02 Multi-Mode 4WD Grinding (OTF Only)

[AZSportRunner]

Alright boys I've got a weird one.

My 2002 SE has been an amazing truck for as long as I've owned it and I've never had any issues with the 4WD until now...

When engaging the AWD (shifter push button w/out center diff locked) the truck makes a terrible grinding noise that I can literally feel bringing the truck to a halt if I don't slow down.

Now here's the kicker, if I come to a complete stop and THEN engage the AWD it engages fine and I can drive around completely fine up to speed and stop no problem. :redbrick: The center diff locks up immediately (4H) and putting the trans in neutral and then placing the t-case into low range (4L) work as they should.

The only time the noise occurs is if I shift "on-the-fly" so to speak, Toyota says you can do this up to 55MPH but I can't do it even below 5MPH.

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01 and 02 Multi-Mode Avengers Assemble
[MENTION=102606]infamousRNR[/MENTION] [MENTION=75316]jgue467[/MENTION] [MENTION=55891]Bandit Runner[/MENTION] [MENTION=44220]BigFishAllDay[/MENTION] [MENTION=173813]blackhammer0331[/MENTION] [MENTION=161842]Mtns_Yo[/MENTION] [MENTION=107971]derpiful[/MENTION] [MENTION=119532]Road Bull[/MENTION] [MENTION=116470]Tyler James Inc[/MENTION]

Maybe even the illustrious and gone but not forgotten [MENTION=57546]4-Ripcord[/MENTION] would like to make an appearance?
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Could this be something as simple as needing to change gear oil in the t-case?

Both Front and Rear Diffs have fresh fluid. Actually come to think of it I'm waiting for ECGS to finish my new 4.88 3rds (True-Trac and E-Locker) however I don't think that is the issue considering once the truck is in 4WD it drives as it should.

Maybe this is a sensor issue? The grinding doesn't necessarily point that way but the condition it occurs under might...

 

[brillo_76]

Sounding like a synchronization issue. Like the front differential isnt spinning the front driveshaft. So when stopped it goes right in.

You have any odd mods like manual locking hubs or anything that can interfere with the normal operation of the differentials.

That's odd for sure.

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[AZSportRunner]

Not sure how I forgot these crucial bits but:

T-case gear oil was done when the trans was rebuilt ~20k miles ago
Noise seems to be coming from the front (ADD malfunction maybe?) but I know drive line stuff is hard to pin down...
Going to have a friend try to engage it while I'm walking alongside the truck to see if I can confirm this.

 

[AZSportRunner]

Hi Brillo, no manual hubs or anything like that... Odd for sure.

 

[Tyler James Inc]

Obviously a synchronization issue.
I would start out by seeing how your front driveline is behaving during the grinding. Have someone else driving, and hang out the pass door to watch the driveline- in a wide open lot. Have them drive as slow as possible, as you REALLY want to avoid damaging anything by whatever is causing the mis-alignment. That might help you nail down if it’s an issue in the tcase or front diff. Both front axles are in, right? �� Electrical connections are secure on the ADD motor on the front diff?

You say it’s acts as it should in A/4WD- are you 100% certain of this? 100% certain there is drive going to the front tires? Obviously something isn’t spinning that is typically spinning while driving.

 

[brillo_76]

I am suspecting the ADD motor on the front differential not functioning properly. As the T case is functioning if you stop and shift into 4wd.

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[AZSportRunner]

Obviously a synchronization issue.
I would start out by seeing how your front driveline is behaving during the grinding. Have someone else driving, and hang out the pass door to watch the driveline- in a wide open lot. Have them drive as slow as possible, as you REALLY want to avoid damaging anything by whatever is causing the mis-alignment. That might help you nail down if it’s an issue in the tcase or front diff. Both front axles are in, right? �� Electrical connections are secure on the ADD motor on the front diff?

You say it’s acts as it should in A/4WD- are you 100% certain of this? 100% certain there is drive going to the front tires? Obviously something isn’t spinning that is typically spinning while driving.

Hi Tyler, appreciate the quick response.

Both CV's are definitely in and all of the connections on the t-case and ADD motor/tube are connected. The t-case actuator engages immediately as does the ADD motor when stopped (the distinctive clicks are almost instantaneous).

