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I have a rebuilt transmission I installed last summer, it's been doing well, though I'm getting some strange RPM bouncing on either the TC lock up or on the 3-4 shift or both.
The original transmission had a similar 3-4 shift I believe, though currently it seems worse. RPM bounce is kind of a herky jerky shift, more noticeable under load but it's there on slow acceleration shifts too.
Any thoughts on this? Other people have 3-4 shift that's not as clean?
I'm wondering if custom tunes would help. I've got a tugger shift kit among other engine mods that might benefit from custom tunes, though would like to better understand what might be causing the odd shift.
In attached image you can see the RPM bounce around and TC bounce too.
I had to drop the pan after install to replace a defective shift solenoid, this is what they sent me with the new solenoid.
I'd never seen it before, guessing it is inexpensive. Ive read on different posts that you are a fan of Mobil 1, do you think fluid type could be contributing to the wonky shift?
The graphs you posted showed what looks like torque converter clutch shudder. Converter clutch shudder is often caused by the wrong coefficient of friction in the fluid.
Update on this: replaced transmission fluid to Merc V. I feel better about having that in there and did seem to help a bit but problem persists.
I changed all of my tunes to modified valve body on the Hydra and that definitely helped with the feel of all shifts, way less harsh, much crisper. Should have done that a long time ago.
Still getting lurching during the TC lock up and 3-4 shift (SS1 and SS2 both off)
When I graph it the TC begins to lock up, and then during lock up the transmission shifts into 4. This is when I get the lurching, RPM bouncing. It is noticable with both light acceleration and heavy acceleration, but seems worse kind of at mid-level acceleration.
Does the graph look normal? I think I've read that the TC usually locks up after the 3-4 though mine seems to be locking up and shifting at the same time? Normal? I need some schooling on TC lock up parameters.
Would love to see some other graphs of TC lock up for comparison.
What I see happening is that the converter begins locking immediately after the 2-3 shift. The TCC percentage is reduced when the 3-4 shift is commanded to allow some converter clutch slip during the 3-4 shift, then it increases the percentage to relock as the shift is completed. This is normal operation.
The bouncing of the RPM signal is not normal. It could be from the old fluid. If so, it will work itself out after some more miles. If it doesn't, it could be from an aftermarket torque converter. If the converter clutch has more torque capacity that the stock converter the stock programming might not be able to handle that. It may take a custom tune to make this right.
I'd drive it for a week or so and see if the MERCON V fixes it.
What I see happening is that the converter begins locking immediately after the 2-3 shift. The TCC percentage is reduced when the 3-4 shift is commanded to allow some converter clutch slip during the 3-4 shift, then it increases the percentage to relock as the shift is completed. This is normal operation.
The bouncing of the RPM signal is not normal. It could be from the old fluid. If so, it will work itself out after some more miles. If it doesn't, it could be from an aftermarket torque converter. If the converter clutch has more torque capacity that the stock converter the stock programming might not be able to handle that. It may take a custom tune to make this right.
I'd drive it for a week or so and see if the MERCON V fixes it.
Thanks for sharing your knowledge, much appreciated.
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