Board-

I have a dilemma. I recently aquired a 96 740iL with 137k miles from a friend who has experienced some financial issues. I paid the what was owed on this vehicle ($5800).

Here is the deal; shortly after the BMW inspection, the check engine light went on. It would cycle on and off every few weeks or so until this day.

When he checked the code-it came up P740 Torque Converter CKT/Open-no driveability issues were experienced even with the light on.

Since I have aquired the vehicle-I am experiencing the following driveability issues....

Scenario 1) Car will shift from 1, 2, 3 then tacs out to 5k and wont shift to 4 or 5. IF I manually down shift to 4th then back to drive...it sometimes will go into 4th and 5th by itself (upshift)...IF I were to not manually intervene-most often than not, it will not go into 4th by itself.

Scenario 2) Car will be driving along just fine, but will completely lose power by itself...and will be completely disengaged from drive. Eventually, it will re engage and begin to move...very unnerving.

Observation: I noticed prior to this shifting issue becoming more prevalent, when I would try to put the car in manual mode-it would not always go back to automatic when toggling the M/A switch.

I spoke with a mechanic (Not a BMW Tech)..who assisted me with trying to id this fault. We were able to pull some tech pics of the tranny, and it appears this sensor is accessable by the pan...

If so-does this sensor require special tools/software to access/replace/adjust?

I am a competent garage mechanic-but am not knowledgeable of BMW's yet.

Any ideas/assistance is truly appreciated.

Respectfully,

David

I really am not an expert on bmw tranny's but I like to trouble shoot the easiest things 1st and hope I get lucky (rarely is this the case). That being said I would have the tranny software "flashed" by for senario 1. Not sure how much it would cost but could not be that much. As for senario 2 hmmm, not usre but I would NOT do any passing any time soon!!!

I am sure many posts to follow with help you more. Just my 2 cents.

That post was just a little too long for me. I have a pretty short attention here is a website that I have used for finding good, independent http://www.bimmershops.com/bmwshops/california/

maybe a tranny flush and fill?

maybe a tranny flush and fill?

That would be my first instinct for all things transmission related

Drain - remove sump - change filter - clean magnets - refill to correct level

137K on the same fluid seems way too long if it's never been done before

My Transmission had very slow slurry changes before I carried out the above process and the difference was amazing - all the slurry changes became crisp and positive without being noticable if you see what I mean

PS it was a long post :D

That would be my first instinct for all things transmission related

PS it was a long post

Ya-I know...too much info!

I can see that the oil change may affect shifting-but what of the P740 code?

What type of tranny oil is recomended? How many quarts?

Thanks!

Ya-I know...too much info!

I can see that the oil change may affect shifting-but what of the P740 code?

What type of tranny oil is recomended? How many quarts?

Thanks!

Guessing here but the fluid degrades with time - most gearbox ecus are fed with information on engine RPM, gear it's in and rear wheel speed. They the ECU's have parameters that when exceeded will throw trouble code - my money is on the level of slippage in the torque converter is monitored - too much slipage and a trouble code is stored.......

I did a post here showing fluid change with pics - can't be more than a few pages back - it is VERY important that you use the correct fluid - I think there is a label on the gearbox itself

Thread on tranny fluid change is here

http://forums.bimmerforums.com/forum/showthread.php?t=886214

Can't help with how many quarts - we work in litres in the UK and my conversion skills aren't up to much especialy when UK and US Gallons are different sizes

I had the same problem with this Code, associated with it is a slight tapping noise coming from the tranny. It shifts perfectly and drives very smoothly except with the noise. I suspected the Torque converter to be bad and purchase a Reman for $260.00. I replace the TC, front shaft seal and replace the fluid using VW, filter and gasket. Put everything back together and my nightmare just started. Now it wont shift at all.

