- Joined
- Dec 25, 2002
- Location
- mont, AL
We'll refer to this as "beating a dead horse", since the first inception of this was called "polishing a turd"
Referencing this thread of course: http://forums.turbobricks.com/showthread.php?t=64408&highlight=polishing+turd
Started by Aaron(sp?).
At any rate, as some/many/none of you know, i've yet again ventured back to the venerable, but ostensibly weak volvo automatic.
Namely the AW71.
Since the writing of this article, a few neat hacks have become popular, the somewhat legendary valve body hack, which comes back into and out of fame (and has been around longer than Aaron and probably myself were members of this forum), but most notably the 'Accumulator mod', which essentially locks the accumulators to reduce shift time (and both combine to really reduce shift time).
Building on what aaron has started, lets open this discussion on a slightly more technical note, and start from the get go with the box as a whole and see if we can't work forward from there.
The ATSG guide for most of the pertinent A series transmissions can be found online here: http://www.pbase.com/sam3481/aw_manual
There is an older volvo specific guide which can be found elsewhere with a cursory search on the forum, and its host might (hopefully will) grace us with his presence and insight.
After spending some time thinking about this issue, some degree of trial and error and mild success, I've decided to commit a little more money to my own project in an attempt to see what can be done to get one of these transmissions to hang on to some serious power for at least a little while. Since I personally tend to spend most of my volvo quality time either in the driveway or at the drag strip, I'm not concerned in the least with longevity, within reasonable bounds (and I'm also a fair bit ahead of most in the power output side of life, so I would imagine what can take my level of use and abuse for a little while will serve many others for quite some time).
So let's start with the stipulations and reasons therefore (and i'm going to borrow heavily from aaron's thread. Consider it a prerequisite for this thread, so get to reading it and come back):
1) I would rather not increase line pressure unless we have to, and then, only a moderate amount. Reason: Cavalier increases in the operating pressure will blow the seals out in the clutch engagement pistons, and this would be considered counter-productive. Besides, higher pressures beget more strain on the pump and more power robbed from the engine, and enevitably this will result in more heat. Heat is a bad thing.
2) While it would be really nice to use "all volvo" stuff, I'd much rather be smart about it, if we determine that we can stuff the C2 carrier from a higher output unit in the volvo unit, lets run with it.
3) We're not getting into full swaps here, the goal is a unit with volvo dimensions and similar linkage that "bolts in".
4) Valve body is fair game, I disagree with aaron on this, I don't feel that flow modifications inside the VB will greatly increase the load on the pump (aside from shimming the hell out of the main pressure relief valve).
Brainstorming:
Aaron mentions in his thread something about slow disengaugement/engagement of the brake clutch packs, I'm thinking something along the opposite lines, i.e. weaker/less springs for the main clutch disengaugement. The idea here being that more springs resist pressure and slow the engagement of the clutch and simultaneously reduce the overall clamping pressure being applied by the engagement piston..
Alternatively, by swapping springs with the brake clutches, perhaps we can kill two birds with one stone. Thoughts comments?
I've been digging through the power flow diagrams for the aw-7X transmissions (oh by the way, if you haven't already figured out they're all essentially the same, minus some key differences in friction material and perhaps amount of friction material i.e. number of clutches, you needa go back and study some more).
Some background info from the green book and nomenclature (from now on lets try and keep with whats in the ATSG/Green manual, since there isn't a "gear set" per-se, just a series of locked and unlocked planetary gears, however I realize that generalizations will be needed for the sake of sane discussion, but when dealing with specifics, lets try and keep to the manual).
Primary Clutches:
C0, C1, C2.
C0 can be thought of as "overdrive", however this is only partially true: the only 'gear' that C0 is NOT locked up is overdrive,C1 and C2 will likely be the focus of most of our discussions.
Brakes:
As stated in the previous thread these are basically the same thing as brake bands in other automagics.
B0 can also be thought of as "overdrive" as it locks when C0 unlocks to overdrive the transmission.
There are two Free wheel locks, these are basically one way clutches, and are subjected to most of the brutality the transmission will see, from the green book, when in first second and third "the highest power is transmitted by the freewheel". So, also fair game.
I will attach an image here when I find a suitable diagram/get my scanner back to show the approximate locations of the above components in the transmission.
So. Open. Lets talk. And I don't care about a gm transmission, if I want one I'll swap in a t56.
***NEW INFO***
We can narrow down changes from the AW372 and 71:
C0 Has two clutches instead of one. Swap the uber thick steel for a steel and clutch.
C1 and C2 are identical to the aw71
B0 has one LESS clutch than the volvo (however I think this is more to discourage towing in OD)
B1 has an extra clutch, this requires a different clutch carrier than that which is found in the volvo. It is interchangeable. You want the part number, go dig one out of a jy your damn self.
