namasgt

That oil pump has to come out. The assembly looks very different to the 3 speeds. Can you see a way to take that spring assembly apart, so that you can get to the oil pump bolts. Also can you see the bushing behind the main seal. If you have the main seal off you should see it.

Bill Ball

Greg Brown commented that the friction plates in the B3 stack are the first to go and that they are easy and cheap to replace and will save the band. I'm going to wait a bit and do a proper tranny pull before I delve into that. I have an LSD to install, etc. I looked at the WSM - most of the good info is in the re-assembly section, which I didn't get to, so that's why I didn't find it too helpful in the disassembly phase.

Where is the B3 piston you say that has no signs of wear? [EDIT. Oh, so this is the B3 piston. Yep, it looked like new.]

Bill Ball

OK, I did not understand the oil pump disassembly. The WSM volume 3 seemed to skip that, but I just found it after the valve body section, starting on 38-150. OK, it's all there, just not anywhere near workflow order - I should have known better than to expect that. I see what you've been trying to tell me about it now. Thanks for holding my hand on this process.

namasgt

On the 3 speeds there is a bushing (bearing) on the inside of gear number 13 on page 143. S4 may not have this from the looks of it, but please post pics of each piece of the oil pump. On this picture below from WSM page 145 Vol_3, you can see the bushing behind the main seal that I mentioned. If this is worn out it will cause too much oil pressure behind the main seal, enough that the drain hole is too small to take care of it. Therefore, it just leaks out. Note that they say change the pump, which is about a $1100 from Porsche for the 3 speeds. However you can get the bushing from Mercedes for around $10-$23. there should be a Mercedes part number on the oil pump body.

Bill Ball

Excellent. I found the pump specifics in volume 3, section 38, starting on page 150. I will disassemble and take pics on Monday.

Bill Ball

Exploded view of primary pump, for those following along this blow-by-blow learning experience. Item 16, the main seal for the TC, was the only thing I originally planned to replace, although I also have item 15, the pump's internal o-ring. Stan has advised to leave item 8 alone, and I presume the same applies to item 7.

borland

The B3 piston on my 90' S4 had no wear too, but it would slip in Reverse when backing up a hill, then unexpectantly grap, making it unsafe to drive.

I believe the wear appears where I have the arrows pointing, as these tines push on the clutch pack...

Bill Ball

Thank you, Brian. I have no shifting problems, just an unfortunate self-induced TC leak, but I will look over B3 more closely.

Bill Ball

Based on the exploded view I show in post 66, it appears there is a circlip (item 3) holding the primary pump together. The WSM does not indicate how you take this thing apart. I can't find any good exposés on this procedure. What Adam did on a different but similar assembly was use a press on item 4 to compress item 5 (springs). Adam used a section of PVC pipe with a window cut into it to access the circlip. I would suppose you need to use a press to reassemble. The WSM shows a guide tool to avoid screwing things up on reassembly. How have you guys done this?

Leon Speed

Never did this but maybe a couple of large screw clamps can be used on the spring plate.

Bill Ball

OK, I have forged ahead and am in the reassembly phase. I tried to hold the gear assembly up and centered as I snugged up the pump. As I snugged the bolts, it lost the lateral play and the shaft would not rotate. I loosened the bolts and pulled the cover out a slight amount and tried to recenter the gear set, holding it while snugging the pump, only hand tight. Same problem. Do I need to do something about that? [EDIT: OK, I got it on the 3rd try. Held the shaft more firmly and made sure it had lateral play as I snugged the bolts slowly and evenly. It's rotating now even after torquing the cover bolts. Thanks for the warning, Ali.]

namasgt

No Problem Bill.

When you replaced the main seal, could you take a good look at the bushing?

Bill Ball

SOMEONE here claims to have installed the TC with the transmission horizontal. I'm beginning to have my doubts about that. There are two sets of splines that have to engage. The inner set is part of the TC core which is separate from the rest of the TC and it falls off-center so the two sets will not line up with the TC held horizontal. I've tried moving the TC around as I try to install it, which is basically a no-no, hoping to get the shaft to line up with the two sets splines in the TC, but it's a no go. I'm risking mooching the seal as well. Whoever has done this, and I know some have claimed to, now is the time to step forward.

If anybody ever again says you can remove the TC and replace the TC seal with the tranny in the car, at least on a 4-speed, I will request they be banned for life.

Ali, the bushings were good. The new seal may be mooched already. Is it a real tight fit getting the TC snout through it? I don't have the weight of the TC to assist me. I have a load of Vaseline on it. Maybe I'm just feeling the resistance of getting centered and going through the seal initially, but I've put some weight against it.

[EDIT: To answer my own question...I did some measurements and the snout gets to the seal about an inch before the splines make any contact, so the resistance I'm running into is the seal.]

Bill Ball

OK, the TC is in and buttoned down. It required a remarkable amount of pressure to get the TC through the seal even when properly centered and only minor joggling to get the splines and shaft to fully seat and engage the gear set. Just need to reinstall the TT, fluid lines, lift the rear back into place and install the bellhousing and flexplate and odds and ends. About the only thing I did not have to do is detach the parking brake and ABS/brake pad sensor wires. Whooptidoodle.

I hope you've enjoyed following this tale of frustration. "Look! Bill's acting like an idiot!" It was a valiant experiment. Had it worked as I thought it might, it COULD have been a time and trouble saver. I can now say conclusively - DROP THE REAR SUSPENSION AND THE THE TRANNY OUT ALL THE WAY, like the good book says. I actually generally do what the good book says with only a few deviations that work for me. This did not work. Oh, I got 'er done, with a lot of hair pulling and a good chance that the repair might fail from manhandling the TC on reinstalling with the tranny horizontal. If it does, the tranny will come all the way out and get a complete going over, by the book.

namasgt

Bill,

When I did this repair on the 78, the rear of the car was on jack stands and the front on the ground. I used two floor jacks one to support the transmission and another to hold the rear suspension. Once the rear suspension was undone, I lowered it and moved it out of the way. Then I slowly lowered the gear box, enough so that I could undo all the 6 bolts holding it to the torque tube. I am saying enough because the engine is still bolted to the motor mounts and they could flex a lot while doing this, also there is not much room in the engine bay and you don't want the engine to hit the lines on the fire wall (don't forget to undo the whole air box and cross brace in the engine bay!). Once the gear box was down I moved it away from under the car. I generally try to spend as little time possible under any car. The torque converter went on easily, I just had to make sure the slotted end aligned correctly to the inside shape of the small oil pump gear. You have to be very careful doing this not because of the main seal but because of the bushing, don't want to gouge it. If you feel resistance slightly rotate it to left or right, it should go in.