So leute,
da ich ja auch dieses "kleine" problem mit meinem allrad habe und ich und Christian dabei nicht weitergekommen sind habe ich mich auch mal hier angemeldet: Bitte melden Sie sich an, um diesen Link zu sehen.
Habe denen mein Problem beschrieben und sie haben auch recht schnell darauf geantwortet. Der eine hat mich dann zu einem Beitrag geleitet wo die Funktionsweise der Underdruckdose sowie den Verlauf der Schläuche erklärt wird.
Ich finde dies sehr hilfreich. Auch weil er da schreibt wo schwachstellen sind die häufiger ihren Dienst versagen.
Jetzt aber genug gelabert.....hier den Beitrag (hoffe Forumsklau ist in Ordnung O-) )
ZitatAlles anzeigenThe S-Series trucks (GMC too) have several options for the Transfer Case. The Transfer case or t-case for short takes power from the engine/transmission and splits it to the front and rear axle. Thus driving both axles under the truck.
The 2 common versions of t-case are;
1) Manually shifter via a floor shifter.
2) Electronically shifted via a push button on the dash
Regardless of t-case they all have one thing in common. A vacuum controlled engagement of the front axle. When you push the button, or shift the lever the vacuum switch in the t-case provides vacuum to the actuator which in turn pulls a cable that locks the front axle. Vola 4x4.
To rule out the t-case as being broken, start the truck, leave the tranny in park, put the truck in 4 hi mode, reach under the drivers-side and grab the front driveshaft. Try to turn it by hand, if it turns your t-case is not in 4x4 mode. If it doesn't turn then your t-case is in 4x4 mode.
If the t-case is locked in 4x4 mode, then the problem lies in the vacuum system.
The vacuum system consists of a switch on the t-case, vacuum hoses, vacuum actuator, cable and front axle.
Lets take them one at a time.
The vacuum switch is located on the t-case between the front driveshaft and tranny. It has three hoses attached to it.
The three hoses- one provides vacuum to the vacuum switch. One is a vent line and has a tee fitting on top of the t-case that goes to another vent line on the back of the tranny, and then up next to the battery and has a little filter on the end to keep debris out. The last hose provides vacuum from the switch to the vacuum actuator.
The vacuum actuator is located under or next to the battery. Older trucks have it next to the battery tray. Newer trucks have it under the battery tray, you have to remove the battery and battery tray to access it. Battery tray bolts are above the tire in the fender well.
There is a cable that runs from the vacuum actuator down to the front alxe. The vacuum from the t-case pulls the cable and it engages the front axle. Rare for this cable to break or get stuck, but it happens. A quick easy check to make sure the cable works and the vacuum system is broke. Pull the cable about 1/2"-3/4" and attach a pair of vise grips so it wont retract. Drive the truck and see if the 4x4 is working.
You keep saying vacuum, where does this vacuum come from?
Good question. It comes from the engine. I wont go into how the engine creates it, just know that it does.
There is a vacuum port on the back side of the intake manifold next to the distriburator. This provides vacuum to more then just your 4x4 system, it also provides power to your HVAC (heater and A/C controls), and a few other things. There is a tee fitting shortely behind the distriburator, look for it. It splits the vacuum, one hose goes down to the t-case, one hose to the center of the firewall and feeds your HVAc system, and one hose oges to the big black ball. A leak in any of those hoses will cuase your 4x4 to stop working, and you might have trouble with your HVAC controls.
The vacuum hose runs down to the t-case, remember the three hoses attached to the t-case I wrote about earlier? The vacuum switch sends that vacuum up to the actuator by the battery. To test the actuator you have to pull the vacuum hose off. Then depress the rubber diaphram with your finger and place your thumb over the hole the vacuum hose was on. The object is to stop the air from going past your thumb. If the diaphram moves, its defective and needs replacing. It the diaphram holds vacuum, then your trouble lies elsewhere. More then likely in the vacuum hose.
All three hoses run from the vacuum switch on the t-case, over the tranny, and follow the tranny dipstick tube into the engine compartment. There is a bracket that holds them in place. The bracket is bolted to teh top tranny bellhousing bolt hole on the passengers side. This bolt is a real bear to get too.
__________________
"Some people spend an entire lifetime wondering if they made a difference.
The Marines don't have that problem."
-President Ronald Reagan
Ich hoffe das es nciht nur mich weiterbringt sondern auch euch anderen.
Also viel Spaß beim lesen und übersetzen :happy:
mfg Booker
