1 Attachment(s)
SP400 No Passing Downshift
I am looking for some guidance diagnosing my SP400 in my '66 Riviera. This is one which is described as "3-2 valve used on 1st jobs only". And, yes, I rebuilt it:(, and someone had been into it before.
The transmission works well other than when cruising if you accelerate hard you should find the transmission downshifting from into either 2nd or low depending on speed. It does not.
If you come to a full stop, it will move away in low normally. But, if traveling at, say 30 or 40 mph, and boot it, it does not downshift. The torque converter does shift.
I have gone through the detent switches carefully and everything seem to be in order. If you energize the detent solenoid, I can hear it click.
This transmission is early and does not have a spring in the 3-2 solenoid. If you look at troubleshooting 400s not downshifting, "missing or broken spring" is one of the problems.
The modulator originally was a large one with a metered vacuum line. I replaced it with the one from the kit, it was a normal smaller one typically supplied for a 400 rebuild. I am wondering if this could be my problem. I may not be able to use the updated modulator with this early transmission.
Some guidance for troubleshooting this early transmission would be appreciated as it is different than most 400s.
Thanks