4R70W trans clunk on downshift

'Microsquirt' Transmission Control development and support.

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pcf_mark
MS/Extra Newbie
Posts: 33
Joined: Tue Feb 24, 2015 9:09 pm

4R70W trans clunk on downshift

Post by pcf_mark »

Details:
5.0 Ford running MSII on stock engine (late model roller engine)
4R70W stock trans and converter controlled by Microsquirt using Ford sensors / hardware with custom wiring harness

Trans shift very smooth and clean through each gear. Very conservative tune shifting at 2k or so gets to 4th pretty quick. Converter locks in 3rd and 4th. When decelerating to a stop the downshifts are smooth except 2-1. On this shift I get solid clunk that is abrupt and startling. It has been doing it for a year / 4k miles so I do not think it is harmful. I added a relay to ground a wire on the microsquirt when the brakes are applied this was identified in the software as a way to tell the micro that to unlock the converter.

Tune is attached maybe someone can see an errant setting. I'll try to save a log tonight on my drive home.
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: 4R70W trans clunk on downshift

Post by Matt Cramer »

Maybe a little less line pressure at low load downshifts?
Matt Cramer -1966 Dodge Dart slant six running on MS3X
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