Going to have a friend drive it while I hang out the side later tonight when I'm off work and check back in.

As for whether or not the front wheels are getting power... It certainly drives like it's in 4HI (heavier steering, more grippy, etc.) but I guess the only way to be sure is to get it off the ground and see if the front wheels spin so I'll go ahead and do that tonight as well.

Will update once I'm done.

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[Road Bull]

Hard to say for certain. But from what you are describing, it sounds like when you are engaging AWD, something is moving, and something is at rest. The sudden introduction of movement to the "at rest" component is in conflict. But exactly WHERE that conflict is, is hard to say. But, my first guess would be either an actuator or a synchronization issue like brillo_76 mentioned.

I might take a look at post #3 here. It lists the section of the 2002 manual that goes through some inspection steps.

SOLVED 2000 limited stuck in awd/4wd, multi mode issues. Blinking 4wd lights

When was the last time you used your AWD and 4WD without issue? Has the 4runner had any service done between then and now? Just trying to narrow down what might have changed besides something going bad or seizing up.

 

[AZSportRunner]

Road Bull, thanks for the FSM/thread link!

Going to borrow a multimeter from a friend and do some testing on the harness/actuator because come to think of it the last time I tried engaging the AWD on the fly was prior to the trans rebuild (done by a reputable local shop however it is an old truck with brittle wires). Not sure how this didn't cross my mind as it was the last major thing done to the truck.

I have used the 4WD (CD Locked) a few times since the rebuild but always engage it at the beginning of a trail head while stopped and have only done light trails to go shooting or to the lake since then.

I actually discovered the issue after it recently rained and I engaged the AWD while leaving my neighborhood just because the roads were wet and I hadn't engaged it in a while.

I'm off Tuesday so by then I'll have had some time to trouble shoot and provide a proper update.





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[Bandit Runner]

I agree with the above - sounds like a synchronization issue. Other than that, I'm no help. Good luck.

 

[phattyduck]

The standard j-shift transfer cases have a synchronizer in the shifting mechanism to get the front driveshaft up to speed when shifting on the fly (then the ADD engages to lock the front drive in).

I wonder how the multi-mode / AWD transfer case does this same function. With an open center diff, there would be nothing to get the front drive spun up to speed unless the ADD actuator locks first - but it couldn't do that because there is no synchronizer up there (just splines and a shift collar/sleeve).

-Charlie

 

[im_cpr]

Sorry to bring back an old thread. AZSportRunner, I'm having the exact same issue as you in my 2001. Did you ever get it solved?

 

[AZSportRunner]

[MENTION=762848]im_cpr[/MENTION] Sorry, I should have provided some kind of resolution on this...but to answer your question I ended up using contact cleaner on the connections for the ADD motor and t-case position sensors and connectors to clean everything off as well as replacing the fluid in the t-case. It has been problem free since then.

If I had to guess which of these fixed it I would go with replacing the fluid. At the time I had believed that everything was fine because it had been refilled by the transmission shop that rebuilt my transmission about 20k miles prior to this problem appearing. They may have used the wrong weight of gear oil or not filled it quite enough although it seemed normal when I drained it.

 

[im_cpr]

[MENTION=762848]im_cpr[/MENTION] Sorry, I should have provided some kind of resolution on this...but to answer your question I ended up using contact cleaner on the connections for the ADD motor and t-case position sensors and connectors to clean everything off as well as replacing the fluid in the t-case. It has been problem free since then.

If I had to guess which of these fixed it I would go with replacing the fluid. At the time I had believed that everything was fine because it had been refilled by the transmission shop that rebuilt my transmission about 20k miles prior to this problem appearing. They may have used the wrong weight of gear oil or not filled it quite enough although it seemed normal when I drained it.

[MENTION=121269]AZSportRunner[/MENTION] hey man you're an absolute legend for helping answer this 4 year old question, much appreciated!

I did a drain/fill of the TCase yesterday, and cleaned off all the electrical harness. Unfortunately that didn't completely fix the on-the-fly shifting issue, but it does seem more willing to go into 4wd after a stop.

I'm following this thread here to continue do some debugging, maybe pull off the actuator motor or the various tcase/diff sensors to test further.