After a summer of driving the '88 740T with the AW70L (lockup torque converter) in place of the non-lockup AW71, here are some observations:

* Mileage went up (~1mpg in town, ~2mpg highway); expected more
* Less hwy engine noise
* Bogging feel around 50mph
* Impossible to have 4th without lockup over 50mph

I like the improved mileage, even though it is minimal. I like the driveability except for the case where I need decent power (but not full power) around 50mph. If I'm in 4th over 50mph, the transmission goes into lockup regardless of throttle (unless I give it enough throttle to force 3rd). If I do give it enough throttle to force a kickdown to 3rd, then I get more power than I wanted (and passengers start waking up wondering what's going on).

To overcome this problem, I'm forcing 3rd by disengaging OD. This lets me get somewhere in between "bogging" and too much power, and it prevents shifting back and forth between 3rd and 4th (lockup) when I back off of the throttle momentarily.

Overall, I like the AW70L, but it would be useful if the lockup worked more like a 5th gear and could engage/disengage according to speed and throttle input rather than just speed (50mph).

Any other experiences with this combo?

-Adam