blacktail hunter

Weird problem. 89 DLX with 3.0 and auto trans, manual hubs.

Every so often, when you start the truck and put it in gear it will be in 4WD. The dash light is not on and the tranny shifter is in 2WD, but you can tell it is in 4L by the way it drives. Sometimes I can get it back in 2WD by slamming the shifter from 2wd into 4L and back to 2WD a few times. Other times it just seems to come out on its own as nothing I do works. I dont have any problem using the 4wd when I need it, it shifts in and out fine. This problem only happens at startup.

Could this be a vacuum issue? Electrical? I havent really dove into this issue because I really dont know where to start looking. Everything on the underside of the truck seems to be in order as far as I can tell, all wiring plugs are connected and wires seem to be ok.

Kingjerd

Make sure you keep those hubs unlocked unless off road. Degraded wiring could be the issue. I know my wiring harness in my 88 is quickly becoming brittle and close to needing replacement.

blacktail hunter

Yeah, the hubs are of course unlocked.

scope103

Then how do you know it is in 4Low? (4High?) If the hubs are unlocked, there is no drive to the front wheels, and it should not affect the way it drives.

Chickenman

4 low is 2.2:1 while 4 high will be 1:1.
So its gonna feel a little different...

edit: 3.0 might be different ratios but still 4 low is recognizable

nieb15

Does this happen on its own? Or only after putting the truck into 4WD?

If you engage 4WD in those trucks on a surface with no give it can damage the drive and make it hard to engage and disengage. Mine sometimes is tricky to disengage, but if I drive forward and back a bit it will go easily.

RJR

The transfer case has two shift rails inside it, one for 2WD/4WD, and the second for HI/LO. The 2/4 rail operates the switch that lights up the light in your dash. The dash indicator knows nothing about the position of the HI/LO rail.

Normally, there is an interlock pin that prevents the HI/LO rail from moving unless the other rail is in 4WD. If I understand you correctly, you're finding yourself in LO range even with the shift lever in 2WD. For that to happen, there would have to be some broken or worn parts in the transfer case shifting mechanism.

It's pretty easy to pull the cover off that holds the transfer case shifting lever, from inside the cab. You just have to remove the console, unscrew the shift knobs, remove the rubber boot, and then undo the 4 cap screws holding the shifter plate onto the case. Then you can see the shift rails and the notches that the lever engages, as well as the little ball on the bottom of the lever. Any undue wear or damage should be obvious. You can also move the forks by hand and check whether the interlock is working as it is supposed to. For reference, the shift rails are laid out like this.
- driver's side -- HI/LO Forward is HI, back is LO
- passenger side -- 2WD/4WD -- Forward is 4, back is 2.
They're just the opposite of the shift diagram on the knob.

So, if you pull the passenger side rail to the rear, the driver's side rail should be locked in place. You should only be able to move it if the passenger side rail is forward. That prevents you from shifting into LO range while in 2WD.
Conversely, if the driver's side rail is rearward, the passenger side rail will be locked. Again, that prevents you from shifting out of 4WD while in LO range.

I don't believe, on a truck of that vintage, that there are any electrical or vacuum actuators involving the transfer case itself. I think the T-case is purely mechanical.

Seems like an odd problem - I hope you get it figured out.

ldivinag

the other issue is the link from the shifter to the t-case broke off.

have someone lie underneath. trace the linkage.

on my 90 4runner with v6 and auto tranny, it broke in the the most crucial place: dusy/ershim trail.

the way the linkage works is there is a top and bottom ball joints. well what keeps the ball joints in tact are two semi-circular thingees. then it goes inside this cup thingee.

toyota in their infinite wisdom, made this setup twice. on top and the bottom. so we were in the dusy/ershim trail and the next thing i know, i can shift the shifter, but yes, once in 4wd, it wont shift out since the ball joints just kinda flops there.

for the next 3 days on the trail, if i wanted to get out of 4wd, i had to stop, jump out, go underneath and manually shift the t-case back into 2wd. weird part is, if i wanted to go into 4wd, the shifter works just enough to actually go into 4wd.

so, after the dusy trip, i visited the master of all toyota trucks. sure enough, MARLIN (or marlin crawlers fame) immediately knew what i was thinking about. he even pulled up a micro-fiche of his toyota parts and gave me the part numbers i could get locally. he didnt have them and it was like close to 11pm at night when i left his shop, after speaking for close to a couple hours... he is truly DA MAN...

blacktail hunter

You can feel that the gearing is much lower.

It does it all on its own, at cold startup. I too usually have to try and disengage it with the wheels moving.

RJR: Good info there, thank you.

I dont believe the shifter linkage is broken. I have no problem using the 4wd when I need it, it shifts into and out of each range just like it should. This problem only happens once in awhile, first thing in the morning at startup.

