Inconsistent shifting: any ideas?

-
Trevor B

Trevor B

Well-Known Member
Joined
Nov 2, 2014
Messages
509
Reaction score
140
Location
Novato, CA
When racing, I am experiencing shifts all over the map from 1-2. Sometimes they feel crisp/firm, other times, "stock," and sometimes very soft. Starting in Low, shifting to 2 at 5500 RPM, then to 3 at 5500 RPM.
1973 Plymouth Duster
Torqueflite 904 with TF-2 shift kit (installed by my trans guy)
Mopar factory high stall torque converter (so 2500 or so)
Lokar kick down
3.55 Suregrip rear end
Powered by Mopar Performance Magnum crate motor (380 hp 360).
Here are some videos where you can hear the shifts. Please excuse my bad racing skills - still learning but much more concerned about getting the car to perform consistently.
1) 1-2 firm, 2-3 firm

2) 1-2 medium, 2-3 firm

3) 1-2 soft, 2-3 firm

4) 1-2 soft, 2-3 firm


Anything I might be able to consider doing here to get all of my shifts firm? It always feels firm during normal street driving!
 
Is the fluid level correct?

I would strongly suspect your throttle pressure (kickdown) linkage is hanging up or binding causing the erratic shift points . To troubleshoot, disconnect it and wire it 2/3 to all the way back and see if the shift points stop changing. Dont leave it like this though.....

Could also be governor weights or spool valves in the valve body sticking.
 
If you're just running that in Drive I would be looking at that kickdown linkage has a possible problem.

Is that engine and drivetrain out of balandce is that what we're hearing in those videos. Did you balance that torque converter or flexplate for that Magnum motor.
 
Fluid level normal.

Manually shifting: starting in Low and shifting to 2 and then to Drive at 5500 rpm.

Driveshaft wasn't balanced right - had that vibration before engine swap. Flex plate specifically for magnum engine to non-magnum TC.

Regarding linkage binding... Wouldn't it always be the same at wide open throttle? As in, cable pulled all the way when pedal to the floor?

Probably have to ask transmission guy about checking governor weights and spool weights. He rebuilt transmission a few years ago.
 
At wide open throttle the kickdown lever should be all the way back minus just a touch to keep it from hitting on the stop.
 
So it isnt the shift point that changes, just the shift quality. I dont believe that this is related to governor weights or kickdown linkage.

I would suspect that it could be related to fluid temp. Did it shift best early in the day when the fluid was cooler? Do you have a good cooler installed?

Do you have a deep pan? If so is the filter extension installed?

Type F fluid causes firmer shifts if you wanted to try changing it.
 
d55dave said:
So it isnt the shift point that changes, just the shift quality. I dont believe that this is related to governor weights or kickdown linkage.

I would suspect that it could be related to fluid temp. Did it shift best early in the day when the fluid was cooler? Do you have a good cooler installed?

Do you have a deep pan? If so is the filter extension installed?

Type F fluid causes firmer shifts if you wanted to try changing it.
Click to expand...

My first though was fluid temp variances also.:D
 
d55dave said:
So it isnt the shift point that changes, just the shift quality. I dont believe that this is related to governor weights or kickdown linkage.

I would suspect that it could be related to fluid temp. Did it shift best early in the day when the fluid was cooler? Do you have a good cooler installed?

Do you have a deep pan? If so is the filter extension installed?

Type F fluid causes firmer shifts if you wanted to try changing it.
Click to expand...

Yes, but... The shift quality on most runs was my problem. However, on one run when I shifted Low to 2 at 5500, it actually allowed the engine to continue to rev to nearly 6000 before settling in on 2.

The first run of the day was not the most crisp, it was just okay. The second run was the best, shift-wise, after 45 minutes of sitting. The third was after nearly an hour of sitting and the temperature was dropping fast, it was much sloppier!

I recently installed a new radiator (which is actually keeping the engine a little too cool!) and also a transmission cooler. I kept the electric fan on while warming up the car through staging through the run to try to keep the transmission cool.

Stock 904 pan. Can certainly try the Type F fluid.
 
Trevor B said:
Yes, but... The shift quality on most runs was my problem. However, on one run when I shifted Low to 2 at 5500, it actually allowed the engine to continue to rev to nearly 6000 before settling in on 2.

The first run of the day was not the most crisp, it was just okay. The second run was the best, shift-wise, after 45 minutes of sitting. The third was after nearly an hour of sitting and the temperature was dropping fast, it was much sloppier!

I recently installed a new radiator (which is actually keeping the engine a little too cool!) and also a transmission cooler. I kept the electric fan on while warming up the car through staging through the run to try to keep the transmission cool.

Stock 904 pan. Can certainly try the Type F fluid.
Click to expand...
Well that seems to shoot the temp theory down.

How is the shifter, linkage and engine / trans mounts? Any worn parts or slop?

Is the shifter properly adjusted?
 
accumulator piston spring [Just a guess] or a slow releasing manual low band.[maybe servo]. How does it shift when just placed in drive [from a stop].
 
Something I just noticed, listening to the engine in the videos - the 2nd run, (first video in the thread), which had the tightest 1-2 shift, is also happening a few hundred RPM lower than the others. So I either shifted below 5500, or in the other runs I'm shifting over 5500. Anyway, they're not the same.

Does RPM affect shift firmness?
 
You must log in or register to reply here.
-

Back
Top