2.5 TDI AUTO TRANS thread

**Greg Roles** · 08-06-2023, 10:24 AM

Originally Posted by Sunny43.5

Not only that which you explained but also blocked filter will also lead to failure as was the case with ours .

Yeah, many modes of failure possible, sealed for life - HA!

Anyway here's my loom out, oddly enough only certain colours went hard and are all shrunk and cracked, other colours are perfect still. The lemon, 2 blue and 3 greens are all had it, but black, red, white, grey, browns and purple are still pliable, intact and fine. I'm going to replace the cracked wires for the interim till my China loom arrives.

I think I will need to vac test my valve body, and pressure test the clutches etc and will need to buy the gear to do so. I will wait till I have the new loom and test tools before pulling this thing apart again, and then decide if I am getting the valve body rebuilt, or an going into the box itself, which looks like a ton of fun - getting it out will be challenging!

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**Greg Roles** · 08-06-2023, 12:33 PM

Rebuilt interim loom, and go easy on the "not matching colours" comments, I left a bit of the real colour at each end!

Old failed insulation appears to have shrunk and split more than gone overly brittle, very odd.

Pause in proceedings due to real work interruption.

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**Greg Roles** · 13-06-2023, 04:55 PM

Well she drives fine around the block, will take it for a decent drive next few days, the box is going to have to adapt to the shift kit, and I don't trust my ability with auto gearbox repairs as yet!!!

Arrived today, all the secrets for $120. Pricey for a book, but a quick flick shows it was worth it, wish I had it when inside the valve body!!

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What I suspected, all the same box with a few differences in gearing, clutch packs, coolers etc.

**Greg Roles** · 18-06-2023, 05:28 PM

Did some decent driving today, amazingly everything is working. Got a flare from 3-4 at times, but the fluid was low when I returned and checked it again, had to get it hot to get the external cooler to open up and become part of the total ATF volume. See how the top up goes, but overall the box seems FAR better than before. Still it's relearning from scratch so early days....

So far so good....big trip planned next weekend, so that will be a true test.

**Rebuild** · 19-06-2023, 10:53 AM

Well done.

**Greg Roles** · 24-06-2023, 11:08 AM

Originally Posted by Rebuild

Well done.

Thanks! I'm actually amazed it drives OK after being in there with no prior auto experience.

I finally found my Vag Com cable and turns out it had an old error on the trans speed sensor from before I owned it, so it can't re-learn or adapt till it is error free from all I've read. Interestingly the Shift Kit has changed the box a lot even without any adaption, and increased the 3-4 flare in certain situations dramatically ( could just be my mechanical ineptitude too ), so it has sure changed something, but I'm out later today to do the full laborious box relearning process with Vag Com running, so see how it goes after that.

One thing I discovered last night is my TCM, the brain of the box, was coded for the 5k Golf, and not for the 7 series Transporter. I'd guess the unit has been replaced in the past with a Golf one, and nobody bothered changing the god damn software!! I changed that quick smart and it accepted it happily. Wonder how much that changes things!!!

I've come across a LOT of interesting info on this box, and the summary is the valve body and the over-reactive adaptive software is almost always the problem. I'll post up some info on this thread to help future readers, but I'm happy to hear the mechanicals are rarely the issue, more the problematic valve body being overcompensated for by the software causes clutches and drums to prematurely burn out. Sonnax and other name brand auto companies have all manner of upgraded solenoids, piston kits and oversized rebuild kits for the valve body, and if I continue to have drama's I think I'll just send it off to the USA for a full Sonnax oversize makeover, which they claim makes the box far better than stock, and guaranteed ( rebuild for free wise ) for the life of the box.

I was worried I'd have to venture into the box itself, and it sure looks complex, but seems that starting with a healthy valve body and readapting it properly is the key first step. I've also read more than one trans place saying NO additives to this "delicate" box, so if and when the valve body is out again I'm gonna just stick with 100% ATF. For sure seals and the many o-rings can perish and leak, so the box itself may have to be done in time, but cross that bridge if and when I get to it.