and does anyone know where to get the input shaft seal and the vacuum switch? or their part numbers? i just went to autozone and they couldnt find anything that had to do with those things

 

I don't know about the gasket but the 4wd switch is on sale on Amazon.com. Listed as ACDelco D1754C Inlet Air Valve Thermal Actuator for under $29 and free shipping. Don't worry about the title of the switch it has nothing to do with a thermal switch, it is the correct one. I replaced my switch with a Dorman in September and it started leaking vacuum in Feb. This vacuum leak caused my floor heat and defrost not to work so I had to get a replacement ASAP so I got another Dorman switch. I then found the ACDelco on Amazon and have it standing by for when the Dorman breaks again or the weather gets warmer.
Buy the ACDelco part!

I am so tired of having to work on my 99 Jimmy every couple of weeks, two weeks ago my defrost/heat vent quit again and I thought it was the Dorman switch, so I checked it with my trusty hand vacuum/brake bleader pump and found out the bad news was that the Dorman switch was still good, but I had a vacuum leak in my heating lines. It turned out to be a bad vacuum actuator that controlled my vent doors. What a pain, and a lot of lost blood.

 

so your saying you switched the vacuum switch on the transfer case and it was just a bit different from the old one?

i only ask because i just changed my input shaft seal along with the vacuum switch. before i did this i had 4x4 but now i magically dont... i did have transmission fluid in my lines i tried sucking out with a shop vac before i put the transfer case back in. could this have damaged the lines maybe? i am thinking about just taking out and replacing all my vacuum lines. if this would even help at all.

 

We just worked on a 96 that had vacuum to everything, but I could tell the actuator under the battery was only sucked in about 95% of the way. I disconnected the cable and it was hard to pull, tried oiling it and it was a little easier to pull, and I could pull hard enough to get everything engaged. We put the cable back on and it still wouldn't engage. Turned out to be a bad cable towards the bottom. Replaced the cable and the 4wd worked.

I also had no heat going to the floor and defrosters on my 99. There are two vacuum actuators that operate the doors in the heating ducts. You can see them move when you operate the heating controls. The top one with a yellow and brown vacuum lines was the bad one. I managed to get a hand vacuum/break bleader pump on the unit and it would not hold a vacuum.

Replacing it was a bear. You don't have to pull the dash as some people write. Pull the bottom panel, and remove the light socket. Then remove the panel below the steering wheel, 4 screws I think. I could not get the handle for the parking brake off so I got a piece of string and tied it up out of the way to the steering wheel. Next remove the steering wheel knee plate, 4 #10's deep socket. My book said to remove the brace next to it, but it was looked to hard to do.

The new actuator comes with a new white spring loaded clip that fastens to the heater door arm. Study the old one to see where and how the old one's spring is loacted at. Also look at the new one and you can see how it clips on the the door's arm. It takes a really small screw driver to push it the clip out of the way so it can be slid off. Not having a 90 dregee small screw driver I found something in my tool box that was the diameter of a 12 guage wire, but was strong steel, and sharpened it to a point and it fit into the old white clip and I was able to get the clip out. Then grasp onto the old actuator and pull hard towards the steering column. It is hard to pull, but it only clips in to it's bracket, no screws. After you get it out you can then remove the vacuum lines.

I put the white controller on the new actuator and lubed it with some vaseline on the pivit point, then the vacuum lines, slid the new actuator in it's slot and replaced the white part onto the door arm. This was hard to get done because you have to get it set up right and get the spring in the correct spot. You might try installing the white clip on first, then the actuator and then clip the actuator and white clip together.

Prepare to bleed. Due to the close quarters the back of my hand was a scratched up mess from when I was checking it out. Before repairing it, TSC and other places that sell work gloves carry a pair of thin gloves with a plastic coating on the palms and front of the fingers so you can grip things, what you are working on is too small to use the gloves, so I cut off half of the thumb anf first two fingers of the gloves. I could now grasp the small items and no cuts on the back of my hand!

 

Litterbug, To specifically answer your question, the switches were the same, just the wall thickness was smaller on the caps of the new switches causing a small vacuum leak using my old vacuum cap on them. I talked to a machanic who has replaced many of these switches and said he has never had this problem. I doubt he ever checked for a vacumm leak after installation. He only uses ACDelco, which I could pull a vacuum on, but slowly lost it so it would have worked. The dormans thickness was much smaller and they would leak enough vacuum that they would not engage the 4wd. That is why I cut out the cap that goes to the switch and ran my lines directly to the top of the switch.

 

okay. thanks for the help. i might try doing this to see if i can get it to work. seems simple enough. do you know if it matters which line goes to which hole? i assume it does since one line is thicker than the rest.

 

If you determine the 4wd switch's cap won't hold a vacuum and you have to bypass the cap look at the top of the 4wd switch. You will see a guide pin which is there to make sure the cap goes on correctly. Hold the 4wd switch so the pin is at 6 o'clock. The input line at the right, or 4:30 is the vacuum line, the one to the left or 7:30 is the vent and the one at 12:00 goes to the actuator. I actially made a drawing of this on the front of my shop manual. The vacuum lines are 3/16 or 5/32 and the vent is 1/4 inch. I can't remember if there was enough room to get the 1/4" line on the switch with the other two on or not. I may have used the smaller line and used a 3/16 to 1/4 adapter/connector to get all three lines on the switch.

I spliced all three lines together on the passenger side of the tranny, then fed the lines over the trannny to the switch. I left the lines a little long so I had plenty to work with on the switch. I marked both vacuum lines with different collored tape so I new which was which when hooking them up. No need to mark the vent line since no tape = vent line.

You might want to wear a thin glove with the fingers cut out of the glove to work above the transfer case. I got pretty cut up on the back of my hand working up there.

 

yeah. my hand is pretty chopped up from taking the transfer case out. and i got my 4x4 working yesterday. i just took out the little rubber adapter and slid the lines directly on the switch. it sounded like there was a leak by the switch and i thought it might have been the adapter since it slides on and off easy unlike the original. and i also had trouble getting the actuator grabbing onto the cable to pull the axle into gear. i ended up using one of my body clips off my T-MAXX and it holds very firm. thanks for all your help!!!

 

i found the source of my no 4x4. i traced it to not having enough vacuum so i put the old vacuum switch back on the transfer case and it works like a charm again. i think the new one is updated and doesnt allow enough vacuum to go through