Odd transmission problem

Big_John

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1965 300L. 413 with 727 with console and cable shift.

Driving it today, I went to downshift into 2nd gear as I was going down a long hill, 35-40 MPH

I pulled the shifter back to 2nd and it didn't shift. Nothing. I shifted back to drive.

When I got a little farther down the hill and slowed down, I tried it again and still no shift. Slowed down a lot more (almost stopped) and tried to shift into first. The shifter wouldn't move into 1st.

When I got home, engine off, I tried moving the shifter, figuring it might be a cable problem, and it went into first with no problem. It was nice and smooth.

So, figuring that maybe I didn't push against the gate right, I tried it again out on the road. Same thing exactly.

Everything works great, upshift, downshift etc. Drives great. The trans was rebuilt by a local shop by the previous owner. It's not a shop I would go to, especially for transmission work, but there it is.

I'm thinking it's some sort of valve body problem, but my transmission troubleshooting knowledge is a bit limited. It works, so I'm not breaking my neck to pull anything apart, but I'd like to figure out what's going on and correct it.
 
Somewhere, years ago, I read that when you do a manual downshift for engine braking, that the trans will go into the lower gear when it gets ready to do that, not specifically in response to the shift lever movement. Allegedly, if you go from "D" to "1", it should physically go into "1" with the linkage, but what happens inside the trans is related to governor pressure and road speed.

In reality, to me it would be insane to put the car in "1" from "D" at 50mph or so. Into "2", no big deal, all things considered. Perhaps you might re-create your conditions on a flat road without closed throttle and see what might happen, then try the downshift into "1" at about 25mph or so?

It just sounds like something to do with the governor pressure and such. More research might be needed to see what's going on and why. Including looking at the fluid circuits vs. shift lever positions in the FSM, for good measure.

Just some suspicions,
CBODY67
 
Somewhere, years ago, I read that when you do a manual downshift for engine braking, that the trans will go into the lower gear when it gets ready to do that, not specifically in response to the shift lever movement. Allegedly, if you go from "D" to "1", it should physically go into "1" with the linkage, but what happens inside the trans is related to governor pressure and road speed.

In reality, to me it would be insane to put the car in "1" from "D" at 50mph or so. Into "2", no big deal, all things considered. Perhaps you might re-create your conditions on a flat road without closed throttle and see what might happen, then try the downshift into "1" at about 25mph or so?

It just sounds like something to do with the governor pressure and such. More research might be needed to see what's going on and why. Including looking at the fluid circuits vs. shift lever positions in the FSM, for good measure.

Just some suspicions,
CBODY67
Yes, I considered the speed when downshifting and at 35MPH and less, shifting into 2nd shouldn't be a problem. Shifting into first means you speed has to be down to ~25MPH or less.. But that's a moot point because the shifter won't move into first.

My second trial run with this was on a flat road, driving a steady speed, so the throttle would be open slightly. The throttle link to the trans (incorrectly called "kick down") is adjusted correctly although I may double check that tomorrow.

I have a couple more transmission books I need to dig out and skim through. I did look at the FSM first. I do need to (as you said) study the hydraulic circuits. I'm hoping to get some input for a direction to go.

FWIW, one of the things that you have to watch with certain shift kits is they will let you downshift to first at any speed.
 
The governor on a 727 will over ride the shift valve, but it still should shift down when it is ready. There is not any good reason why the cable would not allow the shifter to access the Low gear position, re-check the cable adjustment. After that is verified, start by checking the adjustment on the kick down band. if that is correct, there is a test port on the tail shaft housing to check governor pressure. At idle it should read about 2psi. With the rear wheels off the ground, the pressure should increase about 10psi for each 10 mph. If those readings are correct, there is probably a problem with the shift valve and the valve body will need to be removed for service, usually shift valve issues are the result of debris getting into the unit.

Dave
 
Could the kickdown linkage / vacuum modulator (if an 727 even has one) affect the manual gear engagement?

I am not familiar with the 727, but if I remember correctly, the kickdown linkage/vacuum modulator can affect manual shifting in Ford C4 and C6 transmissions (and I bet FMX too).
 
This does sound strange. Yes the trans may not downshift into first gear even though you have selected first but by the sounds of it the shifter won’t physically go into first gear. Might be worth pulling the pan to see if something is coming loose. Just guessing. It might be that once pressure is applied the loose components may be interfering.
 
How do the motor & transmission mounts look? I'm wondering if when you are going down the road, something in the driveline is moving a little and causing the shift cable to bind up?

BTW, don't know if you've encountered it, but the drivers side motor mount & the trans mount are oddballs, and all of the parts stores will try to sell you the wrong thing.
 
The governor on a 727 will over ride the shift valve, but it still should shift down when it is ready. There is not any good reason why the cable would not allow the shifter to access the Low gear position, re-check the cable adjustment. After that is verified, start by checking the adjustment on the kick down band. if that is correct, there is a test port on the tail shaft housing to check governor pressure. At idle it should read about 2psi. With the rear wheels off the ground, the pressure should increase about 10psi for each 10 mph. If those readings are correct, there is probably a problem with the shift valve and the valve body will need to be removed for service, usually shift valve issues are the result of debris getting into the unit.

