4wd not working

[mtmer1]

I cannot get the 4wd to work on my '93 yj. I understand that it's vaccum controlled[and very prone to failure] and I see the two vaccum lines going into the diaphragm thing. Where do these lines run to? I see them going under the body, looks like towards the tcase or tranny. If I pull these lines off, air should be sucked into the lines if I engage the 4wd right? Is the diaphragm supposed to swivel back and forth a little bit? The 4wd light doesn't come on either but the guy I bought the jeep from said that after he replaced one of the front axle shafts the light quit coming on, but said the 4wd worked but I had no way to test it given the condition of the jeep when I bought it[all torn apart]. When I put it in 4wd the tcase is engaging so I know it's something in the front axle. Thanks for any help.

[rdnkjeeper]

I have seen many different things go wrong with the 4wd system. I have seen the "switch" on the transfercase stop working. I have also seen the lines get cut and melted. The only thing I have done with mine is break the forks that engage the front axle. I broke three forks, after that I rotated the fork and put a bolt through the housing to hold it engaged all the time. I have heard of people putting TJ shafts in to get rid of the fork and vaccum system, I put in a completely different axle!

Good Luck

[mtmer1]

Alright I have vaccum on both lines, one line has vaccum in 2wd and the other has vaccum in 4wd. However, there's still no 4wd. I'm thinking that maybe that diaphragm that the two lines run into is siezed up since the jeep sat for a long time. Could I just spray wd40 or PB blaster into it and give it a few taps with a rubber hammer?

[rdnkjeeper]

Why don't you pull it off the axle and see if it is moving or not? If it is moving I would bet you have a broken fork. My first one didn't look broken until I took it all apart.

[mtmer1]

I took it off and the collar that connects the shafts moves freely and the fork looks ok but it doesn't move. There's play in the fork but it doesn't move side to side, I think that's what its supposed to do right? How can I free it up. One of the wires is also broken but thats just for the 4wd light right? Also, since I've never messed with gear oil before I noticed it has kind of a "gritty" feel to it. I know with limited slip differentials they have friction modifiers that give it the gritty feel but the front end of the jeep is open so I'm not sure if thats just the way the fluid is or what. How strong does the vaccum need to be? Just the regular amount of suction that you get with any vehicle?

[rdnkjeeper]

Look inside where the fork goes, there should be a collar there....well if you move it towards the drivers side it should click the front axle in. The way I freed mine up was moving it with my hands.

Good luck

[mtmer1]

I got the 4wd working. The fork was stuck in place because the diaphragm was full of dirt. I pried on the fork with a pair of pliers until it started moving and then I just kept moving it back and forth by hand and dirt would get pumped out of the diaphragm. I'm probably going to get a new fork and a posi lok kit though since the fork is pretty loose and I don't trust the 13 year old vaccum lines. Winter is coming and I need this thing reliable to go to work on snowy days, now I can get out and do some wheelin too. On a side note, the guy that I bought it from told me it has a limited slip rear, it's a really aggressive one whatever it is. I can hang a tire in the air and still get power to the one on the ground. Found this out while testing 4wd A friend of mine has an eaton limited slip and sometimes can only get one wheel to spin. Thanks for the help.