Transmission Issues

Taylor Jones · July 23, 2018

Hey guys, new to the forum. I signed up to try to get help with this problem. I'm always looking around to see if I can find good info here. I own a 2003 Chevrolet 1500HD. As you guys know it has an LQ4 4l80e transmission and 3.73 gears. I recently put a cam in the truck and dropped the transmission to change the rear main seal oil pan gasket and some other gaskets. I put it all back together and I'm loving the idle of the cam, but I'm having some pretty serious transmission issues.

I'll preface this by saying...fluid is topped off, still looks red on dipstick. Some fell out of the TCC when we dropped the transmission and it was pretty dark, but didn't smell bad. I have triple check the wiring harness and I haven't found any unplugged wires, also no MIL codes for transmission.

Issue #1 it gets hot. I can just be idling for 15 minutes or so and the transmission will get to almost 200 degrees. If I jump on the highway it drops about 10 degrees but as soon as I slow down it jumps back up there.

Issue # 2 If I drive it cold I don't have this issue, but as soon as it warms up I notice it tries to take off in 3rd gear with torque converter locked. It will unlock enough to not let the engine stall but as soon as I jump on the gas to take off it lugs the torque converter locked and seems like it's in 3rd gear. I've done 2nd gear starts and it doesn't feel like that. As soon as I give it a little extra gas though it jumps down into 1st and drives normal. Goes through every gear just fine. Torque converter locks and unlocks perfectly fine. Only problem I have beyond the takeoff is its getting to warm for my liking. Warmer than I used to remember.

Issue # 3 When I put it in reverse torque converter is unlocked, but when I start to roll at idle it locks the torque converter. This causes the truck to stall sometimes if I jump back on the brakes. If I just let it roll the truck will get up to like 10 mph without any throttle or rpm change. If I understand correctly the torque converter should never lock up in reverse or first gear.

Issue #4 I found this out by fluke... I engaged tow/haul mode and the truck will not get out of first gear. I haven't tried putting tow haul mode on while rolling over 30 mph, but even at that speed it jumps into first and unlocks TCC. it'll idle even at 20 or 30mph but as soon as I get on the gas you can tell it's in first. RPM skyrocket till it catches up with driveline speed.

I had a tuner flash a mail order tune for the cam. I was going to see him this weekend for a Wideband tune. He said that this funky transmission stuff shouldn't have anything to do with the tune. The only thing that he changed is making gear changes firmer. With that said I'm guessing that's line pressure that he adjusted. I could be way off base here, but Would a weak pump or too low of idle cause the TCC to not unlock, or do these funky things? Truck seems to drive fine above 1000rpm, but at idle is when I have my issues.

To answer further questions. I have no Transmission codes. Only MIL I get is P0101 and my tuner said he would fix that issue when I saw him this weekend.

I appreciate any help or advice I can get.

sefiroxx · July 23, 2018

Shift points are tied to gear, speed, rpm, and gps so a tune could have affected it , but unlikely.

The symptoms of lots a 3rd gear problems sounds like the tranny could be in limp mode. Make sure the wire harness is plugged in properly and there are no broken wires.

Taylor Jones · July 23, 2018

Any ideas on the TCC Lockup in reverse? Also I was thinking limp mode with these transmissions was 2nd and reverse only, unless there's a couple of different ways it could respond.

So I checked the wiring harness yesterday and nothing seemed out of place, all was plugged in good. Only wire I've had issues with was a dark green wire that goes into the harness on the park/neutral Solenoid. It was broken before I took the transmission out so I fixed it, but then started having all these issues, so I cut it again thinking what the heck. Didn't seem to change my scenario. I'll fix the wire again and make sure I have a good connection though I don't think it has anything to do with my issue. Looking at diagrams shows its for the park/neutral location of gear shifter.

I'll look around and make sure I didn't miss anything. Would I not have MIL Codes for transmission though if something was unplugged or plugged in wrong?

sefiroxx · July 23, 2018

Normally yes, it would throw a code, but if not properly set, then partial operation would be symptom.

The green wire/neutral setup is there to prevent starting when in gear. Once started, that pay of the circuit is ignored.

You might have a short in the internal wiring harness. My 01 FSM has a procedure for checking the harness and solenoid. Not sure if its the same on 12 with 80e

Supreme Pizza · July 23, 2018

If you disconnected the coolant lines, are you sure they are hooked back up int her corrector?

If I had to guess, I would say that the computer is freaking out over something to do with the cam swap. For example, a bad throttle body and cause very odd transmission problems. Its all computer controlled, and you know how computers can be.

Did you try unplugging the battery for a bit?

Taylor Jones · July 24, 2018

I’ve unplugged the battery a few times. Even held leads together for 30 seconds to clear the computer but if the truck is warm it fires up and drives the same exact way.

I disconnected the cooler lines, but didn’t remove them from the truck, it’d be impossible for me to have swapped the lines accidentally mainly because they’re solid aluminum lines all the way up to the radiator cooler.

Taylor Jones · August 7, 2018

So I had a transmission guy look at my truck and drive it. He connected a Matco Tools Maximus 2.0 diagnostics tool. He confirmed that shifts were all good, and TCC was unlocking and locking as it should. He is pretty convinced that I have a bad MAF. My tuner said that it is throwing the code because the truck does not know how to idle properly with the new cam. So he suggests its fine to drive up to see him for the Wideband tune. What I need to figure out now is if I need a new MAF or if it really is a value that needs to change for the MAF to read properly. I have images of the live data values that I'll upload. I'd love some help deciphering it. IAT Values look good. IT's been hot here so I looked for low temps first off, but it normally reads about 99-110 degrees. It's been about 98 here lately. At idle MAF values show an actual value of around 1.513 lb/min. MAP values are 21.0 in/hg. Short range fuel trims and long range fuel trims show a high negative value of about -18 to -22 when warm. When cold a different story. I will say fuel economy has been horrible. About 8.8mpgs on the last tank of 200 miles. I averaged about 12-13 before the cam and tune. I haven't even been able to drive it hard so there's no excuse for the poor fuel economy except that I guess the tune is causing it to run extremely rich. UNLESS...I actually do have a bad MAF sensor causing it to overfuel like crazy. The guy tuning my vehicle has done thousands of these engines, and had personal experience with this exact cam several times. So much so that he sells this cam in his shop. No doubt in my mind he knows what he's doing. I'm trying to decide if I want to drop $80 on a new MAF or drive the truck up and get the tune finished before I do that.

I should mention. His shop is almost 300 miles from me which is why I'm contemplating. If he was right down the road I would make no question about it.

swathdiver · August 7, 2018

You've got a pretty big vacuum leak, probably intake gaskets or something loose or forgotten when putting it back together. Once that's fixed then consider the MAF and tuning.