Dave
I think the cable is adjusted OK as it moves through the range just fine with the engine off. Engine running, it shifts correctly into park/reverse/neutral/drive/second but not first while driving. I haven't tried it with the engine idling and the car sitting.

Testing the governor pressure sounds easy enough.

The shift valve sounds like the culprit. I'll have to reserch that some more.
 
Could the kickdown linkage / vacuum modulator (if an 727 even has one) affect the manual gear engagement?

I am not familiar with the 727, but if I remember correctly, the kickdown linkage/vacuum modulator can affect manual shifting in Ford C4 and C6 transmissions (and I bet FMX too).
No vacuum modulator in a 727.
 
This does sound strange. Yes the trans may not downshift into first gear even though you have selected first but by the sounds of it the shifter won’t physically go into first gear. Might be worth pulling the pan to see if something is coming loose. Just guessing. It might be that once pressure is applied the loose components may be interfering.
That's correct, the shifter won't physically go into first gear when driving the car. It will go in with the engine off.
 
How do the motor & transmission mounts look? I'm wondering if when you are going down the road, something in the driveline is moving a little and causing the shift cable to bind up?

BTW, don't know if you've encountered it, but the drivers side motor mount & the trans mount are oddballs, and all of the parts stores will try to sell you the wrong thing.
Mounts look OK, but another look at them is in order.
 
does it go in with the engine running? if it goes in, try taking off with the shifter in low 1. it'd be interesting to see what happens if upshifted from 1'st to 2'nd manually at speed then attempt to return the shifter to 1'st.
I need to try this.

As it stands, it won't go into first with the car driving, but I haven't tried it with the car sitting still.
 
does it go in with the engine running? if it goes in, try taking off with the shifter in low 1. it'd be interesting to see what happens if upshifted from 1'st to 2'nd manually at speed then attempt to return the shifter to 1'st.

I need to try this.

As it stands, it won't go into first with the car driving, but I haven't tried it with the car sitting still.
I just tried this and it does go into first with the car sitting still.

I started it, put it in first. Tried moving the shifter through all the gears and it seems to be fine.

I haven't tried it out on the road. Miserable showers right now, so it'll have to wait.

But wait... There's more!

I just went through the notes that came with the car. All 39 pages... Mrs. Big John mumbled something about "manifesto", but it's really detailed with everything done to the car.... And guess why the trans was rebuilt? Yea... This. The PO is pretty competent so I can take his notes as being good. He tried some cable adjustments and they didn't have any effect. The issue wasn't corrected with the rebuild. Another guy looked at it and found some junk in the valve body, readjusted the bands, put the correct early filter in it and still couldn't find the problem. He also checked the number of balls (important on many levels) and their location etc.

The plot thickens...
 
i did a google search for "727 first gear lockout" and came up with nothing. was wondering if there was some police car option for that. no good. so, no roll around jacks for that drive on? they'd come in handy right about now.
 
Genuine police cars did have a "low gear blockout" feature, but what that was was to prevent shifting from "P" or "N" into "1" and skipping "D" in the process. The shifter would not go below "D", mechanically, as I understand it. A friend bought a used Colorado state police car at an auction, back in about '75 and it was that way. It was a fuselage Plymouth Fury.

The feature kept the officer from, in the heat of battle, from inadvertantly shifting into "1" and heading off at WOT, not worrying about anything other than catching the perp . . . until the engine coughed and/or lost power.

CBODY67
 
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i did a google search for "727 first gear lockout" and came up with nothing. was wondering if there was some police car option for that. no good. so, no roll around jacks for that drive on? they'd come in handy right about now.
Right at the moment, it's under the lift with my Barracuda on top. Not enough head room to jack it up.

My brother had an ex-NYS Trooper car back in the late 70's with the low gear lock out.
 
Per @rags suggestion, I found I could shift to first when the car was stopped.

So.... I left the driveway in first and it held there until I shifted it. It seemed to shift directly into third... I couldn't really tell, but when I stomped the gas, it did downshift to second... Got to the end of the road (stop sign) and just for laughs, I tried pulling it down to first and the shifter would not move to first. Stopped and I could shift to first again, so I tried it again and shifted it and this time it went into second and stayed there.

I tried playing with the shifter, thinking that maybe if I shifted to neutral, something would happen.... and it was not good. The shifter was now stuck in drive, but car was in second gear. I could move the shifter to drive, first and second, but no change in gears.... Until I saw my turn coming up to get back home. Just for laughs, I put it in first and when I got down to ~25MPH, the car downshifted to first.

Around the corner and the shifter freed up to shift to neutral, but not to first. The trans also shifted normal at that point.

I'm going to have to make a video... It's really hard to explain this.
 
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