78 chevy wants to gallop? help doc?

Hey all
got a 78 1/2 ton 4x4, just got the brakes fixed(booster) anyway, around 30 or so, it wants to buck, not like a vibration, but like a damn gallop?
Anyway, I just had the tires balanced and rotated, didn't help a thing. any help would be greatly appreciated
thanks! TB
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250 straight 6 or 350? Is it like: full power, no power, full power, no power about twice a second?
Doc

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350; It's running ok, not like throttle's skipping. It just feels like it's going over a washboard or something, but it's only around 32-33 mph?
Thanks again TB

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nope, replaced about 5 months ago
TB

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btw, it bucks about 2 times a second though, if i were going to put a time frame on it.
TB

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My truck did the same thing about 3 months ago. I would double check those new u-joints. I wound up launching a cap off my rear joint. The joint was 6 months old.

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Have the rotors and drums turned and then check for brake pedal free play. Its possible that the rod wasn't adjusted right when the new booster was installed and you had brake drag that warped your rotors and/or drums. I have come across it before.
| Hey all | | got a 78 1/2 ton 4x4, just got the brakes fixed(booster) anyway, around 30 | or so, it wants to buck, not like a vibration, but like a damn gallop? | Anyway, I just had the tires balanced and rotated, didn't help a thing. any | help would be greatly appreciated | | thanks! | TB | |
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Do you have an extra tire? Try changing one at a time or if you can come up with an alternate pair of 4 try out the alternate. Tires may miss a weight or more confounding the tires themselves can de-laminate from the inside. I had a pair of G60R15s on the back of a camaro that bucked at ~30 and also bucked over 60. If you're sure it's not wheels then Doc's suggestion on the U-joints sounds likely. Elliott
Shades wrote:

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