Quadratrac Vacuum Routing - PO Hack Job

[RPO]

Hey guys!

Recently started digging into a '79 Cherokee that I purchased and it looks like the previous owner removed the E-Drive switch in the glove compartment and replaced it with a T-Fitting that connects all 3 of the vacuum hoses together. This is my first foray into Jeeps and the Quadratrac system as a whole so my knowledge is next to none on the topic. That being said, I can't imagine both ports of the E-Drive receiving engine vacuum at the same time is good? Until I get a proper switch replacement, can I just connect the "Normal Operation" vacuum line directly to the "Engine Vacuum" line and leave the "Emergency Operation" line uncapped? Or will that E-Drive line need to be capped off? Or is this T-Fitting setup somehow ok?

Thanks for any insight y'all can offer!

[Holland Waggy]

When the QT is in normal operation, you could leave the vacuum hoses off. The switch membrane doesn't need a constant vacuum once it's in position. But that's my humble opinion. Be sure your Emergency Drive- warning light works though, so you know when it's engaged or not.

With a T-fitting the switch should be somewhere in the middle, which should give a rattle from the clutchring, resulting in serious damage. If you are sure that you warning light works, you could try to put one vacuumline at a time direct to the manifold vacuum and see whether it shifts in and out to ED and vice versa. So then you know which line to use for normal operation, and be really sure the clutch ring is fully engaged. The vacuum membrane needs to be in a proper working order offcourse!


Gilbert

[fulsizjeep]

Welcome to the QT world... That T fitting is a klooge. Holland Waggy is right.

[RPO]

I have zero confidence that the E-Drive indicator light is functional. Guess first order of business is to test that then see if I can verify which vacuum hose is for normal operation and which is for emergency function. Thanks guys!

Sidenote: where on the dash is the e-drive indicator located? Is it just in the general dash cluster?

[Holland Waggy]

The indicator light is inside the speedometer, on the right side of the dial

[RPO]

Soooo...I finally had a chance to dig around and see what I could figure out with the vacuum routing. Turns out that NONE of the hoses coming into the cab and ending in the T-fitting are attached to anything. Poked my head under the hood and the source hose is just laid off to the side by the driver side fenderwell. Visually identified the other 2 hoses from the T-fitting coming out of the firewall and saw them routed back towards the undercarriage. Crawled underneath and apparently neither of the hoses are attached to the diaphragm, it's just chillin there.

Guess I'll use this as a good time to run all new hoses from the diaphragm to the dash and engine bay. In the meantime, what is the best way to determine if I'm currently in E-Drive if I can't trust that the dummy light on the dash is operable? Or can I just run temporary vacuum to the "release" side and assume that it's in normal operation?

[fulsizjeep]

Assume Nothing. A hand held vacuum pump is very handy in tracking down vacuum leaks that are beyond the obvious.


https://www.walmart.com/ip/HAND-VACUUM- ... qDEALw_wcB

There is no reason to replace all the hoses yet if the shift diaphragm on the QT is leaking. Check that first. There should also be metal vacuum lines that run from transfer case to the firewall. If they are missing, you can run it all with rubber hose but I have had limited success with it. The longer distance of rubber hose tends to collapse under vacuum after a while. It also sounds like you need the vacuum switch that is normally found in the glove box.

[RPO]

Yeah, the glove box switch is long gone. Previous owner pulled the glove box completely out and installed the MSD ignition box in its place. Looks like BJ's has a knob type replacement...any feedback on its usefulness?

Sidenote: Vacuum pump arrived in the mail today...stay tuned!