Still at it with the 4x4 gremlins

2001, AC SR5 4x4

I've read the 4x4 stickies/threads, and google'd the hell out of this....

Bought the truck with no working 4x4. Both dash lights, 4hi+4lo, were continuously blinking.

Removed the transfer case actuator. Cleaned, greased and retimed it (was previously incorrect).

This improved the situation. The 4lo light no longer blinked, 4hi link still blinking continuously.

Important to note, when I activate 4hi the system cycles correctly and everything seems to engage properly, 4hi dash light goes solid. When trying to disengage from 4hi there is a loud pop from t-case and the 4hi light goes back to blinking continuously.

Been working a lot so I confirmed t-case was in neutral (actuator shaft all the way in) and left it alone for a while. Recently, it seems like the transfer case has developed low speed knock...

Popped the Tcase actuator off again and no change, timing still good, actuator shaft still all the way in the transfer case indicating it is in neutral.

As a test I've tried cycling in and out of 4hi a few times. When 4hi is engaged there is no tcase knock, all functions smoothly. When disengaging there is that loud pop and the knock comes back.

Trying to drive it as little as possible for now to hopefully keep the tcase from destroying itself any further.

Checked the ADD actuator for shits and gigs. Seemed like someone had replaced it before but it was clean.
Checked all Ujoints for play, all seem good.

At this point I'm at a loss. There seems to be a mechanical problem causing that knock and 4hi light. Hoping I don't need to source a replacement transfer case, but wouldn't be the worst thing imaginable.


Going to try replacing the tcase fluid tomorrow, any further advice appreciated.

 

Consider the 4WD ECU may be bad. I think you’d have been better to post this in the diagnostics thread, someone there maybe been able to offer up advice on how to potentially test.

 

Hey @shifty` thanks for the reply.

At this point I'm less concerned with the 4x4 functionality and more concerned with the transfer case seizing while in two wheel drive.

Going to take the actuator back off tonight and give the shaft a whack or two with a mallet. Maybe it's not in all the way?

Hoping that along with the fluid change will help things along.

I'll let ya'll know if metal nuggets fall out when the drain plug is removed

 

What do you mean by low speed knock? Once per revolution? Like 4 times per wheel revolution?

Look for plastic chunks while draining, too.

 

@Sirfive Yes exactly, roughly 4 times per wheel rotation. And low speed knock as in it's really only noticeable at low speed. When the trucks get's moving faster the knock get's drowned out by road noise and exhaust. But it being about 4 times per tire rotation, it probably turns into more of a hum at higher speeds.

I had hoped maybe a dry U-joint but couldn't find any play in them (front or rear driveshaft) and the knocking noise goes away when 4hi is engaged. It is only there in 2wd.

Copy that will keep an eye out for plastics as well.

Thanks for reply!

 

If the t-case hasnt been used in a while sometimes it just needs to be fiddled on/ off a buncha times, but if you’ve had em off they shouldnt be bound up.

 

Been doin some research, on company time .

There's been some posts online about a potential needle bearing failure in the driver side front axle that describes the exact knock I'm having. But having a hard time narrowing this down between second and first gen trucks.

Plan for now is to grease all the zerks (needs to be done anyway), change the transfer case fluid, tap the 4wd selector shaft all the way into the case (maybe the actuator isn't getting it all the way in) and hope for the best because that needle bearing job looks like a bitch and a half to do in an apartment parking lot.

 

Needle bearing woulda warned you with a roar before it started to click. But that would be once every wheel rotation.

 

That's great news to me. Thanks for the input. Will update tonight after I get the work done

 

U-joints were definitely overdue on greasing, what came out looked like melted rubber...

I found a tiny bit of play on the joint connecting the front driveshaft to the transfer case. I believe that's where the knock is coming from but can't be sure.

I think that would make sense why the knock would go away in 4x4 since it would be under load and tight, but allowed to wobble a bit in 2wd. Thoughts?

Removed the transfer case actuator again and tapped the selector shaft maybe a quarter inch deeper into the case.

Holding off on the transfer case fluid change until I have a 6 sided 24mm. Fill plug is on there very tight and I really didn't wanna push my luck with a 12 point.

The knock has lessened a bit but definitely still there.

Planning to take it to and from work tomorrow (about 15-20 each way). Hoping that will warm up the fresh grease and let it really settle into the joints.

 

I apologize in advance if this is no help to you. When I bought my Tundra, it had 201,000 miles and I have no idea if any of the 6 previous owners (according to the DMV) ever put it in 4wd!

I had the stealership drain and refill both differentials, put in a new cv axle, grease the transfer case, plus do a tranny flush and refill (among a ton of other items). The OEM cv axle is not currently available from a dealer so they put in Duralast (?) from an Autozone. They said they couldn't get the OEM boot kit I had bought to fit the original cv axle so make of that what you will. Anyway....(I kept the original cv axle and hope to rebuild it at some point and put it back in).

First couple of times using 4wd Hi she went in OK but out, WHAM! Very loud sound and I had to drive her forward to get out of 4wd. This got better and better as we use the feature a few times a month. It's gotten much better now and we've been driving the truck almost daily since April. The last couple of times I used 4wd she came out without a sound at all. (It's my primary "work truck" mostly pulling a trailer full of lawn mowers).

Hopefully yours is a similar issue. Good luck brother.

I have not tried 4Lo but I should. She did go into Shift L without issue when I tried last week.