OT Auto Transmission

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1997 Vortec 305 4L60E K1500
What does a bad torque converter sound like?

Lately when towing the truck seems to be very hard to get up to speed and maintain it. It slowly seems to get worse. Normally I can stay below 195F, and maintain around 60mph,(minus bigger hills) but the last few times I"ve towed, I have to baby it to stay below 210F.

The very last time it got a very loud vacuum/jet engine type sound. Happened very suddenly, couldn"t hear anything else. Lockup barely works. Happened at around 3500-4000rpm. Got out to look under the hood after it happened and the manifolds were red, likely because of how hard it was working to even attempt to maintain speed.
Transmission still shifted fine, but somewhat excessively. Haven"t read any codes yet. Absolutely no slip, which is what confuses me. Sound seemed to be coming from the torque converter area, so it could be the rear of the engine, or it could be the transmission pump. Transmission oil is 50:50 DexIII and Dex VI. Engine is using a Wix filter and Valvoline synthetic 10W30. Sound was there in all gears, including park and neutral.

No sounds the next day. Stall still seems to be around 1600rpm. It doesn"t seem sluggish. If you hit the throttle, it goes. Haven"t driven it anywhere, just around the yard to move it out of the way. No detectable lateral play in the crankshaft. My first thought is it may have ballooned because of the rpm"s involved when towing(up to 5000rpm), but can"t really see anything. 1997 Vortec 305 4L60E K1500

"Hashy"/"marbles in a tin can" sound when in gear and not moving. Quiet in Neutral and Park.

I think you are dealing with a set of plugged catalytic converters. That 'jet' sound is the exhaust trying to escape.

Allan

When you describe red hot manifolds it sounds like your catalytic converter is plugging up..that will result in power loss and I've seen plugged converters get red hot

If you break the ststor loose it will kill the engine under load and boil all the oil out. Since you seem to have intermittant symptoms the stator clutch might not be letting go at full speed. That will allow you to pull good but overheat at hwy speed. An oil change would tell a lot.
Later Bob

..guess we were posting at the same time..Hey We AGREE! lol.

Red hot ex manifolds leads me to believe you have plugged cats.

I would bet big money that you have a catalytic converter failing.
Here is how it works:
The catalytic converter has a ceramic "honeycomb" inside of it that contains the catalytic material. It fits tightly inside the outer shell of the unit. When the unit begins to fail, it loosens up inside the housing, and begins to rattle. This erodes the ceramic material away and it continues to get smaller - and noisier. At some point, it becomes small enough to turn on its side and block the exhaust flow. Symptoms are as you describe: rattling, overheating, and red-hot exhaust accomanying lack or loss of power.

The fact that the transmission is still shifting correctly and not slipping confirms my diagnosis. Had you gotten the transmission that hot, it most certainly would have damaged the friction materials as well as melting the plastic parts on shift solenoids and the EPR solenoid.

As a matter of proof, you can remove the catalytic converter from the vehicle and shake it. Bet it rattles!

I will have to go with the popular diagnosis of plugged Cat. converter. I had a Chrysler that was plugged, if you took off slowly it did OK, but if you hit the gas very hard it sounded like someone trying to shove a tornado through a keyhole.

I'm with Allen.Acts like plugged cats to me.