Anyone well-versed on A-904 tranny?

['74 Sport]

My son Aaron (DartThis74 here on FABO) called a couple of weeks ago to tell me his slant's throttle cable snapped. I sent him a few various spares we had stashed away, and he used one to get back up and running.

A few days later, he noticed his transmission (A-904) was acting funny. He said it was hesitating to upshift from 1st gear. Also, from a dead stop, it would sometimes act like it didn't want to get moving - like his foot was on the brake at the same time he was pressing the accelerator pedal.

I told him that the transmission issue was probably related to his replacing the throttle cable and the kickdown linkage not being adjusted correctly. He tinkered with different throttle cable positions (clamped the cable at various lengths) and took it for a test drive each time.

Suddenly, he was suprised to find that on one setting the ol' slant just "came to life". Before, when he would step on the pedal, it would take a bit to get up to speed to attempt passing anyone. That time, it bolted quickly and set him back in the seat - seemingly finding some hidden power he never saw before.

When we rebuilt the 225 slant we installed a Comp Cams RV cam (264S-10), Super Six intake w/ 2bbl Carter BBD, 2-1/4" exhaust, and turbo muffler. Since we never had an opportunity to drive the car in its stock form before rebuilding the engine, we had no basis to compare the relative "seat of the pants" power. All Aaron could say is that is now had a lot more power. Based on our experience, I could never understand why everyone was so excited over their upgrade to a Super Six - I thought it was kind of doggy.

When Aaron came home this weekend from college, we made some adjustments to address the shifting problem. I had read, and we did, the following:

1. Loosen the locking nut on the end of the throttle pressure (kickdown) rod.
2. Push the throttle pressure lever on the transmission all the way forward.
3. Make sure the end of the rod is fully forward in the slotted linkage near the carburetor.
4. Tighten the locking nut.
5. Loosen the locking nut on the throttle cable hold-down clamp.
6. Make sure the engine is warmed up so the choke is off and the carb is set to curb idle position.
7. Pull backwards on the outer sheath until all the slack is removed.
8. Ease the cable forward approximately 1/4" to give a little slack.
9. Tighten the locking nut on the throttle cable clamp.
10. Since the throttle plates would not open completely at wide open throttle(it needed about 1/8" more), we pulled the extra 1/4" of slack back out of the cable and clamped it down.

After doing all of the above, the car does have more power than I have ever seen before. When you step into it, even at 65 mph, it kicks down and GOES. The only continuing issue is that it still has a bit of hesitation upshifting out of first from a dead stop. The rpm has to get too high before it shifts, or you have to stomp on it to get it to shift. I believe Aaron says that once it warms up, the shifting issue seems to lessen.

Questions: Was the kickdown rod adjustment done correctly? Would it help the shifting problem if the throttle pressure lever is locked down in a position farther back down the rod, rather than fully forward? Will that make matters worse?

Any help is appreciated,
Jerry

 

[player1up]

sounds like the adjustment was done correctly. I adjusted mine the same way and it didn't want to shift out of 1st either. Push the throttle pressure lever on the transmission all the way forward, then back it off a little (1/8 inch) and then tighten it. My downshifts aren't as aggressive now but at least I can cruise in a school zone without the motor turning 2500

 

['74 Sport]

I think you hit the nail on the head, Player.
I finally got hold of the transmission shop that did our original rebuild, and they told me basically the same thing.

If I understood what they said, it goes something like this:
When the throttle pressure lever is pushed all the way forward and locked down with the throttle cable at curb idle, the transmission is "thinking" that you are already hard on the pedal when you start off. So it really takes some heavy pedal or higher rpm to make it shift. The solution is to leave some slack in the lever (as you just said). They said to place the lever in its rearward position and lock it down with the throttle cable at wide open. This should result with a little slack left in the lever in its relaxed position when the throttle is back to curb idle.

We will test this theory and post the results. Now I need to spend a little quality time with my new A-727 transmission book and read up on the actual mechanics of what is happening.

Any further thoughts are welcome,
Jerry

 

[player1up]

yeah man! you heard the guy right.
That little lever might as well be called a throttle position sensor. It tells the trans when to shift. I check the adjustment whenever I do a tune up, Also if you change/add a carb spacer you'll have to adjust it again.
I was a little surprised at how a small movement of the lever made a HUGE difference in how the trans felt. Too far forward and you get long gears and quick jutting shifts, not to mention the instant downshift when you even think about hitting the gas.
Too far back and you get early soft shifts, not enough RPM to keep the thing moving and run the risk of burning out the bands.
The key is to set it up for the way you drive. then put a mark on the linkage so it can be put back that way after you're done tinkering. It is zippy in the forward position but too twitchy on wet roads.

where do you have the initial timing set? there might be more fun to find

 

['74 Sport]

It's been about three years since we finished the car, so I'm a little fuzzy on the details. I believe we set the timing around 10-12 BTDC, but don't take my word for it. It's probably time to check it again, as well as the valve lash.

Jerry