2-3 shift on an "A904-LA" question.

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ProjectBazza

ProjectBazza

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I just brought Bazza's car home from the alignment shop (pic below), and during the drive I noticed something I thought was "a bit weird", so I paid close attention to the tach, and the shift points.

P6030321.JPG


The 1-2 shift seems nice and firm, and the RPM's drop noticeably, but on the 2-3 shift, not only is there NOT much of a drop in RPM's, but it's not that noticeable. (If you held a gun to my head and forced me to pick a number, I'd say it dropped maybe 300 RPM or so.) I stopped and started about 4 different times, and it was always the same- a nice 1-2 shift, and a "meh!" 2-3 shift, with little RPM drop.

(I should probably add that this is all relative/subjective, as I'm used to Ford C4 and C6 transmissions.)

Because of this, I can't say for certain that it actually did shift into third/drive, so I noted I was running 2,100 to 2,200 RPM at 50 MPH, with a 24-1/2" tire (BFG Radial TA's, P205/75R14). According to the Manual I have, the car came with a 2.92 (open) rear, and I have no reason to believe it's been changed.

I'll find an online RPM/tire diameter/rear end ratio calculator of some sort after dinner, but here's my question: Are 904's known to have a "close" 2-3 shift? (I hope that makes sense.)

Please note that the car is going back to Bazza this weekend, either way, so I'm not going to do anything about it right now, if this is indeed an issue. I'm simply putting together a list of items for next year, and I don't know if I should add this to it or not.

Thanks!

Jim
 
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  1. Is the kick down lever installed and adjusted properly?
  2. Was this under light throttle?
 
Dana67Dart said:
  1. Is the kick down lever installed and adjusted properly?
  2. Was this under light throttle?
Click to expand...
1. I didn’t check (or even think of) that. Since this car has been a jigsaw puzzle for me, I just put it back together.

But I have the Manual, and I can certainly can check it!

2. Light/partial throttle only on this drive.

Jim
 
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IMHO...

Unless it is a HP trans with a shift kit my guess is it is shifting just fine.

Especially if it has a bunch of miles on it.

Not a lot of load or HP needed going from 2 to 3 at light pedal
 
Forgot to mention I dropped the pan and drained the converter when the engine was out. Old fluid looked good, but I didn’t know how many miles were on it.

Fluid level right now is damn near perfect.
 
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Dana67Dart said:
IMHO...

Unless it is a HP trans with a shift kit my guess is it is shifting just fine.

Especially if it has a bunch of miles on it.

Not a lot of load or HP needed going from 2 to 3 at light pedal
Click to expand...
I agree. Your gonna have less drop on 2-3 and with a light pedal at low rpm's you wont notice much. Your cruise rpm surely shows it's in high gear. Next time out, get into a bit, like 1/2 to 3/4 throttle and i think you'll see it's working fine.
 
Can you shift it manually and hold it in 2nd gear a few hundred, maybe a thousand, rpm and then shift 3rd? You’ll probably notice quite a bit more “shift” and rpm drop.
 
My dart 273 2bbl just shifts into 3rd at the end of the quarter mile at full throttle not much of a feel of the shift.
 
The TF ratios are 2.45-1.45-1.00 and the splits calculate to .59- .69
so then, at Part Throttle, going to 50mph, at a throttle setting that outshifts first at say 2800 rpm, the 1-2shift will be at ~26 mph with an rpm drop to ~1700 rpm. which is a drop of 1100rpm
so then, now you are in Second gear at 1700 rpm. Continuing at the same throttle setting, and if the VB is properly calibrated, the 2-3 shift should also occur at 2800...... which will be at around 45 mph, with the Rs dropping to ~2000, a loss of just 800 .
depending on the actual stall, the convertor efficiency, the TV pressure setting, and most especially, the 2-3 shift command calibration, these numbers could be from a little to a lot different.
I have only rebuilt about a dozen or so TFs but have yet to see the 2-3 shift happen where I wanted it to, compared to the 1-2; they have always shifted early.

BTW your tach looks to be about right.
My calculator spits out 50=2016 at zero slip.
2150 would be 2% slip, sounds very good.
 
ProjectBazza said:
I just brought Bazza's car home from the alignment shop (pic below), and during the drive I noticed something I thought was "a bit weird", so I paid close attention to the tach, and the shift points.

View attachment 1716152374

The 1-2 shift seems nice and firm, and the RPM's drop noticeably, but on the 2-3 shift, not only is there NOT much of a drop in RPM's, but it's not that noticeable. (If you held a gun to my head and forced me to pick a number, I'd say it dropped maybe 300 RPM or so.) I stopped and started about 4 different times, and it was always the same- a nice 1-2 shift, and a "meh!" 2-3 shift, with little RPM drop.

(I should probably add that this is all relative/subjective, as I'm used to Ford C4 and C6 transmissions.)

Because of this, I can't say for certain that it actually did shift into third/drive, so I noted I was running 2,100 to 2,200 RPM at 50 MPH, with a 24-1/2" tire (BFG Radial TA's, P205/75R14). According to the Manual I have, the car came with a 2.92 (open) rear, and I have no reason to believe it's been changed.

I'll find an online RPM/tire diameter/rear end ratio calculator of some sort after dinner, but here's my question: Are 904's known to have a "close" 2-3 shift? (I hope that makes sense.)

Please note that the car is going back to Bazza this weekend, either way, so I'm not going to do anything about it right now, if this is indeed an issue. I'm simply putting together a list of items for next year, and I don't know if I should add this to it or not.

Thanks!

Jim
Click to expand...
Another thing to remember is that the difference between 2nd and 3rd is about 31%. If, and that's a big if, there is no slippage in the drive train then there should be a corresponding drop in RPM. At 2000 rpm the drop in rpm going from 2nd to 3rd will be ~31%, or about 620 rpm. If there is slippage like in the converter then the rpm drop will be less. I have a higher stall converter in my Duster and at low rpm and light throttle the 2/3 shift is almost unnoticeable. However, at the drag strip...you can definitely feel the shift.
 
At what speeds are the shifts? What is the rear end ratio? All these things will effect what you are feeling. W/O this you are probably normal.
 
You can screw your kickdown adjustment say 2 turns counter clockwise on the linkage at intake manifold and test it.
 
Turn up the line pressure on the valve body 1/2 turn. Install a part throttle kick down valve on the valve body and a lighter 340 governor piston in the governor on the tail shaft. All can be done in the car. You won't believe the difference.

If shifting manually with a auto trans pull out in drive then after the car is moving then pull it to low/1st. low gear is different in drive verses low gear in the 1st position when pulling out from a stop. You'll feel the difference when doing this. There will be no overlap and have a crisper shift. from low to second.

The pressure adjustment is the allen screw on the side of the valve body.
 
Quick update: All three gears "Present and Accounted For"!

I drove it out of the neighborhood in "D", and at the Stop sign at the County Road I manually shifted it, as recommended by "TT5.9mag" yesterday. Result: Three gears, no waiting!

I played around with that for a couple stops, and then I decided to "get on 'er" a bit in "D" and see what happens. Yup! Three gears, and the 2-3 was definitely there! She also downshifts (3-2) just fine, but it takes a little more "reach" than I'm used to with my Fords. But again- this isn't my car, so other than making sure the adjustment is correct (yet to do this evening), I'm going to leave well enough alone.

Couple more things to do on the punchlist (And, yes. It's on cardboard), and she should be ready to hit the trailer this weekend.

Thank you, everyone!

Jim
 
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