Been a long time lurker of the board. I have a 4L80E transmission issue. Ok a little history on the transmission: Unknown year 4L80e from a junkyard core bin, I know its got to be before 1996 due to the cooler ports are close to the bellhousing. Tore trans apart Summer of 2014, found forward and direct clutches welded together. Found transmission had been rebuilt before I got ahold of it as it had a transgo shift kit installed into it. Repaired everything I found wrong and internally dual fed the direct clutch pack by removing second sealing ring from the top of the center support, left out the inner seal on the direct drum before reinstalling the direct piston and plugged the low/rev port in the transmission housing to effectively dual feed the direct clutch pack. Reassembled transmission and installed into car. I just got the car running in January 2016. I went to do some burnouts in my garage, transmission made one heck of a bad noise, also acted as if it wasn't in first gear. Pulled a fluid sample and found the fluid burnt and metal in fluid (under 20 minutes of run time). Removed transmission again and tore down. Found Forward clutch pack metal on metal again due to my stupidity in ripping the forward clutch seal. At this time, I knew the transgo pressure relief setup was going to become a issue at some point. So I ordered a used valve body for a 92-96 4L80E. Tore valve body apart and inspected all valves. I replaced the manual valve. The old one slid in and out a little to easy, like it was going to cause a cross leak, new valve repaired the feeling and felt "good" on reassembly. Updated both the forward and direct clutch pistons to the newer steel pistons with molded rubber seals. Was VERY VERY cautious on reassembly to not rip the seals, installed good. I installed a sonnax self regulating boost valve to prevent case blowout. Removed the wavy plates from the direct and forward clutch packs. Set pack clearance at: 0.050" on my forward clutch pack and 0.060" on my direct clutch pack. Replaced the output shaft bushing with the sonnax no walk bushing. Drilled these shift holes out to 0.094"



Reassembled transmission and reinstalled into car. Checked my shifter adjustment 4 times thus far. Shifter adjustment is correct. Transmission is wired for full manual valve body. This is how the transmission connector is wired up. Pinout:



Wiring setup: Pins N-R-A together and tape into the harness.
Pins P-B together and tape into the harness.
Supply switched power (ex. 12VDC Ignition switched power) to pin E to power up the transmission solenoids.

Issue. Transmission is starting out in second gear. With the rear axle up on jackstands I pull the shifter into manual low. Throttle engine, rear tires start spinning really fast then I am experiencing engine braking and it "finds" first gear. Stop tires with brakes. Restart, again starts in second gear I believe, I shift the shifter to 2nd, no change, Shift to 3rd, if its shifting I'm not super expressive. Now gearshifts 3-4 and 4-3 are VERY evident.

I'm about at a loss.. Any help would be GREATLY appreciated.

 

I was recommended to check the intermediate sprag to see if it was installed backwards. I tore down the trans last night. The intermediate sprag IS freewheeling clockwise and locking counter clockwise as it says it should be in the 4L80E manual. Any suggestions on diagnosis would be GREATLY appreciated. Thanks!

 

Checked both my forward clutch packs and my directs. Loosened up my forward clutch pack a little bit, it did have the signs that the pack was a little to tight (clutches were lightly glazzed). Air checked both packs - work as intended. Checked the forward clutch pack through the front input shaft holes - works good still. I disassembled my valve body, no sticking valves. The shift solenoids O-rings felt nice and tight but I replaced them anyhow because I was right there. All the filters are clean, no metal or debris in them. Checked the checkballs in the valve body, not sticking and working good also. I'm about at a loss. I'm going to reassemble the trans and just start air checking EVERYTHING to figure out what on earth is going on.. Also going to make up a line pressure setup so I can see what kind of pressures I'm seeing whenever I get it back together. Everything inside the transmission though looks good... This one has me totally confused..

 

Did you take apart the valve body and ensure no crap was binding valves?

 

Yes Sir. No sticking valves in the valve body. I'm reassembling the transmission tonight to perform air checks. I'm starting to think from the heat shown on the forward clutch pack clutches from about 3/4 of a hour of run time is from a leak from the input shaft seals, but I'm going to test that theory hopefully tonight or this weekend.

 

Did you ever figure out what the issue was with this?

 

might be in limp mode,if it stuck in 2nd gear, have you got the tune checked out

 

Did you verify operating pressures? AFL problems I had caused low pressure, 2nd gear only operation as well. Low pressure contributed to me toasting clutches during a spirited test drive.

D'oh!