Ford Muscle Cars Tech Forum banner

1 - 20 of 26 Posts

·
Premium Member
Joined
·
5,887 Posts
Discussion Starter #1
I don't have a return spring on my kick down rod though i see some people do. Is it necessary? On my Cruisomatic (MX) the passing gear kicks off by itself, no return spring required.
 

·
Registered
Joined
·
96 Posts
I don't believe this is a must-have item, but it will keep the rod from bouncing around as much as it might without it. They actually are available new through the catalogs. I recently had a question about the proper placement of these, and discovered through some more investigation that the spring attaches to the dashpot bracket through the small hole near the bend in it. I prefer to have things setup as they were engineered, so I definitely wanted it installed.
 

·
Registered
Joined
·
88 Posts
Jazzmeister, any chance you could put a picture of your return spring/kickdown rod setup? Would be curious. Or your sources to discover the proper placement?
 

·
Registered
Joined
·
88 Posts
Thank you! That does mirror what I have on my car also, I just forgot where I found that info, but glad to see that I have done it correctly as you have.
 

·
Registered
Joined
·
622 Posts
How many think "passing gear" is something different than second gear?
 

·
Registered
Joined
·
965 Posts
Technically, it could also be 1st gear, no?
Sure, if the vehicle speed is below 40-50 mph,
depending on diff gear ratio it could go all the way to low 1st gear on "kickdown" passing gear.....

But there are some folks that think "passing gear" is some kind of "special" extra gear that is in the trans.
This is not true for our dinosaur 3 spd automatics...

That said....

Believe it or not, there are some modern electronic computer controlled automatic transmissions that have what is called "second prime".
This actually IS a different "second gear" that does not get used EXCEPT during kickdown, or "passing gear".
It is used most notably in the Chrysler 45-RFE and 545-RFE transmission.
The purpose is to provide a smoother 4-2 kickdown at highway speeds.

45-RFE ratios.

Gear Ratios:
  • 1st 3.00:1
  • 2nd 1.67:1
  • 2nd Prime 1.50:1 (only used during 4-2 kickdown)
  • 3rd 1.00:1
  • 4th 0.75:1
  • Reverse 3.00:1
545-RFE ratios are the same with an added 5th gear overdrive.
  • 5th 0.67:1
So the 545-RFE is sometimes called a "double overdrive" transmission.

:)
 

·
Registered
Joined
·
622 Posts
Sound like an electronically operated combination of second and overdrive planetaries. The double over drive would be a substitution of another overdrive planetary in place of an underdrive planetary in the same transmission case.
 

·
Registered
Joined
·
88 Posts
I checked out my kick down and spring, and I always have wondered what is up with an adjustment bolt on the kickdown rod bracket. To me, it would make sense if the adjustment bolt would move forward and touch the dashpot bracket. Then you would have something to adjust, that would make sense. But, that kickdown rod lever does not move any more forward than where it is and if it moved that close to the dashpot, then the spring would be tiny, as that would be a very small gap between the hole on the dashpot and the bracket of the kickdown rod.

My car is has an automatic trans, so hence the dashpot. Jazzmeister, the pic you posted about 3 months ago, shows that same adjustment bolt, here is a refresher for those who have not seen it:


Anyone have any idea what that adjustment screw on the kickdown rod bracket that is not near anything that an adjustment screw would be useful is for?
167863
 

·
Registered
Joined
·
965 Posts
That screw is adjusted at WOT.
Wide Open Throttle. (engine off)

It sets the maximum amount the throttle arm pushes on the kickdown rod.

Set too tight, the kickdown "hits bottom" inside the trans before WOT.

Set too loose,
Kickdown does not work, or does not give "enough" kickdown at highway speeds.
 

·
Registered
Joined
·
96 Posts
That is the adjustment bolt for the kickdown. It doesn’t touch anything until the accelerator lever is fully depressed, and then it will/should reach that bolt and press back on the rod. Until you floor it, it should not do anything, but that’s the idea. Mine seem to need turned in all the way to work, but I think that’s due to wear/slop on the rather Rube Goldberg-esque kickdown rod and 56 years of use.
 

