Driveline vibration!

[Sketch_hs]

PAGE 3, CHANGED TO SOFTER BUSHING IN SAMBERG DIFF MOUNT AND HAD GREAT RESULTS!


Car is 1jzgte vvti, tr6060, 4.3 jdm diff, samberg diff mount, driveshaft shop CV joint front, ujoint rear aluminum driveshaft

Never ending quest to fix the vibration, i've had different transmissions and 3 different drive shafts. Measured and played with angles all day long

Was hoping that the DSS shaft would fix this but it's got a vibration starting at about 75mph that gets worse with speed.

Im starting to think it's mostly just the stiffness of the samberg fd diff mount. It's nearly solidly mounted with their bushing.


Ideas?

[largeorangefont]

What are the angles of the pinion and the trans?

[Sketch_hs]

I'll need to remeasure this weekend to double check but I remember them being pretty good. I may also have a left / right offset, not sure how to measure that accurately

[Sketch_hs]

Also, with a CV on the transmission side, it shouldn't matter much, no? I mean i'm sure the angles are good for this type of shaft

[Supe]

Does it do it on stands in neutral?  Have you tried swapping wheels and tires?  How are engine and exhaust mounted?

[Sketch_hs]

Does it do it on stands in neutral?  Have you tried swapping wheels and tires?  How are engine and exhaust mounted?

No it's only with the driveshaft spinning. With the driveshaft out you can run the engine / trans to the same speed with no vibration at all.

Even with the diff mounts not attached and the diff supported by a hydraulic jack (drive shaft attached), I can run up to the same speed and get no vibration. It's crazy, you can crawl under the car and the diff feels like it's vibrating a little at 80mph, but it feels worse in the car in the driver seat!

[MPbdy]

I'm curious about mine.  I've gone through two different driveshafts and had them in and out multiple times.

Also have the samberg rear mount.

I've never been happy with the amount of vibration in my car.  It's insanely frustrating.

I might try your test of undoing the front diff mount sometime.

[largeorangefont]

Did yours get better with the new driveshaft balance and u joints Daniel?

[MPbdy]

I tried all I could with the steel one, then had an aluminum one built, and then had it out once already with a worn u joint. It's got better u joints in it now and seems smoother, but it still buzzes quite a lot.

It was honestly one of my concerns about running the big track. I have no way of diagnosing a problem that only shows up really pronounced above 120. I'm thinking it's best to just save my pennies and replace the entire driveline from the clutch back to the rear.

My 80 Malibu drag car with a solid mounted ls3 turning above 7500 and solid rear heims is smooth as glass compared to the fd.

[largeorangefont]

That is a bummer.. Weird.

[Sketch_hs]

Frank as DSS recommended a few things:

Flip the flange 180 at the diff

make the diff to ujoint angle as close to zero as possible (1.5 degrees is the max)


I'll be working on this and will post any results.

The other possible issue is that it's a natural harmonic of the FD diff and the samberg kit simply mounts the diff too solidly, causing the harmonics to be amplified and transferred to the chassis

[Mik3ymomo]

So I know 2 people who bought brand new Driveshafts from the driveshaft shop in the past few years and both had a vibration and both were fixed by getting them balanced. Seems the QC at the Driveshaft shop let an unknown number of these thru without balancing them or thier balancing process was flawed.

Start there.

[halfspec]

So I know 2 people who bought brand new Driveshafts from the driveshaft shop in the past few years and both had a vibration and both were fixed by getting them balanced. Seems the QC at the Driveshaft shop let an unknown number of these thru without balancing them or thier balancing process was flawed.

Start there.

I'm one of those two. I would like to clarify though that my driveshaft was rebuilt by DSS (graciously, 5 years out of warranty I might add) because after they verified my measurements from trans to diff they concluded the DS was originally built too short. Since the DS was rebuilt, they never put the original on the balancing machine.

I also spent a lot of time getting my angles perfect on my setup. It's a confusing process. Not to say you're not doing it right, or not working with all the variables. All I'm saying is there was more to it than I first expected.

In the end my issues were 60/40 between the engine and the rest of the driveline. When my driveshaft was out I cranked the engine and continued to feel a good bit of vibration just from the engine. Not excessive, but it was there. I expect I'll get even more out with a good tune as my current tune has a lot of surging which only multiplies the issue, but I walked away from this resolved that the LS mounting platform in the FD is a stiff mofo. Add that to a rigid chassis, stiff suspension, and aftermarket bushings and you're going to end up with more vibration than the original rotary, even if everything is 100% perfect.

Lane

[gnx7]

A combo of poly engine mounts and poly trans mount can also create odd vibrations.  Try swapping in a factory style trans mount and leave the poly engine mounts. 

[MPbdy]

I like that idea too... I've got an energy suspension one.