Iv always been curious as to what you do when towing. We also have a 4Runner, with that, you're supposed to leave O/D off. Do you use 5th gear on the highway with the trailer? Do you notice a difference when the trailer is plugged in and Trailer Stability Control is the tranny program being used when in auto mode? Thanks.

BTW, im guessing it wont let the torque converter fully lockup when towing. :dunno:

X5 Towing 101
 

My 2001 4.4i S/P has the Dinan throttle body, engine and transmission software which gives the engine about 300 hp and 350 lb/ft of torque. The transmission is the 5 speed Steptronic. It does not have "Trailer Stability Control" (TSB) as that functionality wasn't available until about 2003, BUT it is my understanding that TSB does not have anything to do with the transmission while towing. It only kicks in when the sensors detect a "sway" condition (tail wagging the dog) upon which it will de-throttle the engine and apply the X5 brakes in an effort to counteract/correct the "sway".

The “Dynamic Stability Control” (DSC) on my 2001 X5 should also kick in if my tail starts wagging my dog, so I would guess that the TSB is either DSC by another name or a more sensitized DSC since the X5 has no OEM trailer brake interface to independently apply the trailer brakes to straighten out a “sway” condition.

The 5 speed Steptronic locks-up the torque converter clutch (goes into direct drive as per a manual transmission) at an “indicated” 62 mph (about 58 gps mph) and un-locks the torque converter clutch at an “indicated” 60 mph (about 56 gps mph). The 6 speed probably has different lock-up parameters which would need to be explored. That being said I tow in MANUAL MODE as follows when accessing an Interstate Highway:

In MANUAL MODE 1st ALWAYS start off VERY SLOWLY with partial throttle since the drive train needs to be turning to provide “hydrodynamic” lubrication (see my post “Lubrication 101” @ http://www.xoutpost.com/articles.php?...cle&artid=208).

If not on a grade, shift to 2nd at about 2,500 rpm (I back off the throttle just like you would do on a manual transmission to allow the shift without engine torque), then you can “floor” the throttle WITHOUT DEPRESSING THE KICKDOWN BUTTON at the bottom of the throttle travel if you wish.

If not on a grade, shift to 3rd at about 3,000 rpm (back off the throttle, etc.), again you can “floor” the throttle. IF YOU ARE ON A CONSIDERABLE GRADE, hold the throttle down until the tachometer hits about 4,500 rpm (indicated 62 mph) when you will see it drop about 700 rpm as the torque converter clutch locks-up putting the transmission in “direct drive”. As the torque converter clutch locks-up I always IMMEDIATELY back off the throttle to allow it to do so without engine torque (the lock-up occurs much more quickly with much less slip). Then go to the floor with the throttle to continue accelerating.

If not on a grade, shift to 4th at about 3,000 rpm, etc. etc.

If not on a grade, shift to 5th at about 2,200 rpm (62 mph). You’ll see the tachometer start to drop (back off the throttle) as the transmission locks-up the torque converter. Go to the floor with the throttle and accelerate to an indicated 70 mph (about 2,600 rpm). ENGAGE THE CRUISE CONTROL and set it at 70 mph (gps 66 mph). LEAVE THE TRANSMISSION IN MANUAL MODE!

The cruise control is far more sensitive in maintaining speed and it’s mind doesn’t wander. The cruise control, with the transmission in MANUAL MODE, will max throttle the engine WITHOUT “KICKING DOWN” THE TRANSMISSION. I use 70 mph indicated because it gives me a 10 mph locked-up torque converter “zoom” over grades.

THE MAIN POINT TO KEEP IN MIND WHILE TOWING IS TO KEEP THE TRANSMISSION OFF THE TORQUE CONVERTER AND FROM “HUNTING” GEARS IN AN EFFORT TO MAINTAIN A GIVEN SPEED. Hunting gears wears the clutches, heats the clutches and the transmission fluid. Additionally, when the torque converter is UN-LOCKED, the transmission fluid is being heated within the torque converter due to fluid friction. HEAT IS THE ENEMY OF ANY LUBRICANT!

When climbing a grade in 5th gear with cruise control engaged at 70 mph speed will bleed off (throttle at max) right down to an indicated 60 mph and the torque converter will remain locked-up. If the grade is crested the throttle will remain at max until 70 mph is restored.

If the grade is such that the indicated speed drops below 60 mph (about 2,000 rpm) the torque converter will unlock and your rpm will increase to about 2,700. At this point I manually depress the throttle to the floor (don’t depress the kick-down detent) and simultaneously disengage the cruise control. If the grade is such that it is almost crested I leave the transmission in 5th, torque converter un-locked, until the indicated speed reaches 62 mph and the tachometer starts to drop indicating torque converter lock-up at which time is back off the throttle for lock-up, and then press the cruise control resume which max throttles the engine until 70 mph indicated is restored.

