1972 Riviera Kickdown

[Ernie Woodburn]

Hi all, I've restored this car and runs great, however, I cannot find a kick down cable or where it would go.  Does it even have one?  I'm sure it must.  There is a vacuum line that goes down to the modulator.

[JZRIV]

Do you have a factory chassis service manual? Info will be in there. If you do not have one its best money you can spend.

The kickdown for passing gear is electric operated. Can't for fact recall on 72 but in 73 the switch that activates the transmission solenoid is under dash on gas pedal linkage.

In my 73 the pedal had to literally be to the floor before the switch activated to kick down. I wanted it to activate much sooner so I removed switch and slotted/modified mounting to accomodate.

Edited March 6, 2018 by JZRIV (see edit history)

[Ernie Woodburn]

interesting.  I've never heard of that.  Always was a lever or cable.  Must be only the TH400.  Ok thanks.

[Rivman]

What Jason says makes sense, I did not look at my service manual, but I do have an assembly manual on my computer and there is no mention of a kick-down "cable".

 

My '72 Riviera GS does have an electrical connector in the side of the trans so I am sure Jason is correct, the kick-down is an electric function ...

 

 

I can look at the '72 service manual and see what it says if you need more info.

[NTX5467]

ALL of the THM400s have electric WOT kickdown.  On the earlier models, it was an electric switch on the lh rr mounting stud of the carb, activated by the throttle linkage.  A plunger-like affair which contacted a "paddle" mounted on the carb throttle linkage.

 

Along about '70, after they'd started using throttle cables rather than solid rods, the kickdown switch was mounted to the top of the accel pedal mount.  The top of the accel pedal rod was extended to contact the switch's "rod" and move it.  No adjustment, unless you modified the mount as mentioned above.

 

The wires go to the lh side of the trans, as pictured.

 

Many THM400s would not downshift into low gear at WOT unless the vehicle was going about 10mph or so.  That's how our '69 Chevy pickup was.

 

There is another "downshift" other than at WOT.  This is the part-throttle downshift which is controlled by the vacuum modulator on the rh side of the trans.  Hopefully, it's still the "big one"?  When manifold vacuum drops past a certain level, the trans will downshift to the next lower gear.  Like if you're going 45mph and throttle into it (not WOT) to pass a slower car.  Downshift from 3rd to 2nd, then upshift back into 3rd when throttle is decreased and manifold vacuum increases.

 

The vacuum modulator also controls shift quality at higher elevations, which also decrease manifold vacuum.  Sometimes, the external stud can be adjusted to fine-tune the sensitivity to downshifts.  The "small" modulators can also do this, but with a hidden adjustment inside of the vacuum nipple, like the vac advance on the distributor, on the replacement units.

 

The basic shifts are modulated by the transmission governor.  Swing weights working or helped by springs.  This, plus the vac modulator determine normal driving shiftpoints and max upshift speeds at WOT.  One basic system (governor-controlled) fine tuned by other systems.

 

NTX5467

[telriv]

What I've found is over the yrs. the round rod used for the gas pedal get bent from yrs. of constant use. A stronger than nec. return spring also has the same effect & bends the rod sooner. So no matter how you adjust the cable you never get WOT. Hence the kick down won't work either. Put a block of wood near the top of the pedal rod. Grab the bottom of the rod where the pedal is & lift/bend up.

Also carpet savers & improperly installed carpet causes the same as the pedal CAN'T go to WOT being restricted by the mat & carpet.