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Rocking on bump in

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386 views 10 replies 6 participants last post by  Third Gen Racer  
B
#1 ·
My car rocks back and forth quite a bit upon bumping in.

I'm using a Pulse Leash set at 0.042 for 1 move

I know I can dampen the aggressiveness of the bump by setting it to more moves with lower time for each move, and I realize it's common to have a little bit of rocking but the distance it moves back and forth seems excessive to me. I feel like even if I dampen the bump settings it will still roll back and forth the same distance just perhaps more slowly and less number of oscillations. It's the distance that I'm asking about.

Inside the transmission what exactly determines the amount of "play" or distance it can move back and forth? Could something be wrong inside my trans?

Here's clip. It's in super-slow-mo, so you might need to increase playback speed.

 
E
#2 ·
What transmission?

Not having any experience with a trans brake but just looking at the vid, it looks like reverse is overriding the forward clutch pack just after bump and the car is actually backing up Vs just springing back.

I wonder if it would be worth installing brake pressure gages then dragging the foot brake at a specific pressure during bump in.
 
C
#7 ·
Econo Dragster said:
Is your shift pattern PRND21 or PRN12D ? REV might be the latter ( Reverse pattern valve body )

C/N might be Clean Neutral ( I've heard of this but don't know what it means, maybe something to prevent the planetary from being back driven and over speeding when coasting in neutral. )
Click to expand...
Clean neutral is so you can click it into neutral at the finish and not over speed the drum.
 
#11 ·
IMO you are not having a trans problem, your bump needs tuning. It has been a while since I used a PulseLeash. But you need to set it up for multiple pulses with one tap of the button. Try .005 and 6. If it doesn’t move try .010 and 6. Keep increasing the time until it moves the (agressiveness) you are looking for. Then set the number of pulses (6) to make it move the distance you want it to move. This has to be on the normal staging two step rpm. My PluseLeash was set up so that if you didn’t get all the way in, another tap of the button only gets you one hit of your time setting to move the car only a touch more. I think that was the default.

I know I don’t need to mention but I will. Do this testing safely. And trans temp makes a difference. When you get this setup it does work well. Where you stop in the prestage will determine where you end up in the staged beam.
 
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