RealLiveMD

iTrader: (1)

I used the bmr torque relocation to take the stress off my tailshaft. Now I feel a lot of vibration at high speed and when off the throttle. I have some bushings for a swaybar. I'm thinking of buying longer bolts and using these to buffer the vibration. Has anyone done this? Are the vibrations wnl???

01ssreda4

iTrader: (96)

Have you measured you pinion angle, it may need to be adjusted slightly.

RealLiveMD

iTrader: (1)

I'll recheck it but i got -2 initially. maybe the shocks hadn't compressed completely
The vibration is most apparent when not under load.

RealLiveMD

iTrader: (1)

Looks like its at neg 4 but I used red loctite on my lock nuts. I can't break it a loose. Will have to use torch in am. Gonna go for neg 2

01ssreda4

iTrader: (96)

Let me know how it turns out. Im chasing a vibe that started with a relo crossmember. I've replaced the tranny, DS, and rear end and its still there. I never checked pinion angle during the swaps though

dlandsvZ28

Find a hoist where you can drive the car on the hoist and run it up to about 25-30 mph.

I think you find that it is your front u-joint that is vibrating bad. You will be able to see it from under the car.

It's cause? The tranmission is too high causing the front u joint to be out of phase with the rear u -joint.

For me - a Yank transmission crossmember was the culprit - it was too low by a half inch - so we added spacers between it and the tranmission (A$) to gain the extra half inch. The vibration when away.

I reinstalled the stock crossmember - problem solved.

So why the Yank crossmember? I wanted to try a tunnel mount torque arm instead of my articulating Spohn torque arm which can be annoying and noisey.

But IMO I couldn't get the (won't mention name) torque arm to unload after acceleration and it would cause vibration. Stop the car with hard braking which would force the TA to unload and the vibration would go away.

IMO the TA just wouldn't slide back and forth in the poly bushing that was mounted on the Yank crossmember.

To fix I reinstalled the stock crossmember and reinstalled the Spohn TA and set my pinion angle at -1 degrees. No more vibration - although the annoying clunk when stopping at stoplights is back. Plus the Spohn TA with driveshaft loop is one heavy mother.

But the clunk is solveable by tightening the lower nut on the lower articulating bracket just a tad. Problem is that it needs to be retightened periodically and it is very difficult to adjust when the car is on jack stands instead of a hoist.

http://www.flickr.com/photos/1835930...57623345499537

Note: I still think these TA's could be built with lighter components and still not break with 5 - 600 rwhp. As I said above the Spohn is very very heavy. Sure would be nice if it was lighter.

RealLiveMD

iTrader: (1)

My vibration is driving me crazy. I'm at -2 to 2.25 pinion angle. I will adjust down to -1 this weekend. My vibration is when the clutch is engaged or speeds above 80mph. I took it up to 110 today and even though the car was stable it felt as if I was in one of those vibrating beds that you put quarters in. As far as the torque arm relocater. I'm using BMR. Don't know if I need to try to lower the trans or get it to move up

guppymech

iTrader: (7)

You would think that these companies that make the relocation trans crossmembers would design them to position the transmission mount in exactly the same spot as the stock crossmember. It's threads like this that are keeping me in my stock junk.

dlandsvZ28

What I finally had to do was start at zero which is stock and then went negative until it started vibrating. Since I will be doing little if any racing I went back to -1.

I will also be driving on Nitto's (not the 555r's or NT05') that don't have a lot of traction. So for me it's doubtful under any circumstances that from a dig or hard accelleration that I would go positive a full 2.5 degrees (such as your setting) to get to zero or even worse go to plus 1 which would be a full 3.5 degrees. With a dead hook and a lift of the front end off the ground - yes - but not many of us can do that.

IMO - 2.5 might be a little much dependent upon your circumstances.

As for the level of the tailshaft housing in relation to transmission crossmember - the tranmission mount bushing might not be the correct height either. There are separate threads you can search about this very issue. Not all aftermarket bushing heights are equal to the height of the stock rubber bushing.

Before working on the car again - I would do a full search on pinion angle and read every post.

Figure 3 in this 'How To' explains how to measure and adjust tranmission angle if you think it might be off a little bit. This is what I had to do (shim) when I had the Yank crossmember which was too low causing front pinion angle to be incorrect causing a terrible vibration. Once that is corrected, next step is to get rear pinion angle correct.

http://www.hurst-drivelines.com/file...roc_111606.pdf

dlandsvZ28

And you would think aftermarket companies that make transmission mount bushings for a particular make, model, and tranmission would make the bushings all the same height as well - but they don't.

Unfortunately, it's the price we pay, when we install 500 -700 rwhp engines in cars that were designed for less than 325 rwhp.

RealLiveMD

iTrader: (1)

-1 helped a lot. Weird thing is that my angle was actually a positive 1 at first. It Seems that the reading that I got when had the rear axles on jackstands was different than the reading with the rear tires on ramps.

dlandsvZ28

When measuring pinion angle the suspension must always be loaded (entire weight of the vehicle on all four wheels either on ramps or on the ground) per instructions. Obviously it would be difficult to measure and set if the car is on the ground unless you had access to a shop with a pit.

"Note that the car does not need to be level; however the car’s weight must
be on its suspension."

As for positive and negative -always make the readings from the driver side.

RealLiveMD

iTrader: (1)

I couldn't leave well enough alone, So I went out and set the pinion angle to -2 and vibrations. returned. I'm going to go back to neg one. I also noticed my driveshaft yoke angle are way off. It seems that my transmission is sitting too low with my bmr relocation kin. the rear angle is a -4 the rear is pointing down. The angle on the u joint going into the trans is 8. with the u joint point down toward the front of car.

dlandsvZ28

Seems as you have the same issue as I did with my Yank transmission crossmember. As I recall it was to low by a 1/2 to 3/4 inch. To fix I had to place shims (big thick flat washers) between the mount and the transmission stock rubber bushing.

From the instructions posted earlier in link above.

"Front and rear ujoints should not be allowed to have operating angles of more
than ½* apart from each other. An example would be the front joint being 2*
down while the rear u joint is 2-1/2* up. A greater angle than this will cause some harmonic vibration."

With my car on the hoist it was quite a sight to see the front of the driveshaft vibrate as much as it did at 30 mph on the drive on suspension loaded lift we used.

You will have to shim the mount to get it back to within the tolerances suggested in the 'How To'. I would go for zero tolerance to account for the motor mounts as they degrade over time.

It would be interesting to know how they made the measurements when building the jig.

Was it a with car with new motor mounts, used motor mounts, solid motor mounts or an aftermarket k member, etc. ? Was the engine supported or was the engine unsupported and left to hang out where it normally does when the car is supported at the lift points, or was the car on a drive-on hoist with car supported by it own weight?

A half inch sag isn't a lot.

hth - good luck I think you are on your way to getting rid of your vibration.

01 ss vert

iTrader: (1)

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