Am I in Limp Mode or is my tranny in trouble?

[Shaun091382]

Hi i have been having problems with my tranny shifting into neutral on its own. I have been reading about this limp mode setting and to reset it is to disconnect the batter for 10 to 15 min well i did that and no effect my tranny is still going into neutral as i climb to 60km/h tops in drive. Sometimes it sticks in 1st sometimes into neutral sometimes from 1st to 2nd and then back to 1st and not back to 2nd i dunno i am hurting on this one..my fluid is fine and isnt burnt and no visible leaks..i dont get any DTC codes so i am at a loss any ideas or suggestions would be appreciated thanks, oh and my truck is a '93 4x4 Chev (4L80e) with 6.5TD

Shaun

[ 10-01-2003, 04:42 PM: Message edited by: Shaun091382 ]

[Dimsdale]

Remember that EVERYTHING is pretty much controlled by electronics, so a good starting place to check is the wiring harness. Clean and grease (dielectric) all plugs, check all wiring for grounding. That includes the PCM plugs and firewall connections. Check and clean all grounds. As note above, check for codes. Not all produce an SES, particularly if they are very intermittent, although yours doesn't sound like that. Check the internal harness and all its connctions, and look at the bottom of the pan for crud. Change the filter and pan fluid at minimum.

[Cowracer]

The classis limp mode symptoms are:

</font> Speedo sometimes will drop to zero</font> The tranny will stay in its current gear until speed gets low enough to shift into first.</font> Once in first, the tranny will stay in first. Occasionally, if you rev the hell out of it, somthing (maybe line pressure?) will force a real hard shift to second.</font> the SES light will not come on.</font>
Usually, replacing the input and/or output shaft speed sensors will solve this problem.

If the tranny is putting itself into neutral, I would be that something with the bands are screwed up. I doubt it is in the electronics. Of course, I have been proven wrong sometimes, too.

Tim

[Shaun091382]

I took my 4l80e into my local dealership they said there is nothing error wise in their scans and that all the electronics are working fine they are saying that my clutch pack is leaking i dunno my tranny has 332,000km and has never had been replaced or rebuilt and i wont lie it has not had regular interval maintenance