Need help diagnosing funky rebuilt transmission I did

[ALIKA T3]

Hello folks!

I rebuilt my transmission a couple months ago and it is far from working correctly.

I'm looking for minded people to help me diagnosing what the hell is going on, and hopefully this thread can serve to other people as well in the future.

The rebuild thread: https://www.thesamba.com/vw/forum/viewtopic.php?t=675821&highlight=automatic+rebuild

I have brand new bushings, pistons mostly VW brand, discs, frictions,brake band, well everything that gets usually worn out got replaced, and even a brand new valve body from Porsche.

So now with the problems, that the new valve body didn't address :
The fluid level is good, type F Ford fluid per TK, I went driving around about 1000 miles before replacing the valve body and brake band that got messed up with by me from tightening it too hard somehow (bad torque wrench?) I also had a plastic thrust washer breaking, that's mostly why I re-opened everything.

>>>If I set the brake band with the torque wrench at 87 then 43 Inch pounds, the van can move in D in the carport, but I loose the Reverse. I didn't go driving around like that. The engine is forcing and cannot rev' high, similar feel to if I had the parking brake ON. For having tightened it with the transmission open to loo at how things work, I don't understand how the hell the D/R clutch drum can be spinning at all with this setting, unless pressure is building at the brake band cover to release the tension from the brake band squeezing the drum. So maybe my pump is bad? I don't have anything to test the pressure from the ports.

>>>>If I loosen the brake band and adjust it barely hand tight, the van has a fully functioning reverse, and can only move in position 1, once I have speed in motion, it can be switched to D. Depending how hand-tight the brake band is, if the van downshifts at low speed, the tranny will slip.

The play is a tiny bit too high in the stack of discs in the forward clutch, 1mm vs 0.9mm max. I plan on re-opening the transmission again and address this issue.

But that wouldn't explain why I have no reverse with the brake band adjusted in specs?? Do I understand things correctly thinking it's pressure related at the brake band?

Also how does one know what a bad torque converter does?

One of the oil pump teeth had a groove on the side of it, but it is not at the mesh part of the gear, so I left it alone. Should I install a brand new pump?

Thank you very much for your help, you knowledgeable you!
_________________
Silicone Steering Boots and 930 Cv boots for sale in the classifieds.
Syncro transmission upgrade parts in the Classifieds.
Subaru EJ22+UN1 5 speed transmission
http://www.thesamba.com/vw/forum/viewtopic.php?t=416343
Syncro http://www.thesamba.com/vw/forum/viewtopic.php?t=4...num+gadget

[MarkWard]

Reread how to adjust the brake band. The torque specs are only to seat the band assembly. Once you have seated it, I recall you back off the adjuster 2 1/2 turns and lock it down. Mark
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[pablum]

I'm close to certain backing off occurs between the torquings down.

Look for SSP8 to see how the band piston is pushed in to relax the band: it's just as you surmised and there is a port into the space beneath the piston to relax the band and one above it to tighten it.

For no reverse and draggy forward, I think the only thing is to remove it again, see if you get a similar result hand turning it and then careful inspection during disassembly for further clues. This goes a bit beyond the diagnostic tables.
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The wise man learns from history, the fool from experience.
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I see [a cat] in the street and i aim for the pest with my car. -- bluebus86

[Terry Kay]

[pablum]

Checking your work, all I can think of for now are

Did you replace the brake band you installed wrong? It's surely nogood

Did your replacement Pistons match the tranny? Some require a ball check valve and some do not.
_________________
The wise man learns from history, the fool from experience.
-
I see [a cat] in the street and i aim for the pest with my car. -- bluebus86

[ALIKA T3]

[ALIKA T3]

[pablum]

[pablum]

[ALIKA T3]

[pablum]

[ALIKA T3]

[ALIKA T3]

[MarkWard]

I don't know the answer to your question. I've never misadjusted one, drove it, and then tried to adjust properly.

I am pretty sure the manual also has a pressure table. Since you are on a learning curve, it might be worth hooking up a high pressure gauge and getting some readings.
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[ALIKA T3]

OK, update time!

I dropped the transmission yesterday and opened it.

I bought a air nozzle with a rubber tip, fixed up an old air compressor found at the trash, and was ready for some tests!

