4L80 No 1st Gear

[L31MaxExpress]

I'm sure as of the last time I checked fluid level which was after running it up on the lift through all the gears and then after an actual test drive.

Did you check the accuracy of the dipstick. The unit I just worked on was 2/3" above the stock full line using the OE tube and stick to get the fluid the recomeended 1/4" above the pan rail. With the Moroso deep pan my Express van takes 3 gallons to do a drain and fill or filter service. Verified the stick on it when I swapped the Moroso pan on and it was about 3/4" off on it. The van is tricky though, have to pull the stick out 4" and shove it back in a good 2-3x before the stick inserts all the way into place. I have gotten in the habit of jiggling the stick in and out listening for the click of the stick bottoming out in the pan before checking it. Stock van stick bottoms out in the pan to get an accurate reading, with the stock pan it was right at the pan rail, with the Moroso pan being taller it moved the full mark because the same stick drops further into the unit.

 

[Supercharged111]

I mean it's the same trans with the same dipstick and tube as before and it never did it.

 

[NickTransmissions]

Failure with heat sounds electrical in nature. Think heat soaked starter or alternator here. Works when cold, fails when hot. I would think a roller clutch would just outright fail and be done once it failed. Been wrong before though. I just went into a 4L80E that would not shift above 2nd and it was corrected by addressing a sticking 2-3 shift valve, replacing the solenoids and internal harness. From memory 1-2 solenoid has to energize to have 1st gear and de-energize for 2nd gear and the shift valve has to move forward and away from the solenoid when it applies pressure to obtain 1st gear. If the electromagnetic coil in the solenoid is failing with heat you will not get 1st gear. In theory a failed solenoid would also make 4th disappear as well as it re-energizes 1-2 for 4th. Does it still have 4th gear after 1st disappears? Even after driving it 20+ miles around town up to as much as 60 mph in 2nd gear with the shifter in Drive the unit I was working on never set a single code.

Electrical gemlins can cause all sorts of problems. The four speeds wont throw codes for mechancial issues unless the logic is specifically coded into the PCM to look for those mechanical failures. In your case, a stuck 2-3 shift valve without a voltage-related solenoid failure wont throw a code. Nothing surprising or unusual about your situation as it was constant.

@Supercharged111 's is intermittent with a bias towards failure when hot which can be eletrical or mechanical, depending on the character of the symptom.

Supercharged 111 - what ended up being the cause in your case?

 

[Supercharged111]

A couple days ago he poked it with his scanner and did a visual once over. Today he took a ride with the scanner and got it to drop first gear like it does for me, so next week he'll dig a bit deeper. I just need it fixed by the end of September which is when I'll head back to CO to pick it, the camper, race car, and trailer up.

 

[Supercharged111]

He was able to replicate the malfunction as I observed it, 1st gear until 160 then no more despite being commanded. He put a new 1-2 solenoid in and now it's good to go. Been on multiple rest drives and never lost 1st. But I won't see the truck for another month.

 

[NickTransmissions]

He was able to replicate the malfunction as I observed it, 1st gear until 160 then no more despite being commanded. He put a new 1-2 solenoid in and now it's good to go. Been on multiple rest drives and never lost 1st. But I won't see the truck for another month.

Was that solenoid bad out of the box or did he not replace the solenoid to begin with?

Also, ask him if he still has the bad solenoid and if he has the equipment to test it for mechanical function. If not, Id like to get my hands on it to test as I have the equipment to do that kind of testing..

 

[Supercharged111]

Was that solenoid bad out of the box or did he not replace the solenoid to begin with?

Also, ask him if he still has the bad solenoid and if he has the equipment to test it for mechanical function. If not, Id like to get my hands on it to test as I have the equipment to do that kind of testing..

I can ask if he kept it, I believe it was my original reused. I know I p!ss3d one off on a 4T65E replacing an overdrive drum I think it was. Somehow the shift solenoid got ruined in the process and shot out a ball and spring, but its symptoms were consistent with a bad shift solenoid.

 

[NickTransmissions]

I can ask if he kept it, I believe it was my original reused. I know I p!ss3d one off on a 4T65E replacing an overdrive drum I think it was. Somehow the shift solenoid got ruined in the process and shot out a ball and spring, but its symptoms were consistent with a bad shift solenoid.

If he did, id pay him to ship it to me so I can do a video testing these solenoids, talk through the symptoms and use your situation as an example of what symptoms can present with bad shift solenoids. Id never mention any names just a an overview of the problem, symptoms and cause while i do the testing...

 

[Supercharged111]

If he did, id pay him to ship it to me so I can do a video testing these solenoids, talk through the symptoms and use your situation as an example of what symptoms can present with bad shift solenoids. Id never mention any names just a an overview of the problem, symptoms and cause while i do the testing...

I can quietly get it from him (if he didn't pitch it) and just ship to you on my dime.

 

[NickTransmissions]

I can quietly get it from him (if he didn't pitch it) and just ship to you on my dime.

Awesome, man - thank you! Please reach out via PM if you can secure it and ill provide my shipping info...