Auto transmission GURU's need help!!!

[jahnaboi]

Long story short:

Friend has a 1991 325i 4 door auto. Friend's girlfriend was driving on the freeway, car made weird noises and shut off on its own.

Brought it to me, only to find out 3 of the wrist pins on the pistons came out causing the rods to fly freely through each revolution. Cylinder 4 and 5 had punched windows where i believe the rods came out (couldn't find them anywhere, probably fell on the freeway). Messed up block and some bent valves meant we needed a new working block and some valves.

Got the motor running good, transmission bolted up and never touched it. Start the car, and the automatic transmission has no oil pressure. Figured he was low on ATF oil, checked it and it was full. Disconnected the top cooling line and started the car waited for fluid to squirt out but none. Not a single drop.

Cliff Notes: Transmission was functioning perfectly fine before the incident occurred. The motor giving up should have no relation yet it seems rather weird as to why it would go out as well.

My question:

1) Does the automatic transmission build pressure based on revolving gears/flaps or does it have a pump to build pressure?

2) Because there is no pressure but full fluid, is it possible that just the pump went out?

3) If the pump did go out, has anyone documented this repair?

4) If it isn't the pump, what else could it be?

5) Help me, as my friends car has been sitting in my driveway for a week.

-Jasper

[jlevie]

Something doesn't sound right. There's no way for the wrist pins to come out and free the upper end of the rods. They'll hit the cylinder walls if the snap rings aren't in place. While one can through a rod in any engine, I have to wonder how you'd manage that with an automatic transmission that was working properly. Unless the car was doing well north of 100mph in 4th gear the engine rpm won't be high enough to throw a rod, let alone a couple. But if the transmission went berserk and down shifted while the car was at highway speed to say 2nd, I could see bent and/or broken valves and thrown rods. That could explain the current transmission problem.

[jahnaboi]

That does sound feasible. I'll have to ask my friend to ask his girlfriend the exact details what she experienced. There's nothing harder to figure out when a girl is the one driving the car.

[SpecM]

There's nothing harder to figure out when a girl is the one driving the car.

I know what you mean there

[whodwho]

Most likely the torque conv was not fully seated when you bolted the two together and tabs of the conv and pump weren't aligned and broke the front pump.

Motor or tranny would have to come out pull the conv and the pump is visible and removable without getting into the tranny.

[jahnaboi]

Well when I put the transmission together we put them together by hand (a lot of strength to hold that sucker up, that transmission is heavy!) and got them sitting properly with a 1/4 inch gap between the transmission housing and block. Then I used the transmission bolts to bring it in, tightening each bolt by little increments. If the shaft did break (for the pump) wouldn't it leak oil? So the pump is just inside the bell housing where the torque converter meets it?

[whodwho]

That sounds like what happen, they should go together flush without having to draw them together. That last 1/4 inch was probably where the tabs of the TC and pump weren't aligned. It would be the pump gear that broke and no it won't leak. Yes when you pull the TC you will see the pump bolted on in the center of the bell housing.

#5


You can see the tabs on the TC and pump gear in these pics

Tabs on converter


Tabs on pump gear

[jahnaboi]

Interesting. So the pump gear would be damaged not the TC itself? Guess since it requires removing the transmission again, I'll have to put it on hold till after my 4 tests coming up.

[whodwho]

There is a possibility of damage on it as well tho I suspect just the gear. also hopefully there wasn't much in shavings from any of the damage. You will want to find a used trans(or pick-a-part) to get this from as new it would have an outrageous price.

Don't know if you have pulled an auto(with engine still in) and especially if on the ground it is not all that much fun...been there done that a couple times.

Good luck and let me know if you run into any issues along the way.