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Old 08-08-2019, 11:36 AM   #21 (permalink)
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Oil gets hot going over relief in a hydraulic system, So if there is a mechanical relief in your transmission that may be a problem. I think the computer controlled transmissions just control the pressure with no relief. High line pressure is only commanded when needed so fuel mileage is out the window at full throttle anyway. It may cause extra load when not needed for normal driving.

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Old 08-21-2019, 02:05 AM   #22 (permalink)
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How much power will it hold? It depends...on size/diameter of the clutch, how worn it is, line pressure, fluid condition, and engine torque. A good one can hold a surprising amount of power before slipping, but a worn one might slip all the time.
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Old 08-21-2019, 06:57 AM   #23 (permalink)
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How much power will it hold? It depends...on size/diameter of the clutch, how worn it is, line pressure, fluid condition, and engine torque. A good one can hold a surprising amount of power before slipping, but a worn one might slip all the time.
That makes sense, thank you. My TCC is a ring about 9 inches in diameter and 1/2 inch wide. I calculated that the surface area of the clutch is about 13.3 square inches.

In my opinion the TCC seems quite small to me considering the size of a manual transmission clutch for the same car, especially since it's a wet clutch. Unless the hydraulic pressure holds the TCC with way more force than a manual trans clutch is held?
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Old 08-21-2019, 11:55 AM   #24 (permalink)
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It really depends on clutch material, line pressure and how much surface area there is for the fluid to push on.

Clutch material can vary quite a bit. You can buy "soft" clutches for manual transmissions or you can buy a ceramic clutch that you cannot slip and it grabs instantly(like in the big trucks).

More line pressure equals more clamping force. The same goes for fluid surface area. The more area there is for the fluid to clamp the clutch together, the more it will hold.

You can buy torque converters for pickups that have multi-disc clutches that can hold a ton of power.

A smaller tcc or smaller car will have less holding power, but they make less power to begin with.

If you want to find out for sure, use a tcc switch and give it the beans in each gear, watching for slippage.
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Old 08-21-2019, 05:29 PM   #25 (permalink)
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It really depends on clutch material, line pressure and how much surface area there is for the fluid to push on.

Clutch material can vary quite a bit. You can buy "soft" clutches for manual transmissions or you can buy a ceramic clutch that you cannot slip and it grabs instantly(like in the big trucks).

More line pressure equals more clamping force. The same goes for fluid surface area. The more area there is for the fluid to clamp the clutch together, the more it will hold.

You can buy torque converters for pickups that have multi-disc clutches that can hold a ton of power.

A smaller tcc or smaller car will have less holding power, but they make less power to begin with.

If you want to find out for sure, use a tcc switch and give it the beans in each gear, watching for slippage.
That makes sense, thank you! I never feel any slipping when the TCC is locked, even flooring it at peak torque. However, my concern is that I may not necessarily feel if it is slipping. The PCM on many cars (including mine) slips the TCC quite a bit by default and it is never felt. If it is in fact slipping under load am I likely to feel it, or will it slip itself to death with no warning that it is self destructing? Thanks in advance!
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Old 08-21-2019, 10:42 PM   #26 (permalink)
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Do you have a tach or a way to see your rpm? If your rpm's never change when you goose it, you're fine.
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Old 08-22-2019, 01:46 PM   #27 (permalink)
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Do you have a tach or a way to see your rpm? If your rpm's never change when you goose it, you're fine.
Thanks. When I floor it with the converter locked the RPM never changes until the car starts accelerating, like a manual transmission. But Is it possible that it is slipping and not showing on the tach? Like if it is only slipping a tiny bit?
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Old 08-22-2019, 01:48 PM   #28 (permalink)
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If your tach doesn't move, then it's most likely not slipping. Being a wet clutch, a little bit shouldn't hurt it like it would on a dry manual clutch. Still not good, but not as bad.
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Old 09-05-2019, 02:31 PM   #29 (permalink)
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Static friction is higher than sliding friction so if your TCC slipped, you would notice it because it would probably slip quite a bit. Because of that differential, it's very unlikely to slip a tiny bit.

This same situation is why it's very difficult for a human to ride the optimum pressure while braking. Tires have the most stopping power when rolling but once they lock up suddenly you need a lot less brake pressure to keep them locked. Modulating that by feel is very difficult. Computers are much better because they can keep the tire slipping just a bit which is an indication that tire friction is highest.

PS. My TCC and trans are just fine after ten years of using a lockup switch so all those nay-sayers can eat crow now.
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Old 09-05-2019, 03:15 PM   #30 (permalink)
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I've been using a TCC lock switch on my Chevy 1500 2wd for close to 15 years now. (4L60E). Initially I discovered that the PWM valve (electronic pressure modulation valve) would reduce the pressure to the clutch and slip it, so I also had to disable that. I tow large loads all the time....... far larger than the pickup is rated for. I lock up once I get moving, and I shift manually, as I also have a switch wired in that prevents the 3:2 downshift and the 4:3 downshift, though I NEVER use 4th when pulling. As I know when my transmission will downshift, I can let off the throttle momentarily during the shift... again, I'm manually shifting while towing, and often in normal driving. This relaxing of the throttle before a shift is far different than the violent shift one gets when a vehicle downshifts under full throttle.
I have had zero problems with my tranny, which has right at 200K on it (1997 year). I do a flush every few years, by just changing the filter, and refulling, then pumping fluid out a cooler line through a clear plastic tube until I see bubbles, shut off, refill, etc... until I runs clear new fluid....... About 4 gallons total.

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