I think any time you have the pinion higher than the transmission with the transmission pointing down it’s going to be a problem. That’s a classic example of when the transmission needs to be raised. Either that or raise the ride height.

I don't have the final angles handy right now. Donny may be able to chime in. I don't believe I had a vibration. At least I didn't notice one. The harmonic noise is what I have. It's very annoying and sticks with you when you get out of the car. Through the three different gear sets (by manufacturer) in this car, none have made much of a difference in the sound. That's why I believe at least some of it has to do with the TruTrac. The only way for me to have anything done with that is to buy another and pay to swap it in. That's rather costly to just try. I still may. It's no fun pulling the 9" and even less putting it back in without damaging the Lube Locker gasket. I'd still like to try a WaveTrac.

I did look at the 8.8 but it would not be a direct swap due to the way the torque arm attaches to the case of the 9" in Speedtech's design. That would've definitely been something I would've rather went to as I'm a fan of it. I didn't ask Donny if he saw a way to do so without a lot of re-engineering. That and rubber bushings may help at least in theory.

Finding NOS Ford gears in a ratio other than a non-street friendly ratio is impossible. I have no interest in anything over 3.25 and would ideally like below 3.0 these days.

It never occurred to me that it wouldn’t work with the torque arm.

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.

Damn, I have 3.70 gears for my Buick 9 inch…. :bang:

Don, hope you're one of the lucky ones that gets a quiet setup. While I'm at it I'm hoping mine are quiet too... :lol: :thumbsup:

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.

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... :lol: