Torque On Demand 4x4 trouble

[paul_smith_347]

So I finally had some time today to check out the underside of the expy today and do some diagnosis. After pulling the shift motor off the T-case, I started the expy and moved my selector switch to 4HI. I wheeled under it again and saw that the motor had not moved a bit. The motor case is completely covered in deep rust, so I'm assuming the motor is siezed.... easy fix. Then I put everything back together and put the rear on jack stands to check the Torque on Demand system. With the rear on jack stands, I put the expy in 1st. The wheels spun around about 1 time or so and stopped. I figured the TOD had engaged. I eased on the gas and felt it get a load. Just and the truck started to go foward, there was a heavy "cluck" in the driveline and all load was gone off the motor. I repeated this two more times and the same thing each time. So then I put her back on the ground. I went to a gravel road and did a break torque to see if the sytem would engage...... Nothing with the rear wheels on the ground and spinning... No TOD engaging, no clunks, just spinning rear tires..... Anyone know whats going on with that? Possible the vaccum actuator not engauging the hubs all the way or what do I need to check next? I have a feeling a new shift motor and Brown wire mod are in my future...... Any help is greatly appreciated.. LOL if that wasn't enough trouble for one day, I noticed that my rear upper and lower trailing arms have several spots where they are rusted ALL the way through. I have a feeling a lift and tires are gunna have to wait untill all this stuff is repaired. Also, my factory tow package has 355's instead of 373... been a dissapointing afternoon.....

 

[toms89]

So I finally had some time today to check out the underside of the expy today and do some diagnosis. After pulling the shift motor off the T-case, I started the expy and moved my selector switch to 4HI. I wheeled under it again and saw that the motor had not moved a bit. The motor case is completely covered in deep rust, so I'm assuming the motor is siezed.... easy fix. Then I put everything back together and put the rear on jack stands to check the Torque on Demand system. With the rear on jack stands, I put the expy in 1st. The wheels spun around about 1 time or so and stopped. I figured the TOD had engaged. I eased on the gas and felt it get a load. Just and the truck started to go foward, there was a heavy "cluck" in the driveline and all load was gone off the motor. I repeated this two more times and the same thing each time. So then I put her back on the ground. I went to a gravel road and did a break torque to see if the sytem would engage...... Nothing with the rear wheels on the ground and spinning... No TOD engaging, no clunks, just spinning rear tires..... Anyone know whats going on with that? Possible the vaccum actuator not engauging the hubs all the way or what do I need to check next? I have a feeling a new shift motor and Brown wire mod are in my future...... Any help is greatly appreciated.. LOL if that wasn't enough trouble for one day, I noticed that my rear upper and lower trailing arms have several spots where they are rusted ALL the way through. I have a feeling a lift and tires are gunna have to wait untill all this stuff is repaired. Also, my factory tow package has 355's instead of 373... been a dissapointing afternoon.....

I believe the 99's are like the 2000 expys. No center axle disconnect or IWE's. They also have no 2wd setting.

What does it do in 4hi on the gravel road? If no 4 hi then clutch in transfer case is likely not engaging and auto 4wd will not work either. Think the shift motor you are looking at is for 4 low or to shift between the two but not engage the clutch. At a minimum if the clutch and transfer case were working the front driveshaft would be spinning.

 

[toms89]

Try putting vehicle in neutral and then 4 low to see if the shift motor moved. Should hear a solid clunk. If so the shift motor works...but still will have no 4wd if clutch not engaging. Be a really nice low gear for 2 wheeling though..!?

 

[paul_smith_347]

Try putting vehicle in neutral and then 4 low to see if the shift motor moved. Should hear a solid clunk. If so the shift motor works...but still will have no 4wd if clutch not engaging. Be a really nice low gear for 2 wheeling though..!?

My next step is to put it back on jack stands and have someone work the switch and apply throttle. It sounds like you might be onto something with the clutch not engaging. That might explain why it wanted to start pulling the truck foward with the rear tires off the ground, clutch would slip and all the load would be gone......but front shaft had to be spinning somewhat to start pulling it foward.

While it was on the stands last time I tried switching into 4HI and 4LO. Neither position caused the shift motor to move. I have tested the switch, it OHMs out correct. The shift motor looked like it had been sitting in salt water since it was new from the factory.....Deep heavy rust covering the whole motor segment of it..... Im almost sure that the armature is siezed to the windings inside.

On the gravel road when I put it in 4HI it did nothing. No dash lights to indicate 4x4, and spun the rear wheels while on break. No clunks or bangs while spinning either.

 

[toms89]

My next step is to put it back on jack stands and have someone work the switch and apply throttle. It sounds like you might be onto something with the clutch not engaging. That might explain why it wanted to start pulling the truck foward with the rear tires off the ground, clutch would slip and all the load would be gone......but front shaft had to be spinning somewhat to start pulling it foward.

While it was on the stands last time I tried switching into 4HI and 4LO. Neither position caused the shift motor to move. I have tested the switch, it OHMs out correct. The shift motor looked like it had been sitting in salt water since it was new from the factory.....Deep heavy rust covering the whole motor segment of it..... Im almost sure that the armature is siezed to the windings inside.

On the gravel road when I put it in 4HI it did nothing. No dash lights to indicate 4x4, and spun the rear wheels while on break. No clunks or bangs while spinning either.

While in neutral?

Didnt realize you were testing it with rear up and front down!? If functioning properly it would pull it right off the jack stands!

My shift motor looks pathetic also... completely rusted on the outside but works fine.

 

[paul_smith_347]

While in neutral?

Didnt realize you were testing it with rear up and front down!? If functioning properly it would pull it right off the jack stands!

My shift motor looks pathetic also... completely rusted on the outside but works fine.

That was the plan, I figured I would know if TOD was working if I was able to pull off the jack stands (Rear tires only about and inch off ground so wasn't worried about pullin off of them). Yes the trans was in N with a stick holding break down. Really hoping its not the clutch in T-case.... That would mean a new one correct, or at least a rebuild kit?

 

[toms89]

That was the plan, I figured I would know if TOD was working if I was able to pull off the jack stands (Rear tires only about and inch off ground so wasn't worried about pullin off of them). Yes the trans was in N with a stick holding break down. Really hoping its not the clutch in T-case.... That would mean a new one correct, or at least a rebuild kit?

Could be a variety of reasons for it not to work. May not have power getting to it. Did you check the 4wd fuse in engine compartment fuse box? Pulling it would disable all 4wd functions.

 

[paul_smith_347]

Yes. Fuse 104 is in place and in good condition.