S2Forum - The Audi S2 Community - Member's Area

Automatic Transmission troubleshooting

JayCab — Sat, 26 Sep 2026 23:38:50 GMT

Hello Forum!

I have the following problem with an 01N DFM 4 speed auto in my Cab;

1. Primary complaint: Sometimes, especially on initial pull-away, it's slow to change into 2nd gear. When it does this, it always changes at exactly 3.5K RPM, and usually for one shift during a drive cycle, and usually the first shift. The delayed first 1-2 shift is never at any RPM other than 3.5K when it happens.

2. Point 1 is in the presence of no other problems.
More symptoms:
--> Fluid is genuine, clean, with no metallic shrapnel or particles ever seen coming out of the pan or shimmering in the fluid on fluid change
--> Filter is genuine , new, clean.
--> Zero fault codes sustained over 1K+ miles for both ECM/TCM.
--> Car (and original transmission) is at 88K miles (I owned it from 69K @ 23 years old)
--> No transmission slipping (it pulls like a train at full torque in all gears with no flaring)

.....

Troubleshooting performed so far:

A: Fluid / Filter change. All genuine parts/fluid, G 052 162 A2 fluid, which is rebranded Mobil LT 71141.
--> Immediately following the fluid change, it drove like silk, better than ever, with imperceptible changes, feeling more or less like a 1 speed box.
--> Gradually, the gear changes went back to perceptible (what I call "normal", you can feel it shift, but it's smoother than any manual)
--> The occasional slow 1-2 shift at 3.5K still happened occasionally

B: Replacement Valve Body, sourced from USA, overhauled with Sonnax parts (Central Valve Bodies)
--> This made matters worse, and was jolly expensive
--> The vehicle still had the occasional 1-2 delayed shift, but also gained a 3-4 flare shift where it would rev high and thud into 4th. Undrivable unless shifter is left in 3rd, ignoring 4th gear.

C: Light overhaul of original Valve Body (UK Firm, Valve Bodies UK)
--> Replaced the TCC lockup valve / sleeve / spring with no re-boring of VB
--> Machine dyno tested original VB, sent it back to me, in-spec by their judgement
--> Car shifted like silk once again after re-installing + new fluid (again)
--> 1-2 late shift initially improved seemingly, but has since resumed occasionally happening (the same 3.5K RPM late change)

D: Testing of electronic inputs to TCM according to Audi factory manual (Erwin)
--> All tested in spec except for the shift lock solenoid being a bit high on resistance (the solenoid that locks the lever in P/N, not a shift solenoid)
--> All shift solenoids are at correct and same resistance tested at both the solenoids themselves and at the TCM harness fully installed in the vehicle
--> Speed sensors both test in spec by resistance (but I'm aware that says nothing about magnetic pulse strength)
--> Nonetheless, no fault codes

E: TCM electronics -
--> I have replaced the main MOSFET power control transistor on the TCM mainboard, being the main power control component that can wear with heat/age.
--> This seems to have changed the shift behaviour for the better, but not fixed the occasional 1-2 slow 3.5K RPM shift.
--> Now the vehicle more readily downshifts when the throttle is pressed. I spend more time driving at <20% pedal for the same performance, and it more rarely needs manual intervention going up steep hills.

F: Cruise Control / Air Conditioning
--> Both these systems input to the TCM. Both work.
--> TCM binary output seems to indicate it is not aware of when the Cruise control is switched on. Nonetheless, C/C seems to work, cut out on brake / resume when told to/etc.
--> The A/C seems to cut out when the car is put in reverse. This seems odd. I know newer cars close the recirc flap on reverse, but I don't think this one is supposed to do this.
--> A/C correctly cuts out on kick-down. That's normal

......

For all that, I have yet to fix the occasional 1-2 slow shift at 3.5k RPM.

Questions for the forum:
1. Does this sound more electrical or mechanical to you? With the always exactly 3.5K RPM, my money is on electrical / logical, but I'm not sure where yet and more than happy to hear other suggestions...
2. Can anyone tell me where the grounding point is for the transmission harness? is it multi-point grounded? I've only found the ground points by the A pillars next to the doors behind the trim so far. I know the control logic depends on accurate consistent resistance on the harness, and it's a 26 year old harness now.
3. What parts would anyone change next?
Speed sensors, Solenoid ribbon, Replace TCM itself, Cruise module, A/C module, other electrical ideas?
4. Is the fact of "no codes" on a car of this era necessarily indicative of perfectly good electrics?
5. Would anyone still vote this being a valve body issue given the above (which was my initial thought)?

