On a slightly seperate topic, how does the lockup occur? Is it mechanically selected (hydraulic valve internal to the trans) or electric? (much like the od, but probably controled by a computer) Also, is the trans externally differnt? (legth / bell housing / flywheel / etc) I am thinking of trying to mount one behind a b21ft in my 85. Is it possible to set it up with an external lockup switch so you could control the lockup the same way the od is? Probably not if it's hydraulic. Also, how do the ratios compare to the aw70/71? And what's the differnce for a 72?

And most importantly, how much a differnce does it really make?
Thanks ~ John

Lockup is hydraulic/mechanical, not sure the mechanism but it is NOT electrically actuated. Fitment and outside appearance are same as the non-L. However the bell housing inside dimensions are slightly different. Either the normal converter won't fit in the L bell housing or vice versa. So make sure you get the right converter with the tranny.
It makes a difference with my 740. Drops the revs about 300 rpm when it engages. I think it'd result in substantial improvements in gas mileage with the turbo, but it'd make the car really sluggish on the highway below 60mph - until revs were up enough to make boost. There's enough lag as it is. AND, the turbos come with a higher stall speed converter than the NAs, so if you do this try and get the turbo-specific tranny from a 940, as I suspect that the locking converters would have different stall speeds for turbo than NA.
--
Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf, 90 740 Rex/Regina

Dear Alf,

Good p.m. and may this find you well. I believe turbo-equipped cars were not equipped with the locking torque convertor. The reason: the extra torque might be more than the tranny could handle.

I recall a post or two, long ago, the sense of which there may have been a few cars made, with the locking torque convertor. I do not recall the details. Perhaps one of the Board, turbo experts will have the details.

The transmission dataplate (driver's side, USA/Canada models) shows the type of unit. Those with locking torque convertors have an "L" at the end, e.g., AW71L.

Hope this helps.

Yours faithfully,

spook

According to the simplified Volvo North America Vehicle Specification documents, there is no mention of 940's with lock-up torque converters. However, according to the on-line owner's manuals all 940's ('92-'95) have the lock-up torque converter feature. Additionally, all 700/900's from '89-'91 with the B234F 16-valve engine had the specially geared AW72 transmission and it was only available as the AW72L with a lock-up torque converter.

This is all not to be confused with locking *differentials* (aka. limited slip or traction control) which were on all 940' since 1991, at least according to the on-line Vehicle Specifications.

Anecdotally here on the board we pretty much agree that all (North American) '94-'95 940's got lock-up torque converters and at least some '93 940's. I can confirm that my '95 940s have the lock-up torque converter (AW71L on the 940T, AW70L on the 940NA -the latter is contrary to what I had previously posted). I can also confirm that an '89 740GLE (16-valve) had it. My experience is only with the Canadian market, but everything was pretty much common throughout North America in regard to drive trains. Also anecdotally, it isn't clear that all the early 940's got the locking *differential*.

The fuel savings when you're driving long distances in lock-up are significant. Under hard acceleration, I do not find kick down response out of lock-up to be an issue, there is no appreciable delay in jumping down to 3rd or 2nd. A lot of differences there may be attributable to kick down cable adjustment. Under mild acceleration, I do find kick down response to be slightly aggravating -you always jump right down from lock-up to 3rd when a simple drop out of lock-up into 4th would suffice. Unfortunately, lock-up mode is speed related, not torque related. Because of that I find the transmission will easily hunt between lock-up and 4th when driving at the lock-up shift point, especially when going up hill.
--
Dave -own 940's, prev 740/240/140/120's & quasi-expert only on a good day

Dear Dave,

Good p.m. and may this find you well. Your reply should be in the FAQs, as it is very much FAQt-based (pun intended)!

My normally-aspirated 1993 and 1994 940s have the AW71L tranny.

Yours faithfully,

spook

I was under the impression my 93 940 Turbo does have an AW71L.

Can this be verified by driving it? I'm thinking that:

- with most automatic transmissions, if you're cruising on the highway, and you blip the accelerator pedal a little, you will see rpms jump more than what your immediate speed increase is - ie. there is some slippage

- with lockup torque convertors, if you do the same, you won't get this rpm jump - there is no slippage. It will react just like a manual transmission where engine rotations are locked to wheel rotations (I used to use this as a clutch slippage test).

I know on my 940 Turbo, I don't get slippage with this test.


--
David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near Toronto

Obviously, the sure test for the "L" transmissions is to get under there and look at the ID plate, as mentioned by Spook. (Mine reads "03-71L"). Another way is to accelerate fairly moderately, and, at about 2300RPM in 4th/OD you'll feel a slight jerk like a gear change, and RPM's will drop 2-300.

One poster here related a story of swapping an AW-71L into his turbo and having it fail while accelerating strongly, locked up in 4th. It was a used trans, however. See the URL posted in another message here.

On mine, once it's engaged there's no unlocking the converter clutch with the gas pedal, until you've pressed it far enough to cause the trans to downshift out of 4th. With a turbo car this would put a lot of stress on the little clutch.
--
Bob (son's 81-244GL B21F/M46, dtr's 83-244DL B23F/M46, my 94-944 B230FD; hobbycar 77 MGB, and a few old motorcycles)

I understand there were a few lockout trannys factory mounted in US and maybe more in Canadian turbos, but more common in Europe.

http://www.brickboard.com/RWD/index.htm?id=1032781&show_all=1

Inside the torque converter there is essentially one fan at engine RPM, blowing fluid on another fan connected to the transmission, (pump, stator and turbine). With lock-up, a clutch plate in the torque converter engages thus forcing the tranny to turn at the same RPM as the engine revolutions eliminating wasted energy. Yes you are correct about the slippage. Without lock-up, increasing the engine RPM quickly, or torque, spins the engine side of the fan or pump until the turbine side catches up. On the other hand, accelerating in a tranny with lock-up forces the lock-up clutch to disengage which is a nuisance. European turbos with lock-up are equipped with a kick down inhibitor which prevents the shift out of OD at certain RPMs and speed and I assume prevents a nuisance kick out of lock–up.
--
Tom F. Three Bricks, maintain two more.