69Camaro427

The truck is my 5.3L work truck all stock except for CAI and muffler. NOT tuned, 120K stock 4L60e

The truck unlocks when going down a hill if I take my foot off the gas or just giving it 5% throttle down the hill. It then stays unlocked for several miles up and down hills till finally it locks up again. I don't think the transmission is getting hot b/c it has be below 50* the past few days. Also this is with me never touching the breaks.

What do yall think the problem is?

slowmo934

May not have anything to do with it, but if a misfire is detected it won't allow the TC to lock up.

69Camaro427

I just changed the spark plugs, unless the coil pack are going bad. I haven't really heard or read anything about these coil packs going out before 200K though. The mis fire you speak of.....would it be noticeable to me or so minor the ECU picks it up and I would never know?

Been researching, and a lot of people say it has something to do with a valve body. I would hate to start buying parts and they not fix it.

All my money is for the truck in the sig haha not this one

rel3rd

iTrader: (42)

The older 4L60E's had issues with the valve bodies, but usually would throw a P1870 code as well. Even a misfire that isn't felt, or not enough so that the PCM throws a code, can keep the converter unlocked...BUT, my old Silverado had this code pop up intermittently, and when it did, it also shifted VERY HARD from 1-2 when it was acting up.

FWIW, my present truck, a 2002 Z71 w/5.3, would unlock similar to as you describe, until I changed a few transmission & torque converter clutch settings using my HPTuners.

If you have a scanner, or code reader, you might want to see if it has a "pending" code for the TCC (torque converter clutch), or any random misfire pending code. It's worth a look at least.

rel3rd

iTrader: (42)

The older 4L60E's had issues with the valve bodies, but usually would throw a P1870 code as well. Even a misfire that isn't felt, or not enough so that the PCM throws a code, can keep the converter unlocked...BUT, my old Silverado had this code pop up intermittently, and when it did, it also shifted VERY HARD from 1-2 when it was acting up.

FWIW, my present truck, a 2002 Z71 w/5.3, would unlock similar to as you describe, until I changed a few transmission & torque converter clutch settings using my HPTuners.

If you have a scanner, or code reader, you might want to see if it has a "pending" code for the TCC (torque converter clutch), or any random misfire pending code. It's worth a look at least.

69Camaro427

It drives and shifts like normal stock crap when I get off the free way or if I slow down to 55-60mph it will lock back up. I guess it only happens going 70-80 down a hill. I have local shop in town with a scanner. I'll swing it by tomorrow. What if it is not throwing a code? What else would yall look into besides the valve body?
Oh and it is a 2002 forgot to mention that!

69Camaro427

No transmission code. Well s***
The only code was my little eye in the dash for the headlight was dead.

Oh side note real quick, when my cut outs are open on the truck in the sig, it has a back fire popping noise when exiting the free way and letting it engine break " take foot off gas". Is this just lack of back pressure pop or misfire as well?

Suburbazine

That's a normal sound for lack of backpressure.

69Camaro427

Well have done several 100 mile trips with the truck this month and it has been working properly, staying locked when going up and down hills. The only conclusion I can come up with is the cooler weather Texas has been having. Maybe the ecu adjusted something?

I bought a vette servo and thinking of ordering a larger transmission cooler for it. Hopefully this will make it last a year or two longer. I don't really beat on the work truck either, it is slow regardless lol

What transmission fluid do yall recommend/prefer?