4X4 vacuum selector bypass
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Record Breaker
Joined: Jul 2014
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From: Wisconsin
The other way to test it is to put the vacuum lines on the correct way in 2 HI. Your front driveshaft should turn. Now pull the transfer case into 4 HI, the driveshaft should be locked now. It sounds like you might have problems in the transfer case if you can't shift into neutral or 4 LO.
Veteran
Joined: Dec 2019
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From: Texas
Nope! My CAD system was shot, and my driveshaft still spun when I engaged 4WD. In simplified terms, unless you engage 4WD via transfer case, you won’t be in 4WD even if you permanently lock your collar in. The driveshaft will still spin, but there won’t be any power.
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Professional
Joined: Jun 2020
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From: Michigan
If true you have an internal problem in the t-case. Vacuum has absolutely zero to do with the 'case powering the front d/s. It's 100% mechanical and dictated by lever position.
Now I suppose it could also be a worn or disconnected linkage or linkage bushings.
I also saw your post about elevating the front right wheel and d/s turning. This means your CAD is engaging but the t-case is not in 4wd.
DO THIS TO BE POSITIVE:
- start truck
-leave your CAD hotwired so it's engaged
-pull lever to 4hi and be sure you're confident it's truly clicked into position
-drive forward say, 20'
-put vehicle in P or if manual N and set parking brake, leave it running although really it shouldn't matter
-repeat elevate right front wheel and spin. Front d/s should NOT spin because it should be LOCKED (basically tied together with the rear d/s) if t-case is truly in 4wd.
If it's not working next inspect all linkages and linkage bushings/pivots. If nothing obvious, disconnect linkage at t-case and see if you can click it to a spot where front d/s engages. You may need to use a pry bar or pliers or other mechanical advantage to move the shifter. If you can find 4hi, compare where it is vs where the shifter puts it and if a discrepancy, WHY?
If you're unable to get 4hi (or 4lo I suppose) manually, it's probably time to yank the 'case and open 'er up.....but this is the final step after exhausting all other troubleshooting
Now I suppose it could also be a worn or disconnected linkage or linkage bushings.
I also saw your post about elevating the front right wheel and d/s turning. This means your CAD is engaging but the t-case is not in 4wd.
DO THIS TO BE POSITIVE:
- start truck
-leave your CAD hotwired so it's engaged
-pull lever to 4hi and be sure you're confident it's truly clicked into position
-drive forward say, 20'
-put vehicle in P or if manual N and set parking brake, leave it running although really it shouldn't matter
-repeat elevate right front wheel and spin. Front d/s should NOT spin because it should be LOCKED (basically tied together with the rear d/s) if t-case is truly in 4wd.
If it's not working next inspect all linkages and linkage bushings/pivots. If nothing obvious, disconnect linkage at t-case and see if you can click it to a spot where front d/s engages. You may need to use a pry bar or pliers or other mechanical advantage to move the shifter. If you can find 4hi, compare where it is vs where the shifter puts it and if a discrepancy, WHY?
If you're unable to get 4hi (or 4lo I suppose) manually, it's probably time to yank the 'case and open 'er up.....but this is the final step after exhausting all other troubleshooting
ive read that the transfer cases have a servo motor in them that can go bad is this true for my second gen? if i remember correctly I have the NP231 t case
Legend
Joined: Nov 2014
Posts: 8,098
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Ok followed directions and no dice. shaft still spins. i disconnected the linkage and shifted the transfer case by hand no matter what position its in i only have 2wd.
ive read that the transfer cases have a servo motor in them that can go bad is this true for my second gen? if i remember correctly I have the NP231 t case
ive read that the transfer cases have a servo motor in them that can go bad is this true for my second gen? if i remember correctly I have the NP231 t case
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Professional
Joined: Jun 2020
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From: Michigan
Legend
Joined: Nov 2014
Posts: 8,098
Likes: 318
If you indeed engage the 4wd with the transfer case selector (linkage removed) and the front driveshaft still spins it's bad. You would need to move it one indent forward (towards the front of the truck) that would be 4hi
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Professional
Joined: Jun 2020
Posts: 245
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From: Michigan
i can grab it with two fingers and move it back and forth its loose enough that if i were to leave the linkage removed and drive down the road it will move from one position to another just from the bumps in the road.
from what i know i should be able to feel it click through each indent when moving it by hand at the t case but its basically just flopping back and forth.
i guess my only chiice now is if i want to find a rebuild kit, rebuild it, and pray that fixes it... or just drop a few hundred on a remanufactured one or something and be done with it.
i can pull the old one and swap it with a new one in like an hour or two no biggie, never rebuilt one though. guess its youtube time lol.
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Joined: Jan 2004
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From: United States
The best scenario for a rebuild is open it up, determine what you need and then order. But obviously more down time.
The big(ger) expenses can be the chain and planetary assy. I'd probably leave both alone and it sounds like your problem is unrelated here, anyway.
I'd encourage you to rebuild - it's fun and easy. Complete reman 'cases sell for stupid money.
I'd probably just open it up, find the problem and replace only that. Honestly not sure I'd even bother with bearings, but maybe throw some new shift fork pads on IF they appear worn
The big(ger) expenses can be the chain and planetary assy. I'd probably leave both alone and it sounds like your problem is unrelated here, anyway.
I'd encourage you to rebuild - it's fun and easy. Complete reman 'cases sell for stupid money.
I'd probably just open it up, find the problem and replace only that. Honestly not sure I'd even bother with bearings, but maybe throw some new shift fork pads on IF they appear worn
Administrator
Joined: Apr 2010
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From: Clayton MI
I am going to guess something in the shifter mechanism inside the t-case is broken. Only way to find out though, is open it up, and see. If you have something else to drive for a bit, all well and good... If you don't, then maybe getting a reman/used unit would be a better plan.