I had the same problem with this Code, associated with it is a slight tapping noise coming from the tranny. It shifts perfectly and drives very smoothly except with the noise. I suspected the Torque converter to be bad and purchase a Reman for $260.00. I replace the TC, front shaft seal and replace the fluid using VW, filter and gasket. Put everything back together and my nightmare just started. Now it wont shift at all.

Question; is the check engine light still on and the code present? or has another code become evident?

IF the Torque Converter sensor is bad/open-I can see that the tranny computer would not know what to do.

Do you know what type of tranny you have? According to the TIS Program I have - I believe I have A5S310Z.

I have the A5S 560Z (5HP30)
Codes are gone.

Board-

I have a dilemma. I recently aquired a 96 740iL with 137k miles from a friend who has experienced some financial issues. I paid the what was owed on this vehicle ($5800).

Here is the deal; shortly after the BMW inspection, the check engine light went on. It would cycle on and off every few weeks or so until this day.

When he checked the code-it came up P740 Torque Converter CKT/Open-no driveability issues were experienced even with the light on.

Since I have aquired the vehicle-I am experiencing the following driveability issues....

Scenario 1) Car will shift from 1, 2, 3 then tacs out to 5k and wont shift to 4 or 5. IF I manually down shift to 4th then back to drive...it sometimes will go into 4th and 5th by itself (upshift)...IF I were to not manually intervene-most often than not, it will not go into 4th by itself.

Scenario 2) Car will be driving along just fine, but will completely lose power by itself...and will be completely disengaged from drive. Eventually, it will re engage and begin to move...very unnerving.

Observation: I noticed prior to this shifting issue becoming more prevalent, when I would try to put the car in manual mode-it would not always go back to automatic when toggling the M/A switch.

I spoke with a mechanic (Not a BMW Tech)..who assisted me with trying to id this fault. We were able to pull some tech pics of the tranny, and it appears this sensor is accessable by the pan...

If so-does this sensor require special tools/software to access/replace/adjust?

I am a competent garage mechanic-but am not knowledgeable of BMW's yet.

Any ideas/assistance is truly appreciated.

Respectfully,

David

I have had a little experience with the tranny's in these cars. First thing you should do is drain fluid and replace the filter and have the tranny reprogrammed at the dealer. Do not flush just drain. There are several sensors accessable in the tranny however you should get a code for input or output speed sensors if they are bad. I have had to replace one of these but I got a code and the trans failsafe message and was a speed sensor. Could also be a bad trans module causing some of your problems since you had some changes when you put in manual. When you go to manual or sport mode it does change the pressures in the tranny. If you have a known good module you could switch it out and see if that is the issue. I would try drainning the fluid, filter and then refill with correct fluid take it to the dealer and have the tranny reflashed first. You will have to take to the dealer to have reflashed as you need the BMW computer to do this. Should be 1 hour of labor to reflash - this generally what the dealer will do for most tranny drivability issues - there are 3 computers on board and they all have to be in sync and the tranny is especially sensitive to bugs in the program. If that does not work you need an experienced BMW Transmission mechanic to diagnose - if you let the wrong mechanic start messing with this you will be looking for a new or rebuilt tranny. I drained, new filter, speed sensor and reflash at 118k I'm at 166k on the clock and the stealership told me I needed a new torque converter...what BS

Thanks Rob for the info;

As I am still learning-there are a few different types of oil....what do YOU use? I will need a filter too...and am looking to buy an ODBII scanner.

Thanks!
David

Oils..


EDIT: Sorry, I didnt resize the pic.

Cashmere posted the oil info. The obd II will read general codes and clear the check engine light. Only the dealer can read the bmw codes and reprogram the computers or an indy that has the bmw computer - they cost about 15 grand so not all indy's have them.

Cashmere posted the oil info. The obd II will read general codes and clear the check engine light. Only the dealer can read the bmw codes and reprogram the computers or an indy that has the bmw computer - they cost about 15 grand so not all indy's have them.

Not only indy's and dealers ;)