Speed sensor question

[airtech]

Can anybody tell me what the symptoms of a bad speed sensor is off of a 97 k2500 4x4,8600gw with a 4l80e tranny.
Thanks

[gmctd]

Should set several "ratio" DTC's, with MIL indication.
Trans may go into "limp" mode.

If SES lamp has been on, pull the codes and post them here for more specific data.

If not, what symptoms were you seeing?

[airtech]

Thanks gmctd for the reply. When the truck is cold, my tranmission has problems shifting from 2nd to 3rd.After it warms up it shifts alright but shifts kinda rough.Fluild and filter is new and I have no codes and no lights.
I was just trying to fiquire out what makes the tranny shift.I went back threw the arkieves and was reading what other people with same problems on there trannys.There was 3 things that i read that might be the problem instead of transmission problems.which i don't even want to think about.I read speed sensor,solnoid problems and a bad crank sensor.By the way can you tell me what shifts these trannys?I know from older trannys they had vacuum operated modulaters
Thanks

[john8662]

These trannys are shifted by electronics only. There isn't a Vacuum modulator or a TV kick down cable anymore (thank goodness). Being that you have a 97 you'll need to have the computer scanned for codes, once you have the codes, bring them back here, and we can probably figure out whats going on. Autozone does free code scans, might try that if you have them available to you. Otherwise you'll have to pay someone to get the codes for you, or buy a code reader, I think that some parts places sell those at a reasonable price.

[GARY PAGE]

Seems like the engine misses sometimes once in a while, it was really the torque converter jumping out due to a poor signal from the speed sensor..my experence...

[airtech]

I went by Autozone and they put there code reader on my truck, I have no codes. Any more suggestions??

[gmctd]

Try shifting manually thru the gears - pull it into low, shifting to second, third, and fourth at similar speeds to automatic shifting.
See how it handles manual second to third shift when cold.
Could be a sticking third gear solenoid, or leaky o-ring.

No codes would appear to indicate the PCM is satisfied with operations. Possibility fluid level is incorrect.

Being that it's a 4x4, try unplugging and reconnecting the main transmission harness connector, a large round plug about three-quarters way back on the driver's-side of the transmission.

Or, just drop the pan and see for yourself if all is ok - should be minimal quantity of metal, aluminum, or fiber particles.

[airtech]

I drove it in low and shifted gears manually and it still slipped only when cold so I drained the fluid and dropped the tranny pan to look inside.All looks great.I pulled the bigger solenoid to see if those little screens around the shaft was dirty,They looked fine.While i had it out I put some power to it to see if it would pull in or click.It did.
I found two sensors on the back of the tranny,one on top of case and other on side of tailshaft.I unscrewed the tailshaft one, (since it was the easiest to get to)and cleaned it up to see if it might be this sensor.It changed nothing.One has three prongs and the other has two prongs.What do they do? Would TC have anything to do with these systoms?
Doing all of this and still can't find anything wrong does this mean I need tranny rebuilt?I would hate to rebuild tranny and stick it back in and it still do the same thing and find out it was something else.
Thanks for your feedback.