2nd Gen Non-Engine/Transmission No 4 wheel drive

[Plow Man]

Having a problem with 4 wheel drive engaging. Truck is a 99 automatic 2500, Suspected it might be a vacuum problem , so I remove the vacuum block at the transmittion, put a vacuum pump on all lines and could hold a 25lbs vacuum on all lines except green line wich splits and returns to transmition so I pinched off return line but still no vacum ,I beleve this line is a vent line? also remove wires no front axle they seemed fine But don't know how they are supposed to work I don't have a manual can anyone help!!! PLEASE snow on way.

 

[Sticks]

Chase all your vacuum lines from the beginning in the engine compartment along the top back edge, down to the transfer case then up to the front axel. At least I think that is how the 99’s are. Try this website. It is directions on how to convert to 2wd low, but it explains how the OEM system operates and the location of the lines.

MikeR's 2wd low conversion

Hope this helps.



Sticks

 

[Herebytheowl]

You might also want to check your linkage on the transfer case. After about 30K, mine would not go into 4 high (4 low was not a problem) ended up being a linkage problem from the factory. Mechanic was surprized that it had ever worked.

 

[Big_Daddy_T]

I just spent 1200 on mine to get it working again. Many moons ago I powerbraked in 4-lo and It made a bad noise (not one of my brighter ideas). I suspect this is the cause of alot of my problems. The tcase works great still. I gotta say that with the miles and abuse. I certify the tcase as very durable.

 

[CFAR]

I assume you have a vacuum pump?

Hook it up to the vacuum motor on the front axle and then check your 4x4 light, should be on. There is a switch in the front axle to turn the light on and off.



If your light comes on the you either have a vacuum line problem or a vacuum switch problem. its not really that complicated if you crawl under there and look around.