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

A few thoughts on the subject. The valve body in the AW70L that you swapped into your turbo vehicle is expecting a torque/HP curve for a non-turbo engine. The AW71L was developed for the turbo vehicles, and aside from having more robust components (to handle the higher torque loads), it should also have a different valve body and thus different shift pattern behaviors. Just curious, have you tried adjusting your kickdown cable? Is it set properly for normal driving?

Your observation about having to force the tranny out of lock-up with a downshift to 3rd is not uncommon. I was working on a 940 recently where it would only disengage lockup when you put your foot to the floor (wide-open-throttle) or dropped out of overdrive (shifted to 3rd). You could have some sediment or buildup in the valve body, a check ball is wearing down, or the kickdown cable is out of adjustment.

I would have expected a bit better gas mileage, unless most of your driving is city or has a lot of stops and starts.

"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)."

You've accurately described how it "should" work. The Aisin Warner transmissions in or Volvos us a hydraulicly acutated lockup unit. General Motors used an electronicly actuated lockup system, and it does work decently well especially after 10-15 years of use. -until the solenoid valve blocks up with metal shavings/sediment and then the lockup gets stuck on all the time and in all gears (usually stalls the car).

God bless,
Fitz Fitzgerald.
--
'87 Blue 240 Wagon, 247k miles.
'88 Black 780, PRV-6, 145k miles.

Yes. I was concerned that there might be a problem using the 70L in a turbo, but I thought I'd give it a try anyway since non-turbo transmissions are so easy to find around here.

I am using a new kickdown cable, and I adjusted it according to Haynes. Beyond that, I try to adjust it so that it shifts just before the driver starts to think "Shouldn't it have shifted by now?" when driving normally. In other words, I don't want to end up backing off of the pedal to force a shift. It's the scientific method. :)

To clarify: It will go out of lock-up if I slow down below 50MPH, and it re-engages lock-up somewhere around 52MPH.

So are you saying this transmission "should" vary/delay the lock-up speed in 4th if there is sufficient throttle input? Do you happen to have any diagrams of this transmission valve body so I'll know where to begin the diagnosis? Since the transmission is otherwise working fine, I assumed the 52MPH lock-up was not variable. I noticed the flyweight on the tailshaft, which I assumed served as the 'switch' for lock-up.

So are you saying this transmission "should" vary/delay the lock-up speed in 4th if there is sufficient throttle input?

If I remember correctly, that's how it should work. Somebody correct me if I'm wrong. If you're accelerating with a heavy foot on the gas, I believe you should see something of a delayed engagement.

Do you happen to have any diagrams of this transmission valve body so I'll know where to begin the diagnosis?

No, not yet. But it's on my list of manuals that I'm actively looking for. I've got an AW-70L in a partial state of teardown/rebuild in my basement that I'm indending to install in my '87 240 Wagon. The previous owner of the transmission said it worked flawlessly, but I'm replacing a few of the check balls in the valve body before I install it.

God bless,
Fitz Fitzgerald.
--
'87 Blue 240 Wagon, 247k miles.

I wasn't aware that the AW70 came with a lock-up of those years 740. I had an '86 745 GLE that had a ZF transmission w/lock-up. It got fantastic mileage (32mpg) for an autonatic and was very smooth compared to the AW70/71 which I had in an'87 740T and '91 740T. It did however have the lock-up come on at 52 mph and would slip in and out, but did so seamlessly. You could apply a little pedal and it would disengage. Since it was not an OD trans, you needed to manual shift to 3rd to get it to take off, but had hardly any noticable shift points or bogging when in Drive.
--
'89 245 Sportwagon, '04 V70 2.5T Sportwagon

The AW70L I installed came from a '91 or '92 740. I still can't make this thing get over 25 MPG highway. The next thing I need to work on is the exhaust. P.O. put non-turbo exhaust parts, and there's a strange, narrow (small diameter) section of pipe welded in the part that passes over the rear axle.

32 mpg ?????!!!!! What did you put in that thing ! Seriously though, are you sure about the mileage ? I believe the average is more like 23 or so. And in California it will be slightly worse (due to the excess oxygen in it's reformulated gas). I have an 85 740 / ZFHP22 and live in California, and I probably get about 21-22.

Noel

Yes, it really got 32 mpg!
My wife and I took it on the 'break-in' trip from Austin, TX to Conn and back in '94 when it was new to us with 121k miles. It was a Volvo select pre-owned in mint condition. Our two best tanks of premimum gas were one on the Blue Ridge Parkway driving most of the way in 3rd, about 31.5 mpg, and we drove the last leg from New Orleans to Austin, 475 miles on 14.9 gallons, which was typical of the mileage we got for the whole trip.
too bad the wife got the car after the divorce, with new IPD bars and Bil's, not too mention the $800 Michelin's. It was one of the smoothest Volvo's I've ever had.
--
'89 245 Sportwagon, '04 V70 2.5T Sportwagon

I've been thinking of changing my AW71('90 765T) to an "L"; thanks for the post!