Towing advice to protect the transmission for xDrive35i?

[andrewwynn]

Monitor in/out of xm will tell you if TC locked. You can also check any time with a tiny boost of right foot. The xm algorithm is very biased to keep it locked!

Example if you watch throttle position on bimmerlink and going 65 mph, you can probably go from 10% to 40% throttle with almost no change in RPM.

I teach people the method to force shifts which would be very helpful for you when the E Gate error is troubling you. (More on that later).

If you are climbing a hill or just want to boost your speed 10-15, a gentle push of throttle will always just lug the engine and never down shift, often not even unlock the TC.

Give the throttle a quick jab than drop. Example: if you are at 15% (guess I can't recall what steady state driving is), jab the throttle to 80% than instantly back to 40-50%. You'll get the xm to unlock the TC and and instant downshift exactly as if you put the gear shift request into Ds.

I use that method more often than Ds.

Now back to E gate; a motor prob exactly the same type as in the door lock actuator fails and causes this grief. I was about to pull my gear suggestion input device apart to either fix that motor or just pull the plug on it and manually defeat the gate permanently (you'd have to manually push the gear suggestion lever back to right when done driving before you can start the car (from experience)).

I happened into a replacement gear suggestion input device so I just did a swap and no coding needed I took from a 50i e70 and put in my 35i.

There are videos for teardown. New the part is close to $1000, used they are often $300. Not sure the expected lifespans but it's a common fault so I'd prob tear mine down and fix/hack before paying $250+ for used one. I just happened into a free one so the issue was eliminated.

I had a different problem occur while I was towing: turbo solenoid failed and I lost turbo! Towing though the mountains!

Praise Jesus I had swapped the gear suggestion lever so I could use Ds and on occasion manual shift.

In almost every case, Ds did a perfect job of picking gears and TC lock. I had to MS less than 5% of the time.

The xm of course had the easiest time ever due to the roughly 45hp drop in power. I fixed the turbo for the drive home and what a difference.

If you can't find YouTube video for fixing the E gate send a PM I'll do a little digging.

Swapping it in/out is the easiest repair I've ever done on a BMW in case you can find a replacement.

[RhythmMachine]

Originally Posted by andrewwynn

Monitor in/out of xm will tell you if TC locked. You can also check any time with a tiny boost of right foot. The xm algorithm is very biased to keep it locked!

Example if you watch throttle position on bimmerlink and going 65 mph, you can probably go from 10% to 40% throttle with almost no change in RPM.

I teach people the method to force shifts which would be very helpful for you when the E Gate error is troubling you. (More on that later).

If you are climbing a hill or just want to boost your speed 10-15, a gentle push of throttle will always just lug the engine and never down shift, often not even unlock the TC.

Give the throttle a quick jab than drop. Example: if you are at 15% (guess I can't recall what steady state driving is), jab the throttle to 80% than instantly back to 40-50%. You'll get the xm to unlock the TC and and instant downshift exactly as if you put the gear shift request into Ds.

I use that method more often than Ds.

Now back to E gate; a motor prob exactly the same type as in the door lock actuator fails and causes this grief. I was about to pull my gear suggestion input device apart to either fix that motor or just pull the plug on it and manually defeat the gate permanently (you'd have to manually push the gear suggestion lever back to right when done driving before you can start the car (from experience)).

I happened into a replacement gear suggestion input device so I just did a swap and no coding needed I took from a 50i e70 and put in my 35i.

There are videos for teardown. New the part is close to $1000, used they are often $300. Not sure the expected lifespans but it's a common fault so I'd prob tear mine down and fix/hack before paying $250+ for used one. I just happened into a free one so the issue was eliminated.

I had a different problem occur while I was towing: turbo solenoid failed and I lost turbo! Towing though the mountains!

Praise Jesus I had swapped the gear suggestion lever so I could use Ds and on occasion manual shift.

In almost every case, Ds did a perfect job of picking gears and TC lock. I had to MS less than 5% of the time.

The xm of course had the easiest time ever due to the roughly 45hp drop in power. I fixed the turbo for the drive home and what a difference.

If you can't find YouTube video for fixing the E gate send a PM I'll do a little digging.

Swapping it in/out is the easiest repair I've ever done on a BMW in case you can find a replacement.

This is really helpful - thank you so much! So I'd be able to monitor the in/out based on the transmission turbine speed (in) and output shaft speed (out)? I assumed that when those values were matching up I was locked, but your suggestion of making small throttle adjustments to test it will be reassuring.



A question about this part: "Example if you watch throttle position on bimmerlink and going 65 mph, you can probably go from 10% to 40% throttle with almost no change in RPM." Is this because it's using the turbo instead of increased RPMs to provide more power?


I hope I won't need your technique for forcing shifts if the gate gremlins act up again, but I can't say I'd be shocked if they do. I have pulled apart the shifter assembly once already to address this. I'm not the most mechanically inclined, so I was pretty proud that I got it apart, back together incorrectly, apart again, and back together correctly without losing or breaking any parts, but it's not something I'd want to be doing on a regular basis. Like you, before buying a replacement I'd see if I can just remove the gate completely and, as you said, make sure I push the shifter back to regular auto mode before my wife tries to start the car the next time. If I could be sure that a used replacement would resolve the issue completely I'd be more open to it, but I'd rather not spend several hundred dollars to end up with the same issue before long.



And I feel your pain with your mountain towing adventure. I had issues with the turbo actuator on my previous tow vehicle (MB ML320 Bluetec), which is when I discovered that a 3L diesel without a turbo is a scary place to be on the highway with a trailer.