Hi Gentleman. Over the weekend I was attempting some 0-60 passes using the Torque app. I drove a good 10 minutes to an open road so everything was at operating temp prior to any WOT runs. On my first run, I floored it, lost a bit of traction, hooked up but when I reached 5500 RPM in 2nd gear (50-55mph), the car instantly stopped accelerating. Immediately I let off the gas, thinking it was a fluke as this has never happened before.

Run #2. Same thing, but this time I was anticipating the slip. Against my better judgment, when I reached 5500 RPM, the trans slipped again, I kept flooring it for 1-2 seconds and the tach remained at a constant 5500 rpm without accelerating AND I heard a grinding sound; soundedlike the teeth of 2 gears that weren’t engaged properly. I couldn’t even reach 60 mph. When I let off the gas it upshifted as necessary. I stopped in a parking lot and it smelled like burning something. Almost like burning rubber, but not exactly. I let it cool down for 30 minutes and drove her home. Drove like normal on the way home…normal throttle.

Drove to work this morning…again, seems fine. Seems ok as long as I’m not heavy on the throttle.

So I was thinking that maybe the transmission overheated. But what would cause it to overheat? About 2 months ago I had a local shop perform a trans flush with a new pan/filter, using Mercon SP. Seems that others have used this fluid with no complaints, so I don’t think that’s the problem. Anyone disagree?

I’m concerned as a trans rebuild would be hard on my wallet at the moment…and in turn, hard on my marriage. Do you gents have any ideas?

 

Grinding seems unlikely since there are not really gears that are meshing and unmeshing. Was it maybe more of a vibration or shudder? Like a clutch chattering?

Seems like the sort of thing that might happen if low on fluid... Are you sure that the place that did the flush got it full again? Wouldn't hurt to check, either way.

Were there any logged or pending trouble codes? The TCM will (usually) log mismatches in the speed sensors, gear slips, etc.

 

I didn't feel any vibrations. I could only hear it. Chattering is a good word to describe the noise. The only thing I actually felt is that I immediately stopped accelerating when the symptoms occurred.

Am I sure they filled it correctly? No I'm not...because I wasn't physically there, but that is what I paid them for...and I'm confident in his work. I don't have the time to check the levels for at least a week, as its not as easy as pulling a dipstick.

No logged or pending codes according to Torque as of this morning, but I'm not sure if Torque gets info from the TCM??

 

If the TCM registered a problem, it should show up as a P code that a standard reader can get.

The 6HP in general is not known for slipping or blowing out drums like the 5HP was.

The failures I have heard of in the early ones are related to the torque converter clutch failing to lock up. My car does this when cold, actually, but never misbehaves at WOT even with the extra twin screw power.

My bet would be that it's low on fluid. The fill procedure is kind of a PITA, similar to checking the level.

The only other thing I could think of is something wonky in the valve body, but most often these issues are because of worn bores causing leakage and the pressure is too LOW, meaning they misbehave at low RPM. At high RPM with the pump spinning faster, I wouldn't expect low pressure would be an issue unless it was picking up air because of a low level or frothing because of contaminated fluid or something like that.