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Deleting lockup via valve body (AW71L)

Broke4speed

Broke4speed

Well-known member
Joined
Oct 5, 2009
Location
Marionville, Ontario, Canada
Long story short, I hate the 71L I put in my car, because I cruise too low for my big 16G (8cm hotside) to spool at highway speeds (canadia, 80-100kph or 50-62mph). If the converter wasn't locked to direct drive, and I could take advantage of the converter stall speed, it would be fine...but that lockup clicks in at 81kph and sucks the fun out of the car. Finding and rebuilding an AW71 isn't going to happen, so...maybe there's a way I can modify my current one, I hope.

Here's a picture of the valve body from the ATSG manual:

8ZGAO7y.jpg


There's two valves, a signal and a relay. Here's some helpful info from an old thread ( http://forums.turbobricks.com/showthread.php?t=121456) that explains what they do and how:

Linuxman51 said:
Lock-up signal Valve: Line pressure is supplied to one end of the valve and governor pressure to the other. Two line pressure inlets are provided, one for selector positions 1-3 and one for selector position 4. when 4th gear is engaged and the governor pressure (i.e. speed of the car) increases, oil flows at line pressure from the control valve to the changeover valve.

lock-up changeover valve: The valve is actuated by oil at line pressure from the signal valve. Opening the valve reverses the fluid flow from the torque converter, operating the lock-up clutch plate and activating the lock-up function.
Click to expand...

Now, I'm wondering if I were to shim one of those two valves, or both, could I prevent the lockup from engaging? Any thoughts?
 
Woah woah woah...before you go and wreck a perfectly functioning AW71L, ask around and find an AW71. I'm sure someone would gladly offer to meet and swap trannies with you. If you were closer, I would trade my AW71 out of my car for your AW71L.
 
KeizerBrickGuy said:
Woah woah woah...before you go and wreck a perfectly functioning AW71L, ask around and find an AW71. I'm sure someone would gladly offer to meet and swap trannies with you. If you were closer, I would trade my AW71 out of my car for your AW71L.
Click to expand...

This. Might be a lot less work as you'll need to pull the AW71l anyway.
 
I'm in agreement with these two, but I'm also not sure what you're asking would work.

First... what is your desired outcome? You want to have more boost by using the converters stall speed which I get... but maybe I'm missing how this happens at highway speeds?
 
The converter locks to direct drive, which locks me at 2000rpm-ish. My 16g only spools at 3000, which means part throttle boost is impossible...and unless I make it kick down (which drops it from a 0.76-ish ratio to a 1:1...which is a very aggressive downshift for just needing to gently pass someone). I essentially have almost no power, since going from 2000 to 3000 in '5th' gear with an 'A' cam sucks without boost.

I'm in Ontario, which is pretty much as far as can be from swapping my box for someone else's, and I don't really want to do that, since my L is a roller-bearing tailshaft, and freshly rebuilt. I need to work with what I've got, and frankly, unless I swap to a 13C and 4.10 gears (which is what the turbo 940s with lockup came with up here in Canada), there's NO way I'm going to be able to get the part-throttle boost I want at cruising speeds. Being able to load the engine with the stall of the converter, at part throttle, will really help with the driveability I'm after.
 
a stiffer spring on the signal valve *should* delay lockup, but I suspect you'd be in for a lot of experimentation getting that where you want it to be.
 
you answered your own question, change the rear gear instead of messing with the trans. first i would figure what r.p.m. you need at your cruise speed tire size ect then pick a gear
 
freevolvos said:
you answered your own question, change the rear gear instead of messing with the trans. first i would figure what r.p.m. you need at your cruise speed tire size ect then pick a gear
Click to expand...

This is truthfully probably the path of least resistance.
 
I recently read that the lockup only comes on after the shift to overdrive. Would messing with the lockup also be messing with overdrive?
 
freevolvos said:
you answered your own question, change the rear gear instead of messing with the trans. first i would figure what r.p.m. you need at your cruise speed tire size ect then pick a gear
Click to expand...

I honestly thought the lockup would be great...but it sucks. This is a 'toy' car for me, so I'm not trying to milk it for maximum fuel economy. All I want is more part-throttle spool :).
 
You are better off finding a lower rear gear and fixing your spool issues. A TD05H with a small hotside should spool fairly early.
 
EivlEvo said:
This is truthfully probably the path of least resistance.
Click to expand...

My path of least resistance involves no money spent :lol:. I have the time, and I'm reasonably certain that shimming the lockup signal spring will effectively cancel the lockup function of the converter. I've been doing some research and it looks like this process is done on other makes/models of transmissions (big 3, mainly) to disable the lock.

It all depends on my enthusiasm for being covered in ATF this weekend, I guess.
 
Harlard said:
You are better off finding a lower rear gear and fixing your spool issues. A TD05H with a small hotside should spool fairly early.
Click to expand...

Honestly, the lockup SUCKS for anything other than a 13C or MAYBE a 15G. If our speed limits were higher up here, like the 75mph I cruise at when I visit northern New York state, it wouldn't be an issue...but Canadia is slow.

If I had the unlimited money I used to have as a young buck (which usually meant skipping eating or being late on my rent), I'd replace the rear end AND the hotside...but I'm a fat old homeowner now, who is also saving for retirement, so...:-(
 
Circling back around to swapping to a non-lockup AW71...why is it that you're totally fine for doing something that a 71 could do, when I'm sure someone in the NY, VT, ME, PA States would gladly help? Or someone in your territory? I'm just having a hard time with the fact you're wanting to tear into a perfectly-functioning AW71L to make it an AW71...:wtf:
 
KeizerBrickGuy said:
Circling back around to swapping to a non-lockup AW71...why is it that you're totally fine for doing something that a 71 could do, when I'm sure someone in the NY, VT, ME, PA States would gladly help? Or someone in your territory? I'm just having a hard time with the fact you're wanting to tear into a perfectly-functioning AW71L to make it an AW71...:wtf:
Click to expand...

Mine's a very late 71L with the roller bearing tailshaft, which is much more durable. I also rebuilt it tip-to-tail before I installed it, so I'm not quite sure I'd be able to come away with a transmission that's as good as the one I have now.

The modification is completely reversible, and will result in no damage whatsoever to the box, so I can go back at any time if I want. I'd much rather drop a valve body than a transmission :).
 
lummert said:
I recently read that the lockup only comes on after the shift to overdrive. Would messing with the lockup also be messing with overdrive?
Click to expand...

Not that I can see. The fluid signal comes from the governor, and '4th' gear (which would be O/D), so that when both signals are received there's enough pressure to move the valve, which opens a channel for the ATF to flow to the lockup function.
 
Broke4speed said:
Maybe I'll give it a try this weekend, since I have some time. I'm not really concerned with keeping the lockup, so a wee shim, a la accumulator mod-style, might be the ticket for me.
Click to expand...

if you don't care to have lockup work at all ever, you could just shim it up so that the signal valve can't move, that would in effect prevent it from engaging.

shouldn't hurt anything, wouldn't be a big deal to undo later either.
 
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