Driveline angles and vibration concerns lowered LT1 T56 Dana 60
 

Greetings,

I have searched and found some good sources for setting up driveline angles.. My concern is vibration in the car.

Here's what I have:
95 LT1 car
T56 manual transmission
Energy Suspension motor mounts and trans mount
Sam Strano lowering springs
Koni Shocks
Strange Engineering Dana 60
Strange Engineering chrome moly driveshaft
Spohn adjustable torque arm

I have purchased a digital angle finder and each angle is 2.9 degrees, but in opposite directions.

The motor slopes down front to back \ drivshaft slopes up front to back / and dana is set with the nose up \
So the angles look like this if viewed from the driver side \ / \

I know this isn't ideal, as you want the nose of the pumpkin facing down. However, with the car being lowered and the dana being massive, it just isn't possible unfortunately.

The car still has a driveline vibration up around 70mph. The freeways out here can reach 80mph, so obviously I'd like to drive that fast. :drive:

I've got the trans shimmed up as high as it will go - the top snubber is now touching the tunnel. It won't go any more.
I don't think it is feasible to lower the motor in the cradle, I can't see how it would be possible.

Research indicates the 3 degrees is about max for minimal driveline vibrations, and I am just under it at 2.9 degrees.

Has anyone found a way to get that angle better with a lowered T56 car?

Would switching to another brand poly trans mount help? I'd still shim it up, but maybe this brand is the problem. Has anyone gone from Energy Suspension trans mount to the Prothane brand with a reduction in vibration afterwards?

I don't know what else to do, so suggestions welcomed!

Thanks!

Unfortunately, you're going to have to get an adjustable torque arm.

Crap, sorry, forgot to add that...

I have a Spohn adjustable torque arm as well. :cheers:

What ends do have on your torque arm and lower control arms. Because if its rubber. Your rear end is moving way past tolerance when its under load. How low do you have this thing sitting? We have a LT1 car as well, and it only sits about 3 or 4 inches off the ground. We had to put a half inch shim under a energy suspension trans mount that almost put the motor level. Slightly leans back. Our drive shaft is almost level with a very slight 1 degree angle down towards rear end. We have heim joints on ours so we only have the nose of the rear end 1 degree down. With 0 vibration. We have a full cage so there is very limited chassis flex if any. We have the same rear end and the pro series Spohn torque arm with QA1 coil overs. If your rear end is higher than your trans, do you even have any suspension travel left? Your torque arm has to be close to, and may be hitting the tunnel if its that low. Should have went with coil overs so you could adjust your ride height. Also at ride height you want the panhard bar to be level. If not it will cause handling problems when going over bumps and dips in the road or track. Just my 2 cents. Best of Luck.

Well, I have a 2002 that sits lower than stock an inch or so. That isn't the issue. When I had the oem LCA's, torque arm, trans mount and drive shaft - no vibration. Each oem piece I replaced with aftermarket parts to "improve" handling added more noise/vibration. Eliminate the insulating effects of the oem pieces & you're going to feel things like you wouldn't otherwise. One of the worst is the driveshaft. I replaced my oem aluminum driveshaft with the rubber insulator on the front joint with a steel driveshaft, and every little thing resonates through the driveshaft like it's a noise chamber.

As for the angle of the engine/drivetrain, I'm in the same boat with you. There's no way I can get the mythical perfect 3* angle. The transmission is as high as it can go. The bottom line is that after spending way too much time measuring angles, I just started nosing the pinion down about 1/4* at a time until it got better and then worse and then raised it back up 1/2*. It's livable, but not like stock. GM didn't put all of those soft suspension and drive train parts on the car because it was less expensive, they built the car with that stuff so it wouldn't act like a gokart or riding lawn mower. You, me, and a whole host of other people have removed all of the things that absorb all of the vibrations the car produces.

Angle of trans and rear end is pinion angle. Angle of either of those to driveshaft is u joint working angle. The pinion angle for high speed needs to be zero. We generally set -2 for hard launches due to when the rear squats you usually go positive a degree or two, but flatline high speed running the car will be basically level. Working angle is completely different, but you want it low as well but it's more forgiving. If your trans is down, and your rear end is up you have a positive pinion angle. I can assure you from experience this will create massive vibrations and is not good for the driveline. Your only correct option is to fix it.