While you're there get the C2 carrier, the volvo one doesn't have enough depth capacity.
B2 is the same
B3 is the same
The middle/rear planetary is different, I believe this is more related to a lower ratio for towing than a strength issue, however if one wishes to use this, you will also get the privilege of swapping out tailshafts or making a custom driveshaft. (one is far easier than the other)
The lock up and non-lockup pumps are different.. the lockup pump is larger internally. The ports are the same on both stators, however you CANNOT use a non locking converter with a lockup pump.
Regarding the difference between the aw70 and the aw71. This is an oft debated topic that no one seemed to have any really hard info about. Well here's (most) of the skinny:
Different pump and OD housing (at least up until 88/89). The pump 'intake' is bigger than that of the 71/72/43 pumps, however the OD housing flares out to accomodate this, the reality of the issue is that due to design (either poor or other) the feed for B0 just 'happens' to come up in the middle of what would be the intake. So the net result is a reverse funnel of sorts. Not sure if this is a good thing or not, or if machining out the intake to flow more would be of any help at all.
Overdrive brakes are smaller on the aw70(same size as the other clutches), B2 piston has 8 fewer springs than b2 in the 71.
B1 piston has the same number of springs.
The valve body & governor are likely to be a bit different as the aw70 runs different line pressure than the 71. The other internals back to B2 are the same (same count, etc).
Externally the valve body, case, etc are the same, so the usual aw71 mods apply to the aw70, and it seems likely that the gov and vb swap would result in one effectively having an aw71. If there are spring differences in the clutches and brakes, its not immediately apparent, I might take a closer look later this week.
The gear ratios between the aw's of this series (basically the A4X) are controlled by the size of the planetary gears & these are all pretty much interchangeable, provided you get the correct carrier with them.
Failure points are somewhat random so far in the transmissions i've examined, the most common seems to be B2 and B3, with C1 and C2 following closely, however I've also found a destroyed B3 pack, and know of at least one instance where B0 was starting to let go.
C0 for some reason doesn't seem to be failure prone, however I would not hedge any bets on this. it might be possible to retrofit a different shell into C0 to get more than two clutches with reasonably sized steels in it, that will, however, be an exercise for the reader.
As for differences between the 71 and 72, it would appear on the surface that the governor is the same, the valve body will certainly be different to accommodate the lockup converter (among other things it has an extra valve).
Referencing this thread of course: http://forums.turbobricks.com/showthread.php?t=64408&highlight=polishing+turd
Started by Aaron(sp?).
At any rate, as some/many/none of you know, i've yet again ventured back to the venerable, but ostensibly weak volvo automatic.
Namely the AW71.
Since the writing of this article, a few neat hacks have become popular, the somewhat legendary valve body hack, which comes back into and out of fame (and has been around longer than Aaron and probably myself were members of this forum), but most notably the 'Accumulator mod', which essentially locks the accumulators to reduce shift time (and both combine to really reduce shift time).
Building on what aaron has started, lets open this discussion on a slightly more technical note, and start from the get go with the box as a whole and see if we can't work forward from there.
The ATSG guide for most of the pertinent A series transmissions can be found online here: http://www.pbase.com/sam3481/aw_manual
There is an older volvo specific guide which can be found elsewhere with a cursory search on the forum, and its host might (hopefully will) grace us with his presence and insight.
After spending some time thinking about this issue, some degree of trial and error and mild success, I've decided to commit a little more money to my own project in an attempt to see what can be done to get one of these transmissions to hang on to some serious power for at least a little while. Since I personally tend to spend most of my volvo quality time either in the driveway or at the drag strip, I'm not concerned in the least with longevity, within reasonable bounds (and I'm also a fair bit ahead of most in the power output side of life, so I would imagine what can take my level of use and abuse for a little while will serve many others for quite some time).
So let's start with the stipulations and reasons therefore (and i'm going to borrow heavily from aaron's thread. Consider it a prerequisite for this thread, so get to reading it and come back):
1) I would rather not increase line pressure unless we have to, and then, only a moderate amount. Reason: Cavalier increases in the operating pressure will blow the seals out in the clutch engagement pistons, and this would be considered counter-productive. Besides, higher pressures beget more strain on the pump and more power robbed from the engine, and enevitably this will result in more heat. Heat is a bad thing.
2) While it would be really nice to use "all volvo" stuff, I'd much rather be smart about it, if we determine that we can stuff the C2 carrier from a higher output unit in the volvo unit, lets run with it.
3) We're not getting into full swaps here, the goal is a unit with volvo dimensions and similar linkage that "bolts in".
