vacuum lines to transfer case

I just got my first 4x4, an 86 XJ 4dr w/ 2.8 auto. The vacuum lines to the switch and transfer case are burned on the exhaust manifold, so it won't switch into 4x4, sshould I just replace the vacuum lines or is there a mechanical way to switch this eliminating these vacuum lines?


Paul Miley

I've heard of homebrewed mechanical systems, but they seem like more trouble than their worth.
You also have a vac-operated disconnect (the 'vac-disco') on the front axle (the lump on the passenger side) that is connected to that same system, so that would need to be changed to mechanical, also.

Just cut the existing lines clean, and splice them together with rubber vacuum hose from Checker/AZ/PB of the proper inside diameter. Then, use some plastic zip-ties to secure them away from the hot stuff.

vac lines

I had the same problem,got to nosin around under the hood,noticed 2 or three of the lines were broken(CHEAP PLASTIC)
Spliced w/fuel line hose.
Here is some advice,check all vacumn lines especially the one coming from the canister behind the front bumper.Due to time and bouncin around these pos plastic lines can rub against the body n leaks will show up.
Went through mine completely found 2 or 3 that needed to be fixed.
Vacumn leaks can also cause crappy fuel economy.

Thanks for the help guys, I am going to replace several vacuum lines and check out the rest.

Paul Miley

A couple of contrary opinions:

1. The original lines were/are plastic, but it's not cheap/chinzy. It's a specially formulated high density polyethylene that is highly-resistant to the oil, brake fluid, fuel, water, slat and heat of an engine compartment and underbody. It won't survive direct contact with a hot exhaust manifold, but it will survive 18 years (mine) of generally nasty exposure.
This same material is used in virtually ALL vehicles to this day for vacuum lines.
It doesn't kink like rubber vac hose, resists minor impacts that would crush a small alum or stainless tube, and it has small internal diameter (which is actually most desirable in a vac line).
2. If replacing it, you really want to use either the same plastic line, or rubber VACUUM line, but not fuel line.
Fuel line is very durable, but it's meant to carry pressure and is rarely found in anything less than 5/16. It's stiff, and can easily kink shut if bent too tightly.
Because of fuel line's greater cross sectional area (5/16 vz 1/8-3/16 for vac line), every time a control is changed there is 2-3 times as much air to be withdrawn from the tube before the respective device is actuated.
Fuel line is OK for a short splice, but anything longer results in slow response of the control/device, and can easily kink shut at tight bends.

-Rick