Shaking or vibration at highway speed

[96cheyene]

I got a 96 k1500 350 5 speed, when I'm cruising and coming up to about 60mph shifting into 5th gear the truck starts to vibrate or shake. Once I get to about 65mph or 70mph it goes away and is smooth. Im not sure if its the engine, transmission, tires, or rear end. It doesnt shake the steering wheel and I had the u joints replaced. Any help would be appreciated

 

[bugdewde]

50-60 mph issues sometimes are a result of a tire issue. At those rotational speeds, broken belts, out of balance and other tire issues tend to be very noticeable if everything else is good.

Infamous "death wobble" occurs around those speeds as well. Shaking appearing at a certain speed and then disappearing at a faster speed or during cornering/braking. Worn or loose front components (suspension/steering) that have slop in them cause "death wobble" .... mostly front wheel bearings, tie rod ends, CA bushings, Idler arm/mount, etc. With slop in them, they can vibrate/oscillate at a certain speed and then as forces increase on them (steering angle, braking, suspension load/unload), those forces tend to dampen the oscillation/vibration. Imagine a loose front wheel wobbling. Then toe (adjust) the front wheels in or out a bunch and the force pushes the loose wheel to its limits in or out and stops the wobbling. We Jeeper's deal with this on a very regular occurance (Google Jeep TJ Death Wobble). That's my bet.

Also, it could be missing transmission mount bolts.... As was my issue.

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[skylark]

Tires you'll typically feel in the steering wheel for the front and in your butt for the back.

 

[98chevy2500SS]

x2 on the tires, my 98 does this around 65-75 sometimes, my 97 do this too, but not as much as the 98.

 

[95C1500]

Doesn't hurt to get the front tires rebalanced (probably all as well as a rotation if you're due for one).

After that, I'd check into worn suspension/steering parts.

 

[Schurkey]

Truck in 5th gear, at whatever speed the vibration is worst.

Vibrates with clutch pedal kicked in and engine at idle? Not an engine problem.

Vibration ends when clutch pedal pushed in and engine idling? Engine issue. MIGHT be a driveline issue, for example failed U-joints that aren't transmitting power may not show symptoms. Same with broken teeth on a transmission gear. When coasting, the problem is reduced.

Does the truck shake if you go the same speed in 4th gear instead of 5th?

 

[96cheyene]

It will do it slightly while gaining speed going through the gears but once I get into 5th gear at 60 is when it does it the most. The shifter shakes as well and I had the tires recently put on 285/75/16. I've got the engine codes p
Come up relating to a random misfire crank and cam sensor and catalytic converter which has been gutted out. I've replaced almost the whole ignition system

 

[96cheyene]

Truck in 5th gear, at whatever speed the vibration is worst.

Vibrates with clutch pedal kicked in and engine at idle? Not an engine problem.

Vibration ends when clutch pedal pushed in and engine idling? Engine issue. MIGHT be a driveline issue, for example failed U-joints that aren't transmitting power may not show symptoms. Same with broken teeth on a transmission gear. When coasting, the problem is reduced.

Does the truck shake if you go the same speed in 4th gear instead of 5th?

The truck idles fine and pretty smooth, the only time it shakes or jerks is when im driving and acceleratin . Doesnt do it when I let off the gas