Strange gear change issue with TH350 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

NaturalSnapple · 08-14-2018, 01:44 PM

Hello Everyone,

After a top-end rebuild on a 1971 C10 (250 and TH350), when under full throttle, the transmission will alternate between 2nd and 3rd gears. For instance it'll downshift to 2 and then shift to 3 at the correct moment, but then it'll downshift back to 2, and then back to 3, all with the gas pedal held down without lifting.

It does not have a detent cable, and only has a vacuum source going to the manifold. I have very little knowledge of transmissions so thought I would reach out here to see if someone has had a similar issue.

08-14-2018, 01:44 PM	#1
NaturalSnapple Registered User Join Date: May 2017 Location: Raleigh NC Posts: 34	Strange gear change issue with TH350 Hello Everyone, After a top-end rebuild on a 1971 C10 (250 and TH350), when under full throttle, the transmission will alternate between 2nd and 3rd gears. For instance it'll downshift to 2 and then shift to 3 at the correct moment, but then it'll downshift back to 2, and then back to 3, all with the gas pedal held down without lifting. It does not have a detent cable, and only has a vacuum source going to the manifold. I have very little knowledge of transmissions so thought I would reach out here to see if someone has had a similar issue.



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