4L80 lost reverse and 3rd partially

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92Raiderburban

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Manually shift '93 4L80. So about 3 months ago, lost reverse and 3rd. did a partial fluid change after changing the filter. Got 3rd and reverse back. Been fine up until a bout a week ago. Same symptom. This time check filter to make sure wasn't clogged up. Wasn't. I have 1st and 2nd. Shifts into 4th (via visual rpm drop) but when opening throttle to half way, rpms jump to 2200. TCC locks up but only drops about 200 rpm roughly. B Solenoid dead ? Or my clutches toast?
 

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This is a '92 converted to carb 'n' non-electronic spark advance. Manual shift because there's no computer to do it properly?

My first guess would be the direct clutch, although that should affect overdrive as well as 3rd and Reverse. If it was the shift solenoid, you'd lose 4th gear, too.

Overall, I'm not sure what the issue is. I suppose it could also be a fault in the trans controller or controller wire harness between your trans controller and the transmission.
 

92Raiderburban

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This is a '92 converted to carb 'n' non-electronic spark advance. Manual shift because there's no computer to do it properly?

My first guess would be the direct clutch, although that should affect overdrive as well as 3rd and Reverse. If it was the shift solenoid, you'd lose 4th gear, too.

Overall, I'm not sure what the issue is. I suppose it could also be a fault in the trans controller or controller wire harness between your trans controller and the transmission.

You must be registered for see images attach

This is a '92 converted to carb 'n' non-electronic spark advance. Manual shift because there's no computer to do it properly?

My first guess would be the direct clutch, although that should affect overdrive as well as 3rd and Reverse. If it was the shift solenoid, you'd lose 4th gear, too.

Overall, I'm not sure what the issue is. I suppose it could also be a fault in the trans controller or controller wire harness between your trans controller and the transmission.
Yes manually shifted via toggle switches
 

Schurkey

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How are you controlling fluid pressures? Isn't the pressure regulator PWM? If there's no pressure rise under load or in reverse, I can easily believe you're having clutch/band problems.

I've never been inside a 4L80E. Rebuilt a few 400s, though.
 

tayto

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did you do any internal mods to support running full line pressure all the time?
 

Schurkey

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Lol, can you please expand on that? I've never heard of a toggle upgrade for the -80.
Oh, it's NOT an "upgrade". It's prehistoric tech--Purely Primitive Pete.

You have three toggle switches within easy reach. One for the 1-2 shift solenoid, one for the 2-3 shift solenoid, and one for the converter clutch.

You throw the shift lever into "Overdrive", and flip the 1-2 solenoid switch "on" while leaving the 2-3 solenoid "off". You have first gear. When it's time to shift, you turn the 1-2 switch off. Second gear. Time to shift again? Flick the 2-3 switch "on" for third gear. Flick the 1-2 switch "on" while leaving the 2-3 "on" for overdrive. Somewhere in there, you turn on the converter clutch. I think the converter clutch switch can be left "on" because it's inactive in first gear anyway--won't stall the engine at stops, but also no torque multiplication from second gear onward.

Reverse? Put the shift lever in "R", and turn on the 1-2 switch.

This could be wired to a multi-position rotary switch, you'd have to turn the knob for each gear change rather than moving individual switch levers back and forth. Kent-Moore sells a "special tool" with a heap of wire harness adapters for all sorts of electronically-controlled transmissions across the GM lineup; you plug in the tool to the adapter harness, plug that into the big connector on the side of the transmission, and you can shift gears by turning the knob back and forth. I bought one from eBay, but I don't have the harness connector to go with the vehicle I bought it for--an early-90s Lumina that won't move under it's own power.

It would take significant convincing before I'd accept this sort of trans control as anything other than a diagnostic aid; and as said--how do you control trans pressure? Sounds like a trans failure waiting for enough mileage to happen.
 
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tayto

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while I would not control the 4L80E this way myself, you can do it, but some internal mods that should be done. also a note if you are not running a small diameter torque converter be conservative on shift hole orifices as the transmission is running at full pressure regardless of throttle position or engine load. hard on the drivetrain, transmission, engine blah blah blah race only blah blah blah
 
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