Driveline angle questions with Speedtech components

[cpd004]

Originally Posted by dontlifttoshift

When we were done with the tunnel and raising the transmission in CPDs car, working angles were 1.2* front and rear. Thats about as ideal as it could be.

Before we raised the tunnel and the car still had the 10 bolt when we initially set up the torque arm, working angles also matched but we were a tick over 2* and it was a lot of work to get there with the torque arm as we needed the roll the pinion down to get there.

We did a FN88 in a 55 chevy. I purposely put a 3.70 in this one as that is notoriously the loudest 9" ring and pinion. Rear end is dead quiet, I was elated. There is no easy way to make that work with the SpeedTech torque arm, but it's not impossible. It would also need new axle as the center line of the differential is different.

Currently doing a 67 Camaro with a S197 8.8 and a quadralink. As I reassemble my car it is also geting a S197 8.8 and a quadralink. Also setting my car up with a Cortex torque arm so I can make some comparisons but that's a different thread.

The angles did seem to smooth things out somehow. At least that’s what I thought upon that first drive when it returned.

In my opinion only, it’s not just the gears. 3 different sets by 3 different manufacturers and 3 shops. Either they’re all no different from one another, this is just common with all torque arm 9’s and/or it’s that TruTrac. The only parts that did not go back were the axles. Nothing obvious was found there. I do regret not at least having them looked at.

The FN988 is around $2800 with associated parts last I looked. Plus new axle and the fab work would be an extremely considerable investment. I believe I’d need both axles as if I recall correctly I have 35 spline and not the 31 needed for the 8.8.


I’d be happy to offer the car as a test mule for development to adapt the 8.8


Coincidentally all three shops found things they did not like as done by the previous shop when tearing down the center. I was hopeful each time one found the culprit.

[dhutton]

Originally Posted by cpd004

The angles did seem to smooth things out somehow. At least that’s what I thought upon that first drive when it returned.

In my opinion only, it’s not just the gears. 3 different sets by 3 different manufacturers and 3 shops. Either they’re all no different from one another, this is just common with all torque arm 9’s and/or it’s that TruTrac. The only parts that did not go back were the axles. Nothing obvious was found there. I do regret not at least having them looked at.

The FN988 is around $2800 with associated parts last I looked. Plus new axle and the fab work would be an extremely considerable investment. I believe I’d need both axles as if I recall correctly I have 35 spline and not the 31 needed for the 8.8.


I’d be happy to offer the car as a test mule for development to adapt the 8.8


Coincidentally all three shops found things they did not like as done by the previous shop when tearing down the center. I was hopeful each time one found the culprit.

Based on everything I have read it’s the gears. They are all noisy. Just some worse than others. Your torque arm with solid mounts may be amplifying the noise.

[dhutton]

Would be interesting to calculate the resonant frequency of that torque arm. Last time I did that was 45 years ago in university.

[camcojb]

Originally Posted by dhutton

Would be interesting to calculate the resonant frequency of that torque arm. Last time I did that was 45 years ago in university.

You're definitely a brainiac Don...

[dhutton]

Originally Posted by camcojb

You're definitely a brainiac Don...

Ya no… . I was navel gazing and wondering if the resonant frequency of the arm was anywhere close to the driveshaft or axle speeds.

We need a real engineer like Stielow to weigh in… . Or Donny likely has an idea on this.

[cpd004]

Originally Posted by dhutton

Ya no… . I was navel gazing and wondering if the resonant frequency of the arm was anywhere close to the driveshaft or axle speeds.

We need a real engineer like Stielow to weigh in… . Or Donny likely has an idea on this.

Stielow is an FN988 guy as well in his latest build.

I believe they tossed around a few ideas at Donny's shop. Ultimately it would have been a trial and error and see what works thing. If he does think of something to try, I'd be all for it.

I would not go Speedtech for the rear again. Go Detroit Speed. The front is another story.

[cpd004]

Donny, if you have both the 9" and FN988 can you post a side by side? Interested in how much more aside from the pinion support would have to be made to swap the 8.8 into the Speedtech torque arm.

Are the bolting locations in the same place (distance) from base of the housing?