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Old 05-19-2022, 10:11 PM   #67
billr
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Join Date: Jul 2013
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Default Re: 1999 SOCH auto transmission problems

OK, I watched (and listened) all the way through the "manual switching" video; that one only.

Can I assume you have no power to either the LP or TCC solenoids? The hard shifting is due to the LP being forced to full high, and timing/sequencing of the other solenoids is probably not optimal. Are you using a multi-pole rotary switch to change all solenoids kind-sorta simultaneously, or manipulating three individual switches?

For each gear (selected manually) I would like to have you hold the car with the brakes and apply full-throttle to fully load the TC. Doing this, the turbine speed should remain near zero, while the engine speed will get up to about 2500 rpm and go no further. If the trans will not hold the turbine still, then the clutch in that gear must be slipping. If you do get a clutch slipping, back off of the throttle immediately to keep from damaging the clutch (any more). Also, stalling the engine against the TC like that will heat the trans fluid fast, so only do it long enough for engine rpm to stabilize (a few seconds), and let the trans cool for a few minutes after several of these runs. Since you have live-data, look at trans fluid temperature, use that as a guide. I would not want to see it get up higher than 275F.

If you do get clutch slipping, then you really need to pull the trans pan, remove the VB, and do the air-checks. If it passes the air-checks, then the problem is almost certainly in the VB. By "VB", I mean the mechanical/hydraulic components, the solenoids, or even the wiring bus from the solenoids to the external 10-pin connector.

I assume you have already read solenoid resistance. How about drive current in each solenoid coil? Have you ever tried 4th, now that you can force it to 4th at a low speed?
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