Front locker actuator replacement trouble

bpenn1980

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Hi all,

Bought a SAT-002 Aisin replacement locker for my front axle and tried to get it in this afternoon. I've had the locker apart twice now (to verify motor works on 9v and to make sure the internal gear assembly thing is "clocked" in the locked position for installation. I followed the below instructions that came with the actuator EXCEPT that on the removal phase the actuator was not installed. I had already removed the old crapped out one, so I turned the dial, moved the fork manually, verified locked on the dash, and then disconnected battery. Not sure if that could be buggering it up somehow.

After installation of the actuator, turning truck back on and turning dial off, the locker disengaged (verified with front axle jacked up) but will not re-engage. In fact, I enlisted the help of my 9yo to listen and the rear actuator makes a distinct noise when activated by the dial whereas the front doesn't. I spun the tires a bunch to see if it was trying to lock, but I'm sure when I pull the actuator again the fork rack will be in the disengaged position.

Not sure what I am missing. Kind of bummed because I had hoped this would be an easy swap and the FSM isn't super clear to me. The actuator motor works, the gears/springs work (you can see tracks in the grease from the contacts and tested springs with a crescent wrench on the output shaft), the fork rack can be manually moved to lock/unlocked, the locked sensor works as confirmed when manually locked it shows on the dash. I'm hoping someone knows what step I'm missing.

Will try clocking one tooth off in the morning. See if that works.

Happy weekend! :beer:


A couple threads I've been referencing in case anyone comes after:
locker actuator rebuild - https://forum.ih8mud.com/threads/locker-actuator-rebuild.551069/page-2
Front e-locker install: Solved - https://forum.ih8mud.com/threads/front-e-locker-install-solved.1195484/
Locking Diff Actuator timing - https://forum.ih8mud.com/threads/locking-diff-actuator-timing.588139/#post-8819324


PXL_20210912_014641578.jpg
 
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Have you confirmed the vehicle is in low range? IIRC the lockers won’t engage unless the vehicle has the centre diff lock actuated (put it in low range or if you have the centre diff lock button on the dash push it).
 

bpenn1980

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Have you confirmed the vehicle is in low range? IIRC the lockers won’t engage unless the vehicle has the centre diff lock actuated (put it in low range or if you have the centre diff lock button on the dash push it).
Hey feistl, yep in low and center is locked. I definitely hear the rear locker actuator wind up, so I dont think it is a switch issue with the CDL. Good suggestion though. Start simple.
 

Squash

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Leave the unit powered up!
By disconnecting the battery you are killing the circuit.
Keep it in locked position during install.
 
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Leave the unit powered up!
By disconnecting the battery you are killing the circuit.
Keep it in locked position during install.
What about when pulling it? Instructions say to disconnect battery but isn't there a spring return or only on the rear?
 

Squash

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If it's manually locked at the axle and the actuator is installed in the locked position then everything should be good. I normally get the wheels off the ground in order to feel and see what's going on.
There was a thread about crossed OEM wires who knows what happens.
Maybe the actuator timing is off because he did run the unit.
Also power up, diff switch engaged, now grab actuator and plug it in being careful to watch gear rotation right at the diff.
This is a PIA alone but works.
 

bpenn1980

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Leave the unit powered up!
By disconnecting the battery you are killing the circuit.
Keep it in locked position during install.
I'll plug it in to the harness while out of the diff this morning and make sure it cycles.

I wasnt sure what the 'disconnect battery procedure' accomplished, but I did use it as an opportunity to replace a battery terminal clamp with one from Slee. Very nice product.

Also, I did note the motor cap on the actuator was hot (very hot) yesterday after messing around trying to get it to engage. Odd, but the spring it has to wind up is pretty beefy.
 

bpenn1980

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Interesting. It only cycles to unlocked and then wont cycle locked. Did that on the truck too (installed in locked position, cycled unlocked, but wont cycle back to locked). I pulled it and confirmed this w 9v as well using landtank's method of installing the gear between the unlocked/locked position. I then ran to locked, then unlocked, then nothing. Reset the gear, then ran straight to unlocked, then nothing.

Have a couple ideas and will report back.
 

bpenn1980

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I bent the contacts that ride on the gear assembly up a little to ensure good contact and make clean trace marks and it looks like the correct range of travel and correct direction of travel. Still not sure why it wont cycle from unlocked to locked.

