4wd System Operation & Help Thread

Good day all, sorry for my late reply, been sent out to work in a hurry, I shall be back in Canada by the first of July. Yes I will try this to confirm the grounds for engine and frame; otherwise I guess I'll go camping with my OBD connector in hand! haha

Thanks a lot, and happy riding!

cheers, Steph

 

+1 on Engage it from time to time... And try this experiment: engage it cold when it's sitting in your driveway tomorrow: on mine the 2H to 4H is fairly uneventful; (its summer now) different story on the 4H to 4L shift: lots of drama: medium metallic bang on the shift, some kind of whining sound: Makes me wince. But: after a couple of miles running around doing errands and getting back to the driveway, the 4H to 4L shift is civilized and drama-free. Night and day. Makes a believer out of you on the "exercise regularly" advice. Good for your heart and blood pressure, good for your mid 80's vintage 4WD "pinball machine" system under the truck. I love it, but the clicks, whines, blinking lights and bangs remind me of old original Star Trek episodes and the robot on "Lost in Space".

 

Just figured I'd toss this in the thread to help others with troubleshooting as far as tools go. I just picked up a set of these fluke TP40 back probe pins, they fit perfect into insulated/non-insulated banana jacks. They work for non weatherproof and also weatherproof connectors as they are thin enough to get behind the weatherpack seals without damaging. Pair that with a nice test set and you'll have all the tools needed to troubleshoot the 4wd system and just about any other issue on a vehicle really. Plus they fold up nice into a to go pouch. I was using paperclips and alligator clips before this, got too cumbersome so these are just what the doctor ordered.

 

Nice, how much that setup cost? I know Fluke stuff can get pricey.

 

The back probe pins were cheap, I think $15 or so. The test probe set not so much, I think around $120 or so I've had the test set for a number of years now.

https://www.fluke.com/en-us/product/accessories/test-leads/fluke-tl81a

The 325 meter is pricey as it uses hall effect to measure DC with a clamp on, but I find it very useful for automotive troubleshooting because sometimes breaking the circuit will impede troubleshooting and a clamp on is what is needed to properly diagnose something. I have a few cheapo meters from Harbor freight I keep in my glove boxes of all my vehicles too "just in case".

 

Yea I have a Craftsman clamp meter, works good the only downside is it doesn't have min/max memory but I have my scope if I need that.

 

So, I’m finally back from deployment and while I was gone I bought from Toyota a front diff actuator and T-case actuator, installed today and still doesn’t work. Bummer but for sure know that’s not the issue, I can hear and feel the actuator at the T case actuating when I select 4hi, however checking the front drive shaft it still feels like it’s in neutral. Front diff actuator still ain’t doing nothing from what I can tell. All 6 connectors on my transmission are connected, and the two grounds on the back of the block are as well. 4x4 computer in the cab is swapped with a known good too. Could the issue be the actual t-case?

 

At this point sounds like actuator timing and wiring are about all that's left, did you try to shift the transfer case manually while you had the actuator off?
The ADD won't engage until after the transfer case has completed it's shift so not surprising it's not doing anything since the transfer case isn't yet in 4wd.
If timing checks out and you can shift the transfer case manually your gona have to go back and check limit switch voltages and see what's going on.

 

so I’ve shifted both by hand and 4x4 does work, but just won’t shift itself. I went ahead and took readings off each actuator at the connection with them still plugged in. These are the numbers that I got it seems to me that the front actuator is just completely not communicating with my ecu/t-case for some reason even though it’s connected at all points

 

Sorry for the late reply, was super busy at work and haven't had time to look this over.
Your limit switch voltages look right as far as the transfer case motor goes but you didn't check the 4wd position switch, the 4wd ECU will not engage the ADD until it sees the 4wd position switch close (0v) so check that next.

 

Damn not gonna lie I didn’t even think about that, haha I’ll get the checked first thing in the morning

 

Also make sure you don't have the wires reversed on the 4wd and low range detection switches.
Red/Blue goes to the switch closed to the transfer case and Yellow/Black goes to the rear switch.

 

I just checked because this is driving me nuts, I feel better and worse knowing they are in the right place lol, those switches did get smashed bad by my driveshaft last year when It blew up going 80mph, I will get voltages in the morning

 

the plugs are different so there’s no way to get them mixed up, unless someone put two of the same switches in the transfer case and a different connector on one of the vehicle harness side.

 

Ah ok I wasn't sure as I've never looked at mine that close.

 

Okay so I checked everything out this morning, these are the numbers I got. Nothing changes between 2wd to 4hi shift, im just hoping for the best at this point lol

 

So I’ve been doing my reading on this forum and saw this post, the way I’ve replaced the T-case actuator was by taking the top triangle plate off, removed the small gear and pulled off the rest of the actuator leaving the shaft in t-case, would that lead to the actuator loosing its timing?

 

Yes, it has to be retimed properly upon reassembly se whatever position the transfer case shift fork is in is where the limit switch contacts on the gear have to line up when it's reinstalled. Since your 4wd detection switch isn't changing your either out of time or that switch is bad.
See the timing the actuator link in the post below.
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/#post-26430335

 

Excellent write up OP. The dang things are finicky everything has to be just right! I had no issue getting out and locking the hubs then manually shifting the lever on my older one it worked fine! Hey the newer ones spin the axles any way so in the dead of winter I just let them spin Maine is just kinda that way.

 

I’m feeling good, I timed the T-case, front shaft is locked when in 4hi, light still flashing and front diff still not engaged however. Gonna get the 4x4 shift sensor readout now:

**still same readings**