BMW 1996 730i transmision problem

[lav4u]

I have this transmission problem for long time, I hope if I can have a solution with anyone from you.
I was facing shifting gear problem, all the gear was changing smooth but when it reach 3 to 4 it doest change until i change manual from D to 4 and then back to D so all the gear will change 3 to 4 and 4 to 5.
They told me its transmission problem and the gear box must be overhaul. I listen to them and they put down the gear box and overhaul it.. but when the put it back
all gear was changing smoothly, but with new problem. When it change from gear 2 to 3 a big bang or knock with it.. same when it change from 3 -2
They say this is the valve body must be changed…I listen to them and they changed it…but still the problem was there.. until we figure it out it was air mass problem..
So when I changed the air mass, the car was changing smoothly..
But again I faced new problem…
All the gear was changing smoothly… but when I be stable in speed of 120km/h the shifting gear between 4-5 or 5-4 get jam mean it keep changing from 4-5 every second unless I press the accelerator and the problem goes a way…

Now can anyway tell me what this might be the problem?????

Some say its still the valve body problem… and some say.. it must be the transmission computer( cuz I believe maybe its not the 7 series computer, it was replaced with 5 series)
Will this affect the transmission???

I hope to find answers from u guys..
Appreciate all your support.

[lincolnmaster80]

The transmission ECU can and can't affect your shifting. Because it's the 730i, the same engine and transmission was used in the 530i, so the chances of it being interchangable are very good.

Try disconnecting your main battery for a few seconds. This can solve some gremlins.

What you are describing sounds like a difference in tire pressure. Make sure all the tires have the same pressure. If one tire reads 38psi, and another tire reads 34psi, fill the lower inflated tire to 38psi. The difference is this:

When the underinflated tire spins, the overall diameter is smaller, thus it spins faster than the properly inflated tire. The ABS sensors detect this and sends this information back to the ECU. The ECU then tells the transmission to shift down or up, and happens very often. Make sure all your tires are properly inflated to 4psi under the maximum pressure rating. (exampe, if your tires have max pressure of 44psi, inflate to 40psi.)

[lav4u]

Thanx for the valuable information, but about disconnecting the battery, I did this, and it’s the same thing happening..
I didn’t thought of tire pressure, but I will do that… what if the same problem is still occurring after I balance the tire pressure???

Anther issue I forgot to mention, if ECU is replaced in 730i with 530i, will this stop accessing the car with a computer?? Cuz I have been facing this problem.
And many computers can't access the car..
What I can do or where I should look so I can solve the problem of accessing the car with a computer?

[lincolnmaster80]

It's possible that the systems on the E38 (for instance, stability and/or traction control, etc) that didn't come with the similar model 530i's is affecting it, even though they are the same tranny, the tranny ECU might be programmed differently for the 5-series. So this very well may be your problem.

If you have on handy, try swaping out the ECU with a known working one from a 730i, preferably the same production month and year as yours.

http://www.bmw-z1.com/VIN/VINdecode-e.cgi
Enter the last seven digits of your vin to find out the production month and year of your BMW. None of this information is stored anywhere, it just decodes it is all.

[lav4u]

i tried to find out the month of production and year, i could log to the sight as my ip is not accepted, can u please u find out from u side there and post it to me here..
its WBAGF21030DF77640.

[lincolnmaster80]

Chassis number DF77640
Vehicle code GF21
Series E38
Model 730i
Body type saloon
Catalog model ECE
Production date 1995 / 10
Engine M60
Transmission Automatic
Steering Left
Catalyzer YES


Additional Information for Vehicle code GF21
Production FROM : 1994/03/01 TO : 1996/02/29
Engine M60/1
Engine Oil 7.50 Liter
Transmission Automatic
Transmission Model A5S 310Z
Transmission Oil 3.00 Liter
Rear Axle Oil 1.40 Liter
Coolant(w/o Air Conditioner) 12.50 Liter
Coolant(with Air Conditioner) 12.50 Liter
Brake fluid 1.00 Liter