4WD Doesn't Work: Need Advice Please
 

Hi Folks,

I have a 1997 Dodge RAM 1500 Laramie SLT. There is a 4WD shifter on the floor, but it has never worked. When I bought the truck the owner said it stopped working at some point and he never got it fixed.

I haven't taken it to a mechanic to have it estimated yet, because I'm leery of mechanics. This is the first truck I've owned and it's been years since I worked on any vehicle, so I thought first I would ask here if anyone would have any advice or suggestions on what to check/look for so I could possibly find out why it's not working myself.

If you need additional info just ask me and I'll try to get it.

Thanks.

High probability that the vacuum for the CAD system is not working properly as one place to start.

See this link to see how it all works and to diagnose for starters.

http://dodgeram.org/tech/repair/4X4/4x4_engagment.htm

It's mostly a visual check of the small vac lines that go from the engine bay down to the transfer case and to the front axle.

Does the lever move? If it does, then is it very easy or very hard?

Hi Whit. Thanks for the reply. I'll check that link out. The shifter does move, but I'm hesitant to move it again since the last time I did the truck wouldn't start.

just make sure you move it with the truck on and runnin but with it in nuetral, and when you do it, dont stop the xfer case in nuetral i know it says it has one, but you dont wanna do it trust me. just one solid fluid motion forward or back to get you into the 4wd setting you want.

the CAD has 2 vac lines, one should have vacuum when in 2wd, and then when you shift it all into 4wd, it should swap vacuum to the other line. if it doesnt do this then you know its the vacuum. easy place to start, and 90% of the time its that. just unhook the 2 lines at the CAD and put ur finger on them and feel for it. sometimes they break and crack, or get clogged. you can clean them and cut off the bad section and splice in a piece of hose or what not to get it going again.

3 separate pieces to troubleshoot and verify operation.
transfer case must shift (floor shifter). it has 4 stops. 4hi, 2 hi, neutral, 4 low. if the shifter doesn't work right, look underneath and find the lever on the t-case and move it manually. front output shaft should turn with the engine when engaged in any gear except neutral. as long as the tcase is not banging and grinding, its probably ok.

next check that you actually have a front drive shaft. sometimes it'll get removed when something major goes wrong.

the last piece is the troublesome CAD (central axle disconnect). 99% of the time the problem with it is either a broke or missing 50 cent vacuum hose, or a sticky/rusty shaft inside the cad. don't pay a lot of money for a new cad. you can almost always fix the old one, or better - buy a posilok from Alloy.

Thanks for the great information guys. I'm studying that link that Whit gave me so I can familiarize myself with how this thing works. Today I'm going to climb under the truck and start checking this stuff out that you've all told me about. I'm sure with this 4WD the old boy has a few rusty parts down there. Heck, I know I do :)

Do you guys know where I can find an actual schematic of the 4WD for my truck? I figure if I have something visual to look at, then it will make it easier for me to find these things.

Thanks again :)

I started the truck, put it in Neutral and then pulled the shifter back to 4H. It pulled back into 4H easily enough although I had to do it a few times before it went all the way back. I assume this is because it hasn't been moved in a while. There was no noticeable sounds or changes in the way the truck was running. Once I had moved it a few times it became easier to shift into 4H.

Vaughn said to move the shifter through all the settings, but you are saying I shouldn't do that? I assume that's what you meant when you said "dont stop the xfer case in nuetral i know it says it has one, but you dont wanna do it trust me."

I bought my truck in 2006 and the 4wd didn't work then 6 months later the tranny quit and i was gonna fix it then and we split the t-case in half and it was in pieces inside so i threw it in the scrap pile and got another one !

With the engine running, if you put the t-case in neutral, it tends to grind badly when you try and hit any other gear. Even with the trans in neutral. If you want four low, shift quickly from four hi, to low, don't even pause in neutral... otherwise, you will have to shut off the engine to get it back into whatever gear.