You will have to down shift to 4th if it is required to climb a grade (use manual max throttle). If you’re indicated speed reaches 62 mph in 4th the torque converted will lock-up (release throttle for it). After lock-up go to max throttle and engage cruise control (in 4th). Monitor the “Miles per Gallon” gauge to judge engine loading. It will be maxed out at 8 mpg at max throttle until 70 mph indicated is attained, then it will rapidly go 20+ mpg at which time you’ll know the engine torque to the transmission has abated and you can up-shift to 5th WITHOUT DISENGAGING THE CURISE CONTROL.

You’ll find that 4th and 5th gear will handle 95% of grades. I’ve been over the continental divide 3 times and had to use 3rd gear often on the climb but only had to use 2nd about 3 times (it was too low as I could accelerate the grades in it).

When descending a grade or approaching a stop down shift through the gears (“feathering” the throttle) to take advantage of engine compression.

If you are towing any load of consequence (4,000 lbs+) I highly recommend using a 5W-50 or 15W-50 engine oil as the 50 viscosity will protect the engine MUCH BETTER during heavy load, low rpm duty.

Additionally, if you are towing a large rig like mine seriously consider the purchase of the Hensley “Arrow” hitch interface which I use. It completely negates sway without friction devices; no smoke and mirrors. You can find details on it at: http://www.hensleymfg.com/

I’ve told you more than you EVEN WANTED TO KNOW! Hope some of it helps.

Lot of good info. Anyone know what the lockup speed is for the 3 liter? By reading your post, i guess it would be best to cruise at a speed above the Lockup speed to save the transmission, etc. BTw, what is tranny? After years of driving manual, I realize there is alot to know about auto!

Yes, towing with the torque converter clutch locked-up causes the transmission to be in "direct mechanical drive" just as a manual transmission always is, and it is MUCH more efficient in both power transfer and fuel mileage which is why modern vehicles all utilize it.

The torque converter supplants the manual transmission clutch. It is a turbine like device which acts like an engine driven fan blowing oil at a fan on the transmission. In between the two fans is another turbine like device which redirects the oil and effectively MULTIPLIES the engine torque. It is the torque converter which allows an automatic transmission to be engaged while stopped. The oil being blown from one fan to the other causes fluid friction = heat which is deleterious to the transmission and oil. The torque converter has a computer controlled clutch which locks-up the fans, putting it into direct drive. This lock-up is perceived as a shift because the engine drops 500 to 700 rpm, but it is not a true shift to another gear.

BMW will NOT give you any details about the Steptronic functionality, believe me, I tried! When you’re not pulling a trailer the torque converter lock-up is subtle and hard to discern, but if you’re pulling a trailer of any consequence it becomes VERY obvious.

You can determine when lock-up AND un-lock occurs on the 3.0i by doing what I did on my 4.4i, and that’s simply by watching the tachometer AND the speedometer WHILE IN MANUAL MODE. When accelerating with the torque converter un-locked you can see the tachometer “vary” as you “vary” the throttle. At lock-up the tachometer will drop 500 to 700 rpm and your “varying” of the throttle will NOT “vary” the tachometer. When locked-up above a certain programmed speed (60 mph on my 4.4i) it will not un-lock even with max throttle (unless you depress the kick-down button at throttle bottom). While locked up as speed bleeds off due to a gradient down to the programmed speed you’ll perceive a down shift, i.e. engine rpm/noise will increase as the torque converter un-locks. Remember those speeds PLUS about a 10 mph gradient "zoom" factor (i.e. 70 mph on my 4.4i) and drive accordingly.

Also, “tranny” is just short for “transmission”.

Withidl, thanks I will try to figure out the the lockup speed.
So if I understand that correctly, the Kickdown button unlocks the torque converter so the engine can rev higer for more HP, which is why I noticed it wont let you downshift due to engine overspeed!

Well not exactly. If the engine is lightly loaded as in sustaining speed on a level road the computer will keep the torque converter locked-up even when you are below 60 mph (my 4.4i). Below 60 mph as the throttle is advanced the computer senses its position / engine load and will unlock the torque converter to allow torque multiplication and higher engine revs toward the engine's torque peak. When the detent is reached the computer down shifts the transmission to 4th, 3rd, etc. and keeps the torque converter unlocked to increase torque to the wheels.

If you are above 60 mph with the torque converter locked-up advancing the throttle to max will not unlock the torque converter until the detent is reached, at which time the computer will down shift the transmission to 4th or 3rd AND SIMULTANEOUSLY unlock the torque converter.

The computer will not allow a downshift into any gear which would red-line the engine.

