I've tried searching, but don't know which terms work for this.

When I am stopped at a stop light, I will let off the brake and apply the gas. At that time, the car seems to not really bog, but noticibly use the engine's power, but I move almost nowhere. After maybe a second, the car starts moving forward.(I relate it to what happens if you have an RC car and push down on it while applying forward trigger, and then let off ofit so it can move, you can tell its trying to move but just doesn't until you let off of the car itself). Does this sound like a transmission problem, or maybe a rear diff problem?

 

Please put your vehicle information (year, transmission, 2wd or 4wd) into your signature so we can help you.

 

Guess that might help.

2000 GMC Jimmy SLS
2-Door
4-Wheel Drive w/ Auto
Automatic Tranny
4.3L Beast

 

It could be as simple as low on tranny fluid.
Drive the truck for 20 minutes, park on flat level ground, leave the engine running and check the fluid level. Not the color and smell.

Sounds like your torque converter is going out, if the tranny is full.

 

I've checked the tranny fluid recently, seems full. What's the Torque Converter cost to replace? Better to just do whole tranny rebuild / remanufacture at same time? When it goes, does the symptom continue to get worse, or does something snap and I'm on the side of the road?

I should add the other symptoms my truck has just in case any coincide:

HORRIBLE gas mileage (never gotten above 13, usually 12, and I do 50/50 highway/city)
Voltage gauge will dip from around 14.5-15 down to 12 when at idle or coasting.
Car did die twice when putting into gear (reverse)
The headlights dim unreasonably at idle or when coasting
Has a slightly rough idle

See this post for my original post (before I started singling out this specific issue as the worst of them):
https://blazerforum.com/m_124648/tm.htm

 

Generally it just gets worse, eventualy the end result is the same, your starnded on the side of the road.

Get it rebuilt, you have to remove the tranny to replace the torque converter. Before you get to that step, take it to a reputable tranny shop and hav them take a look at it. Ask them for a quote while your there. Shop around, call em on the phone first. Find a shop that you feel comfortable dealing with. This tranny has been around a long time, almost 30 years. If they dont know how to fix it by now they never will.

 

I edited my post after you replied, just in case the additional info helps anything. Thanks a lot for the help so far.

I was reading up on your rebuild thread. Do you by chance have a full list of the parts you purchased? You seem very happy with your tranny, and I'm tempted to just take your list, make a purchase, and hand it all to someone to be rebuilt (I don't have the knowledge nor time to do it). I do want to retain my factory RPMs on the highway. Is your torque converter one meant to be as-factory or is it one you chose to change the setup? Also, was this Midwest Transmissions in Omaha? I've heard of them around here before, but there seems to be a few companies with that name.

 

Ah, engine trouble.
I would get the engine fixed brfore I condem the tranny. The puter controls the tranny based on the engines performance. If the engine is running like crap, so will the tranny.

low voltage- get your alternator tested, it can be done in the truck.

 

It's a brand new alternator (had it tested just to be sure) with a brand new battery. I was thrown the P0171 and P0174 codes once, but they haven't come back. I was kinda hoping those issues had something to do with this cause I'm out if ideas on the other problems.

 

Brakes.
If your brakes are hanging up it will ahve the same feel as a sluggish tranny. When was the last time you serviced the brakes?