4) Valve body is fair game, I disagree with aaron on this, I don't feel that flow modifications inside the VB will greatly increase the load on the pump (aside from shimming the hell out of the main pressure relief valve).
Brainstorming:
Aaron mentions in his thread something about slow disengaugement/engagement of the brake clutch packs, I'm thinking something along the opposite lines, i.e. weaker/less springs for the main clutch disengaugement. The idea here being that more springs resist pressure and slow the engagement of the clutch and simultaneously reduce the overall clamping pressure being applied by the engagement piston..
Alternatively, by swapping springs with the brake clutches, perhaps we can kill two birds with one stone. Thoughts comments?
I've been digging through the power flow diagrams for the aw-7X transmissions (oh by the way, if you haven't already figured out they're all essentially the same, minus some key differences in friction material and perhaps amount of friction material i.e. number of clutches, you needa go back and study some more).
Some background info from the green book and nomenclature (from now on lets try and keep with whats in the ATSG/Green manual, since there isn't a "gear set" per-se, just a series of locked and unlocked planetary gears, however I realize that generalizations will be needed for the sake of sane discussion, but when dealing with specifics, lets try and keep to the manual).
Primary Clutches:
C0, C1, C2.
C0 can be thought of as "overdrive", however this is only partially true: the only 'gear' that C0 is NOT locked up is overdrive,C1 and C2 will likely be the focus of most of our discussions.
Brakes:
As stated in the previous thread these are basically the same thing as brake bands in other automagics.
B0 can also be thought of as "overdrive" as it locks when C0 unlocks to overdrive the transmission.
There are two Free wheel locks, these are basically one way clutches, and are subjected to most of the brutality the transmission will see, from the green book, when in first second and third "the highest power is transmitted by the freewheel". So, also fair game.
I will attach an image here when I find a suitable diagram/get my scanner back to show the approximate locations of the above components in the transmission.
So. Open. Lets talk. And I don't care about a gm transmission, if I want one I'll swap in a t56.
***NEW INFO***
We can narrow down changes from the AW372 and 71:
C0 Has two clutches instead of one. Swap the uber thick steel for a steel and clutch.
C1 and C2 are identical to the aw71
B0 has one LESS clutch than the volvo (however I think this is more to discourage towing in OD)
B1 has an extra clutch, this requires a different clutch carrier than that which is found in the volvo. It is interchangeable. You want the part number, go dig one out of a jy your damn self.
While you're there get the C2 carrier, the volvo one doesn't have enough depth capacity.
B2 is the same
B3 is the same
The middle/rear planetary is different, I believe this is more related to a lower ratio for towing than a strength issue, however if one wishes to use this, you will also get the privilege of swapping out tailshafts or making a custom driveshaft. (one is far easier than the other)
The lock up and non-lockup pumps are different.. the lockup pump is larger internally. The ports are the same on both stators, however you CANNOT use a non locking converter with a lockup pump.
Regarding the difference between the aw70 and the aw71. This is an oft debated topic that no one seemed to have any really hard info about. Well here's (most) of the skinny:
Different pump and OD housing (at least up until 88/89). The pump 'intake' is bigger than that of the 71/72/43 pumps, however the OD housing flares out to accomodate this, the reality of the issue is that due to design (either poor or other) the feed for B0 just 'happens' to come up in the middle of what would be the intake. So the net result is a reverse funnel of sorts. Not sure if this is a good thing or not, or if machining out the intake to flow more would be of any help at all.
Overdrive brakes are smaller on the aw70(same size as the other clutches), B2 piston has 8 fewer springs than b2 in the 71.
B1 piston has the same number of springs.
The valve body & governor are likely to be a bit different as the aw70 runs different line pressure than the 71. The other internals back to B2 are the same (same count, etc).
Externally the valve body, case, etc are the same, so the usual aw71 mods apply to the aw70, and it seems likely that the gov and vb swap would result in one effectively having an aw71. If there are spring differences in the clutches and brakes, its not immediately apparent, I might take a closer look later this week.
The gear ratios between the aw's of this series (basically the A4X) are controlled by the size of the planetary gears & these are all pretty much interchangeable, provided you get the correct carrier with them.
Failure points are somewhat random so far in the transmissions i've examined, the most common seems to be B2 and B3, with C1 and C2 following closely, however I've also found a destroyed B3 pack, and know of at least one instance where B0 was starting to let go.
C0 for some reason doesn't seem to be failure prone, however I would not hedge any bets on this. it might be possible to retrofit a different shell into C0 to get more than two clutches with reasonably sized steels in it, that will, however, be an exercise for the reader.
As for differences between the 71 and 72, it would appear on the surface that the governor is the same, the valve body will certainly be different to accommodate the lockup converter (among other things it has an extra valve).
Last edited: