Sudden downshift while driving?

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mlrailguy

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About 45 minutes into our trip, the transmission felt as though it went into neutral. I had noticed just before that, the alternator had quit charging and the water temp was pretty high. I pulled over and switch one of the coach batteries for the chassis battery and turned around for home. The alt was charging and trans seemed fine on return trip. Found bad connector on alternator and fixed it then went for test drive. Transmission felt erratic, only going up to 2nd gear. It would try to shift into 3rd then drop immediately back into 2nd. The fluid levels were fine.
 
"Hunting" (The tranny shifting up and down and up and down hunting for the right gear) can happen due to a combination of road and speed conditions. 1 or 2 MPH more or less and it settles down.. Sometimes. But there are other things as well.. Overdrive off if this kind of thing happens.

I sometimes talk about my "new" used Jeep.. 9 speed transmision.. I've used 8 of 'em.
 
Yes, we need more information to even begin to suggest anything useful.
Took it to trans shop, he took it for a drive and it all worked fine. He thought engine may be starving and recommended changing fuel filter and catalytic converter which I did. Still same problems. Won't go into 3rd gear, acts like it wants to, but just won't catch
What chassis, engine, & transmission are we discussing?
This is a 93 Winne on a Chevy p30 chassis with 454 engine
 
4L80E trans?

I'm betting the internal wire harness is leaking into the external connector. Look at the connector at the side of the trans...see red fluid? You shouldn't. Unplug it as well. There should be no trans fluid.

Replacement requires dropping the trans pan. If you do this. Also replace both shift solenoids (A & B) and turn the force valve up 1/4 - 1/2 turn (clockwise). Also replace the filter. Dropping the pan the trans will only remove 5-5.25 qts of fluid.
 
….He thought engine may be starving and recommended changing fuel filter and catalytic converter which I did. Still same problems. Won't go into 3rd gear, acts like it wants to, but just won't catch
Your transmission won’t shift, and your “mechanic” suggests changing a fuel filter and the catalytic converter?

You need a new mechanic.
 
Ok so you have a 4L80E. I’d start with what udidwht said. Also are you having any low voltage issues?
Finally got it up on blocks and crawled under it. Found a tag says TurboHydramatic and #s 93 2225. On trans itself are these 8680581-4 On drivers side is a bunch of wiring going into it and they are wet with fluid.
I was looking through binder from previous owner and found a receipt for sensors being replaced at 6000 miles. The owner said it suddenly revved up and blew muffler apart
 
Last edited:
Finally got it up on blocks and crawled under it. Found a tag says TurboHydramatic and #s 93 2225. On trans itself are these 8680581-4 On drivers side is a bunch of wiring going into it and they are wet with fluid.
I was looking through binder from previous owner and found a receipt for sensors being replaced at 6000 miles. The owner said it suddenly revved up and blew muffler apart
Did you resolve this. The connector should be dry. Once trans fluid makes it's way into the connector shifting issues will result. It requires dropping the pan and replacing the wire harness (DIY job). If you replace it I also recommend replacing both shift solenoids A & B and turning the force motor up 1/2 turn.

The 4L80E trans will go into 2nd gear when the ECM sees an issue (Limp mode). The only way to reset that is key off then restart.
 

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