[66 chevy truck]

Hey all. I just got done rebuilding the engine (350) for my dads 85 Chevy suburban. I put the engine in and it runs great(thats a first for me) but the transmission(700R4) wont downshift and the shifting is really mushy is there supposed to be a vacuum module on the transmission because when i pulled the engine there wasn't one. but there is 3 wires going to the transmission and im wondering if that doesn't have something to do with it?. Please Help

[tnsmith10]

the 3 wires r for the torque conveter lockup., other than that, it sounds like u didnt set the tv cable correctly. the cable needs to be tight @ WOT. gl

[briscoe]

I agree with tnsmith10. The mushy upshifts and no downshifts point to, not enough tv pressure.[tv cable]

As tv pressure must be great enough to overcome governor pressure,on downshifts. And also great enough to keep your trans from frying[not enough pressure rise].

[66 chevy truck]

well i adjusted mt TV cable just like the book said and nothing changed so i did some more investigating and the wires that go the tranny and one of them is disconnected under the dash and i have no clue where it goes. also is there supposed to be a vacuum module on the tranny?. Thanks for the replies

[Crosley]

Originally Posted by 66 chevy truck

well i adjusted mt TV cable just like the book said and nothing changed so i did some more investigating and the wires that go the tranny and one of them is disconnected under the dash and i have no clue where it goes. also is there supposed to be a vacuum module on the tranny?. Thanks for the replies

The 700r4 tranny never had a vacuum modulator on it.

the electrical wires have nothing to do with the shift timing of the 700r4.

Does the trans shift at the same speeds no matter what adjustment on the TV cable?

this would indicate a stuck internal TV valve , shift valve problems, governor problems.

What is the history of this tranny? Mileage , recent repairs or over haul on the tranny?

[66 chevy truck]

well the tranny seems to shift normal now but when i stop at an intersection it kills the motor just like a manual tranny would without pushing the clutch in

[briscoe]

That sounds like a bad TCC solenoid.

[66 chevy truck]

what is a TCC solenoid?

[briscoe]

If you were to pull the pan,and look towards the front of the trans,you would see a device that has a wire or wires going to it.

This is the tcc,or torque converter clutch solenoid.

This is a normally open solenoid,it will exhaust fluid that passes thru it,until it is electrically energized. Then it will close.

When it does close,fluid will not pass thru it,pressure builds up and this fluid then forces the converter clutch valve to stroke.

Your converter clutch will then apply.

If the tcc solenoid becomes clogged with debris,or is compromised in some fashion,it can become,in essence,a closed solenoid [not good].

When the 1-2 shift valve strokes,to make a 1-2 shift,fluid is then sent to the tcc circut. This fluid should pass thru an open tcc solenoid.

By your description of your problem,it sounds like the tcc solenoid is clogged.

[WagonMan]

Sounds to me like the wire that is not connected to anything under the dash may have come from the brake switch that is supposed to release the TCC. Or did I misread something?

Charles

[briscoe]

Wagonman,the Tcc circut is also affected by tv pressure,as well as governor pressure,and at a stop there is no fluid supply to the TCC solenoid.

Coasting to a stop,if the solenoid is good,there can be no converter clutch apply.

This is not a wire thing. May not be a solenoid thing either,but it sure sounds like it.

[scrot]

There's a little plastic check ball in the TCC valve that gets stuck in the closed position.