A3 Tranny in an A2

[tm america]

hard to see in the pic but what is that rating at 3306? right under the rating for 2700rpm

 

[TexAndy]

the question isnt so much if it will fit but more why would you want to put an a3 trans in an a2? the a3 uses a 3000-3200rpm rpm motor . While the multi only goes to 2600.In other word if you put an a3 trans in a a2 top speed would be about 42mph. Even if you put 46s on it top speed of about 50-52mph.Sure an a3 will dust an a2 up to 50 but the a2 will roll on by it from there.On a long trip the a2 will be so far ahead you wouldnt have to look at that ugly a3 front end in the mirror

I wonder if there are any other torque converters that you could use for less or no gear reduction at the torque converter.

 

[tm america]

torque converters dont provide more gear ratio they multiply the usible torque .they effectively slip in a sense. to allow the engine to pick up rpms while still providing power to the transmission. the are no gears in a torque converter.there are three parts to a converter the pump,turbine and stator. fluid is thrown from the pump across the turbine to the stator as fluid is thrown across the stator it makes it pick up speed .this is how it works a lock up converter eliminates this action when in lockup so it effectively acts like a cluctch when in lock up. there are different stalls of converters. but this only moves the rpm up or down that they engage at

 

[TexAndy]

torque converters dont provide more gear ratio they multiply the usible torque .they effectively slip in a sense. to allow the engine to pick up rpms while still providing power to the transmission. the are no gears in a torque converter.there are three parts to a converter the pump,turbine and stator. fluid is thrown from the pump across the turbine to the stator as fluid is thrown across the stator it makes it pick up speed .this is how it works a lock up converter eliminates this action when in lockup so it effectively acts like a cluctch when in lock up. there are different stalls of converters. but this only moves the rpm up or down that they engage at

Multiplying torque is done at the price of speed. Which is exactly what a gear reduction does, right?

Wheels aren't "gears" either, but they do act like gear reduction in the sense that a smaller wheel will provide more torque and less speed while a bigger wheel will provide more speed and less torque.

I wonder if the A3 transmissions are lockup? The A3s were all done in 1993 or later, right?

 

[nhdiesel]

hard to see in the pic but what is that rating at 3306? right under the rating for 2700rpm

I believe that is max. RPM. 2700 is peak HP, but the engine will turn faster than that.

What happened to your Durango?

Rust. It was up in this area for 3 years, now the rockers and floors are gone, the frame is getting quite rusty, the hatch is shot...there is no resurrecting it. I might put the Cummins in a good 2000 Jeep Cherokee XJ I have.

Jim

 

[tm america]

nhdeisel that makes it a 3300rpm motor with peak hp at 2700 the multi is a 2600rpm motor with peak hp around 2100. ..As for wheels being gears they are in every sense of the word the larger the wheel the less gear ratio. torque conveters act totally different.They act more like a clutch that is being slipped. There is nothing that changed diameter .
the a3 came with two different transmissions .the at545 which had no lock up and the at1545p which was a lock up trans. lock up converters are ussually built a little looser than non lock up converters. Most non lockup converters have about a 6-10%effeicency loose at full rpm while lock up conveters have none when locked up.Therefore they can make them looser to get better acceration and not have to worry about them over heating the fluid on the highway.

 

[TexAndy]

so how does a torque converter multiply torque if it's essentially just a 1:1 clutch?

 

[tm america]

think of a torque converter as a hydrualic pump not as a gear.it works much inthe same way that allows a small gas engine to split a log on a log spliter.not thru gears but thru the use of hydrualic fluid.hydrualic fluid varies the rate that the engine is coupled to the cylinder. much in the way that a torque converter works .there are ratios in use but not like a gear ratio in a trans or rear end ..

 

[TexAndy]

I need to see pictures.

 

[tm america]

just think there is no dirrect mechanical link inside of a torque converter....there are fins that fuild is thrown across. the faster the fuild is thrown the more power is put to the input shaft.it is done with hydrualic fluid not a mechanical link like a clutch

 

[TexAndy]

so there's like an aircraft engine impeller inside the torque converter?

 

[tm america]

very similar to a turbine engine yes. there are three sets of fins one is attached to the pump.the other the stator the other is the turbine.i have a cut open torque converter at work i will take some pics on tuesday and post them so you get an idea of whats happening in there

 

[nhdiesel]

O.K., think of it this way, for simplicity's sake. Think about a clutch that is able to slip at a consistent rate, enough to allow the engine to run at higher RPMs where it makes more power. just for the sake of argument, lets say that slippage is a 500 rpm increase in engine RPMs. So the engine is turning at 2000 rpms, where it makes a fair amount of power. The transmission input shaft is turning at 1500 rpms. That would end up acting like a gearbox that dropped the gearing by 500 rpms.

The whole description about the torque converter multiplying torque isn't really all that accurate. It just allows an RPM difference between the engine and transmission. The main purpose of a torque converter is to allow the vehicle to stop without having to disengage anything. The engine can still turn without the transmission moving. The "gear reduction" is just a side effect of this.

The best description of how a torque converter operates is to think of two household fans. Place them face to face close to each other. Turn one on, and it makes the other spin. The one you turned on is the engine, the other is the transmission. If you turn the fan to high, the other spins faster. If you set it to low, the other may stop moving completely, this is comparable to you sitting at a stoplight in gear.

A lockup torque converter just takes those 2 fans and locks them together under certain conditions. No more slippage acts like upshifting a gear.

Jim

 

[TexAndy]

ok, that's pretty dern clever. the fan analogy worked for me.

I get how the torque converter allows the engine to turn even while the transmission isn't. but I don't understand how that would act like a gearing reduction.

Referring to the analogy, I get that the TC is reducing input speed to the transmission... but wouldn't the energy in those 500 rpms of slippage just be lost as friction heat?

thanks for the lesson, guys. I am totally clueless about transmissions.

 

[nhdiesel]

There is heat created in the torque converter, which is why automatic transmissions need an external cooler. Most of the heat produced by an auto trans is from the torque converter.

While there is heat created, there is still a "gear reduction" happening. It still acts like having a gear reduction box between the engine and transmission.

Jim

 

[TexAndy]

Is one of the internal blade thingies a smaller diameter than the other?

 

[nhdiesel]

Nope, they are the same size. Here is a video explaining it and showing the inside of a torque converter.

[media]http://www.youtube.com/watch?v=Kfksv9jFE4w[/media]

Jim

 

[TexAndy]

ok, I watched the video. That was a big help by itself.

So going back to your analogy, whereas the engine might normally stall at 1500 rpm, the torque converter allows the transmission to spin at that speed while the engine is turning at 2000 rpm... but even though the speed of the transmission is 1500 rpm, it's actually receiving the torque produced by an engine spinning at 2000 rpm, minus friction from oil hitting blades.

I think I get the hydraulic pump analogy now. 100% (minus friction)of the 2000 rpm engine torque is being transmitted to the transmission at 1500 rpm as if it's a closed hydraulic system. The torque isn't lost... it's still expressed as hydraulic pressure on the opposite fan blades, regardless of what speed those blades happen to be turning, right?

Ok, assuming what I just said is true... it *sounds* from the video like the reason for this is because it's not like a friction clutch where lack of engagement means free spinning with no force being applied, but instead it's as if the clutch is *always* engaged. It can't not be engaged. The force is still being applied to the transmission via the TC, even when the vehicle isn't moving. Or when it's moving slower than it should to keep from stalling.

If this is correct (please let it be so) would that not mean that this torque advantage (compared to a manual) decreases as the TC input and output approach the same speed?