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Discussion Starter · #1 ·
This is the TCC Apply/Release table for a stock 2007 TB SS.



Has anyone scanned their TBSS while towing 4000# or more?
I'm curious what TP% a TBSS would have at roughly 65 mph?

I've got a TB LS with the I6, and it's TCC won't lock when I'm
towing 4000# in 4th gear. I'm curious if a TB SS would do the
job better with its higher torque rating? Or if it's also going to
be stuck with towing in 3rd gear, too?
 

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07 Black 2WD TBSS
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You'll put a lot of stress on your trans not towing in 3rd gear. Creates a lot of heat.
If the torque converter is locked, then why would there be excess heat created? Most of the heat comes from the TC slipping from what I understand (when it isn't locked).

I always thought you used 3rd to keep the engine from lugging at too low of an rpm, not typically a problem with the gearing on these trucks.
 

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Discussion Starter · #4 ·
If the torque converter is locked, then why would there be excess heat created? Most of the heat comes from the TC slipping from what I understand (when it isn't locked).
I've been trying to research how PWM TCCs work.
I'm not sure I understand exactly, but it sounds like
they do have very minor slip. And from what I am
hearing there's measurable more slip in 4th than in
3rd, which could generate excess heat or wear. I'm
still trying to figure all this out. It's not my specialty.
 

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'08 TBSS 2wd
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1,496 Posts
I've got a TB LS with the I6, and it's TCC won't lock when I'm
towing 4000# in 4th gear. I'm curious if a TB SS would do the
job better with its higher torque rating? Or if it's also going to
be stuck with towing in 3rd gear, too?
Doesn't surprise me. Too much load for an I6, especially if it has a 3.42 axle. Had a 3.42 axle 5.3L Silverado, and it would NOT pull my 2500# covered snowmobile trailer (its like dragging a parachute) in 4th at 70+...kept unlocking, so I had to use 3rd. Jumped to a 4.10 axle version and it pulled 4th just fine, except steep grades. And yes, a TBSS should be able to tow 4000# on level grades, in 4th, depending on how much wind drag there is. I regularly pull my ~4000# boat, and it RARELY unlocks in 4th.

You'll put a lot of stress on your trans not towing in 3rd gear. Creates a lot of heat.
Not true. There is nothing wrong with towing in 4th, as long as it is not shifting between 3rd and 4th all the time, and running a lot with the converter unlocked.

And yes, the PWM TCC setup does slip the conveter ~20rpm+- depending on load. It reduces NVH a little bit, which most people like. It is such a small amount of slip, that it's not going to hurt anything. The PCM automatically "tightens" the clutch with line pressure, if it is under heavier load, so it doesn't slip too much.
 
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