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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: MyOldScottsdale23 on February 13, 2012, 08:16:06 am

Title: Trans modulator adjustment?
Post by: MyOldScottsdale23 on February 13, 2012, 08:16:06 am

I just bought a 1985 GMC SierraClassic 4x4. SWB Fleet. It has a 350/TH400 the Kickdown solenoid wasn't plugged up so I got that working. It still seems to upshift too soon. I have seen a few mentions on other posts about adjusting the modulator. Which direction and how much would I need to turn it to make it shift at higher RPM

Title: Re: Trans modulator adjustment?
Post by: Captkaos on February 22, 2012, 11:40:07 pm

part throttle or WOT?  WOT is controlled by the governor weights on a TH400.

Title: Re: Trans modulator adjustment?
Post by: MyOldScottsdale23 on February 27, 2012, 01:04:02 am

Both

Title: Re: Trans modulator adjustment?
Post by: ehjorten on February 27, 2012, 09:34:40 am

You need an adjustable vacuum modulator to adjust part-throttle shifts.  The adjustment is done with a small flat-blade screwdriver.  You take off the vacuum hose and inside the modulator vacuum connection is the adjustment.

You need a governor recalibration kit to adjust the WOT shift points.  Obviously, adjusting this will affect the part-throttle shift points as well, but the vacuum modulator gives you full control over both.

Title: Re: Trans modulator adjustment?
Post by: MyOldScottsdale23 on March 03, 2012, 08:00:06 am

Thank you