No forward or reverse. Not new install

[mewinter]

Ok heres the story. 97 k1500 5.7 Tranny has been in truck 2 years with no issues.Driving down the road, went to pass a car and tranny slipped badly. pretty much just coasted home. no bad noises, no grinding.
Now I have no forward or reverse, kinda. Truck will try to move a little but not till around 4000 rpm.
I removed tranny from truck and stripped it to the sun shell and gears expecting to find something but everything looks great.
Fluid is clean and not burnt. Small amount of clutch material in pan but no chunks or debris.
Didnt check line pressure, but when started fluid drops on dipstick. Ears are still on pump.

What could it be? Torque converter? Anything else that could cause this?

 

[98_k1500]

I have seen a torque converter quit pulling. Have you air checked your apply pistons? If everything looks good there, the pump can be checked for clearance with a feeler gauge. Also check your transfer case. Slim chance but it could be stripped behind the trans.

 

[great white]

Sounds like clutches or line pressure from your description. You say the gears and baskets are good, so I'll take you word on that.

Clutches can be measured, but its usually fairly obvious when you take them out. Sudden loss of drive all at once doesn't seem to jive with failure of the clutches. All at once and completely would be pretty rare.

Line pressure sudden drop is usually a valve body, solenoid or pump issue.

Valve bodies wear in the bores, solenoids fail and pumps can shear drives.

I'll assume you scanned for codes so the solenoids are good if nothing showed up.

I'll also assume the pan was clean.

Converter is a possibility, although theres not really a lot to go wrong in there. Maybe a buggered turbine, but I've never seen one. But I'm not a trans guy either.

That leaves valve body or pump in my mind. Pump sounds good from you description of fluid drop when started and visual inspection, although pressure output is unknown. Too bad you didn't throw a gauge on the test port before pulling in down. That would have told you a lot. Should have seen around 200 psi starting off iirc. Less than that indicates a calved pump issue. I can't recall specifically, but I think OBDII will code for low pump/line pressure.

Valve body wear is usually something over time, not a fail all at once.

Seems to be all pointing to a pump issue of some sort.

I'm no transmision expert, just a guy who mostly knows his way around inside them a bit, but that's my take on it.

There's a couple transmission guys on the board, hopefully they will chime in on the matter....