Hey all, i've been navigating on this page for a while, but finally registered as I couldn't find a solution to my problem. Here we go:

I have a 2000 Z-71, 5.3 1500 with the electronic 4x4 switch, with about 125,000 on it. The transmission was completely rebuilt about 2 years ago after it gave out. The truck has been throwing the "Service 4 wheel drive" light for a while. Today it was confirmed that it was the b2725 code indicating that it's a bad switch, which through reading here, i need to either replace it, or check the connections.

What lead me to post this is this: Yesterday, when i was heading down the interstate, i was going around 75mph, when all the sudden my speedo started going nuts. It was bouncing between 70 and 80mph. When i slowed to what i think was around 70, it bounced around 65 to 75. As all this was going on, the E-brake light was fading on and off. I figured I would give it a little throttle to see if something if the speedo would follow, and as I put it down, the engine revved up as if it was going to shift down, but didn't do anything, and acted almost like the governor kicked in. So i did it again, and it down shifted fine.

As I got closer to my exit, which luckily was only a couple of miles away when this all started, i slowed on the on ramp, and at around 55, the speedo remembered what it's job was and went back to normal. The E-brake light also turned off. I called the original transmision guy that rebuilt it, and he said he had no doubt that it was a problem in my transfer case, and that it was probably low on fluid. Well i figured I would check the level at a local mechanics shop, and the level was fine, and the color was good too. A transmission guy took a glance and grab at it and said he thinks it may be my drive shaft coming away from the transfer case due to a bad transfer case output shaft bushing, there by not allowing one of the speed sensor to get a good read on how fast it was spinning. He recommended i drop the shaft and look inside at the bushing to see what kind of shape it was in.

After this, they did a scan and found the B2725 code, to which i was able to get my hands on another switch.

OK, anyone have any opinion, or experience with this? I'm with everyone else in the country right now, and am trying to avoid a full on transfer case rebuild at all cost to save money for all the other bills in my life. All help and information would be greatly apreciated. Thanks everyone, and keep up this helpful site.

 

Well those are all good suggestions.....but why not do the thing that makes the most sense. check the connections on the speed sensor and also pull the sensor and check for any metal stuck to it (its magnetic)...this will send you in the right direction and your next step.

 

I plan to do that this weekend, as well as remove the drive shaft to get a look at that T-case output bushing. I've been driving it still since it's my only ride, with no noise, or grinding or anything. I have to keep it right at 70, cause as soon as it hits the sweet spot of 75, the needle start's dancing, and the down shift is goofed up. If i get it back down to around 65 or so, the speedo needle comes back and everything is back to normal. Overdrive seems to work fine too in it. Thanks for posting.