Author Topic: Trans modulator adjustment?  (Read 2296 times)

Offline MyOldScottsdale23

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Trans modulator adjustment?
« 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

Offline Captkaos

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Re: Trans modulator adjustment?
« Reply #1 on: February 22, 2012, 11:40:07 pm »
part throttle or WOT?  WOT is controlled by the governor weights on a TH400.

Offline MyOldScottsdale23

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Re: Trans modulator adjustment?
« Reply #2 on: February 27, 2012, 01:04:02 am »
Both

Offline ehjorten

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Re: Trans modulator adjustment?
« Reply #3 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.
-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline MyOldScottsdale23

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Re: Trans modulator adjustment?
« Reply #4 on: March 03, 2012, 08:00:06 am »
Thank you