Nubie here so plz bear with me. As title says, I have an 03 TrailBlazer Ext LT 5.3 L V8.. My 3rd gear recent went out.. As in riding down the road headed home from work and notice my rpms spike a couple times a few minutes apart, Then rmps just spiked. That fast.. It goes into 1st and 2nd , and reverse, but no third and I assume forth. So I'm wanting to change transmission and need info on interchanging.. There's a small list of direct fit transmissions, but which tranny's can I use if I swap hell houses? And help would be greatly appreciated.