I am familiar with the ball joint thingies you refer to, as I had to fix the lower one when I first got the truck (it would shift into 2wd and 4H but not fully into 4L). I was not aware there was an upper one also.

ldivinag

yeah, there is that upper one also... IIRC.

at first, i thought i broke the two semi circular thingees when we were in the middle of the dusy/ershim trail so i kinda threw it away.

it wasnt until marlin showed me the drawings of the things when i realized they just "fell" out and i coulda saved myself so much headaches during that trip... doh...

ldivinag

i just reread your OP...

since you dont have ADD, the vacuum is out.

and since you have an 89, everything mechanical.

wait... you manual hubs. but do you HAVE the ADD setup?

XtraSlow_XtraCab

I think ldivinag is trying to confirm your front hub setup... do you have to get out ofr the truck and lock hubs to use 4x4? If they are automatic hubs, which would most likely be add (Automatic Differential Disconnect... via vacuum) then the simple case would be a stuck vacuum solenoid or diaphragm.

RJR

There's no way the ADD (assuming he has it on that vehicle) could cause the transfer case to shift into LO range, which is what the OP is experiencing. (see four posts up where he says "You can feel that the gearing is much lower."). Somehow his transfer case is winding up in LO range, and there's no vacuum or electrical mechanism that can cause that on an '89, as far as I know. Plus he has manual hubs, not auto hubs. He said so in his first post.

XtraSlow_XtraCab

Ah... he did mention manual hubs. Thats my bad man... totally over my head

I've driven my truck with hubs locked and in 2WD, and the extra bit of resistance feels like a crappy 4WD. I was considering that the OP could have been misunderstanding... I guess I just can't imagine such a mechanical oddity in the Yota transmission/t-case.

RJR

It's hard to fit all of the symptoms into a single reasonable theory, I'll give you that. It'll be interesting to find out the actual solution.

blacktail hunter

Yes, manual hubs.

So if there is no vacuum or electrical to this transfer case, it is strictly a mechanical unit......how can the gears be in low when the stick is in 2wd? LOL, it aint possible.

I just remembered one other thing I did notice when this happens....when you brake and come to a stop, its like the truck does not want to stop. I cant really adequately describe what it does. You have to forcefully stand on the brakes while stopped and in drive to remain stopped. You can feel the rear of the truck rising up, wanting to go. And if you put it in park while it is doing this, you can feel the truck rock backward.

This only happens in conjunction with the previously stated issue, at cold start first thing in the morning and it seems that the truck is in 4L. Once the truck is truly in 2wd, it drives and brakes fine.

fride115

just a quick question have you checked out the brake system, not just the brakes but everything involved master cylander power boster and such? im far from an expert but if i cant stop i would start with brakes and maybe see if the throttle is sticking too, just a sugestion though

RJR

Two things, blacktail hunter, based on your last post.
1) If the truck is truly in LO range, it will be a lot harder to stop with the brakes while the auto tranny is in gear, because the idling torque from the automatic transmission is multiplied by 2.5:1. You should notice the same "pushing and not wanting to stop" if you were legitimately shifted into 4LO.
2) It may be that you don't have a transfer case problem at all, but that something is flakey in your auto tranny when cold at startup, particularly in the torque converter. The torque converter is designed, at slow engine speeds but above idle, to generate a roughly 2:1 torque multiplication with a corresponding 2:1 speed reduction. You normally don't notice that because it smoothly transitions to 1:1 as you accelerate. But if something is wrong inside, it might be possible it could get stuck in that mode. That would give you the symptoms you are experiencing, and seems more likely than your mechanical transfer case shifting into LO range all by itself.

Check your transmission fluid and make sure it's full and that it looks and smells healthy (not discolored or burnt).

blacktail hunter

This may very well be the issue. This truck belonged to my grandpa, he bought it new in 89 and he is notoriously hard on his trucks. The engine was rebuilt, and the tranny rebuilt according to him. I found out after I got the truck that he did NOT have the tranny rebuilt, but instead put a junkyard tranny in it. He bought a Tacoma around 2003 or 2004, and the 89 truck sat in his driveway unused from that time until I got it early last year.

I know the tranny filter is good, I had it replaced when I got the truck and the fluid was replaced at that time also. I have very little experience with transmissions, so I do not know if there is a special way to change the fluid in an auto transmission. Do you have to do anything special to get all of the fluid out of the tranny and torque converter? Or is it as simple as changing engine oil (drain and fill)?

Thank you for your help, much appreciated.

RJR

I'm no expert on automatic transmissions, so I can't help you much in that area. I would suggest searching this site for a link to the factory service manual (aka "FSM") and do some reading. I would also suggest googling "torque converters" and learn a bit about how they work. I suspect something is gummed up from sitting so long and only loosens up enough to work when it warms up.

Good luck. Keep us posted.