89 Chev 4WD

[Eric Wettschreck]

I have an 89 chev 1/2 ton with a weird 4WD thingy going on.

A little history....Ever since I've had this truck it took about 20 seconds for the 4WD to engage when I moved the shifter. Going from 4 to 2WD was instant. Then, it stopped going into 4WD all together. I replaced the actuator and it solved the problem. This was a couple years ago.

Now, it still takes time to engage into 4WD but doesn't want to come out of 4WD back into 2WD. I have to stop, put in park, shut truck off, re-start, and sometimes it will be in 2WD. Also, now while in 4WD on things like gravel or tar it really pulls to the right. In snow or mud it doesn't pull.

Any ideas on what to start looking at?

[deadeye]

There is a little actuator switch that screws into the transfer case that has a plug with a couple vacuum lines going into it. The switch will go bad and start leaking fluid into the vacuum lines. It wont get the right amount of vacuum to engage/disengage because the seal is leaking and the fluid that gets in the lines disrupts the vacuum.

I'm kicking my self because I just replaced that on my buddy's blazer last year and cant remember the name of it.

Anyway, its like ten bucks and we got it off the Help section at the parts store.

Im not sure what the pulling may be. Possibly that the actuator on the front diff is not engaging both front axles. I know that was a common problem just like the t-case switch.

[Eric Wettschreck]

Appreciate the input Deadeye....but.....nothing close to the transfer case on this baby has vacuum lines. I just spent aboot an hour and a half underneath this thing looking everything over. No vacuum lines. Everything's electric.

From the tailstock of the transfer case there is a sensor I'm assuming (assumptions are dangerous) is for the speedometer. There is another sensor on top of the transfer case close to above where the linkage couples in. That's it for transfer case thingies.

I'm starting to think that since it pulls to one side while in 4WD I have a faulty hub. But, I'm not an expert and I'm even less of an expert on front ends.

[Big Buck Buster]

Check to see if you have power to the actuator in the front diff with the 4x4 handle in 4x4. You should have good power and ground at the two wire connector. If you have power, and ground, your actuator in the front diff is bad. They make an updated version of this that is an all electric solenoid instead of the gas chamber.

If you don't have power to the two wire connector, check the fuse in the fuse compartment. If the fuse is good, more than likely, the switch on top of the t-case is bad.

Hope this helps.

BBB

[Eric Wettschreck]

BBB, I'll check voltage tomorrow. Thanks.

Why would it pull?

[Big Buck Buster]

I would jack up the front end so both tires are off the ground, and spin the tires to see if there is any binding from one side compared to the other. Might just be a brake hanging up(caliper,brake hose,slide pins in caliper).

If the 4x4 works when engaging, but won't release, I think that the return spring inside on the pass. side of the front diff might be broken. you would be able to check that by taking the actuator out and pushing it in with a similar size pipe as the actuator piston. If it doesn't move in/out, you will have to drop the front diff, and do a tear down to see what is all broken.

[Scott K]

I dont know much about GM's to give much advise, otherwise I would.

[Big Buck Buster]

I forgot to add that when you are checking the voltage at the two wire connector, check it as you shift it into 2 wheel, and see if the test light goes out right away. If you still have a light, even though it is in 2 wheel, the switch in the top of the t-case is bad sending voltage to the actuator in the front diff when it is not suppose to. This won't help the pull, but I think that you have more than one problem going on.

[Eric Wettschreck]

Yeah, I was pretty sure more than one thing was happening here.

I jacked up the front end already, everything seems the same.

The pull problem only happens while in 4WD. And it only happens on tar or gravel, not on the ice or in snow. While in 2WD it's no problem.

Thanks for the tips. I'll check voltage tomorrow after work and go from there.

[Big Buck Buster]

I will assume that all four tires are the same size?

[Eric Wettschreck]

You are correct.

[Jeremy airjer W]

Of course boiler guy has to have a truck that won't come out of four wheel drive!

Simular to 4WE unless it doesn't go in to four wheel drive I would be scratching my head trying to figure out why it doesn't come out. I do like the idea of monitoring voltage at the actuator while you take it out of four wheel drive. If the actuator stays powered up it will not disengage.

[deadeye]

Boy I thought that was a vacuum operated system.

Do monitor the voltage like the others said. It is possible that the switch attached to the 4x4 lever is bad.

[Eric Wettschreck]

Ok, here we go.

Had the neighbor in the cab and I was underneath. He shifted into 4, no volts........15 or so seconds later volage appeared. He shifted into 2 and volts stayed there for a long time then disappeared. I called the parts store and ordered the new switch that threads into the top of the transfer case. I'll have it on Saturday. I jumped said switch and things reacted immediately.

