Still No 4WD

Hello folks, new member here with a question about my malfunctioning 4wd.

Did some research, checked out a LOT of YouTube vids and the TW website. I don't think I am skilled enough to be confident to go through the electrical testing that another TW member thoughtfully posted but will try if I have to.

BTW...had to send the front ADD unit to a machinist to drill & pick out that one screw head that twisted off, facing the unit as installed, it was the right side top. The 4 other fasteners responded well to 24 hours of PB Blaster and a vice grip but that fifth sucker was welded in with rust. The high side and the whole unit was clean and dry inside and out. Why is this same fastener failing in some of the YouTube vids I saw? Is it intentional by Toyota or the ADD maker?

So after I installed the front actuator and road tested it...the 4wd light blinked and I could hear and feel clunking. It seemed to be keeping the truck from moving, especially when turning so I switched it back to 2H, tried forward and reverse in a straight line about 20 feet and finally shut off the vehicle and it all reset to 2wd and ran fine but couldn't get into 4H

Does it sound like I could have just not placed the front ADD shift forks properly?

The sliding "collar" on the axle inside the front differential when moved outboard is 2wd and that's where the shift forks were so it might not have been able to shift left or inboard for 4H due to my misalignment of the shift forks.

Is this likely the issue or should I look elsewhere? Any advice or opinions would be greatly appreciated. Thank you.

 

It's time to take your truck to a pro. It MIGHT cost more, but then again it might not. A pro can evaluate the problem and fix the problem. Right now, you're throwing parts at it without a clue and may well end up spending more replacing parts that don't need to be replaced. I don't recommend the dealer. Find an independent shop with someone familiar with 4X4's

If 4X4 isn't used regularly lubricants can harden and parts no longer move. There is a very good chance nothing is broken. It might just need to have the hubs disassembled, cleaned, re-lubed, and reassembled so the hubs will lock.

If used properly 4X4 components almost never fail. It is when guys don't use it regularly that parts go bad. And when they use 4X4 on high traction surfaces is when parts fail prematurely.

 

Thanks for the reply, Marshall R but where am I "throwing parts at it"?

I fixed the front ADD by resoldering the electric motor contact terminals inside the unit. I did pay a machinist $40 and bought a $9 tube of hi temp gasket maker. I also bought 5 new 5x16 mm screws for the actuator cover ($2) and I had a tube of "never seize" and I already had the gear oil for my regular differential maintenance schedule.

My post asked about shift fork placement.

The sliding collar on the axle inside the front differential had a groove that I thought I slid the fork into but it was the end of the day and tilting the ADD to position it could have resulted in mis-alignment of the shift fork. Before installing the actuator, I lubed the axle inside the front differential with fresh gear oil and slid that collar side to side and it moved freely and easily.

Do you or does anyone have any information about alignment of front differential actuator shift forks? I have searched but maybe because of the inaccessibility of the unit, no pictures or diagrams seem to be posted. Even a schematic would probably help but I haven't found one.

Has no one ever mis-aligned an actuator shift fork?

 

Sounds like you can't get 4H to engage. I recently went through some issues with my transfer case. The transfer case will engage the front drive shaft before the ADD is engaged. To determine if is your ADD or not , I would drive the truck and put into 4H. Then, with the truck in 4H, park it, get all 4 wheels of the ground, and see if the front drive shaft is engaged. Put the transmission in Neutral and spin the rear drive shaft with your hand. If the transfer case is working correctly, the front drive shaft should spin if you have it in 4H when you spin the rear drive shaft. If the front drive shaft is engaged that will at least help you narrow down the issue to the ADD or not.

edit: I have no knowledge about the ADD shift fork.

 

As far as I recall the shift collar (the piece the ADD shift fork moves) should be outboard for 2wd and inboard for 4wd operation.

To troubleshoot you should be able to take the ADD actuator off the truck, suspend it with zipties, bungees cords, etc. and manually slide the shift collar all the way to 2WD. Now start the truck and run through the full shift sequence down to 4Lo and all the way back to 2Hi. If that works then the electrical side is fine. With the truck / actuators in 2WD and the collar all the way over, you should be able to reinstall the ADD actuator. Being careful not to bump the collar. At the point it should be properly aligned.

 

Also see here for a few pics that might help.
https://www.tacomaworld.com/threads/how-to-deleting-add-system.427258/

 

The fork rides i a recessed area on the collar so unlikely you got it misaligned. Soldiering the motor leads is just one of the many things that can break, I’m betting your ADD is toast. Did you take any readings at the ECU while the light is flashing?

 

I did just now take a full set of readings for the "expected voltage" in the chart that DM93 posted.

In 4H the TL1 & DL1 were zero instead of 12 volts.

In 4L the TL2 & DL1 were zero instead of 12
The TL3 & L4 both had 11+ volts that were expected to be zero.

Any idea what I should try next?

 

DL1 staying at zero volts tells me your front actuator never moved, but that could be because the transfer case never shifted, I’d start at the transfer case actuator and take it apart clean it good.

 

OK I will check that out. At least it looks a LOT easier to remove the TC actuator than the ADD on the front...that was a real pisser, 1/8 turn of a wrench at finger tip strength if I remember correctly...DM93 mentioned to unplug both units and retest for voltage and yes, TL1 & DL1 both showed 11+volts in 2H, 4H & 4L. Thank you for the advice.