Troubleshooting manual-trans 4WD, 1999

[ryandc]

The rig: 1999 SR5. 3.4L engine, 5-speed transmission, J-style transfer case. No e-locker, no transmission mods.

The issue: When shifting into 4HI on the J-stick, nothing happens. The 4WD light on the dash does not illuminate. Car does not exhibit issues binding on tight turns that would typically occur when front wheels are locked.

Troubleshooting: Shifting into neutral (on the J-stick) functions properly. Shifting into 4LO illuminates the dashboard 4WD light, properly downshifts the car, and properly locks the front wheels.

Some googling has yielded an acronym soup (VSV, AAD, a few others). Not gonna lie, I can wrench on engines all day and do okay (my rig has 290,000ish miles and never goes into the shop), but transmission and suspension is a bit out of my wheelhouse.

What are the possible points of failure here?

 

[Pyral]

Can you turn the front drive shaft by hand in 4 LO and 4 Hi?

 

[nissanh]

Above^^. Those manual shift levers never fail.

 

[Bad Luck]

The rig: 1999 SR5. 3.4L engine, 5-speed transmission, J-style transfer case. No e-locker, no transmission mods.

The issue: When shifting into 4HI on the J-stick, nothing happens. The 4WD light on the dash does not illuminate. Car does not exhibit issues binding on tight turns that would typically occur when front wheels are locked.

Troubleshooting: Shifting into neutral (on the J-stick) functions properly. Shifting into 4LO illuminates the dashboard 4WD light, properly downshifts the car, and properly locks the front wheels.

Some googling has yielded an acronym soup (VSV, AAD, a few others). Not gonna lie, I can wrench on engines all day and do okay (my rig has 290,000ish miles and never goes into the shop), but transmission and suspension is a bit out of my wheelhouse.

What are the possible points of failure here?

Check to see if the front driveshaft turns by hand with the transfer case in 4hi and 4lo. If the front driveshaft does not spin freely, then remove the switches on the transfer case and check for continuity. When you shift into 4hi the shift lever activates a switch which in turn sends a signal to activate the front add system.

 

[phattyduck]

Check to see if the front driveshaft turns by hand with the transfer case in 4hi and 4lo. If the front driveshaft does not spin freely, then remove the switches on the transfer case and check for continuity. When you shift into 4hi the shift lever activates a switch which in turn sends a signal to activate the front add system.

This is the answer right here. Likely a dirty/non-working switch on the transfer case to engage the front ADD.

Basically, the transfer case is correctly in 4WD, but the front doesn't get signaled to lock in for 4WD operation.

-Charlie

 

[NegroTundra]

Yep, what the two guys above said. Remove plastic bezel/leather around shift knobs. Look down on the right side and you will find a switch that the 4wd stick depresses when engaged (its a tight fit so be prepared to feel your way around). Remove that switch. I just had to bench clean mine with some parts cleaner and it worked again. Or replace it since your approaching 300k.