What I wolud ask if is possible in manual mode, to have locked the converter to avoid the sensation of high rpm without the same high speed. I test other car as Alfa with automatic with torque converter and volvo, but it seems to be without this slip (skid) in manual mode (the gear choosen is exactly the one I choose, not like bmw).
Other thing, at finally I don't understand if with manual use I wear the gear or not? Sorry but my english is not so good to understand every part of the technic details and now I don't know if it is dangerous for the car or not.
Thank you

As you indicated, the language translation is causing some difficulty for me also as I am trying to understand what you do not understand, but let me give a try in answering your questions.

NOTE: The following pretains to the 2001 4.4i engine, the 3.0i probably differs.

In all modes (full automatic, sport and manual) the computer will lock-up the torque converter on the basis of speed and engine load. That is, if you're sustaining speed on a level road in 5th gear at 30 mph (very little throttle) the computer will lock-up the torque converter and you'll be in direct drive (in 5th gear).

In MANUAL MODE 3rd, 4th or 5th gear below 60 mph maximum throttle (without depressing the kick-down detent) will cause the computer to unlock the torque converter and keep it unlocked until about 62 mph is reached (in any of those gears). At 62 mph the computer WILL lock-up the torque converter and you will be in direct drive (in any of those gears).

There is no "slip" or "skid" with the BMW transmission that is any different than the Volvo or Alfa. If you are in manual mode 4th gear, you will stay in manual mode 4th gear. The torque converter lock-up has NOTHING to do with what gear you are in.

Manual mode will NOT cause any additional wear to the gears ("I wear the gear or not?"). In fact, because in sport/manual modes the computer makes the transmission shift FASTER there is actually LESS WEAR put on the clutches which engage the gears. Once a gear is engaged, the wear on the transmission is VERY LITTLE because the gears, bearings, etc. are all "floating" on a film of transmission oil.

I hope this answers your questions. If not shoot at me again! :)

MANY THANKS FOR HELP! BUT SOME THINGS.......YOU SAY:

In all modes (full automatic, sport and manual) the computer will lock-up the torque converter on the basis of speed and engine load. OK! I AGREE That is, if you're sustaining speed on a level road in 5th gear at 30 mph (very little throttle) the computer will lock-up the torque converter and you'll be in direct drive (in 5th gear). NOT OK, LESS THAN 60mph THE CONVERTER IS NEVER LOCK-UP



There is no "slip" or "skid" with the BMW transmission that is any different than the Volvo or Alfa. If you are in manual mode 4th gear, you will stay in manual mode 4th gear. The torque converter lock-up has NOTHING to do with what gear you are in. YES, BUT EXAMPLE: IN 5th GEAR AT LOW SPEED, IF YOU PUSH THE ACCELERATOR, YOU HEAR THE TORQUE OF THE ENGINE! IN MY X5 YOU HEAR THE CONVERTER SLIPPING TILL THE RPM THAT FOR HIM IS OK! IN THE OTHER CARS IT SEEMS TO BE LOCKED, YOU DON'T HAVE SLIPPING.

THE TORQUE CONVERTER CAN SLIP MORE AFTER MANY MILES?

AGAIN MANY THANKS! :wow:

Regarding your statement "NOT OK, LESS THAN 60mph THE CONVERTER IS NEVER LOCK-UP".

You are wrong! The computer WILL lock-up the torque converter below 60 mph IF THE THROTTLE IS NOT MUCH/LITTLE/LOW, and will readily unlock it if you considerably increase the throttle. It is only ABOVE 60 mph that the torque converter STAYS locked up when the throttle is either off or at maximum (except if the kick-down detent is pressed).

Regarding your statement "YES, BUT EXAMPLE: IN 5th GEAR AT LOW SPEED, IF YOU PUSH THE ACCELERATOR, YOU HEAR THE TORQUE OF THE ENGINE! IN MY X5 YOU HEAR THE CONVERTER SLIPPING TILL THE RPM THAT FOR HIM IS OK! IN THE OTHER CARS IT SEEMS TO BE LOCKED, YOU DON'T HAVE SLIPPING".

You can not "hear" torque. The engine does "snarl" between about 2,000 to 2,200 rpm as BMW wants you to know its there, but it hasn’t much to do with torque since the torque peak comes at approximately 3,600 rpm. You simply can not “hear” the torque converter slipping. You can SEE the results of it slipping when you look at the tachometer while varying (changing) the throttle since the tachometer will, in relation to the speedometer, move up/down with throttle variance when the torque converter is NOT locked-up, but will not move up/down, in relation to the speedometer, when the torque converter IS locked-up. I think your confusing engine exhaust pipe tone with the torque converter.

Incidentally, when the torque converter is not locked-up, there is NO WEAR taking place since it is not a physical clutch. It’s called a “fluid coupling” Where wear can take place is if the clutch that locks-up the torque converter is CONTINUALLY locking/un-locking/locking/un-locking/etc. Drivers that are continually on/off/on/off the throttle play hell with the torque converter lock-up clutch.

Shoot at me again if you have further questions!