'73 340 727 Trans - Wont Downshift all else works fine

[Titan1969]

Thx in advance, I searched a few forums here and googled, there is a lot on the net about the 727 so thought Id start here for some advice.

'73 Cuda numbers matching with a new AVS Edelbrock Carb, rebuilt 727 trans ( all stock no stall, no manual valve body)
I did purchased the correct Edelbrock throttle brack so the TV arm and throttle works well with full throw forward and rearward.

I received the car after extensive resto work from prior owner, so no idea if the trans/linkage had issues prior.

Currently I followed the directions to put the gas pedal to the floor and make sure the TV arm moves the trans arm fully towards the rear of the car and it does ( or at least the arm is locked fully back as far as it will go).

The car in drive up shifts at 15mph then 25 mph and also downshifts while in normal cruising condition = no issues here.

Problem is when the pedal is put to the floor, the trans will not downshift. So if going 30mph, it just stays 3rd unless I manually shift it.

Trans fluid is clean and full.

When accelerating from a stop, the trans upshifts at about 3500rpm...this seems to early, further pushing me to think there is some issue with the trans/pressure lever setting.

Can anyone send me a pic of a '73 340 727 trans with the trans pressure lever full pushed rearward??? to give me some idea if the arm on the trans is perhaps not set right, perhaps its the wrong arm?

Any other ideas appreciated.

 

[Chryco Psycho]

Sorry I don't have a picture but if the arm is moving all the way back at full throttle then it has to be working correctly externally so there must be an issue internally with the valve body preventing it from downshifting .
The upshift is controlled by the line pressure set on the valve body + the governor on the tailshaft inside the rear tailhousing , sounds like the wrong weight was used for the governor , it should hold until 5500-6000 rpm at full throttle .

 

[Titan1969]

ok thx. Was hoping not to crack a new rebuild open...but guess thats the next step.

 

[NoCar340]

To my knowledge, the transmission arm only goes on one way, and there's only one option--they all used the same arm. Whenever I set them, I'd use strong springs to hold the throttle-valve arm and carb all the way rearward (WOT) and watch the carb's throttle lever during adjustment. When it starts to move, go back a scosche and it's set.

If that all checks out, I'd at least take the pan down and check to see if the valve body even has the part-throttle kickdown valve installed:

You're only concerned with what's inside that rectangle; the valve body at right is not fully assembled. Without that valve, the throttle must be absolutely mashed for the transmission to downshift at all. If that valve's missing from your car, any and every slant six transmission '66-up has one. Your car should've had one originally, but nothing's guaranteed original unless you bought the car new. It's a two-screw installation. When a car's 50 years old, who knows what's been done over the years. Valve bodies get swapped, etc. The only "numbers" part is the main case.

While the pan is down, look at your line-pressure regulator. The adjustment is a small spring-loaded screw that moves a thin metal plate. Adjust this for max pressure, i.e. there should be as little thread as you're comfortable with hanging out the back side of that plate. I usually leave 1 thread and apply threadlocker. This will both firm up shifts and affect upshift speeds. To my knowledge, there is no drawback to doing this unless you don't like to feel your transmission shift. If you're not comfortable with the pressure adjustment, at least make sure it's to factory service specification.

If you have to drop the valve body to install the part-throttle kickdown valve, fear not. You're not really "crack[ing] a new rebuild open" since you're not messing with the important bits like clutches, steels, and bands. If you drop the valve body and there's a big spring between it and the transmission (the accumulator piston, to be exact), weight-test the accumulator spring. This is an easy process: Throw the accumulator spring in the air; if it comes back down it's too heavy and should be omitted during reassembly. Seriously, losing the accumulator spring is part of every shift kit on the planet and has been a speed secret since these cars were new. The accumulator exists to soften shifts so Grandpa doesn't have to feel them in his Imperial. Flinging the accumulator spring will not affect upshift speeds, but it will get you a tire screech on the 1-2 shift under full throttle. The shift is not particularly harsh during normal driving, just firmer.

When refilling the transmission, use Type F/FA fluid. Even Chrysler's own engineers have been recommending this change since prior to Direct Connection's existence.

If all that fails to improve your upshift speed, then it's time to call Rick at A&A, because you're dealing with a low-upshift (probably truck) governor. Tell him you want 340-spec governor parts, and if you're not comfortable with that process after checking the service manual procedure, start asking the local guys about a trans guru, rather than just "someone that rebuilds transmissions". If memory serves--and it may not--properly swapping all the governor parts requires removing the tailshaft housing.

