Chevy & GMC Vans

I'm sorry about making a new post here but I've read almost all threads referring to this problem and I've still got questions. I've got an 03 astro awd. Bought it used at 110k and it's got 120k or so on it now. We had snow here last week and that's when I noticed the awd not giving power to the front diff. Then I noticed that the awd service light never comes on. So after reading through I found the correct fuse and it was blown. So I pop another one in there and take it for a drive and the light comes on telling me there's a problem. Driving a little farther the light goes out and I look and the fuse is blown again. Just having to put a rebuilt tranny in I don't have alot of cash atm so I hit the pnp and grab a used encoder motor and put er in. Now I'm not popping fuses and I can tell that the tc is trying to send power to the front in a tight turn. But now I'm getting worried because in that tight turn I hear a series of pops and then the light comes back on. In the process of pulling the tranny I changed out the atuo trac in the tc. The reared also has new fluid in it as well. I haven't done the front diff as of yet. Where do I go from here? Im seriously hoping I don't need a new tc, because if I do I'll attempt to rebuild it myself. I'm willing to tackle anything mechanical if it'll save me money.

Encoder motor on transfer case sounds like it is stuck which is pretty common. If replacing encoder motor, use one with the needle bearing and not bushing insert on the drive socket.

Dorman 600-906 uses the bushing style:



Looks like Cardone 48-103 used a needle bearing:

Thanks for the reply. What do u think the popping noise is if it's just a bad encoder? Maybe it's not fully engaging the fronts and that's what's making the noise. When I get off work I'm going to jack up to get all 4 off the ground and see if it engages the fronts that way.

Try driving in figure 8's and changing Auto Trak II fluid again, could be sticking clutch plates.

That's when I'll get the popping noise. When I first start up the van all is good. So I pull out of somewhere making a turn doing so and that's when I get the multiple pops and then the service light. If u had a bad tc is there anyway to tell from this point. When I put in the used encoder motor I read that I should turn the deal that the encoder turns. I did and it moves back to its original position under spring pressure.

Try pulling the fuse and see if the popping continues?

BTW, what as the condition of the original fluid?

To be honest I really didn't pay much attention to the fluid the first time I pulled the tc. I tossed the tranny and I was focused on changing that out. Little update, I've changed out the encoder once again with another used unit. And it does the same thing. Which upon starting the van the awd system is fine. Once I start to drive even going striaght after maybe half a block the awd light comes on and stays on. And the fuse is still good. Now if I have to make a turn right after start up that's when I will get the binding popping somethings not right noise. Even more so if I have to make a right turn vs a left. Also in that turn I have to give er more gas to get er to go. Until the awd gives up trying and the awd light comes on and disables the front. So it's one of the 3 things or combination. A The 2nd encoder is also bad since I am putting in used ones not enough money for a new one right now. B the tc is toast. C something is going wrong with the front diff under load. Which I don't think it is because if I have all tires off ground I can freely move both tires while holding the the input from the tc. This is while the front drive shaft off. Or any combination of holding tire or input. No noises and grinding noticed. Also I forgot to mention that I can start and put the van into drive with van still off ground with everything put back together and I do not get the awd light to come on. It's only while the van is driving and under load do I get the problem. This leads to just give up on this setup since I don't want to have to tc rebuilt. I've also got a 95 awd astro that runs like poop but the drive train other than transmission is in perfect working order. I remember someone on here swapping out the tc from an older van to a new one that has the 136gm like I do. He made a nice pictorial and what all he had to modify to get it work. I'd much rather have to viscous still tc over the computer controlled anyday anyways. I haven't been under the 95 in awhile I need to check to be sure. But he stated that year of tranny had only 4 bolts instead of the 6 that the newer 4l60e has on the tail. Like I said I need to check but I think that my 95 has 6. This might be because its the transition year but I don't know. And the only other difference is the rear u joints are bigger on the older vs the newer years. Any thoughts to either the the problem on my 136gm or swapping to older tc outta my 95?

So if I'm reading you correctly Mojo, when the AWD light comes on and "gives up", the popping goes away? Some things that cause the AWD light to come on are bad TCCM, bad speed sensor, faulty or corroded wiring connections. There are 3 speed sensors on your TC. One for the speedometer and two for input and output shaft speeds. If one of the input/output sensors is not putting out the proper signal to the TCCM, it could be telling the encoder motor to apply front bias when it shouldn't be, or too much bias. I'd check all connectors for sound connections, (especially if you live in an environment with salted roads). Check the sensors for open or shorted readings. Also, and this is not intended to offend, all 4 tires are the same size?

racrx7- good call on tire size. Make sure that not only are the sizes printed on the sidewall the same, you need to make sure your tire pressure is the same all around. Also jack up one corner at a time and measure tire circumference. Any marked difference will show up as difference in wheel speed-cause encoder to kick in and the wheel speed difference will end up as binding in your tc.
Also jack both fronts or both rears off the ground making sure you're well chocked and rotate either driveshaft by hand. You will turn one and watch the other. If they both move within a couple of degrees of each other that's good. If not your chain is stretched and could be your popping sound

Thanks for the reply guys. The tires are just a few months old and are equal in tread. Haven't been on long enough to even rotate yet. Been reading these forums quite a bit lately since this is the best resourse for astro vans. But while I had it up I did rotate the driveshafts and watched for rotatio and all seemed good there. When I put in drive and let it idle off the ground one tire and in the back and one in the front seemed to be spinning at the same speed but it's hard to tell when their going that fast. I thought about the 2 speed sensors on the tc that go to the tccm but haven't thought of a good way to test it yet. So far all that I can think of is either getting all 4 tires back off ground and tapping the 2 wires to each and checking with a multimeter to see what the output voltage is at. Or I thought of tapping the wires at the tccm also but it looks like that thing is buried deep behind the parking brake and I'd have to remove that just to put a hand on it. I wish I could just look at a repair manual for wire color but neither books I have even mention the awd in them. Chiltons or Hanes. If I haven't just somehow came up with a 1000 bucks for a rebuilt tranny I'd have enough money to just replace all the sensors on the tc. The 2 for the tccm and the one for the abs. I've read that the abs one doesn't effect the awd since the tccm is a stand alone from the car ecu.

Here's the sensor circuits.


You can access the wires from the TCCM at the base of the kick panel where they go into the black wire run that is located under the sil plate. The sensor wires are easy to spot as they are twisted together in the harness.

Wow thanks. I'm going to probe the wires up there and then go for drive to see what I get.