4wd not engaging.

[Mountain Fun]

Hi all, any help would be greatly appreciated.

I have a 1999 SR5 4Runner with a 3.4 V6, automatic trans, and J style transfer case shifter.

I installed 4:88 gears front and rear (ordered as complete 3rd members from eastcoast gear) over the summer. I took apart the front axle and installed the diff. Everything went back together and I thought was working properly.

We got our first snow storm so I engaged my 4wd. The 4wd indicator immediately lit solid (didn't blink at all) but not power to front wheels. Shift it to 2wd and 4wd indicator light goes out, shift back to 4wd and 4wd indicator immediately lit solid but still no power to front wheels. It took me a little while to realize it but rear tires spin in snow and it fishtails all over the place. Is it possible I did something wrong when reassembling the front axle and connecting the vacuum lines. It just seems weird that the 4wd indicator lights up solid but no power to front wheels.

 

[TheDurk]

It is weird, because the ADD won't attempt to engage unless the T-Case detection switch reports front shaft engaged, and the ADD light won't go on unless the front diff switch reports front diff engaged.

One of them is lying. I suggest you put it on jackstands with all 4 wheels in the air. Put it in 4wd and see if the front propeller shaft is turning. If it is, issue is front diff actuator. If not, it's the T-case actuator. Go from there.

 

[Nelsonmd]

The 4WD indicator is actuated by a sensor on the shifter fork. If that is actuating but you aren't getting drive to the front wheels, then maybe you didn't get the shit fork into the groove on the 4WD collar.

Check for vacuum on both lines, and if that looks good then you should look at the actuator. The actuator can be taken off fairly easily, though you'll need to put new gasket sealant on it, so you'll have to scrape the old off, clean all the oil off it, etc. You will also lose some gear oil.

It can be a little difficult to get the shifter fork into the groove right. Mine wasn't working though I was sure I had it in right. I took the actuator out again, fiddled with it trying to make sure the fork was in the groove the right way, put it back together and then it worked.

I think there is an pretty detailed troubleshooting guide for 4WD too. Look in the tutorial and documentation reference thread v2, it should be in there.

 

[Mountain Fun]

Thank you Nelsonmd and TheDurk for your quick response, I was really stressing yesterday. TheDurk I think you are right about I must have installed the actuating fork incorrectly, I was rushing and tired when I put the axle back together. That would explain why the 4WD light is in on immediately, the fork is already in the engaged position, but the sleeve isn't.

I found this article online which really helped explain how to troubleshoot it.
Toyota Tech: Defeating the ADD System - ORN

Once our weather gets above 5 degrees I'm going to get under it and fix it. Thanks again.