 

[Chryco Psycho]

In all my life with all of the Auto transmissions I have had rebuilt only 1 has worked correctly , it was in a Lil Red Express & it would hold the gear until 6000 unless you lifted slightly & then it would shift immediately , it was all controlled by the throttle , leaving it in drive & flooring the throttle was all you had to do , it would shift at redline floored & earlier if you lifted . In theory this is not hard to do but why can no one do it then ?
I doubt the trans will have to be removed , I believe the needed adjustment can be done in the car by removing the valve body & tailhousing to access the governor , something is not even close to correct if full throttle shifts are happening at 3500 RPM !

 

[NoCar340]

In all my life with all of the Auto transmissions I have had rebuilt only 1 has worked correctly , it was in a Lil Red Express & it would hold the gear until 6000 unless you lifted slightly & then it would shift immediately , it was all controlled by the throttle , leaving it in drive & flooring the throttle was all you had to do , it would shift at redline floored & earlier if you lifted . In theory this is not hard to do but why can no one do it then ?
I doubt the trans will have to be removed , I believe the needed adjustment can be done in the car by removing the valve body & tailhousing to access the governor , something is not even close to correct if full throttle shifts are happening at 3500 RPM !

Absolutely agreed that 3,500RPM is waaaay too low for a WOT upshift.

My buddy had a '77 Charger Daytona (remember those?) and bought a junkyard 727 to have rebuilt rather than have the car out of service for a few days. Upon installation of the new transmission, WOT upshifts were just under 4,500RPM. The trans was redone by a reputable local hotshot and fully adjusted as per what I wrote above; nothing helped. We scratched our heads, then discovered the yard gave him a truck transmission. We swapped the governer parts from the OE transmission and full-throttle shift speeds returned to the 5,500RPM neighborhood, which would be expected in a smog-era performance car.

 

[Titan1969]

ok all great advice everyone. Im also going to call the trans shop and get their first step advice before I go overboard and pull the pan if there is something Im just not thinking of.
Heres a pic of the Cuda for those interested.

 

[DaveBob]

Thx in advance, I searched a few forums here and googled, there is a lot on the net about the 727 so thought Id start here for some advice.

'73 Cuda numbers matching with a new AVS Edelbrock Carb, rebuilt 727 trans ( all stock no stall, no manual valve body)
I did purchased the correct Edelbrock throttle brack so the TV arm and throttle works well with full throw forward and rearward.

I received the car after extensive resto work from prior owner, so no idea if the trans/linkage had issues prior.

Currently I followed the directions to put the gas pedal to the floor and make sure the TV arm moves the trans arm fully towards the rear of the car and it does ( or at least the arm is locked fully back as far as it will go).

The car in drive up shifts at 15mph then 25 mph and also downshifts while in normal cruising condition = no issues here.

Problem is when the pedal is put to the floor, the trans will not downshift. So if going 30mph, it just stays 3rd unless I manually shift it.

Trans fluid is clean and full.

When accelerating from a stop, the trans upshifts at about 3500rpm...this seems to early, further pushing me to think there is some issue with the trans/pressure lever setting.

Can anyone send me a pic of a '73 340 727 trans with the trans pressure lever full pushed rearward??? to give me some idea if the arm on the trans is perhaps not set right, perhaps its the wrong arm?

Any other ideas appreciated.

This may be an apples to oranges comparison, since I have a 70 full-throttle kickdown trans, but here goes. In my 70 340 Cuda, with a 727 TF trans, it will not kickdown at full throttle, from cruising speeds, if my WOT shift points are set too low. To fix it, I grabbed a pair of pliers, removed the clip to free up the throttle rod (the slotted one) and twisted it out a few turns at a time, tested it and repeated as necessary, until my WOT shift points were at 5000 to 5500. Remember, don't trust the factory tach for the rpm readings. It can read way too high, if it' like mine. If you don't have an accurate tach, calculate the speed at which you hit the desired rpm on your speedometer. For example, with 3.23 gears and stock diameter tires, 5000 rpm will be at about 50 mph at the top of first gear. For me, once I had the throttle rod out far enough to get the right WOT shift points, the trans would kick down properly, too. And that's it. If I'm right, this is a zero-dollar fix and you don't have to open up the trans. If I'm wrong, you didn't lose anything. BTW - check that you have all the linkage parts, and that they are assembled correctly.

