Transmission related death wobble / Vibration / Undrivable!

[James2406]

1996 C1500 5.0L 305ci 2WD Clean title no wrecks, was my grandfathers truck.


I have a bad ass vibration at around 50-80mph, seems like it's gotten worse. Let me list all the stuff that is brand new in my attempt to fix it.

New Steering. Pitman Arm, Idler Arm, Center link, inner and outter tie rods + new sleeves. Then Aligned at a shop.
New upper and lower control arms.
BellTech 2/4 drop kit including New shocks and coils front / New shocks, hanger and shackles rear. Spacers for the transmission, and carrier bearing + 2 degree shims under the leaf springs to fix pinion angle.
New Drums rebuilt, New Rotors and pads.
New Brake reservoir.
New Firestone Destination LE3 235/75 R 15's on the factory saw blades.
The BellTech was installed by me, all torqued to spec and checked by the alignment shop for slop, confirmed good install.
New balanced and shortened Driveshaft from a custom driveline shop today.
Brand new 4l60e Transmission and Torque converter.
All new U joints from the tail shaft to the yoke
New Carrier bearing.

With all this, the truck still has a violent shake/shudder/ wobble.
Driveline shop said today while on a lift the rear wheels had no wobble. Said while in park (not in gear) the vibration didn't occur but when put in drive and throttle applied up to 70mph vibration can be physically felt with a hand on the transmission.

I'm just about at my wits end with what this could be. When I originally got the transmission replaced, I assumed the vibration was the bald ass tires on the front. It WAS present before the rebuild. I have since tried to replace and repair all of what I can think of.

The Vibration after all this is worse than it has ever been. Any help is appreciated.

You must be registered for see images attach

 

[Schurkey]

Engine running at hiway RPM, out-of-gear, no vibration. Therefore, engine balance including torque converter shouldn't be a problem.

In gear, no wheel shake. Wheels, axle shafts, axle bearings likely OK. The bearings wouldn't be loaded, and no stress on the differential, so this isn't a perfect test.

Are you feeling the shake in the seat, the floorboards, or the steering wheel?

Steering wheel would indicate front-end issues. Seat/floorboard but not the steering wheel would indicate drivetrain/rear suspension.

 

[James2406]

.

vibration is at road spead, power braked and not vibration, park with throttle, no vibration. Of course my luck I drive it up and down the street and while the vibration is there, it's really faint now. It's a feeling from under the truck for sure. my steering wheel doesn't vibrate and if it does, it's slight and matched my ass

 

[Erik the Awful]

Wheel bearings tight? Spindles tight to the knuckles?

 

[stutaeng]

I high doubt it would be the transmission. The parts inside are machined to such low tolerances that for something like you describe, the transmission would basically be exploding to pieces. The drums, clutches, bearings, etc. would probably not even work enough to shift correctly if they are out of round that much. "Maybe" a mis-balanced torque converter is more likely, but that would cause vibration at park, revving the engine. I think those are balanced pretty well when they get built/rebuilt.

I would use system of elimination to try to pinpoint this one...get it on the lift and run it, then remove the wheels, then the axles, then the differential, driveshaft, etc. until the vibration stops...

I don't know how you would do the front though. Have you looked at the front hub bearings?

 

[alpinecrick]

New driveshaft--does that include new u-joints?

I have seen a new driveshaft with the splined yoke installed on the wrong end before. This was on a square body truck.

 

[thegawd]

anything to do with the EVO sensor? that sensor is why I got my Sierra so cheap from a buddy... I reached under and unplugged it and drove it home problem free with him following me. this dosent sound like the same problem but it was something my buddy was unaware of.

Al

 

[L31MaxExpress]

I high doubt it would be the transmission. The parts inside are machined to such low tolerances that for something like you describe, the transmission would basically be exploding to pieces. The drums, clutches, bearings, etc. would probably not even work enough to shift correctly if they are out of round that much. "Maybe" a mis-balanced torque converter is more likely, but that would cause vibration at park, revving the engine. I think those are balanced pretty well when they get built/rebuilt.

I would use system of elimination to try to pinpoint this one...get it on the lift and run it, then remove the wheels, then the axles, then the differential, driveshaft, etc. until the vibration stops...

I don't know how you would do the front though. Have you looked at the front hub bearings?

Could be the bushing for the slip yoke allowing the yoke to deflect under load. I ran into that once on a 700r4. Felt like my old G20 van was going to jump off the road above 45 mph.

 

[stutaeng]

OP did mention new D.S. and U joints...

Could be the bushing for the slip yoke allowing the yoke to deflect under load. I ran into that once on a 700r4. Felt like my old G20 van was going to jump off the road above 45 mph.

The rear tail housing bushing?

Yeah, I suppose that could be it. OP mentioned vibration is only driving at certain speed...so that could be it.


I suppose tail housing could be swapped out relatively easily to rule that out?

Anything is suspect here, including new parts.

 

[Pinger]

All new U joints from the tail shaft to the yoke

How many U joints?
Is the shaft in one piece or split?