·
Registered
Joined
·
88 Posts
I understand that adjustment procedure GalaxieX, well written so I can understand that. There will probably be some trial and error involved. I am now curious, as my car seems to have very little kickdown, so maybe this is why, I may be very out of adjustment.
Got it, thanks both for the replies.
 

·
Premium Member
Joined
·
5,887 Posts
Discussion Starter #15
Once activated, what causes the passing gear to turn off?
 

·
Registered
Joined
·
965 Posts
Automatic transmissions operate on hydraulic pressure.

The governor is the main player in upshift timing.

Governor pressure "makes" the upshift.
Governor pressure is proportional to road speed.
Governor pressure starts at "0" at a stand-still, and increases at approx 1 psi per mph.
30 mph = approx 30 psi gov pressure.
60 mph = approx 60 psi gov pressure..... etc....
.....up to the maximum value which is determined by trans mainline pressure.

Throttle pressure (modulator) "delays" the upshift, as does kick down pressure.
Step harder on the gas = more throttle pressure and ... upshifts are "delayed",ie: shifts occur at higher road speed.
Floor the gas and KD pressure comes into play, "adding to" throttle pressure, causing even later shifts (or kickdown depending on "when" the throttle is floored).

But eventually, even with maximum throttle pressure "and" kickdown pressure,
the governor pressure (road speed increases, so too gov pressure) will eventually overcome both KD and Throttle pressure to cause the trans to shift to the next gear.

This is all assuming a "properly" working transmission, AND all adjustments are correct, AND engine tune is correct.

Gear ratio and tire size also come into play.

Change anything, (gear ratio or tire size) or malfunctions (vacuum leaks,engine tune, adjustments) to any of the above can cause incorrect or undesired shift timing.

You can tell when things are "not right" when the trans does not react properly to how hard (or soft) you step on the gas.

The above description of the various pressures is a simplified version of how these things work.
 

·
Premium Member
Joined
·
5,887 Posts
Discussion Starter #18
Thx. Another mystery of the automatic transmission solved, 99 more to go...
 

·
Administrator
Joined
·
21,726 Posts
And easier if you have the traditional shift pattern and not have to go up with the shifter instead of down to get there. I have trouble with thinking in reverse lol Mine isn't right I'm sure or it hates me. It'll kick down when I'm not wanting it to, getting on it real quick to catch up with a friend or something and if wanting it to other wise it's decides if it will or not. But then I don't think anything is adjusted correctly on the car. Several years ago Psig and FEandGoingBroke adjusted the carb, timing and all kinds of things and the car ran better and had more power than it had in years...until i got about 20 miles down the road on a little hill and it sputtered and snorted and went right back to how it had been. Points changes it did same, new points, test drive, snort and cough, sometimes die, start it back up and it was fine for the next 2 or 3 yrs when i thought i should change the points again. I think it's been with me too many years and hates change as I do! LOL



How many think "passing gear" is something different than second gear?
 

·
Registered
Joined
·
965 Posts
And easier if you have the traditional shift pattern and not have to go up with the shifter instead of down to get there. I have trouble with thinking in reverse lol Mine isn't right I'm sure or it hates me. It'll kick down when I'm not wanting it to, getting on it real quick to catch up with a friend or something and if wanting it to other wise it's decides if it will or not. But then I don't think anything is adjusted correctly on the car. Several years ago Psig and FEandGoingBroke adjusted the carb, timing and all kinds of things and the car ran better and had more power than it had in years...until i got about 20 miles down the road on a little hill and it sputtered and snorted and went right back to how it had been. Points changes it did same, new points, test drive, snort and cough, sometimes die, start it back up and it was fine for the next 2 or 3 yrs when i thought i should change the points again. I think it's been with me too many years and hates change as I do! LOL
Sounds like you have a vacuum leak somewhere.
Check all hoses for cracks and hard and/or brittleness.
Vacuum MUST be correct for trans to operate properly.
 
1 - 20 of 26 Posts
Top