Drivetrain Shudder at 71mph

[GreenZ98]

My 06 was doing the same between 56-58 mph. Ended up being the torque converter. I could get to the speed the shudder started at and lightly touch the brakes without letting off the accelerator and it would clear up instantly. Poured a 2oz tube of lubgard shudder fix in just to be sure the touching the brakes thing wasn't a fluke and sure enough it completely quit doing it so then I knew for sure it was the torque converter.

 

[Schurkey]

It will also intermittently through a P0300 misfire code also while doing the shudder.

Is that REALLY a P0300 code, or are you using a cheap consumer-grade scan tool that provides generic codes instead of the specific code?

If you're using a crappy scan tool, the REAL code might have been P0304, for example, misfire on #4 cylinder--but the lousy software in the scan tool ignores the specific cylinder and only reports "random misfire".

 

[Hobie]

Is that REALLY a P0300 code, or are you using a cheap consumer-grade scan tool that provides generic codes instead of the specific code?

If you're using a crappy scan tool, the REAL code might have been P0304, for example, misfire on #4 cylinder--but the lousy software in the scan tool ignores the specific cylinder and only reports "random misfire".

I can see that happening in a newer vehicle, but these older OBDII systems are very straightforward. And anyways it's not the scanner that reads the misfires, the PCM picks up the misfire monitor, and stores the codes. Not the other way around. A P0301 stored in a PCM will always be read as P0301 through any scanner.
The more indepth PCM codes is where I can understand the issues of not using a quality scanner, but a basic misfire monitor should be the same across the board

 

[Schurkey]

it's not the scanner that reads the misfires, the PCM picks up the misfire monitor, and stores the codes. Not the other way around. A P0301 stored in a PCM will always be read as P0301 through any scanner.
The more indepth PCM codes is where I can understand the issues of not using a quality scanner, but a basic misfire monitor should be the same across the board

Okee-Dokee. I've made my point, and I'll bow out.

 

[Hipster]

I can see that happening in a newer vehicle, but these older OBDII systems are very straightforward. And anyways it's not the scanner that reads the misfires, the PCM picks up the misfire monitor, and stores the codes. Not the other way around. A P0301 stored in a PCM will always be read as P0301 through any scanner.
The more indepth PCM codes is where I can understand the issues of not using a quality scanner, but a basic misfire monitor should be the same across the board

LOL

 

[Murdock709]

So I've been looking into the same issue with my 98 tahoe. Couple things I read; TCC itself, or MAF, MAP, TPS issues. Also it could be a clog in the Torque converter causing the shudder.
Those are a lot of things to check, but start simple and unplug and reconnect all those. Might be just a plug that isn't properly seated.