......

I'm hoping there is another 80K miles in the transmission before a rebuild...

Thanking anyone for reading this far!!

Kind Regards,

Jay.

s2 avant from northern Sweden.

SebD — Sun, 20 Sep 2026 10:47:30 GMT

Want to share my project here where I’ve found some good help and info. Feels like the forum era is a dyeing breed. This is my contribution to keeping it alive and to keep share knowledge and tips ??

Bought the car back in September 25. Drove it 800km back home. Clutch started to not return halfway home and the rpm & fuel was living its own life, but I made it home.

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The car has some upgrades like:
Rs2 turbo
Rs2 headers
Vems v3
1300cc injectors

Started right away with an overhaul of the brakesystem. The brake reinforcement was leaking down the pedal. Master had also sized to it but managed to separate them. Bought a new one from “autower”
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Front calipers got stripped and painted sins it had 100 shades of racing colors.

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Installed hel brake hoses all around the car. Had to drill out the holder sins the hel hoses had bigger fittings. Did some cad and 3d printed holders.
Was in a time crunch so had to skip some steps. (Like cleaning up the disc) and "audi sport" sticker was removed after the picture, didnt look good.
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Thought the clutch slave was acting up. New satsh didn’t fit. Made it fit with a anglegrinder. No photos of the job sins I was busy cursing and smashing up my hands.After the swap, a quick bleed. Clutch still the same. Clutch master up next. Wish I did this first, was a walk in the park compared to the slave. Welcome back clutch!

Moving inside. Removed 5kg of speaker cables. Removed the gauges and started to clean up the electrical as well.
New stereo found its way in. will need to see if i can fix the broken dashboard later on. Did the mk2 mod sins my bushing had leaved the car. Moved over the reverse lock. no picture unfortunately.
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Changed the backing in the cluster and oem gauges. Got the oil temp to work after cleaning the sender/ connector from rust.
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Drove it to my home garage. It really put a smile on my face added some new wheels aswell.

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Started to remove the headliner, it was saging so bad that I couldn’t see out from the rear window!
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Changing to black headliner. one clip broke to the sunroof so that will go on the tradition list. need to reglue the doorcard too
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Repaired the wires that someone tried to fix. New grommet front tradition. didnt find matching color unfortunately.
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succeeded to find a new heckblende, had to do some triming to the handle and the locking mechanics to make it work.
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Now we have arrived to nowtime. My plan is to take out the engine and subframes this winter to do a fresh up. (tiered of the oil leaks) all new bushings and a repaint of the frame. convert to vacuum brakes aswell. waiting for the crank locking tool, then i can take out the engine and box.
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Polish red beast (saloon) on the Nürburgring Touristenfahrten 18-09-2026

Joris — Sat, 19 Sep 2026 12:32:30 GMT

I was doing some laps yesterday evening on the ring, and spotted this red beast (black one's me). Not sure if it's a familiar one here but that thing GOES. Respect.

My '91 Avant

dspl1236 — Wed, 16 Sep 2026 12:31:57 GMT

Hello Folks, I have acquired a Pearl White 1991 200 20V Turbo Avant. 220k+ miles. I had one in Back Panther Metallic years ago. I had to get one again. Mid life crisis? Maybe...

Wife and I were at the Loe Show during delivery. Mother-in-law signed for it. Two friends came a picked it up for me.

This avant started in Washington then to Colorado, New Jersy, Connecticut, and now Ohio.

I had a spare 3b ecu and have outfitted it with an RR boost chip and an S2 fuel/ign chip. Plan is to get to a 3071.... after some maintenence items.

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Speedometer gear

geryS2 — Mon, 31 Aug 2026 12:56:21 GMT

Hi, any info if this part is reproduced ?
no longer available anywhere.., and without that part, no speedometer and no MOT !

Number: 012409187D
Supersession(s): 012409187C; 012-409-187-D; 12409187D