tranny
 

a couple weeks ago i posted about my tranny getting fixed by the person who sold it to me. The shop that fixed it ran a dyno test on it and it shows the rwd kicking in 7 times on the first test and 72 on the 2nd test. This test supposedly varies road conditions for 30 min incriments. I thought that awd was 90 10 split so the rwd would be on all the time? maybe it is because it kicks in harder than most in adverse conditions? They are putting a new cpu on the tranny. Also the tranny guy says that this is what they believe burns that back clutches out. Kicking in 72 times in 30 minutes. Doesn't sound healthy for the tranny. I'm a newbie so any thoughts?

The rear wheel drive is always on if everything is working. The clutch pack in the back of the transmission also acts as the front to rear differential. While in the corners the transfer clutches have to slip to allow the front wheels to spin faster than the rear. The amount of slip is controled by the transfer clutch pressure. The higher the pressure the less the slip in the clutch pack.

I do not know the type of test that they did but when the accelerator is depressed the transfer pressure is increased. Stomping on the throttle raises the transfer pressure to the full value.

You can check the AWD without the dyno by raising all four wheels off the ground and making sure they all spin at idle.

If you pulsed your foot on the throttle 72 times in 30 minutes then yes the RWD drive would be kicking in and out as you moved your foot down and up.

tranny
 

they say that this dyno simulates hills, icy etc...... they say that they ran the same test as the first

Okay, They simulate hills and ice. How many times do they say the RWD should kick in? Remember the SVX is always in FWD. No way to take it out of FWD. Every time the car goes up a hill and the throttle is depressed the RWD will kick in. How is the throttle controled during this test?

I have sort of an answer to this one. I own two AWD Subarus with the 4EAT transmission and they act differently. Here is how I understand it. Please correct me if I get anything wrong.

My SVX works like it should. The torque transfer is really smooth. If I'm on snow or another slippery surface, I don't even feel more torque being transfered to the rear wheels. I do not experience any noticable front-wheel slippage - it's just instant.

My wife's Legacy was abused by who-knows-how-many previous owners. On a slippery surface, I notice about a second of front-wheel slippage before I feel a gentle -thud- and the rear wheels get a bigger share of the torque. This is not right - it should operate like the SVX.

I have been told by owners of non-Subaru AWD cars (most recently a CR-V owner) that my description of how the Legacy seems to work also describes their cars - even when brand-new. So it is possible that other manufacturer's AWD set ups, while similar, are just not as smooth as Subaru's is supposed to be when it is operating normally.

Torque transfer is supposed to be smooth and not noticed. There should be no -thud- and there should be no major slipping of the front wheels.

Uh...where am I going with this? Oh, yeah. If this super-dyno is detecting erratic AWD operation, as it seems to be, then I would suspect that you have a problem. On identical sequential tests, it should act in pretty much the same way every time. I would suspect that your car is acting like my wife's Legacy.

But then, what the hell do I know? :)

?
 

I'm guessing but i would think computer controlled. Does a dyno like this exist. I have been to speed shops and ran my motorcycles on cycle dynos. All I am familar with is straight line looking for horsepower. hills and ice i have no clue but you know I saw a mcdonalds in walmart the other day too.

Re: ?
 

HA! :)

What ever happened to the idea of never putting a Sub AWD on a 4 wheel treadmill? B. :eek: