4L80E shift into neutral problem

[Shaun091382]

What would cause my '93 chev 6.5td 4x4 with 4L80E tranny to shift into neutral while driving it happened just for no reason this evening while in drive at about 55km/h it went into neutral and both drive and overdrive would not get me moving i came to a complete stop put it into reverse and it worked then i put it into drive and away i went to get back home with no other problems any ideas?

[tanker]

I would check the linkage, from top in cabin, to transmission, almost seems like something slipped. Then you somehow reset it.Hmmmmm :rolleyes:

[92 Diesel Dude]

I had a similar problem in August of 2003 with my 92 4l80E. It would slip out of gear and land in first gear and stay there until the transmission totally cooled off. Reverse, neutral and park still functioned when hot. Once cool, the transmission shifted normal. It ended up being my shift solenoids which can be accessed without pulling the transmission. At the same time other components where updated to newer specs. This problem flagged no codes.

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[Shaun091382]

I just scanned my codes today and received nothing but a good ol code 12 so no DTC being picked up...my incident did not stop my movement i stopped on my own and then resumed...maybe i am not doing something right when checking my DTC's i just checked them when the truck has been sittin for about 15 hrs with no movement should i go for a drive then recheck them?

[Shaun091382]

Mike i just used kennedy diesel's method of grounding a wire to my truck's ODBI connector and watch the SES light flash code 12 which is for no rpm which is no big deal no other codes came up in regards to the transmission.

[dbryans]

Originally posted by Shaun091382:
Mike i just used kennedy diesel's method of grounding a wire to my truck's ODBI connector and watch the SES light flash code 12 which is for no rpm which is no big deal no other codes came up in regards to the transmission. Shaun,

I've started noticing something similar on my '94 K2500 6.5TD 4x4 Suburban. I notice my problem when stoping on an upward slope while in gear but with the brake on. Sometimes (irregular, not hot or under load, yet) shifting into reverse and back will re-engage, sometimes I need to shift to park wait a sec and then back to drive before it will engage.

I was about to use the method you mention above for testing codes and was curious what you ended up determining the problem was and if you found a solution? Was there a better way to read the codes?

Shane...

[DmaxMaverick]

The only "better" way to read your codes is with a Tech I or II scan tool (GM product..$2K+).

On the '95 and prior vehicles, the code reading is simple. A paper clip to jump two pins, the ignition key and someone to count flashes. That's it.

Kennedy's website, www.kennedydiesel.com (http://www.kennedydiesel.com) , has very simple instructions, and a code table. If you are getting the SES lamp, this is what you want to do....Or, you could see your mechanic and give him $100 to do the same.

[dbryans]

DmaxMaverick,

Yeah, well, I aint got $2K, so.... I'll use the paperclip for now, which is what I had read elsewhere, but thanks for the aternative link.

I was curious though if Shaun ever isolated and solved his problem, and if so, what the solution was.

Shane...

[ 06-24-2005, 03:32 PM: Message edited by: dbryans ]