Help - Catastrophic Failure in Transmission or Torque Converter

[andreasballs]

So last night I was driving my 1987 GMC suburban (3/4 ton, 6.2l Diesel, 2WD, TH400 trans, 189k miles) home from college. I was driving 7 passengers and their baggage, which may have been putting some extra stress on the vehicle - nothing too severe though considering its a 3/4 ton diesel. I'd been going highway speed for about 3 hours, after which I took an exit into a residential neighborhood to drop a couple guys off. While on my way back to the highway, I was going about 20 mph, slowly accelerating from a stop sign. Suddenly, I hear a sound like something sliding against something else under the hood. No grinding sound, though there may have been a subtle clunk. I keep driving, but realize I'm having trouble accelerating. It actually seemed like I was in neutral - there was no power whatsoever going to my wheels. I pulled over to the side of the road and killed the engine. Everything under the hood seemed fine, and the engine would run fine every time I started it. However no matter what gear I put it in, forward or reverse, I'd get no power to the wheels. I had been having absolutely no transmission problems before this, so this literally grenaded over the course of like 5 seconds. I had my friends push the car off the main street to a parking spot. I kept running the engine a bit and putting it into gear - still nothing. I checked the trans fluid, and it looked perfectly healthy - a slightly dark red with hints of rosiness and no metal chips or dust. I looked under the car, and when I put the car in gear I could see the drive-shaft move about a quarter turn, and then stop. Do you guys have any idea what it could be? I know it seems like trans failure, but it seems unlikely that something as relatively reliable as a th400 would just completely die like that, with every single gear non-functional, after no history of problems. I was thinking it might be the torque converter, but are there any other possibilities? I'm a broke college kid and I really don't have the money for a trans replacement/rebuild. Thanks in advance.

 

[austinado16]

Sorry to hear about that failure.

 

[89Suburban]

What about the rear end? Have you been noticing any strange noises or behavior from the drive line at all?

 

[austinado16]

She's a no spinnin' the propeller shafts, so I'd say it's transmission time. Probably an internal failure where it's no longer making any pressure.

The good news is that Aaron, who you took it to a few weeks ago, builds transmissions and you can pick and choose the most updated parts and wind up with an even better transmission.

 

[chengny]

This a long shot but - it's worth a look:

Drop the torque converter/flexplate splash shield and inspect the T/C to flexplate bolting and the flexplate itself.

Look for a completely cracked flexplate at the crankshaft flange or all three bolts having been sheared off.

Either of these conditions will obviously disable the drivetrain from the crankshaft back. But when they initially occur - because some contact generally remains - the transmission will sometimes make a feeble attempt to spin the drive shaft.

As long as there is some friction between the broken components, there is still some power (greatly diminished) input to the transmission.