Sudden Auto Transmission Failure

[4x4hokie]

1994 Explorer 4x4
Automatic
My daughter was returning from work lastnight and experienced a sudden trans failure. She said that when she pulled out onto the highway the trans shifted normally from 1 to 2 and from 2 to 3, but when it shifted into overdrive it suddenly popped and immediately she had no power going through the trans. She drifted to the side of the road and had to be towed home. The trans is totally dead. The fluid, which is about a year old, looks and smells fine. The engine starts and runs fine but the trans acts as if it is in neutral regardless of where the shifter is. Park does work to hold the vehicle as normal.

What could have happened?

 

[Glen4X4]

Torque converter maybe? (im no pro at auto trans) Did you try and jack up the rear and try to put it in gear to see if the trans will run without much of a load on the tires?

 

[4x4hokie]

Did not try that but I'm 99.9 % positive that no power was being transfered to the driveshaft as when I put it in gear, the engine did not react at all. With a torque converter failure I would suspect some noise in the form of rattling parts or screeming fluid flow to be present.

I'm thinking that the shaft that drives the pump has snapped.

Tha's about the only thing that I can think of that would be so sudden and so clean and immediate of a failure.

 

[Glen4X4]

True...didn't think of that....

 

[wood1]

A very easy way to tell if the pump is working is to remove a transmission cooler line and start the engine. If you have flow the pump is OK.

If the pump is pumping and the fluid level is good you will have to get your hands dirty.

I'm assuming there is no reverse either.

 

[4x4hokie]

What would cause a pump to fail so suddenly and cleanly with no indication before it went?

 

[fordnut71]

the pump gear is made from powder metal

 

[BrooklynBay]

Check the pressure with a 0-300 PSI gauge to get pressure readings. The next step would be to drop the pan, and check the Z link. You said that park doesn't work. The Z link might have either bent or popped off. Check the inside of the pan for metal shavings, sprag gear fragments, and band hardware.

 

[4x4hokie]

Park does work. I will drop the pan though and check. I'll also look for fluid flow through the cooler (before I drop the pan). The pump gear theory seems plausible. Does anyone have any other ideas?

 

[fordnut71]

could have blew out the gaskets on the valve body or sperator plate. but you should see trash in the pan if thats the case.

 

[out-of-luck]

also i would check to see if at possible the transfer case is fully ingaged i also had the same problem a few years ago when the gear inside the transfer case became disingaged i had no gears whatsoever i called a friend who is a mech he told me to pull the tranfer case motor off and manually with vise grips rotate it into 4 low and you know what it worked and got me home i would try that because if no problems existed before hand and then all of a sudden bang id try my idea first id rather repair a transfer case than get riped off by your mech for a rebuilt transmission hope this helps