Alright, this one has me stumped. I've looked all over the place and haven't found anyone who's had/having quite the exact same problem or a solution to go with it.

My DD Jimmy has begun to give an issue when it comes time for overdrive. The torque converter isn't locking up right away. After driving it for about 10 to 15 mintues it then starts locking up just like it's supposed to with no further issues. I'm sure it needs a fluid/filter change but the fluid level is good and doesn't smell burnt or anything else. It shifts through all the gears on time and as firm as it was when I first put the tuned PCM in I got from PCMforless. I have several good size hills to traverse during my drive to/from work and when the torque converter is locked it climbs right up them with no shimmy's or indications of slippage. The tach and speedo are both steady all the way up and over.

I'm aware that on some vehicles OD won't kick in until a certain temperature is reached, however the truck is up to temp a few miles from the house so I can't imagine that's a problem and it should toss a code up for that shouldn't it? Aside from a stored P0303 misfire there were no other codes according to the reader. I have read that TPS sensors can cause a multitude of problems and given the truck has 147k on what I have to assume is the original sensor (bought it with 93k on it in 2010) I'm going to go ahead and change it out. I'm also considering changing the shift solenoids while the pan is off for the fluid/filter change as well. Other than that, any ideas?

 

Just a little update. Drove it to lunch this afternoon and had no issues with OD working after the engine warmed up which only took a couple of miles. I would guess the temperature gauge was at about 150deg when it locked.

 

Another update.

Yesterday after work my wife and I went on a trip into town for some groceries, and this morning on the way to work OD would start working after the 150deg mark as it has been this week. However, it would occasionally just unlock while driving. It did it once on flat ground, another time about 30 seconds after accelerating to speed on the highway (got to 60mph, everything was good, then 30 secs later it just unlocked) then about another two miles after that locked back up and was good. This morning it was working until I went around a turn and accelerated back to speed. It locked when I got to speed then immediately unlocked. It remained unlocked for about ten miles then just started working right again the rest of the way to work.

Is it possible the TCC lockup solenoid or modulator is going out? Anything else someone could think of that's going on here?

 

If gear shifts are smooth and tcc lock is firm, doubt it's a pressure {modulator} problem.
What have you done, so far?
- I would start by disconnecting and cleaning the connectors at the transmission. Contact or MAF cleaner should work. Inspect both connectors for anything looking unusual. Then smear dielectric grease liberally on both.

 

Thanx for the reply!

I've not done anything yet, work has been too hectic to get after it. I'll be working on it this weekend though.

I'll definitely be cleaning the connectors. That's an easy and quick troubleshooting check for certain.

 

Sounds like you are having a cross bleed problem with the TCC valve.
If the pressure bleeds off then that will give you the problems you are having.
Sonnex makes a aftermarket TCC valve
4L60E transmission TCC valve Code 1870 Sonnax 77805E-K

This make a noticeable difference in lock up.

 

I know that depending on wind, low tire pressure, out of alignment tires, vehicle load, hills, any of that & especially in conjunction with others tend to make the trans pop out of OD & the converter unlock. When was the last time the fluid & filter were changed in it? Looks & smells good doesn't mean it is good (insert lame joke here lol). It may be time for a change, every 50,000 miles should be a trans fluid, filter change.

 

The misfire can cause that.....Basically the convertor locks up under certain speeds and loads only. It locks up under cruise conditions, and unlocks when you add gas pedal, back out of the gas pedal, hit the brakes etc. It has no modulator so it gets load data from the throttle position sensor and vehicle speed compared. Anything that reduces performance will cause you to be farther into the gas pedal to get the same "pull" your mind is looking for. The vehicle sees this as you wanting to accelerate and delays lock-up until you "back out" or the vehicle speed increases enough for "locked-up rpm" to not be at such a low speed it will bog . Some vehicles are also programmed to inhibit or delay lockup when you have a misfire as the "hammering" from the miss gets transmitted straight to the converter clutch and can damage it. I bet if you fix your miss and eliminate code p0303 it will be fine. If you know someone with a scanner you can drive while looking for convertor clutch command. If it is locking up when commanded you know for sure its not the trans, but something causing the computer to not command it on. The trans temp sensor in the pressure switch or the engine coolant temp sensor can be off and never throw a code unless the signal is totally out of range. How would the computer be able to tell between a sensor off by a few degrees and a trans that just isn't warm enough? Shift solenoids don't affect TCC operation at all. The TCC PWM solenoid by the dipstick hole and the lock-up solenoid sticking into the pump right behind it control lock up. Todd