4x4 trouble

[FishFind]

Ok been doing a lot of work on this 1998 blazer

Yesterday I changed the tranny fluid and internal wire harness on the truck.
I had to lower the support a little for the transfer case to drop the pan.

I wanted to go for a test drive when I was done and all seemed well. I stopped for some gas after about 4 mile drive or so and when I started it back up it was stuck in 4lo.

Today I took a look and found that the actuator under the bat had a tear in it. I replaced that today and reconnected everything.

Now the thing is that if I turn the key to accessory I can get it to change two times and that is it. I can go from 2hi to 4hi. or 4lo to 4hi any combination works but if I try and push a third time I hear nothing. If I start the car I can not change it at all. Only when in accessory and not running.

What could this be?

Did I cause a wire to come loose when I lowered the transfer case a little?

Here are some things that I noticed. When to actuator was torn it leaked some liquid. That is how I noticed it. Second I checked the fluid level in the transfer case and it was well above the fill hole, about 2quarts over.

Third thing is that I k now the selector switch for the 4x4 is defective because the lights would not work before. If I squeezed the switch I could get the lights to go on and off but it always worked before I dropped the pan minus the lights. I could hear the 4x4 engage.

[old_master]

There is a vacuum switch on the transfer case, driver side, next to the front output shaft yoke. If it leaks, it will suck transfer case fluid into the vacuum lines for the front axle actuator and the HVAC system. In extreme cases, it will suck transmission fluid past the seals and into the transfer case causing the fluid level to rise, (check the transmission fluid, it's probably low). If/when this happens, the transmission and transfer case seals must be replaced. In either case, the fluid must be cleaned out of all of the lines. http://www.oreillyauto.com/site/c/de...eyword=600-500

[procaddytech]

The transfer case being 2 qts overfull indicates a leaking front transfer case seal allowing transmission fluid into the transfer case. Over time it will get way overfull and start leaking out of the vent hose. The transfer case must be removed to chage this seal.

[FishFind]

Can this be the cause of my P0740

[old_master]

Nope, P0740 is a problem with the torque converter clutch circuit.

[FishFind]

Can someone show me a pic or a link to a pic of the seals that I need.

[old_master]

As mentioned in post #2, the root cause is a leaking vacuum switch on the transfer case. After the switch is replaced, the transmission and transfer case seals might not need replacement, (they might seal up on their own). Check the vacuum lines at the switch for the presence of fluid. If fluid is sucked into the lines it will cause slow engagement/disengagement of the front axle. The vacuum system is shared with the HVAC system which can cause the blend doors to operate slowly, or not at all, if they become contaminated with fluid. The lines must be cleaned out, along with the axle actuator under the battery tray.

The switch is located on the left side of the transfer case, slightly above and inboard of the front output shaft. Most auto parts stores stock it. http://www.oreillyauto.com/site/c/de...eyword=600-500

[FishFind]

Yes I did replace the actuator and it did have fluid in it. I will grab a new vacuum switch today.

[old_master]

Pick up a couple cans of carb or brake cleaner and clean out all of the fluid in the vacuum lines and actuator. Replacing just the switch will fix the problem, but it may not eliminate the symptoms, (gotta get that fluid out of the lines).

Most of the auto parts stores stock this one: http://www.oreillyauto.com/site/c/de...&keyword=49315 It's made by the same company, exactly the same part with different packaging and price tag

[FishFind]

Ok changed it out and cleaned the lines out. They did have fluid in them.
I will give it some time and check the fluid level on it.

Onn thing that I did notice is when I go to 4lo it kinda bucks into 4lo at like 1,200-1,500 rpm and if I go below 5mph it will do it again when I step on the gas. Almost like it takes it out of 4lo every time I go belpw 4mph. Is that normal

[old_master]

Shifting in and out of 4WD LO should only be done when the vehicle is stopped, or barely moving. If your speedometer says you're moving, you're going too fast. The gear ratio in 4WD LO is exactly that, LOW, lots of power & torque, not designed for speed When accelerating, the transmission will shift into 3rd gear very quickly. The throttle is very "touchy" and the rule of thumb is "don't exceed 20mph in 4WD LO". Never operate the vehicle in 4WD HI or LO when on dry pavement: snow, ice, mud, sand, loose gravel etc, ONLY.

[FishFind]

Ok well checked it out today and it seems that the fluid is still getting in some how. what do I have to do now.
Also the front diff leaks fluid out too. I know it is different fluid but wherewould it be leaking from there also.

[old_master]

If you replaced the vacuum switch and are still finding transmission fluid in the lines, either the switch is no good or you didn't get all of the fluid out of the lines.

Front differential leak could be most anything, cover gasket, case seal, axle seal, pinion seal etc etc. Clean it off and drive it a bit, then look for the leak. There is a chemical dye you can add to the differential fluid and check for leaks a with a black light... shows up florescent green, can't miss it. Most auto parts stores carry it.

[FishFind]

cool I will clean it off and get some dye to see where it is getting out at. I didn't check the vac lines again I just took out the top fill screw on the transfer case and found 1qt-2qt of extra trans fluid.

[old_master]

Did you drain it down to the proper level after you replaced the vacuum switch?