Hello and thanks for looking. Ive got a transmission problem that has been an absolute nightmare to figure out. Early build 03/2004 E55, 116k Miles.

So, the issue is fir first 5 shifts after the car has been sitting overnight. I pull out of the garage and stop at the stop sign at the end of my road, but when I give it gas and ether it hesitates and pulls very slow (similar to a bog down/vibration) stalls or it will go and the 1-2 shift is ridiculous and I get a huge buck from the car. It feels like somebody clutch kicked a manual car. then the 2-3 shift is super hesitant. Almost like it gets stuck in between the gears and the 3-4 shift is the same. Accompanying this, if you get on the throttle to accelerate while you are cruising the car acts like you are in too high of a gear with too low of a speed and shudders, but this also goes away when warm. After the first few shifts and the transmission is warm its silky smooth and normal. I have performed a few different things trying to remedy this problem to no avail. Best part is NO CEL or TCU codes!

Things performed:
new crank sensor
Trans fluid changed 2x- Level is set correct @80*C dip stick level, temp verified temp w/Scan tool
New filter
Valve body cleaned and installed both Sonnax TCC Damper Valve and Sonnax Sleeves (suppossed to remedy this exact problem)
New conductor plate
New 13 pin
Wires are clean- no atf on ECU side or 13 Pin connector side
External trans cooler- At first considered this may be part of the problem, but I doubt that many people warm up their cars until their transmissions are 80*C plus before driving them, also it happened before the switch to the external cooler(in fear of future glycol contamination due to having the valeo rad)

Things Left to try/replace:
TCC Solenoid?- May replace this just as a shot in the dark, hard to find 722.6/nag1 TCC solenoid problems on the internet
Torque Converter?
Prior glycol contamination?
Need to find a star tool to relearn TCC/Adaptations-Currently using icarsoft MB2
Try going back to stock trans cooler
TCU problems?

Other Factors:
1st fluid change had nothing crazy come out of the pan-fluid not burnt- no crazy metal shavings- only thing in question would be prior glycol contamination.
Cleaning Valve body/sonnax kits only produced cleaner, firmer shifts after being warm- cold problems still exist
Possibly related to 72mm FSP?-Doubt it because it would happen w/ my 77 clutched also
Vaccum Leak?- doubtful, I resealed the charger/tb/bypass valve- new seals+small amount of rtv on them to prevent leakage


Thanks for looking, any input appreciated.

Thank you guys for the replies, yep I’m on FSP and this occourred with three different pulleys. Also it was drain through cooler line, no “flush” with the machine.

I am am not familiar with bpv, please explain?

Also, it does NOT occour in manual mode, only in C/S modes. Thanks again

Thank you for your input and the offer on the star usage, I lived in San Diego at one point but now I am in North Carolina. The TCU could be a possible culprit. I have re loaded my ECU tune a few times, as well as performing the sneaky reset for adaptations, along with the battery terminal trick, no dice yet. I had three different ECU tunes, two with a 77 clutched and then with my setup now 72 FSP. Symptoms were the same throughout every tune. I think torque converter is the next step because my transmission holds every gear with no slippage and performs normal at higher rpm(above 4K)

Ok guys, I know my way around a car. I know my way around a scanner and how to spot electrical/sensor problems on cars. How this was the problem.. don’t ask me because I could not tell you.

Symptoms described above have been going on for 3-4 months... more apparent as time went on and power was added, until yesterday. I was on my way home (after installing a new tq converter(definitely part of the lockup issue) upd 3k stall, which is amazing btw. Best bang for buck drives/shifts so much better) the lockup issue was solved but there was an underlying issue and the check engine light started blinking on/off, I had never seen this before. Looked at the codes.. multiple misfires on most/all cylinders while idling. No other codes.. NOTHING! Not even MB specific ones...

spent all day checking for vacuum leaks, put old MAP sensor back in, put old crank sensor back in, cleaned cam sensor, cleaned AIT sensor, put stock injectors back in, stock pulley back in.. even RTV sealed the surge tanks because that was the only gasket on the top end of the motor that I re used when I pulled the charger for a meth install and re-seal.. to no avail.. no vacuum leaks.

sitting, idling, misfiring, staring at my scan tool in 95* for 3 hours.... short term fuel trims would go insane trying to add 20-25% fuel every time the computer handed off the reins to let the sensors handle fueling stalling the motor or causing a rocking idle ... even pulling he surge tanks revealed a very heavy gas smell.

Only thing left was the 02 sensors to replace... I was reluctant because usually they show codes and 9/10 times they will be slow to report voltage or get stuck and you can usually watch this happen and easily diagnose a faulty O2 on the scan tool as well but these gave NO symptoms whatsoever. Finally broke down and bought two new upstream 02’s as I don’t like to buy parts without a solid reasoning .. threw them in. BAM.. no more intermittent rocking idle.. no more misfires.. no more hesitation when rolling into the throttle, just an appropriate downshift and pull. The thing that bothers me most, is that the new 02 sensors voltage is almost identical to the old ones, with a refresh rate that is just about the same(maybe a tad quicker).

This makes perfect sense to be the culprit if you think deeply about it, but I just cannot understand how the computer did not throw a code or they did not show their degradation of signal on a scan tool.

Maybe this needs to be a sticky, maybe someone more experienced would’ve seen this as the issue and thrown the parts at it (even though the 02 behavior was normal) before going towards the trans, but untill yesterday drivability had not been affected one bit, besides a slight hesitation to kick down while cruising and a cold shift issue.

Thank you all for your help MB World

P.S. if anybody buys the transgo shift kit, the main pressure valve is the incorrect size for our valve body. You can use the other parts from the kit, but do not use the main pressure valve. After the sonnax kits, transgo kit, new conductor plate, and UPD 3000 stall.. this car is a rocket that shifts fast like the SLR. I cannot wait to get a TCU time and see what it really does.


TLR Replace your 02 sensors even if they seem fine......

i sure hope so!

looks like we’re going to have to hunt someone down. It might work, although they get a CEL with them usually... worth a try though.