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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Chevytruckin77 on November 24, 2009, 03:37:43 pm

Title: TH350 shifting issues
Post by: Chevytruckin77 on November 24, 2009, 03:37:43 pm

having some shifting issues with my truck, 350/TH350 combo, when you put it in drive and take off it shifts from first to second, immediatly. then it will shift into third normally. If you shift it manually it does just fine. Already replaced the modulator. not sure if the kick down cable would have anything to do with it. any suggestions would be great.

Title: Re: TH350 shifting issues
Post by: VileZambonie on November 24, 2009, 03:52:51 pm

You replaced the vacuum modulator? Did you adjust it? Make sure the Governor isn't sticking.

Title: Re: TH350 shifting issues
Post by: Chevytruckin77 on November 27, 2009, 05:11:16 pm

Yes i replaced the vacuum modulator. A stupid question, how do you adjust it?

Title: Re: TH350 shifting issues
Post by: VileZambonie on November 27, 2009, 05:31:58 pm

By turning the adjusting screw (found in the vacuum nipple) counterclockwise, you will lower the spring pre-load. This will cause earlier shifts. By turning the adjusting screw clockwise and raising the spring pre-load, the shift points will go up. Use a pocket screwdriver.

Title: Re: TH350 shifting issues
Post by: Chevytruckin77 on November 27, 2009, 06:10:54 pm

I"ll give that a shot to see what it does, if that doesnt fix the shifting problem, is there anything else you wold suggest checking into?

Title: Re: TH350 shifting issues
Post by: team39763 on November 27, 2009, 06:56:59 pm

If that doesn't fix it, maybe you need a Governor recalibration kit.  I believe B&M makes one for around $30.  That's what I was told to use when I needed my shift points fixed.

Title: Re: TH350 shifting issues
Post by: Stewart G Griffin on November 28, 2009, 01:11:23 pm

The other thing to check is to see if you replaced the vac modulator with the appropriate one---there are different color "bands."  i think red is stock.

Title: Re: TH350 shifting issues
Post by: ant305 on January 06, 2010, 08:32:12 pm

I have the same issue. I have a 355/350 and the transmissions flying through the gears....im in 3rd at 20 mph....transmission was completely gutted and rebuilt in 2007...

would I need that recalibration kit if its not the governor or vaccum switch?