Quadra-trac won't engage

jay79cj7 · #1 (**permalink**) 07-20-2003, 08:00 PM

I have a 79 CJ7 with the infamous quadratrac transfer case. The previous owner didn't like the full time 4wd and put in one of those part time kits. Now it won't engage for me, and I am stuck in 2wd. I have checked the vacuum lines and switch, and they are working fine. I think that the vacuum actuator on the case might be defective. I have done some looking around and heard that they go bad... Does anyone have any experience here? Anywhere to find good diagrams/instructions for working on this case? How hard is it to swap this vacuum thing out? From a first glance, I can't tell how difficult it will be to get it out and back in. Is there a mechanical replacement for this vacuum switch? These things are expensive, and apparently prone to failure...

I have some other mechanical problems that prevents me from going off-road right now anyway, but it really irritates me to know that my Jeep doesn't have 4wd! Gotta fix that pronto for pride's sake. Please help![addsig]

exjay33 · #2 (**permalink**) 07-20-2003, 08:00 PM

They are chain driven maybe chain broke.[addsig]

mandarrin · #3 (**permalink**) 07-20-2003, 08:00 PM

ok if you are sure is your vacum lines then this is what you need to do:i went to tricksfortrucks.com and found a really need way to hook the vacum lines directly to the from axel. the only thing i did different was that i didn't put an on and off swict,but that work for my 89 fuelinjected wrangler i don't know if it would work for yours.check out that web page to see if you can get any ideas.

it worked for me :-D [addsig]

Bounty__Hunter · #4 (**permalink**) 07-20-2003, 08:00 PM

His CJ has no vacuum needs at the front axle, it's only at the transfer case on a Quadratrac.

Is the vacuum switch at the transfer case have sides you can get a wrench on? Like it's removable?[addsig]

jay79cj7 · #5 (**permalink**) 07-20-2003, 08:00 PM

I don't think it's the chain because the rear wheels still drive, and the picture I am looking at in my Haynes book looks like the one chain should drive both wheels. I am being optimistic that it is the vacuum system because if it's not that, it is probably the differential between the two axles.

I haven't found out how the vacuum actuator is attached yet. It's at a tricky angle to see, and I couldn't really tell how the thing is attached so I figured I would cheat and ask you fellas. Anybody know?

I could take the thing apart and try to figure it out, but that probably means some long down time that I am not prepared for.

Take it easy, and thanks.[addsig]

Bounty__Hunter · #6 (**permalink**) 07-20-2003, 08:00 PM

One of the more common things to go bad in a Quadratrac case is the viscous coupling, it's the differential type thingy in the transfer case that allows you to run 4wd on dry pavement, allowing varying speeds between the front and rear axles. Don't know how you'd confirm this, I'm not a CJ techie :-( [addsig]