Yup. Just make the trans and rear pinion parallel. That's zero degrees. Start there. You might end up moving the rear slightly lower to a -0.5 or something.

I'm not looking to start a war, but that did not work on my car and I have in essence, the same setup as the OP in my 2002. Setting the pinion and transmission parallel when the thing is static or even nosing the pinion down 1/2* will not get you to zero at speed with all of the various drive train and suspension components reacting to the rotational forces at play.

Parallel is a good place to start, but from there you just have to nose the pinion down a bit at a time to find what it likes. On my car, that's with the pinion somewhere around 2.5* down from parallel. However, the old Camaro is a crude piece of automotive engineering and it just isn't going to be perfectly smooth when you remove all of the oem vibration damping rubber.

You're not starting a war. Every car is different. And you're right. There is some oem rubber I left in place for that reason. Like the trans tailshaft mount bushing.

The torque arm is poly mounts.

The lower control arms are boxed stock with 1LE rubber pressed into them. I ended up finding the last 4 in existence at random dealers throughout the country.

I also have lower control arm brackets welded onto the rear end.

My car is 4" to the sub frame connectors, just shy of 6" to the rocker panel.

I have my trans shimmed as far as it will go, its now touching the tunnel. I don't understand how you got the engine level. It's not possible in my car.

I do have suspension travel left. The rear travels enough, Not sure exact measurement though.

The panhard bar is very close to being level with the ground.

Yeah, in the quest for superb handling, I guess the dampening effects go out the window.

I've had the driveshaft balanced twice as I was convinced that was the issue.. the first time the changed the weights slightly, second time no change.

I guess my biggest concern is the vibration increasing wear on vital parts and wearing shit out sooner. Should I not be concerned about this?

BTW Im glad Im not the only one who cant jack up the trans any more to get better angles :cheers:

Yep, I understand what youre saying.

My trans wont go up any further. My only option was to match the pinion angle to be the same, but in the opposite angle.

My working angle is positive 2.9 degrees at the trans to driveshaft, and 2.9 degrees negative and driveshaft to rear end. Net result is cancelled angles, resulting in zero.

This is what I have done. Net is zero.

Why would I want to move the rear down .5 degrees? The angles would no longer be parallel and make things worse, wouldn't it?

Youre not starting a war... Im looking for what others have done.

I had the pinion nosed down 1.5 degrees and the vibration was horrible. That is when I started looking at lifted trucks and that's where I learned about the net zero angle theory. It helped with the vibrations, but it's still there.

That's why I thought maybe the energy suspension mount is harder than the prothane, and switching to prothane might help me if it is more forgiving.. I thought I read a thread somewhere where people were finding using prothane was helpful in reducing vibrations.

I found that I had vibrations under load at net zero and going to -0.5 corrected it. IMO zero is always the best starting point

Everything I have seen points to zero being the best starting point as well.

I think it is important to note this isn't just an "under load" issue, It is coasting as well, or with the cruise on. It is a static vibration regardless of load on the motor.

True. How I look at adjustments is if the vibrations increase under load, I reduce the rear pinion angle. If vibrations increase on coast down I increase the angle. Usually there's a spot where everything is happy. And it's usually near zero.

I gotcha.

Well, I know that it vibrates less at zero.

It vibrates more with the rear end pointed down the 2 degrees.

I cant really adjust it up much more as its already a tight fit under there and I have clearance issues with the rear driveshaft safety loop hitting the driveshaft.

This this is impossible lol.

If your driveline angles are parallel, effective pinion angle zero and you vibe just cruising, look elsewhere...so what's left? Driveshaft weld yoke clocking, I had a driveshaft made where the weld yokes were nearly two degrees apart. Balance would check perfect every time. Have also seen pinion yokes machined off center. Also be sure the rear is centered under the car left to right.

I remember setting up the adjustable panhard bar when I installed it, but I will check that the rear end is centered under the car again.

As far as driveshaft clocking, how the hell do I measure or figure that one out?

How would I look at the pinion yoke to make sure that isn't off center?