The valve body removed, I tried to blow air , the main big piston (1st gear brake piston) works: I could see the clutch packs being engaged with a clear sound.

I've installed a thicker pressure plate for the forward clutch assembly to get back in specs, but it's barely enough... Upon inspection, I've notice some wear on the diaphragm spring that made me look closer at the parts. It turns out the bottom thrust plate is actually worn a little on the conical edge, same with the forward planetary ring gear, but I don't know how it could not touch the diaphragm spring....

I'll try to get good used parts from my local mechanic to replace these, maybe the thrust plate will help get back into better specs.

I looked at the one way clutch with plastic cage, I remember the VW mechanic showing me that it spins only , well, one way... mine goes both ways easily, I cannot find where the mistake could be??
EDIT : goddammit !! Not all Bentley books cover the plastic roll cage! On newer books it's on page 38.16. When I have dirty hands I work with an old book, the one at home explains that the cage should be engaged from the bottom of the one way clutch ring. This works now. Probably one of my main problems right here
I set up the forward clutch assembly and D/R clutch on the oil pump to air test them.

D/R checking: works perfectly. I also replaced the top circlip to get back into better specs. I've installed the 010323157J clip from Porsche, VW book info stops at the letter D.... It's much thicker, but I didn't have anything to measure it.

Forward clutch assembly testing:
It doesn't work, air hisses through the middle. I checked and re-clocked the rings on the pump, no result. I tried with just the piston in with no diaphragm spring, it goes up and down when I hold it with my fingers, so it is definetely sealing, but not enough (it's new but not a VW piston).
I reinstalled the frictions and steels, it worked once very good, then a few more times, then I released the air completely, and it never worked out again. I'm not sure if it's from the pistons or from the rings on the pump. Any helpful remark about that?

Also, I inspected the frictions, and they look like they got HOT! Same goes for the steels. That was before the drum was clearly out of specs. The bottom friction bottom side is still clear looking. Should I replace them or is it "normal" they get discolored after some use?

Aloha!
_________________
Silicone Steering Boots and 930 Cv boots for sale in the classifieds.
Syncro transmission upgrade parts in the Classifieds.
Subaru EJ22+UN1 5 speed transmission
http://www.thesamba.com/vw/forum/viewtopic.php?t=416343
Syncro http://www.thesamba.com/vw/forum/viewtopic.php?t=4...num+gadget

[ALIKA T3]

Alright, end of the monologue with a happy ending:It's all working perfectly now. Schmoode shifting, no reverse clunking. BUTTER.

I put back the transmission today, new frictions and steels in the Forward Clutch assembly because they got burnt. I replaced the bottom conical thrust plate that was worn out and I ended up within specs with the original top pressure plate which now makes sense this I didn't notice any crazy wear on the pressure plate.

Page 38.17 they mention to install a friction disc before installing the forward planetary ring gear. The first time I rebuilt the transmission, I replicated the previous rebuilder's mistake and didn't do it, which was causing the ring gear to bottom out on the diaphgram spring. This is now corrected. I should have paid more attention to the manual and double checked every little detail.

As I mentioned earlier too, the one way clutch with plastic cage on page 38.16 needs to be mounted from below the outer ring. That page is NOT present on older Bentley books. Booo. Mine was mounted from above and not doing its job. One hundred lashes sucka!

I replaced the rings again on the oil pump since I had a leak when testing with compressed air for the forward clutch piston (it was new). I almost never saw it compressing when performing the air test. It was still not working with new rings. I said fnck it, it's full of oil when assembled, it must work better assembled than disassembled.
I installed a black thrust washer on the oil pump, just because I had one.

I've taught the GF how to assemble the transmission. I did the clips and the wiggling but everything else got done by her under my supervision I did tighten the hardware too .

I think I now reached the expert level for these trannies since I had to force myself to understand how they work and dive into them way more than I wanted. I deserve a gold chocolate medal, or not

Sayonara folks!
_________________
Silicone Steering Boots and 930 Cv boots for sale in the classifieds.
Syncro transmission upgrade parts in the Classifieds.
Subaru EJ22+UN1 5 speed transmission
http://www.thesamba.com/vw/forum/viewtopic.php?t=416343
Syncro http://www.thesamba.com/vw/forum/viewtopic.php?t=4...num+gadget