Below is the orientation it will not move from (after starting mid-point, cycling to locked, then cycling to unlocked)
PXL_20210912_160942901.jpg
 

bpenn1980

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Holy mother, this is a PITA. Set up the truck with dial turned, turned off. Reinstalled actuator. Turned on truck and the damn thing cycled unlocked! Guess I'll check to make sure the truck harness is sending power to the correct pin.

haha, the good news is I only get to work in 15min intervals between taking care of kids, so I should be done figuring this out sometime in December.
 

bpenn1980

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Looks like something electrical unfortunately. Is getting 12v to unlock (pin 2 and 3) whether diff is locked or unlocked and in RR and FR dial positions. Checked the signal switch and it is good. Could explain why the original armature burned up.

Will check the actuator and ECU per FSM once my son goes to sleep.

 

bpenn1980

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Wiring harness tested OK, but ECU failed on the below in red with no voltage change when dial was turned, plus I was getting cycling voltage on pins 9-13 and 2-13 with no dial movement.

Not an ace with electronics, but that seems like a clear fail. Thankfully seems like these are still available for a few hundred $$.
2021-09-12 14_31_30-Window.jpg
 

bpenn1980

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Testing ECU components on the bench. I guessed a little at relay +/gnd pins, but all audibly click under 9v power and the 12v side isnt shorted. The only components I could find that seemed off are diodes 9, 10, 11, 12. They all have forward voltage drop of 0.095v compared to every other diode on the board at 0.500v-to-0.600v. I also tested diodes reverse bias and got the same reading compared to every other diode at 0.0v.

Bad diodes? I dont have a lot of experience diagnosing bad components, but my multi-meter manual says these readings are no bueno.
 

bpenn1980

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I got my front locker actuator installed and everything is working flawlessly now, so hopefully a little step by step will help someone else at some point.

Everything I could find on uninstalling/reinstalling the front locker actuator assumed you locked the front diff prior to removal. In my case, the actuator wasn’t working, so I had to remove it in the unlocked condition. This is the source of the problem.

The diagram below shows the actuator output gear orientation for re-installation, but ONLY if the actuator was removed in the locked position.

actuator installation orientation for locked.jpg



My actuator wouldn’t function properly when reinstalled in this orientation because it was removed in the unlocked condition, so last night while bench testing the ECU and actuator again, I stumbled on the solution.

What occurred to me was the number of teeth that exist on the locker fork. The fork can only move so far back and forth and has only 6 teeth. I thought, I should be able to rotate the output shaft/gear from the actuator by six teeth and replicate the position of the actuator in the unlocked position. I did this, manually shifted the locker fork to unlocked position, reinstalled the actuator into the diff, and now everything works perfectly. (Install with locker dial turned off obviously)

actuator fork relationship.jpg

[Note: the above diagram vantage is looking through the actuator from the rear of the axle]

The rest of this post isnt super useful or relevant for the down and dirty of just getting the damn actuator installed and working, but is rather just a casual observation after messing with the thing for too many hours.

After thinking through the gear interplay between the fork/actuator, I thought it was worth while to compare positions with the gear assembly inside the actuator, specifically the contact plate and mechanical stops cast into the actuator housing.

The image below shows the rough position of the contacts inside the actuator when the locker fork is fully locked and unlocked. You’ll notice this is short of the portion of the plate that interrupts the circuit, trips the locker ECU relay, and turns the motor off so it doesn’t burn up. The take away is that the actuator motor continues to run beyond the amount needed to fully mechanically engage/disengage the locker fork. This is where the spring mechanism comes into play. By overrunning the locker fork full range, this design ensures the spring is under tension which keeps positive pressure on the locker fork in both the locked and unlocked position. This is all probably apparent to others, but as a non-engineer I always feel super happy when I can follow the bread crumbs and appreciate the amount of thought and know how that goes into these trucks.

contact position.jpg

[Note: It is possible I have flipped the locked/unlocked positions in the above picture. If so, please let me know and I’ll fix so this doesn’t screw someone up in the future]

Thanks for bearing with my stream of thought problem solving in this thread. Hope this helps someone else eventually.
 
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Testing ECU components on the bench. I guessed a little at relay +/gnd pins, but all audibly click under 9v power and the 12v side isnt shorted. The only components I could find that seemed off are diodes 9, 10, 11, 12. They all have forward voltage drop of 0.095v compared to every other diode on the board at 0.500v-to-0.600v. I also tested diodes reverse bias and got the same reading compared to every other diode at 0.0v.

Bad diodes? I dont have a lot of experience diagnosing bad components, but my multi-meter manual says these readings are no bueno.
You should lift 1 leg of each diode to properly test with a meter. You're most likely reading across other components in the circuit.
The chances of all those diodes going bad is pretty slim.
 

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