Trans messing up - ideas?

[stevensb]

Alright so last night, I was just cruising along, maybe 50 mph and my truck started shifting in and out of 4th, just constantly, if I'd let off gas it would stay in 3rd but as soon as I gave it a little gas it would try and shift back into 4th and then it'd happen again and start shifting in and out. I pulled over and let it sit for a minute, got back on the road and now it wont shift into 4th at all, just stays in 3rd. What you guys think?? It's a 4L80E out of a 99 model with a 454.

 

[KReePiN]

Perhaps a faulty brake switch or tcc


Sent from my iphone while im sitting on the toilet

 

[stevensb]

Is there a sensor on the trans that could be going bad? Or computer? This morning it was perfectly fine, but once I had driven a little while, it started acting up again.

 

[cviola2005]

I had a similar problem with mine. I believe it is heat related. Mine would be going down the road just fine, and then just shift out of 4th. I had to pull over, unplug trans computer for about 30 seconds, replug, and off I went for another few miles. I had a manual TC lockup switch, so I don't think It's related to that.

Mine would do it every time I was in a drive-thru, every single time. That's why I saw it's heat related. But then again, It could be fluid related. I would change the fluid and filter first. While under the truck, I'd pull both trans lines of the trans and blow them out.

I have switched to a manual, that's why I didn't delve into fixing mine.

 

[volunteerff21]

I would suspect TPS (throttle position sensor). They do "interesting" things to the transmission when they go bad. When mine went out it would shift in and out of gears pretty much at random.

Not sure how heat would affect it though......