transmission oil pump (automatic guys)

[new200guy]

Good day everyone,

How you are all enjoying your weekend.

I have a question. I had my transmission rebuilt about 5 months ago (everything to include new valve bodies). GM 5l40e 5 speed automatic. things that i have done since the rebuild are replace the TCU and throttle potentiometer. my problem is when the car goes over 90km/h or 56mph, the torque converter locks up when accelerating causing a drop in the RPM's (2 to 300 or so) and sluggish acceleration. my understanding was the TC should unlock, accelerate, and then lock back up when you get back to cruising speed again. the trans shop says this is NOT the transmission oil pump. could this be caused by low pressure from the trans oil pump? when accelerating from a standstill it goes very well. this also happens in 4th gear when using the steptronic too when over 90km/h or 56mph. there are no codes in the ECU or TCU. any ideas what this could be?

Thanks for the helps.

[rf900rkw]

It is not likely to be the pump. The first step would be to determine if the EGS is commanding the lockup on or not. If it's not, then there is an issue with the transmission. If it is commanding it on, which is most likely, then you have to determine if this is "normal" to BMW shift strategy. That I can not help with, as we have no E39 diesels in this country.

[new200guy]

I am thinking this might be BMW strategy as i had the opportunity to drive a friends 728i and his did the same thing and he has the ZF transmission.

what is the EGS? Transmission ECU? If so, i replaced that as the workshop thought that could be the problem. I did have it reflashed with the newest software. I guess this is normal programming by BMW.

[Mark@EAC]

Yes, the EGS is the transmission computer.

[new200guy]

that is what i though. Electronischesteuergeraete is the German word. again..i think this is probably BMW stratagy. I just hate it when i notice every little thing about a car. squeak here, some noise there. ahg.

[Monolith]

Lockup seems to be at 52mph (true speed, not indicated). I believe it to be a BMW strategy across the board. Indicated speed is around 55mph, and I had assumed it had something to do with US highway speeds being limited to 55mph at one time.

Since you're in Germany, my theory goes out the window.

[new200guy]

do you have that slight loss in power and drop in RPM's when accelerating to monolith?

[Monolith]

The 1.9 is not noted for its torque. It was very noticeable with the US GS8.34 software. Since I merge daily onto a 65mph highway, it was a pretty drastic loss of acceleration. I've since switched to Euro (UK) GS8.34 software and have more throttle control over the transmission. This has lessened the effect but you can still tell it's there.

I'm curious - if you don't mind - can you post the last 7 characters of your VIN? I know that some US designated models are sold in Germany. Just wondering if your VIN is for the German market only.

[new200guy]

I drive a diesel 530 so it is euro only. I know suspension parts and such work with 528i.

LAst 7 is gj64399.

I will look at other software options since you had some luck there. I am using most current transfer software at the moment from BMW.

[new200guy]

I drive a diesel 530 so it is euro only. I know suspension parts and such work with 528i.

LAst 7 is gj64399.

I will look at other software options since you had some luck there. I am using most current transfer software at the moment from BMW.

[Monolith]

Rummaging through RealOEM.com with your VIN, I found 3 or 4 different updates between 1999 and 2002. All are labeled GS20 software. Each has a different part number though. No sure signs that anything was actually changed except the versioning of the transmission model.

In my case, it was known that the 1.9 autos were configured differently in the UK (sport mode 3 position switch etc.). I don't know enough about the diesel models to know if they configured them differently for different markets.

[new200guy]

i don't know either. maybe i will stop by the BMW dealer and see what they can tell me.