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Old 12-09-2010, 03:45 PM
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350C internal lockup mod

To make a long story short, B@M said that a 350C can be internally redone for converter lock up whenever tranny hits fourth gear. Says they do it all the time. Any tranny shop can do it for ya. Well, I'm not a real tranny guy, so does anyone know what's all involved in doing this? Reason is I am using Classic Instrument gauges in my 57 chev pickup, which use a pulse generator attached to speedo cable fitting on tranny. B@M makes a converter lockup kit, but after a discussion with them, they said it would be a lot easier and doable to have the trans modified internally for converter lockup. Any ideas?

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Old 12-09-2010, 04:17 PM
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The TH350C only has 3 forward gears + Lockup.
All you need is 12V+ to the terminal on side Trans plug. It will Lockup when it hits 3rd gear.
You can use a Toggle switch to activate Lockup. Use a Brake light switch from a vehicle with Cruise control, this will deactivate Lockup when Brake pedal is depressed.
12v+ from Brake switch to Toggle switch to Trans plug to TCC solenoid in Trans pan.
Around town the TCC Lockup is annoying, best to use it on the Freeway or open road only.

An adjustable Vacuum switch can be installed to prevent Lockup at a set level but isn't really needed when using manual control.
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Old 12-10-2010, 08:07 AM
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If you wanted to wire it up like it was done in 1980 (before computer controlled emissions, etc.), use a factory vacuum switch in conjunction w/the stop light switch.

The vacuum switch is adjustable, so it can be set to engage the lock up after the engine has settled in for cruising (manifold vacuum higher), and not while accelerating or going uphill (low vacuum conditions).

Be sure and get the small vacuum delay valve. It works with the vacuum switch to modulate when the TC lock up solenoid is activated, and without it the vacuum switch can be made to engage the lock up almost the instant the trans goes into 3'rd, which you don't usually want.

HERE'S B&M's Installation Instructions Converter Lock-Up Control
TH700-R4/4L60, 200C, 200-4R, 350C.

Below are some diagrams showing wiring and components.
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File Type: bmp TCC WIRING DIAGRAM.bmp (525.0 KB, 409 views)
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