legacycentral bbs

ciper wrote:Imagine if the front differential and center differential was open. They both could double the output speed of the transmission if only one front wheel was floating right? Thats where the 3x comes from, it does change depending on load so its not easy to give an exact number.

Right... If you had all open differentials and only one wheel was permitted to rotate, it would turn three times as fast as the ideal final drive. But the example you gave had the rear two wheels strapped to a dyno, and the floating front wheel spinning "three times or more" the rate of the rear wheels, which doesn't seem to make sense to me.

NO subaru viscous unit will ever lock under load. This myth was started by people who didnt understand how the magic LSD fluid works. It does get thicker as it heats, you can feel this if you have a rear LSD and automatic. I didnt write down numbers but when I installed an LSD on one of my cars I put a needle torque wrench on the axle nut and saw the torque increasing.

What fact are these people missing? Just that the fluid doesn't get thick enough to fully lock?

If you ever see a high powered subaru 5mt autocross you should be well aware of how they "light up the inside wheel" at sharp turns. This just doesnt happen in an automatic even with unlimited power.

Hmm... So perhaps the viscous coupling center differential just wasn't engineered for very high torque output. That would explain why Subaru used the DCCD on the new STi. But "plain old" WRXes have always used the viscous coupling, right?

Ive mentioned this before but I feel its time again. The HUGE advantage to an automatic with a turbo is keeping boost DURING the 1-2 shift.

Yeah, and with the stock flywheel and original BC synchros, that shift takes forever, at least on my car. I lose all my boost!

I argue that autos are NOT for "little econoboxes"

I agree with that. As my girlfriend's dad says, how far can you really wind up a little rubber band motor to push through a torque converter and automatic transmission? :)

You definitely need to torque for an auto. So with Subarus its not too bad, the old pushrod GL's front end would jump like a muscle car with the auto and would demolish most anything for the first maybe fifty feet. But a Honda...forget it.

Steve

vrg3
"the example you gave had the rear two wheels strapped to a dyno, and the floating front wheel spinning "three times or more" the rate of the rear wheels, which doesn't seem to make sense to me"
The center differential is so weak that it allows a large speed difference between the outputs under load.

"the fluid doesn't get thick enough to fully lock?"
Yes, Ive read many times about how the differential is supposed to lock under power

"But "plain old" WRXes have always used the viscous coupling"
Im not an expert on the overseas models but I know there are quite a few different versions with both types of differential.


evolutionmovement: "demolish most anything for the first maybe fifty feet"
Thats so true

scottzg: A GMC van? That could be the problem. If you had purchased a Ford E250 you could have driven that 300k on the same transmission.
You replaced the clutch at 72k, so by 200k miles it would need its third clutch while the automatic would be really soft but still drivable (though loss of 4wd is common for people who dont know to replace all four tires).
If your only cruising around at idle speeds then you can shift the car without even using the clutch. Same with the auto, if you drive around never using more than 40% throttle it will last alot longer too.

You say the manual wears out only if you cant drive, why did yours wear out

my car has a replaced clutch, courtesy of the P.O., at 72k

I bought the car with a burnt up clutch and a new hd clutch in the trunk, at 72k. I never drove on that clutch.

yup, if you have one tire that is a different size than the others, awd goes bye bye.

Big fords are much better vehicles, no arguement there. And that automatic is great for towing!