Engine/Transmission (1994 - 1998) 4WD Won't Engage

[Sasquatch]

Last night a neighbor asked for help pulling his Ford out of a muddy ravine. So, my winch-equipped Ram was pressed into service. I got the truck halfway down the hillside, and felt the rear end breaking loose and swinging around; now the cab was pointed uphill, and the rear-end was calling the shots. Only then did I realize I didn't have 4WD. The Ram ended up in the ravine, stuck alongside the Ford.



After much inventive winching, I managed to get the Ram back up the hill, made it fast to a big oak tree, and finally pulled the Ford out, sideways.



This morning I traced the vacuum lines under the truck to where they connect with the axle, and everything seems to be okay. I have no way to test for vacuum, so I've just looked for disconnected or damaged lines. I've also checked the shifter linkage at the transfer case and it looks fine.



When I shift into either 4WD H or L, the dash light won't illuminate, and no power is being delivered to the front wheels. I suspect it's a vaccum-related problem, but don't know where to look under the hood to identify the correct line, or see if it's been damaged, kinked, melted-through, or whatever, someplace in the engine comparment. There is a vacuum "T" on the firewall, and I've traced the vacuum hoses which lead there to the servo for the cruise and the HVAC system. They seem to be just fine.



Can anybody tell me where to look to make sure that there isn't a vacuum hose disconnected (the axle control) for the 4x4? I don't have any idea where it should be.



Thanks Much.

 

[Joe G.]

The vacuum for the 4X4 axle connection is from a plug on top of the transfer case. It has four tubes. Two of the tubes go to the front axle. They go to some steel tubes on the transmission mount cross member. The steel tubes go to the front axle where some rubber tubes make the connection. If there is no break in the connections you want to make sure the four tube connection block on top of the t-case is on correctly. It's hard to do, but possible to get it on wrong.

 

[Sasquatch]

Thanks, Joe.



As far as I can tell, everything (vacuum hoses) under the truck is okay. What I'm perplexed by is where to look under the hood to see where the hose(s) that provide vacuum to the transfer case/axel are made up at.



I think there may be a loose or damaged hose in the engine comparment that feeds those hoses you referred to in your response, but don't know where to look.



Thanks.

 

[Joe G.]

My service manual doesn't say where the hoses go so you just have to start with the hose on the side of the vacuum pump and see where it goes.



You might check to see if the shift linkage is really adjusted correctly. The vacuum switch will not affect what gear the transfer case is in. It only affects the front axle. So if you have the front jacked up you should be able to turn the drive shaft by hand easily when it is in 2 HI. In 4HI you should not be able to turn the drive shaft. Also if you are in 4LO the truck will go ok, but it sure will be low geared. The shift adjust is pretty finicky so it may be off a little.

 

[Sasquatch]

Joe:



I think the problem is that the front axle won't engage. The transfer case shifing feels "normal," and I can tell that it's going into LO and HI ranges normally. I have also traced the vacuum lines back from the pump to the top of the transfer case, and can find no obvious signs of damage or leaks.



I think whatever the problem is is related to the "gizmo" that sits on top of the axle that the vacuum lines lead into. I think it may need to be replaced, because the axle isn't engaging.





Looks like it's a trip to the dealership, next.

 

[Joe G.]

You probably should make some tests. The valve in the T-case could be the problem. Apply some vacuum to the shifter on the axle and see what happens. I don't know which connection is the apply so you will need to try both of them.

 

[illflem]

The gizmo (actuator) is very simple. Just remove it and have someone shift between 2 and 4wd with the engine running and see if it moves. There is a diaphragm in the actuator that could be shot. I replaced one about six years ago, around $35 from the dealer, I was surprised it was so cheap.

 

[pathaymond]

For what ever its worth

My 98 had the same problem ,it was after I had changed the fuel filter and cleaned the strainer. Much to my surprise I found the vacumn line that makes things work. It had become removed from its connection point in my shuffle with the filter and strainer. You may give a quick look in that area for your culprit. It wasnt much fun for me to have to allow a chevy to pull me from my stuck position. So I am more cautious about what I wrestle loose when doing the filter shuffle. Hope you find it to be as simple a solution as I encountered.