Hello everyone!

My brother and I both went into the mountains a few days ago (he only came to get me unstuck lol) to get some firewood. He and I both have 99 Ram 2500’s 4x4’s, with the only difference is he has a manual trans and a long box. We came down the mountain and took our trucks out of 4x4 into 2WD, Some reason or another I noticed my front driveshaft spinning when moving in 2WD. I asked to look at his, and his front driveshaft was not spinning in 2WD. I don’t think my front driveshaft should be spinning at all in 2WD, so I drove back home slow.

Like all 2nd gen 4x4’s, the vacuum axle disconnect should disconnect the passenger side axle shaft, resulting in the drivers side axle shaft being the only thing “attached” to the differential. With only one side moving it should result in the spider gear walking around itself and not moving the ring gear = no driveshaft movement? The transfer case is not connected to the front driveshaft in 2WD, so no movement there either. So my guess is the front driveshaft shouldn’t be moving at all In 2WD.

That leaves me with what’s wrong with my truck? The vacuum actuator is sticking? I just replaced it this summer.. or maybe transfer case linkage got messed up... let me know what y’all think, thanks!

 

See if you can turn the shaft by hand. Truck in park, t-case in 2wd.

Does the 4x4 light go out when you take it out of four wheel drive?

 

Basically right, I'd jack up the right front tire off the ground and try to spin the front driveshaft by hand. If it doesn't spin (transmission in park) it's the transfer case not shifting out of 4wd. If the driveshaft and the right front spin the disconnect didn't unlock. Note that the vacuum is needed to move the disconnect into either position so likely a leak in one of two lines or the switch at the TC itself.

 

Hey You, Glad to see you’re still on this site after many years, props to you!

With the truck sitting in my driveway right now in 2WD and park the front driveshaft won’t move. When I move my 4x4 shifter lever into 2WD the light does go out. With that in mind, the shift fork should be moving over enough to disengage the axle, but maybe not. It might just be moving over enough to make the switch open and the light go out.

 

I will give this a shot!

 

Alright here’s where I’m at, I cannot move the driveshaft when truck is on the ground in park and 2WD. I even rolled the truck backwards in neutral and it was still moving, making me again think that the axles are still engaged. I got my vacuum gauge out and the red line had 17 in/hg when in 2WD. I put it in 4H and the black line had 21 in/hg.

I had replaced it this summer with the cheapest one I could find on Rockauto (why the red line isn’t completely fitting on the nipple), maybe it’s sticking. I’ll have to pull the cover off I suppose to find out. The transfer case felt good In all positions too.

 

Also raised the truck and spun the front tire.. front driveshaft spins. Meaning the actuator is stuck.

 

Vacuum looks ok, very possible it is sticking. Did you add some gear lube to the housing as mentioned in the FSM ?

 

I did not, I figured I’d would get gear lube over time. I’ll pull the cover tonight or tomorrow and see what’s going on and lube it while I’m there.

 

When you have the cover off remove the switch and add 5oz into the hole.