SOLVED Engine stuttering and hiccupping before and after new parts. (transmission cancelling lockup)

roadstr6

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I don't think my US-market A442F will drop out of lockup from throttle alone unless it's enough to trigger a downshift. It *definitely* doesn't drift in and out of lockup just driving down the freeway.

Tapping the brake pedal -- like you might do to disengage cruise control -- will cause it to drop out of lockup.

Have you tried driving while lifting up on the brake pedal with your left foot? (Obviously not in significant traffic)
His truck is a '95. I would assume it's an A343F.
 

lumbee1

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lumbee1

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Mr. Jones,
You might want to inspect those three big harness plugs between the engine and transmission on the driver side. They live in a filthy location. They sometimes get corroded and cause random mayhem. Those connections are not easy to snap open / closed either, so they may not be totally engaging. They would have been opened up when the engine came out and put back together when the engine went back in. Not saying this is your silver bullet, but rather something to check.
Old harness and new harness are doing the same thing but I can check them for corrosion.

While driving to Windrock, the guys behind me said that my brake lights would come on and off with the bumps in the road. This was similar to what I was feeling on the way home for Windrock with the transmission. I just checked and adjusted the brake sensor switch. It was way out of adjustment and the slightest touch would cause the brake lights to come on. Spec is .5 to 2.4mm of the inner black switch showing. Mine was closer to 4mm.
 

lumbee1

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Is it dropping out of overdrive, or out of lockup? An ~8% change doesn't seem like enough to be a shift from overdrive. The A343F has a .753:1 overdrive ratio, and the A442F is .765:1. Both are 1:1 in 3rd gear.

I seem to recall someone having a problem with their 80 dropping out of overdrive due to a bad brake switch or return spring...
Maybe SOLVED.

I adjusted the brake sensor switch and installed new OEM pads (100 in the front, 80 in the rear). Today was the first time I've taken it on the highway since bringing it home from Windrock. I watched the tach like a hawk as I was driving and could not detect a single instance of stuttering or ghost shifting. I'm still not 100% certain why the brake sensor switch would cause the transmission to act up.

After thinking about this some more, here's the recent history of events:
  • Went to the beach in Aug. Brake booster failed.
  • Replaced brake booster and set all adjustments exactly like the original booster.
  • Wheeling trip in Sept and folks are commenting on my brake lights activating with bumps in the trail or road.
  • Driving home from wheeling trip and transmission is stuttering, shifting, etc. I can only assume the brake lights were coming on each time with trans was ghost shifting.
  • Install supercharger and new harness in Oct.
  • Driving to Windrock in Nov and my trans is ghost shifting a bit and folks were commenting on brake lights coming on.
  • Coming home from Windrock and trans is ghost shifting badly with bumps in the road. Again I can only assume the brake lights were coming on each time.
  • Adjust brake sensor switch and one test drive and all is smooth.
Before I change the title, I will drive it a bit more to fully verify. We have a small trip in Dec.

BTW, new OEM pads are worlds better than the EBC greens they replaced. Almost like they were designed, spec'ed, and built for the Land Cruiser. Wish I would have done these pads sooner. My last set of EBC greens lasted 25K miles.
 
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I'm still not 100% certain why the brake sensor switch would cause the transmission to act up.
LC94FSM-Transmission-CancellationOfLockup.png


That's from the '94 (A442F) FSM, but it's probably identical for later models. Certainly with regard to the brake switch causing the torque converter to unlock.

If you mean why it went out of adjustment, did you check that the return spring is intact? Maybe something with the master cylinder means the push rod isn't fully returning? Maybe the push rod lock nut loosened and started drifting?

LC94FSM-BrakePedalAdjustment.png
 

roadstr6

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View attachment 3174047

That's from the '94 (A442F) FSM, but it's probably identical for later models. Certainly with regard to the brake switch causing the torque converter to unlock.

If you mean why it went out of adjustment, did you check that the return spring is intact? Maybe something with the master cylinder means the push rod isn't fully returning? Maybe the push rod lock nut loosened and started drifting?

View attachment 3174058
Now THAT is some good information!
 

lumbee1

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View attachment 3174047

That's from the '94 (A442F) FSM, but it's probably identical for later models. Certainly with regard to the brake switch causing the torque converter to unlock.

If you mean why it went out of adjustment, did you check that the return spring is intact? Maybe something with the master cylinder means the push rod isn't fully returning? Maybe the push rod lock nut loosened and started drifting?

View attachment 3174058
Excellent find! My brake return spring is good. I just think the brake sensor switch has always been very close to the limit. Changing the booster meant that 1mm or less difference put it out of the brake sensor switch threshold.
 
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View attachment 3174047

That's from the '94 (A442F) FSM, but it's probably identical for later models. Certainly with regard to the brake switch causing the torque converter to unlock.

If you mean why it went out of adjustment, did you check that the return spring is intact? Maybe something with the master cylinder means the push rod isn't fully returning? Maybe the push rod lock nut loosened and started drifting?

View attachment 3174058
Easter egg!
 
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Is the small plastic pad (CUSHION 90541-06036) for the Brake light switch present?


 

lumbee1

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Is the small plastic pad (CUSHION 90541-06036) for the Brake light switch present?


I meant to include that the cushion broke when I replaced the booster. I ordered the OEM replacement and installed it a few days later.
 

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