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Three Drivetrain Questions


JasonA

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Car in question: '97 SLS, 127k miles.

1) How is the differential itself lubricated? In conventional RWD vehicles, there is a differential case in which something like 80W-90 oil is used. Is that the case with the 4T80-E transmission also? Or are the differential gears lubricated by transmission fluid?

2) I'm sure it was an old wive's tale, but they used to say that if you haven't changed the transmission fluid often, if you change it way later in life you'll just do more harm than good. The fluid in mine is, I suspect, still original and when I take it in to have the strut mounts done, I'd like to have them change the filters and fluid. I assume that with only 127k miles, it'll be perfectly fine to have this done?

3) Anyone seen the new Sierra commercial where they show it climbing an incline with one wheel on concrete and the other on rollers, to showcase the standard posi-traction axle? Could our Cadillacs do that? I know the traction control has been explained before as mimicking a "posi-traction" or limited-slip device. Under those circumstances though, with that much weight and gravity against it, would it be able to pull the car up the hill? Just curious. :)

Thanks,

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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There is a differential inside a front drive transaxle, and it is lubed by the tranny fluid.

I haven't seen that commercial yet but it sounds cool.

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The 4T80E transmission has a transmission fluid life indicator that should display when you need to change the fluid.

The anticipated interval is 100,000 miles under normal use. If your fluid is bright pink it may have been changed. If it is dark in color it likely needs changing.

The pan is dropped to change the fluid and the side cover drain plug removed to drain it. There is a screen in the pan area that needs to be cleaned and reinstalled.

The filters are hard to get at and normally never need replacing unless rebuilding the transmission.

Some dealers say you can reuse the pan gasket, the service manual states to NOT reuse the gasket. I recommend replacing the gasket ($40) to ensure no leaks. Just have the pan and mating surface clean and DRY, no sealer of any kind.

The gasket is metal shim with double raised silicone beads.

Using clean fluid will never hurt your transmission. Used fluid is damaged by heat and contamination due to clutch material and metal particles from normal wear and tear.

-George

Drive'em like you own 'em. - ....................04 DTS............................

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Car in question: '97 SLS, 127k miles.

1) How is the differential itself lubricated? In conventional RWD vehicles, there is a differential case in which something like 80W-90 oil is used. Is that the case with the 4T80-E transmission also? Or are the differential gears lubricated by transmission fluid?

2) I'm sure it was an old wive's tale, but they used to say that if you haven't changed the transmission fluid often, if you change it way later in life you'll just do more harm than good. The fluid in mine is, I suspect, still original and when I take it in to have the strut mounts done, I'd like to have them change the filters and fluid. I assume that with only 127k miles, it'll be perfectly fine to have this done?

3) Anyone seen the new Sierra commercial where they show it climbing an incline with one wheel on concrete and the other on rollers, to showcase the standard posi-traction axle? Could our Cadillacs do that? I know the traction control has been explained before as mimicking a "posi-traction" or limited-slip device. Under those circumstances though, with that much weight and gravity against it, would it be able to pull the car up the hill? Just curious. :)

Thanks,

Jason,

The "differential" in the transaxle is lubed by the transmission fluid. You called it on the old wives tale about changing the trans. fluid. I've heard this before but do not believe it for a second! What does your trans. fluid life indicator display? It certainly wouldn't hurt anything to change the fluid and clean the screens. Definitely use a new gasket - I've heard of prople reusing the gasket but why risk having to do the job again if the old gasket leaks? Make sure the shop uses an OEM gasket as it has the steel spacer sleeves and the aftermarket gaskets do not.

The red color in transmission fluid will diminish in intensity over time but that does not indicate a problem as long as the fluid doesn't have an acrid, burned smell to it.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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The Northstar traction control would accomplish what you describe easily. If you want proof...find a steep driveway with dry pavement on it and ice or snow or wet grass along the edge. Put one tire in the ice and the other front tire on the dry pavement and drive up the driveway......wouldn't do that without the traction control.

In the last ice storm, I had to use 4wd to get "up" the driveway everytime I came home. Our lot is very flat, and the driveway is just sloped enough to drain water away from the house and garage. But still, with the sheer ice, my truck would slide back and forth. Slap it in 4-wheel and it crawls up. I didn't try it with the Cadillac, but I might the next time it gets real icy like that. The Seville doesn't go out in that kind of weather, but I don't suppose playing around on the driveway like that could hurt much. :)

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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