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07-20-2015, 09:09 PM | #1 |
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Join Date: Jun 2011
Location: Central OR
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81 K30 T400 only shifts via the Gov.
I was cruising along slowly when it would no longer shift without winding her out. Put a new Vac Mod and new rubber hose ends on, tested for Vac at the Mod and pulled the valve out. All looks good and within spec. Any ideas?
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1955 GMC 250 8 Flatbed 1971 C30 157" 350 4spd 10' Flatbed 81 GMC K30 CnC 9' Flatbed 454 T400 89 GMC Jimmy Stock https://67-72chevytrucks.com/vboard/...d.php?t=810958 71 LT1 Convertible, 72 Coupe 69 CJ5, 75 CJ6, 67 M715, 72 M35A2 Bobbed, 95 XLC2 |
07-21-2015, 03:06 AM | #2 |
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Join Date: Feb 2015
Location: Lester West Virginia
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Re: 81 K30 T400 only shifts via the Gov.
I had one doing close to the same thing it was the switch on the pedal that works the passing gear going bad
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07-22-2015, 06:53 AM | #3 |
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Re: 81 K30 T400 only shifts via the Gov.
Good to know. My son's CUCV is doing the same thing after a rebuild and we replaced the module.
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"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ |
07-22-2015, 10:03 AM | #4 |
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Re: 81 K30 T400 only shifts via the Gov.
I pulled and inspected the Gov and the valve moves freely, disconnected the kick down wire, test drove with the same result. Next I am going to swap Mod valves with another transmission.
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1955 GMC 250 8 Flatbed 1971 C30 157" 350 4spd 10' Flatbed 81 GMC K30 CnC 9' Flatbed 454 T400 89 GMC Jimmy Stock https://67-72chevytrucks.com/vboard/...d.php?t=810958 71 LT1 Convertible, 72 Coupe 69 CJ5, 75 CJ6, 67 M715, 72 M35A2 Bobbed, 95 XLC2 |
07-22-2015, 08:28 PM | #5 |
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Re: 81 K30 T400 only shifts via the Gov.
I backed the adjustable modulator all the way out with no results.
I placed a piece of cellophane on the bottom of the PCV valve and reinstalled it with no results. The only vac lines are PCV, distributer, and the vac mod. I tested the integrity of the metal/rubber vac line from the manifold including the modulator and it holds 20lbs fine. Next when the rig cools down I am going swap the modulator valve with one from a spare TH400.
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1955 GMC 250 8 Flatbed 1971 C30 157" 350 4spd 10' Flatbed 81 GMC K30 CnC 9' Flatbed 454 T400 89 GMC Jimmy Stock https://67-72chevytrucks.com/vboard/...d.php?t=810958 71 LT1 Convertible, 72 Coupe 69 CJ5, 75 CJ6, 67 M715, 72 M35A2 Bobbed, 95 XLC2 |
07-22-2015, 10:38 PM | #6 |
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Location: Central OR
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Re: 81 K30 T400 only shifts via the Gov.
Swapped the valve, no change.
Looks like I get to drop the pan. Hopefully something will fall out and hit me in the head so I can get this fixed.
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1955 GMC 250 8 Flatbed 1971 C30 157" 350 4spd 10' Flatbed 81 GMC K30 CnC 9' Flatbed 454 T400 89 GMC Jimmy Stock https://67-72chevytrucks.com/vboard/...d.php?t=810958 71 LT1 Convertible, 72 Coupe 69 CJ5, 75 CJ6, 67 M715, 72 M35A2 Bobbed, 95 XLC2 |
08-15-2015, 08:11 PM | #7 |
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Re: 81 K30 T400 only shifts via the Gov.
Dropped the pan and the detent/kickdown solenoid was hanging by its wire. The welds that attach the 4 feet to the bolt up plate failed. I have one ordered and I hope this fixes it.
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1955 GMC 250 8 Flatbed 1971 C30 157" 350 4spd 10' Flatbed 81 GMC K30 CnC 9' Flatbed 454 T400 89 GMC Jimmy Stock https://67-72chevytrucks.com/vboard/...d.php?t=810958 71 LT1 Convertible, 72 Coupe 69 CJ5, 75 CJ6, 67 M715, 72 M35A2 Bobbed, 95 XLC2 |
08-19-2015, 11:26 PM | #8 |
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Location: Central OR
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Re: 81 K30 T400 only shifts via the Gov.
It shifts now
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1955 GMC 250 8 Flatbed 1971 C30 157" 350 4spd 10' Flatbed 81 GMC K30 CnC 9' Flatbed 454 T400 89 GMC Jimmy Stock https://67-72chevytrucks.com/vboard/...d.php?t=810958 71 LT1 Convertible, 72 Coupe 69 CJ5, 75 CJ6, 67 M715, 72 M35A2 Bobbed, 95 XLC2 |
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