4x4 not engaging

[Guido]

I have an 86 4runner with the turbo. It is an automatic with the "shift on the fly" technology, just the simple shifting lever you pull that seems to activate a switch or something, and I’m not really sure how it works.

When I shift it into 4x4 the light comes on in the dash but the 4x4 is not engaging. Not sure what is going on.

Does any have a schematic of how this system works or can tell me. Seems like the solenoid is not engaging. or is this a vacuum type unit?

I hope this is an easy fix, thoughts and inputs are appreciated.

 

[Hyde802]

There is a collar on your front diff that is vacuum activated. So trace the lines up from the diff till you find a leak.

This could also be a good time to think about switching to manual hubs. Youll get better MPGs out of it.

 

[Guido]

There is a collar on your front diff that is vacuum activated. So trace the lines up from the diff till you find a leak.

This could also be a good time to think about switching to manual hubs. Youll get better MPGs out of it.

Thanks for tip, I'll look at that tonight. Previous owner must have put manual hubs on ride, now they are manual.

When you engage in 4x4 using the lever you can manually turn the front drive shaft. Is there a switch or lever that engages the front transfer case?

 

[Hyde802]

So you do have locking hubs? In that case, you can just lock the shifter fork in place, and git rid of the vacuum system all together.

When you shift the transfer case into 4wd high or low the front shaft should turn.

 

[Guido]

When shifting the lever in 4x4 the shaft does not turn. does not sound like the solenoid or whatever is is engaging.

Do you know where the solenoid is that engages the transfer case? or what engages the transfer case on the "shift on the fly" 4x4?

 

[the_dingman]

An '86 should be Auto-Hubs and manual T-case, it is NOT shift on the fly.

Usually, you have to select 4WD standing still, then move forward slowly for 5-10 feet to engage. To disengage, select 2WD, and back up for 15 feet.

Auto hubs commonly go bad. That's probably the problem if it's not engaging.

 

[KidVermicious]

Wait, what? My '86 has Aisin manual hubs, are you saying they aren't factory?

OP, the front drive shaft should turn freely if you have the selector in 2wd, you shouldn't be able to turn it if you have the selector in 4hi or 4lo. Similarly, both your halfaxles in front should spin freely while the hubs are disengaged, and you shouldn't be able to turn them manually with the hubs engaged.

Are you sure you have manual hubs? Are you sure they're engaged? Have you ever used the 4wd on this rig, or is this the first time you've tried?

 

[Guido]

Manual hubs, i am sure. Shift on the fly technology as well, this is a automatic vehicle. No shifter to yank on just a lever you pull.

when in 4x4 (light on) you can freely spin the front drive shaft. I have the problem isolated to the transfer case! I believe. I just purchased vehicle and this is the first time I tried the 4x4.

How does this work? hydraulic, electric, vacuum?????

I am having problems seeing hot to engage the 4x4 manually if needed.

 

[the_dingman]

Aisin made the factory hubs for Toyota (at least the manual ones).

OP: I assumed you had auto hubs, as you didn't mention anything about having to engage the hubs manually.

Manual hubs will have a knob (should be red) that must be turned from "FREE" to "LOCK" in the middle of each front wheel. If you don't have this, you have automatic locking hubs.

As for how the system works:

The locking hubs connect and disconnect the front axles to the wheels, the transfer case connects the front and rear drive shafts to each other.

The manual locking hubs must be turned to "LOCK" on each hub to attach the wheels to the front axle. If you raise the vehicle, lock both hubs and leave the transfer case in 2WD, when you turn one wheel by hand, the other should turn the opposite direction.


When your front wheels are locked to the axle, you can shift "on-the-fly" from 2WD to 4WD. Assuming the transfer case is the same as the manual transmission version (with just a different selector), the transfer case is chain-driven, which could point to a broken chain if no power is going to the front wheels.


My impression was that auto-transmission 1st gens had automatic locking hubs, and that they were an option on manual transmission models. I may be wrong, or someone may have changed them. As I stated above, automatic hubs tend to be problematic.

 

[KidVermicious]

when in 4x4 (light on) you can freely spin the front drive shaft. I have the problem isolated to the transfer case! I believe.

I think you're right.

I think it's a mechanical linkage, but I'm not 100% on that. I'd look for a rod or cable between the 4wd selector and the TC, and check that it's moving thru it's full range. If that isn't there, then it's vaccuum or electric, and beyond me.

My impression was that auto-transmission 1st gens had automatic locking hubs, and that they were an option on manual transmission models. I may be wrong, or someone may have changed them. As I stated above, automatic hubs tend to be problematic.

I think manual hubs were at least an option on automatic-equipped trucks. Maybe it's a year thing, mine's an '86. I've got manual hubs, and the first two owners weren't the type to add a mod like that (or mod anything, for that matter).

 

[Guido]

i traced it down, there is a rod that engages a lever on the side of the transmission.

This assembly is moving and engaging. when engaging you can still freely turn the front drive shaft with your hand. The transfer case is not locking.

may be a relay or something inside the transmission not giving the appropriate flow to the transfer case to engage the gears.

does this have a relay?