Transmission shifting issues....again. Help!

[Huicho417]

Happy because I have been driving my car finally. But frustrated with the transmission. The car is a 1967 Coronet with a 318 and 727 automatic transmission. I have spent 15 months working on the car mechanically and it sounds great. Last phase was taking out the transmission to change all seals because it was leaking badly. Good new is it no longer leaks at all.

It seems like when I take short trips, say 5 to 7 miles the transmission shifts great. However if I try to take it on a long trip upwards of 10 miles I start having shifting issues. Then if the car sits overnight the next short drive is good again. Todays drive was about 16 miles and a third into the drive my transmission would not shift past second it seemed. At a light when accelerating the car would move and I could feel it shift into second but then would feel forced and not shift past that. I drove for about a mile and a half really slow. Then I began shifting it myself. I am assuming the 1 and 2 on the steering column gear selector refer to first and second gear? Please correct me if I am wrong. I have checked the fluid level and triple checked the kickdown linkage. What I don’t understand is why the shifting issues start after driving a while. Please help, this is the only issue remaining before I feel confident in taking long cruises.

 

[493 Mike]

How many miles/years on this trans?
Mike

 

[Huicho417]

Not completely sure on the years. I purchase the car two years ago and the odometer reads 68,980 miles.

 

[mopar 3 B]

Have you changed the filter or fluid? I would start by having the line pressures checked.

 

[62 Dart Convertible]

I have a similar issue with my '62 PB 727. When hot, the 2-3 shift point increases significantly. Kick down adjusted correctly. Looking forward to responses.

 

[mopar 3 B]

I would suspect governor circuit leakage or blockage. Does it just not shift into 3rd or does the engine race when it shifts as in neutral?

 

[Huicho417]

The filter was changed last month and all fluid was drained and replaced. I also replaced the torque converter with a new one from rock auto. Not sure i understand the race when it shifts as in neutral question. It feels as if it never shifts to third because the car will not go any faster even if I push on the pedal.

 

[1 Wild R/T]

When the trans won't shift into high gear how is reverse? If reverse is also "soft"...

The front clutch seals are probably leaking & not allowing the clutch to apply...

 

[Huicho417]

I drove it earlier to the grocery store and reversed it out of my driveway and it all seemed fine. But yes, when I was having issues this afternoon I did notice I had to really press on the pedal to get it to go one reverse.

 

[Huicho417]

As I am researching this issue in the internet I keep coming across front and rear band adjustment recommendations. Could this have something to do with it?

 

[1 Wild R/T]

Front band is second gear... Rear band is primarily reverse... High gear is the front & rear clutch applied.... This chart shows what elements make each gear...

 

[1 Wild R/T]

Basically you get to rebuild a transmission.... Really not that difficult, torqueflites are pretty basic... I suggest watching a few You tube videos to get a basic understanding & post any questions you run into here.. Plenty of guys here have been through a torqueflite or two...

 

[Huicho417]

Well, I just took the transmission out to clean and reseal. Not looking forward to taking it out again. I am going to exhaust all possible fixes before I have to absolutely rebuild it. I will try the front band adjustment since it seems very easy to do. Thank you for all the feedback

 

[Wietse]

On a hydraulic point of view it seems like your governor pressure is not getting high enough to function the 2-3 shift valve.
Since it does do the 1-2 shift the governor pressure is there to change over the directional valve, the 2-3 valve will require more governor pressure than the 1-2 shift valve.
Looks like oil temperature is involved here as when "cold" it does work (due to higher oil pressure) but once getting warm it stops functioning.
Since the pump is equipped with a relief valve, this also could be washed/partially open or incorrect spring pressure, but i assume you did not work on that and if it worked before it should still work. (unless some dirt is stuck at the seat)
What type of oil are you using? (Brand, type)
By any chance, did you change rear axle ratio or different tire size?

 

[Huicho417]

I did not do any work on the pump or rear axle ratio. The fluid is full synthetic ATF+4 from O Reilly’s house brand. Tire size is 205 66R15.

 

[Tman100]

This sounds like the same problem I had on my 727 in a 66 polara about 20 years ago. The rear band was worn out.(along with everything else) The higher pressure with cold oil would make it work but as the trans warmed up would no longer hold.
I rebuilt the trans and all was good. The trans was behind a 318 poly and had 74,000 original miles. I’d guess if you rebuild it all will be good again. 727’s are really simple and if you put stock clutches back in fairly inexpensive to do.

 

[Huicho417]

Throughout the process of working on this car, rebuilding of existing parts has not resulted well for me. If I do need remove the transmission again I want to make sure it’s the last time. Can anyone recommend a good source to purchase a new transmisión from? And in that case any updates I should be looking for? My inclination would be to look at Summit Racing, but not sure that’s the best option.

 

[mopar 3 B]

This sounds like the same problem I had on my 727 in a 66 polara about 20 years ago. The rear band was worn out. The higher pressure with cold oil would make it work but as the trans warmed up would no longer hold.
I rebuilt the trans and all was good. The trans was behind a 318 poly and had 74,000 original miles. I’d guess if you rebuild it all will be good again. 727’s are really simple and if you put stock clutches back in fairly inexpensive to do.

Rear band has nothing to do with direct drive. I still recommend line pressure testing.
Valve bodies can be tricky and finicky. Any thing that doesn't belong there can cause a problem with a spool.

 

[Dipstick]

The front clutch seals are probably leaking & not allowing the clutch to apply...

Time for some Trans-X additive to rejuvenate the seals.

 

[1967coronet]

More of a question ,
Is it possible the change over to synthetic fluid on this older , not rebuilt transmission to be causing his problems ?
I know from personal experience that a switch to synthetic rear diff oil will cause old seals to leak that had not before the oil swap.
I'm prob nuts but I would try that can of trans X along with a switch back to some regular DeX 3 or type F.