wire plug gets brittle over the years and the tabs that hold the wires in the plug break and the wires slide out.What I did with mine is I put some silicone in the top side of the connections were the wires go into the plug.Let it set up for 24hrs.
 

wildbill23c

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How about trying a different shift motor instead of swapping out TCCM's all the time for no reason. Sounds more like the shift motor is toast or well partially toast.
 

ab_slack

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In my 89 BII (only one I had with electronic shift) I found it somewhat finicky going in/out of 4 low.

There is one big difference going between 2H and 4H verses going from 2H/4H to 4L. If I recall correctly it the auto switch requires you to be in neutral (not just clutch pushed in) with a manual transmission. I believe for an automatic park or neutral is acceptable though I didn't have one of that vintage. My 02 explorer requires park or neutral (maybe just park). You are also supposed to be stopped though I don't know if it has a sensor to know that or not.

I am pretty certain parking brake isn't required as my parking brake always froze so never used it.

I don't know exactly what performs the logic, but in a manual trans the signal from the neutral position switch needs to get to whatever is deciding to allow the switch into 4L. A KOEO (key off engine off) self test test should identify if neutral position switch signal is read by the computer. On 89 since you have a CEL/MIL you can use the flash out codes. If you run the KOEO test with it in gear it should give code saying problem with neutral position. if you run it in neutral it shouldn't give that code. If you get the code with it in neutral then the computer isn't seeing it.

Self test info can be found here: http://www.therangerstation.com/tech_library/OBD_I.shtml

Now since you converted from Auto to Manual trans there may be complications like the thing that does the switch into 4L may expect a different input, or maybe the difference si entirely in the computer. The computer/harness being from a 2WD, yes that is a good question. It may not output signal needed.

Anyways that is where I would start looking. The finicky behavior I experience on my 89 BII came from the neutral position switch being a bit flakey.

I see the OP is a couple months old now, guess probably resolved by now
 
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