'98 4WD operation question

[162435]

This is mildly embarrassing to ask, but here goes. Despite owning my '01 since new, doing all maintenance & repairs on it from day one, and now showing 585,000 miles on the clock, I have a 3rd Gen question that's new to me.

In late 2023, I acquired a '98 5-speed 4WD from the original owner. Around 250,000 miles, a good amount of rust underneath, but remarkably clean inside. Since then, I've slowly gone through the truck, doing every and all maintenance that came to mind. Just yesterday I finished a complete timing belt job, and replacement of all A/C components. While in the thick of it, I also installed new Toyota engine mounts (so fun). It was during this work that I noticed that the steel vacuum line sections for the front diff were completely rusted through. As in, no vacuum could make its way from the VSVs to the front diff.....

So the embarrassing question: since the front diff vacuum lines are obviously out of commission, what exactly happens when the J shift lever is moved from H2 to H4? Until now I've been under the impression that the truck went right into 4WD, since the indicator lights up.

I intend to order about 8' of Toyota vacuum line in order to make continuous connections between the VSVs & the diff. Flame suit on.


Andreas

 

[GhostRing]

I'm thinking just 2WD low? Are you positive the p/o didn't lock out the shift fork? (or is that only a 2nd gen mod?)
Don't think that's embarrassing - I still don't know if the ECT button affects shift points in low range...

 

[brillo_76]

Ghostring is correct... Without the ADD in the non actuator versions 96 thru 2000( non limiteds).. You have 2wd low. Some people have been known to put a switch on those vacuum relays because they wanted 2wd low in the J Shift transfer cases.
Some people even eliminated the front diff fork and put a locker in it. Then put the manual locking hubs in so they can leave one side unlocked for an open diff then turn both hubs in for 4 wd front and rear locked if equipped. Granted that is a lot of modification, however it can be done.

 

[phattyduck]

You'd need to know what else is going on down there... The PO could have either shorted the position switch connector (up where the vacuum lines go to the fender or on the ADD housing, or they could have locked the ADD actuator in the "locked" position, so the switch is reading correctly.

If the ADD is engaged, you have normal 4WD and then an always turning front drive (when in 2WD). If the ADD is disengaged, you have only 2WD (either high or low).

Read under there an try to spin the front prop shaft (between the TC and diff) and see if it spins by hand...

-Charlie

 

[Cement_truck]

hmmm....