4l60e Limp mode after swap 1999 Tahoe

[burnunit]

Hello all, new member here, first post.

Did a search but couldn't find a recent thread with similar problems so here we are.

Bought a used Tahoe with transmission that was supposed to have been rebuilt for my son.

He drove for about 10 months and it went into limp mode, I figured trans went bad and swapped for one out of a donor that was wrecked, didn't know about limp mode yet.

Swapped in the trans and truck drove better than the rebuild, actually went through all the gears, son went to get inspection but needed to put miles on for computer after it reset.

While driving it suddenly went to having nothing when put into drive, google research lead me to limp mode and this site.

What could cause the trans to suddenly go to limp mode while in the middle of driving?

Bad ecm? or bad shift solenoid?

Looking forward to getting some feedback and hopefully being a productive member to the board

Thanks

Burnunit

[sefiroxx]

Limp mode is default solonoid setting that allows for drive as long as there is pressure in the tranny fluid. When the computer can't see the tranny - as not see which gear it is in , it stops sending gear change requests.

Check wire harness, make sure it is plugged it, make sure it is not chafed, rubbing, etc

[carkhz316]

If your truck isn't moving, it's not a limp mode. The transmission can be completely unplugged (at the electrical connector) and you'll still have 2nd and 3rd gears, and reverse. Something else is wrong. Does it have reverse still? Can you tell when you're shifting into D or R (engine lugs a small bit), or does it do absolutely nothing?

Edited January 27, 2020 by carkhz316

[burnunit]

Truck was off the road for a couple months, did transmission swap.

The donor transmission had the connectors attached, guy cut the wires, all looked good on trans, I actually have reverse lights now and didn't before.

Connections seemed to plug in as they should, I will take a look for chaffed wires.

Went to get inspection and guy couldn't do as the computer needed miles since we had the battery undone.

Drove for about 50 miles, went through all the gears no problems and then all of a sudden nothing.

Was able to shift down to limp it home.

What gets me is that it seems that as soon as the computer went through its cycle it shut the transmission to limp mode.

Was able to get it home into my driveway.

Edited January 28, 2020 by burnunit