727 without Kickdown hooked up question

A few years back I acquired a 72 440/727 Plymouth Duster. The seller indicated the car had a manual valve body which I dont believe it actually does since the kickdown lever is still mounted on the trans. I have not drove the car much, maybe 2-300 miles but I have noticed the trans slipping between shifts the more I drive it. I have read somewhere if the trans kickdown in not functioning correctly or connected to the trans it will in fact damage the transmission. If this is accurate, what is being damaged and what is the remedy?

Another question, I was also informed the car has a High stall converter, maybe 2800 stall... The trans clearly slips at lower speeds if driving from a stop under light acceleration. If the pedal hits the floor, the tires blow smoke... I was under the impression that a good converter will not slip under light loads. Is that assumption correct?

Thanks

I can answer one of your questions. The kick down linkage/ throttle pressure linkage being unhooked will cause damage.

Most make it sound like the transmission will burn up if you take it down the street without it being hooked up but, that has not been my experience.

I inherited my car and when I received it, the throttle linkage was not hooked up and hadn't been for probably 1500-2000 miles. Once I identified how important it is, I reinstalled and properly adjusted the linkage rather quickly.

Again, the car was not mine from the last time the trans was rebuilt up until shortly before I reinstalled the linkage. Over the time I owned and drove it without the linkage, I felt like I noticed low speed slippage getting worse. I also noticed that I had a flare between the 2-3 shift but, it wasn't horrible. My car too has an aftermarket converter and there were some other unknowns so; I didn't think much about it. I drove the car another 2-3 years before having the trans rebuilt and I only really had it gone through as I had the motor and trans out. Overall, the trans worked fine and I really only noticed the low speed slippage when I pulled it out of the garage and ran it down the first road. Once it got some heat in it, all seemed fine.

During the rebuild, we found the low/reverse band was burnt up. I want to say there were some other slight issues too but, it's been years so; I can't recall all the specifics.

With the trans rebuilt and reinstalled with the same converter, all the slipping at low speed was gone so; it was the band causing the weirdness I noticed. At the same time I had the trans rebuilt, I added around another 100 HP and 150 lbs of torque. The trans has been run with this combination for probably around 2000 miles and 25 or so passes and has never felt like it did before I had it rebuilt so; I would assume that the low/reverse band being burnt and the slippage I had in years past can probably be attributed to the kick down/throttle linkage being removed for all that time.

yup, i learned that the hard way. When i built my 440/727 dart. I went to the salvage yard and bought the 727 and installed it with the 440. I drove it for a while with no kickdown linkage hooked up and by the time i learned that not having it hooked up will ruin it, it had started slipping and acting crazy. I quickly bought the lokar kickdown cable but by then it really started slipping. Needless to say when i got a new trans it was hooked up! Not sure why it hurts them without it or how it works but it does ruin it without it.

First off: DO NOT DRIVE THE CAR WITHOUT KNOWING WHAT IS GOING ON WITH THE LINE PRESSURE. It can damage the tranny.

What I mean by that is the kick down lever controls the pressure that is applied to the clutches and bands unless it has a manual valve body. If the valve body is not full manual, then the line pressure is at idle pressure all the time with the kick down lever not being tied to the throttle. A manual valve body puts the line pressure above even the normal wide open amount of pressure all the time.

If it shifts on it's own at all, then it is not a manual valve body. There is a lot more to this, but that is enough until we get more information.

If you put it in drive and it shifts automatically it does NOT have a manual valve body
it it won't shift by itself in any other gear it is a manual shifted tranny due to the valve body
If it is NOT a manual valve body it will hurt and damage the tranny very quickly without the kick down linkage hooked up and adjusted properly
The kickdown lever is used to hold the shift lever seal in place to stop it from weeping and or leaking around that shaft and the shift lever shaft is what I'm remembering now.

I’m amazed to see this still going on in the 21st Century!

Before Lokar cable systems were available, setting up a mechanical kick down linkage was a pain.
But still no excuse to leave it OFF.
Most folks just wired it back, to almost fully open and suffered the harsh shifts!

Too leave it dangling in the wind is criminal...

The answer to that is it depends on who made the converter, and it's intended application. whether it was a "tight" (little slippage at low speed) or "loose" slips noticeably until you nail it. There is a bit of black magic in converters and one usually gets what they pay for. Years ago there were 99.00 converters in the magazines

My grandson learned this the hard way. He replaced the carb on his 4x4 truck, and I told him he had to have the kick down adjusted correctly. He wasn't overly concerned, even though I told him it would kill the trans pretty quickly (he didn't think old men knew anything). About a week later, he asked me about a "trans problem" and I asked him if he adjusted the kick down like I told him to? Him and his buddies were going to "adjust it" later that day. I told him it was already too late. His trans only lasted about 2 weeks, but I suspect it wasn't in very good shape before that. The non-adjusted kick down was the nail that finished the job. Gene

"Kickdown" is such a lousy name. It is really a variable line pressure mechanism. The more throttle you give it the more it increases the line pressure for the clutches to be pressed together harder. Without this line pressure increase under load, the clutches slip and burn up. The "remedy" is a rebuilt transmission.

Wow GY3, 10.01 @ 133 superb but so close to a NINE!

Best we managed without Nos was 10.40 @ 130.
I now see the errors of my ways and will be Nossing from now on lol...

Thanks.

It's a very mild (and heavy) street car that see's some track time. It drives like a stock 440 with a cam.