 

[Titan1969]

DaveBob, I have a slightly different rod, it has a 7/16" bolt holding a slide bar and the bar is solid, down to the trans pressure lever, no adjustments other than at the carb/slide plate with the 7/16" bolt.

 

[DaveBob]

DaveBob, I have a slightly different rod, it has a 7/16" bolt holding a slide bar and the bar is solid, down to the trans pressure lever, no adjustments other than at the carb/slide plate with the 7/16" bolt.

View attachment 80371

Does the slotted adjustment at the lower center of your picture allow you to change your shift points? It looks like you have the linkage at its shortest position. As you lengthen it, your shift points should get higher. Have you tried that? The other thing that prevents kickdown at full throttle is not having true full throttle. The throttle cable adjustment needs to be checked to make sure that it completely opens the throttle plates on the carburetor when your gas pedal is on the floor. With two people, have one push the pedal all the way to the floor, while the other person checks to see if they can manually open the throttle further at the carb. If they can move the throttle further, then you weren't getting full throttle.

 

[Titan1969]

UPDATE ISSUE SOLVED
So I sorta created my own issue it seems.
I replaced the THQuad with a Edelbrock AVS2

The AVS2 throttle location is approx 1" closer to the firewall, meaning the pedal in the car nearly lays on the floor.
So I moved the cable bracket on the AV2 forward towards the front of the car, to pickup the pedal resting position.

While this worked, it then created the trans lever issue, which I assumed I could adjust the arm using the slider...nope doesnt work that way apparently. No amount of messing around with the trans arm on the carb would fix my shifting issues.

Soooo...i put the AV2 throttle position back to normal, the trans lever back to normal, then took up the slack inside the car on the pedal side of the cable.
Problem solved!
Car shifts at 15mph, then about 25 under light load and downshifts appropriately.

However like any project/resto now this is solved, I found another issue.

When I press the pedal to the floor, the trans arm down by the transmission is interfering with the shifter arm, so when flooring the car the shifter "pops" into N due to the trans arm hitting it. oye ve....

I think this should be an easy fix, I believe I need to loosen trans arm mount and move it "up a little" or the shift lever "down a little" to create more clearance between them.

 

[lemondana]

Why did you replace the TQ with the Edelbrock? The TQ's are ten times the carburetor that the Edelbrocks are! Also, in your picture above, it looks like a Holley. Which carb do you have?

 

[Titan1969]

Why did you replace the TQ with the Edelbrock? The TQ's are ten times the carburetor that the Edelbrocks are! Also, in your picture above, it looks like a Holley. Which carb do you have?

The picture is not my car, it was to represent the type of trans lever system my 73 Cuda has.

The TQ had be rebuilt 2x times and continued to run rich, foul plugs however I did keep it for someone in the future should I sell the car, they can mess around with it.
The AVS2 other than the throttle placement issue, has been plug and play out of the box. Been running great and Im enjoying my time driving it vs tinkering with the 50 year old TQ.

 

[lemondana]

OK!

 

[Titan1969]

When I press the pedal to the floor, the trans arm down by the transmission is interfering with the shifter arm, so when flooring the car the shifter "pops" into N due to the trans arm hitting it. oye ve....

I think this should be an easy fix, I believe I need to loosen trans arm mount and move it "up a little" or the shift lever "down a little" to create more clearance between them.

Mystery solved. The resto shop installed the shift arm that goes from the vertical shaft to the trans arm, upside down ( linkage was on top of the arms) and backwards lol.
So only needed to pull two cotter pins, pull off the linkage, flip the arm around (fat block towards rear of car ) and install the linkage underneath the arms.
Shaazaamm...working like a charm.
Heres the correct linkage setup...

 

[moparlee]

When I press the pedal to the floor, the trans arm down by the transmission is interfering with the shifter arm, so when flooring the car the shifter "pops" into N due to the trans arm hitting it. oye ve....

I think this should be an easy fix, I believe I need to loosen trans arm mount and move it "up a little" or the shift lever "down a little" to create more clearance between them.

Mystery solved. The resto shop installed the shift arm that goes from the vertical shaft to the trans arm, upside down ( linkage was on top of the arms) and backwards lol.
So only needed to pull two cotter pins, pull off the linkage, flip the arm around (fat block towards rear of car ) and install the linkage underneath the arms.
Shaazaamm...working like a charm.
Heres the correct linkage setup...

Glad you got it sorted out

 

[oldkimmer]

U may have the wrong lever on the kd. 1 curves up and 1 curves down. Which do u have? Of course u can always tweak it slightly for clearance. Kim