I'm still unknown as to why it pulls real hard to the right, in 4WD, under power. No pull in 2WD.

[Big Buck Buster]

That is a positive start. Do you have the old style actuator in the front diff yet?, or did you upgrade to the solenoid already? You would be very pleased with the solenoid. It is instant, and you don't have to wait for the gas to expand like in the old actuator.

For the pull problem:

Is there any chance of loose front end parts? Tie rod ends, ball joints, idler arm, pitman arm?

When you get the new switch installed in the t-case, engage the 4x4, and see if both front axles are engaged. With the front end up off of the floor yet, and 4x4 engaged, spin one of the front wheels to see if the other spins in opposite direction. If only one turns, you have bigger problems in the front diff, or a cv shaft is out.

[Eric Wettschreck]

I don't know if the actuator is old or new style. I replaced it a couple years ago. 2 wire lead. Expansion gas or solenoid??? I don't know. I'll assume it's gas due to it being a couple years old.

Chance there is a front end problem? It's an 89. Pretty good chance nothing is perfect up there. I don't understand how a tie rod, pittman arm, etc would cause pull under 4wd and not 2wd, but I'm no expert.

When I get my new switch installed this weekend I'll do the front end in the air/wheels in opposite direction thing and let ya know. I'm assuming if they don't spin opposite I'll have to go inside the pumpkin and check things out.

I'm not a front end expert. I've been told this style has the constant engaged front end. From what I've learned the past couple days, GM had manual lock outs, went to auto lock outs, went to constant engaged front end, and went back to auto lock outs. This truck does not have the hubs that extend through the wheel so I'm assuming (again, assumptions are bad) it's the constannt engaged front end.

NO wonder it gets such bad MPG.

[Big Buck Buster]

The old style take, I think, a 1-1/4" wrench to get them out of the front diff. The newer solenoid style are all plastic with more than two terminals at the actuator.

If you don't have hubs, you have cv shafts in front. It is more less a constant, but not until the actuator engages the front diff. Other wise, the front cv axles aren't engaged to the diff. The actuator slides the locking collar over to engage both shafts in the diff.

The reason I ask about front end parts being bad, is you said it happens "under load, in 4x4". If there are bad front end parts, the front shafts may make the bad parts more pronounced due to the torque of the front axles driving. When you are in 2 wheel, the front are along for the ride, and for steering.

[Eric Wettschreck]

It's old style then. 2 wire terminal.

Thanks for the CV/front end input. I really appreciate it.

I'll dig a bit deeper this weekend, in my shop at work, where it's warm, and I have a few parts.

Gonna do oil changes and stuff then, too.

[Eric Wettschreck]

Put it in our work shop this weekend for oil changes and stuff.

Replaced the switch on top of the transfer case (that dude did NOT want to come out) and now it engages/disengages nice. Pulled the actuator in the front end to check the return spring. It's still in there and working.

Jacked up the front end. Both tires spin freely. Engaged it into 4WD and both tires still spin freely, in opposite directions. So, this tells me things in the front diff, CV shafts, etc are working well.

Still pulls to the right under load in 4WD on pavement or gravel. No pull on ice or in snow. From previous posts I'm assuming there's something amiff in the front end, somewhere, I just can't figure out what. From just looking at stuff nothing looked broken. Wheels arn't "Wobbly" like a bearing is going out.

[JollyT]

Just a thought? Power on in 4wd means the front tires are pulling wanting to move ahead. Any slop in the steering, ie: tie rod ends etcetera, would cause the front wheels to toe in under power. Since it pulls to the right, I would think the slop is on the drivers side, causing the left front tire to toe in, steering to the right.

I may be way off base, but it's an idea.

[efgh]

My 91 ford 4by4 wouldn;t come out of 4 wheel drive either, I would shift it out of 4 drive on the go and it would still be in. I had to stop, back up and it would be fine. I had put new tires on the front, older ones on the back. this was binding up the drive train and keeping it in 4 drive till I backed up .A local tire dealer told me Different brands on the front and back will cause the same problem.

[Jeremy airjer W]

Brands not so much. As long as they are the same size and about the tread there should be no issues with different brands.

Fords are especially sensitive to having worn tires on one axle and new tires on the other.

[rcatcherman]

Sounds like the actuator on the transfer case is or has a vaccum leak. Not a real big expense to fix. I'd go to napa and try that.

[Eric Wettschreck]

No vacuum in this puppy. All electric.

I fixed the 2WD/4WD engage/disengage problem. Now I just need to figure out why it's pulling so badly.

[Sniper07]

You should definetly check out the front end to make sure every things tight. Also if things seem good lube all fittings (check front end out BEFORE you lube it). If nothing else you'll at least know that it's been done. There are a lot of fittings on those older trucks.