Vacuum 4x4 problem
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Vacuum 4x4 problem
97 F150 V8 4.6L 4x4 ext cab
when i switch the manual 4x4 lever into 4H or 4L, i look at the vacuum motor on front end, and the plunger doesnt push in...but if i take the two vacuum lines under the hood that go to the two 4x4 vacuum solenoids on firewall, and switch sides with them, it pulls vacuum to engage the front end....i can switch them back around and it disengages
it just doesnt recognize lockin the front wheels with the shift lever...also i can keep the transfer in 2WD and switch the vacuum lines over and still lock in the front wheels...i have replaced both vacuum solenoids on the firewall ($110) and put new vacuum lines from the vacuum motor and to the converter which leads to the solenoids....
im getting fed up with this 4x4 problem and cannot figure anything out about whats wrong
...any suggestions are appreciated
when i switch the manual 4x4 lever into 4H or 4L, i look at the vacuum motor on front end, and the plunger doesnt push in...but if i take the two vacuum lines under the hood that go to the two 4x4 vacuum solenoids on firewall, and switch sides with them, it pulls vacuum to engage the front end....i can switch them back around and it disengages
it just doesnt recognize lockin the front wheels with the shift lever...also i can keep the transfer in 2WD and switch the vacuum lines over and still lock in the front wheels...i have replaced both vacuum solenoids on the firewall ($110) and put new vacuum lines from the vacuum motor and to the converter which leads to the solenoids....
im getting fed up with this 4x4 problem and cannot figure anything out about whats wrong
...any suggestions are appreciated
Post Fiend
Joined: May 2006
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From: Central Florida
I am not familar with that system, but I believe it's similar to Chevy's auto system. However, the problem sounds like it is related to the vacuum manifold/solenoid that you are playing with. Sence you have replaced them, I would go ahead and assume they are working. So the next step would be to see if they get voltage when activated and check the connections going to them. Corosion and general crud could be stopping the solenoid to activate.
Hope this helps.
Hope this helps.
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thanx for suggestion but i can switch the vacuum lines over each other, and it pulls vacuum in to lock front wheels, and if i switch them back, then it disengages...so i know both solenoids have got to work..not sure bout anything else
5th Wheeling
Joined: Nov 2005
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Does the 4x4 light come on in the dash? if not it could be the "shift lock switch". it basically is a sensor in the T-case that tells the computer when the t-case has been shifted so it changes the vacum side. it is on the front driver side of the t-case. needs 7/8 wrench (i dont remeber exact size but thats close)
I had the same problem as you same truck too 97 4.6 MSOF, and this was the fix. part was $20 at the dealer, he had to order it took a few days to get.
I had the same problem as you same truck too 97 4.6 MSOF, and this was the fix. part was $20 at the dealer, he had to order it took a few days to get.
Last edited by mkac100; Jan 14, 2007 at 09:03 AM.
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when i shift the lever to 4H, no light comes on the dash, but if i put it in 4L, Low Range light comes on dash
thanx for helpin me, ill have to check it out sometime soon...never knew there was a shift-lock switch
btw, is it "in" or "on" the transfer
P.S. I did change out one switch on the front driver side of the t-case...it was
a "4WD Indicator Switch"...i put it in 4L and Low Range light came on, and
shifted out and the light was still on the dash...so i replaced that
Is that Indicator Switch what you call the shift-lock switch?
Or are there 2 switches on the driver side t-case?
thanx for helpin me, ill have to check it out sometime soon...never knew there was a shift-lock switch
btw, is it "in" or "on" the transfer
P.S. I did change out one switch on the front driver side of the t-case...it was
a "4WD Indicator Switch"...i put it in 4L and Low Range light came on, and
shifted out and the light was still on the dash...so i replaced that
Is that Indicator Switch what you call the shift-lock switch?
Or are there 2 switches on the driver side t-case?
Last edited by Chris 97 F150; Jan 14, 2007 at 11:38 AM.
5th Wheeling
Joined: Nov 2005
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yes that was the switch I was refering to. so you got that already. when you shift into 4H a light on the dash shoud say 4x4. So you got the shift indicator switch, changed the vacum solenoids, vacum hoses. hhmmm.
does the vacum switch hoses (sides) when the t-case is shifted? or vacum is always on just 1 side no matter the postion of the t-case lever?
I would next check the linkage on the t-case lever to see if it is functioning properly. next check the the electrical at the solenoids. also check the electricl connection at the "shift indicator switch" make sure the harness is clean and in good condition. good luck let us know what you came up with.
does the vacum switch hoses (sides) when the t-case is shifted? or vacum is always on just 1 side no matter the postion of the t-case lever?
I would next check the linkage on the t-case lever to see if it is functioning properly. next check the the electrical at the solenoids. also check the electricl connection at the "shift indicator switch" make sure the harness is clean and in good condition. good luck let us know what you came up with.
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i can have the t-case in 2WD and switch the vacuum lines over and still lock in the front wheels...doesnt recognize lockin the front wheels when i move the lever, only by switchin the vacuum hoses
yes i do have the indicator switch replaced, and it turned the Low Range light off, unless i put it in 4L....and also, the t-case engages as i move the lever to 4H and 4L, and also disengages into 2H...just wont lock the front wheels when i move the shift lever...
but yea, i can have truck in 2WD and swithc the vacuum lines over and still lock the front wheels
P.S. about the light on the dash, the only light that comes on the dash is Low Range when i have it in 4L...nothin shows up in 4H
yes i do have the indicator switch replaced, and it turned the Low Range light off, unless i put it in 4L....and also, the t-case engages as i move the lever to 4H and 4L, and also disengages into 2H...just wont lock the front wheels when i move the shift lever...
but yea, i can have truck in 2WD and swithc the vacuum lines over and still lock the front wheels
P.S. about the light on the dash, the only light that comes on the dash is Low Range when i have it in 4L...nothin shows up in 4H
