Time for another Cal Trak Thread? (Long)

So my question is for you Cal Trak users what pinion and Trans angle did you end up with that is working and vibration free?

As some of you know my 68' road runner has been back out of retirement for a year now and I have A small vibration that I can't get rid of, here is where I am at.
The engine /trans is -3.5* (trans is pointing 3.5 down) I think my main vibration is coming from the front u-joint it comes in around 110 mph and lasts till the end of the run (10.5 @ 126mph), then gets quiet for a few seconds and then goes through a few seconds of vibes as it slows down (probably pretty much following the acceleration vibe but from 126 to 110) . The rear pinion is at 0* which I would think would put me in that 2-4* range that Calvert suggests.
I have always had my Cal Traks set up with about 1/2 turn of preload in them, someone at the track suggested that a lot of the stock eliminator guys are running about a 1/8" air gap (so no preload).
I tried that for a couple runs and my vibration got louder, I noticed when you go from nuetral to 1/2 turn of preload on the CT's it is rolling the pinion down 1/2 degree or so, so that tells me the vibration is going away with more negative angle on the pinion but when you do this it will put me way out of the 2-4 degree suggested angle and would be around 6* is my guess? I would shim the trans up but have no room to do so with the CSR trans shield as it is against the floor.
At times the rear sounds like it is climbing up in the car if that is possible but I don't think it is with the CT's? The dana 60 has no snubber to keep it off the floor as it was a truck rear with no tapped provision for it.
If it is due to the tranny being to down at 3.5* I might be able to lower the motor some but trying to avoid that.
I will also add that I have had my driveshaft balanced twice with no difference or improvement.
So any suggestions and where did your angles end up?

Keith

If your angles are good I would say replace the bushing in the rear of the trans and check the pinion. How much does the driveshat pull out of the trans? Also maybe try to let out of it when it is vibrating and see if it stops. That would tell you if it is rear pinion angle needing to rotate down.

You might want to check the length of your driveshaft and has it ever been balanced. I would say it has to do with the clearance of the driveshaft in the trans tailhousing. When you change the preload it will change how much the driveshaft is in the tailhousing. If you know of a good chassis shop it may be good to get the car scaled with you in it to get the appropriate amount of preload and check the driveshaft length and maybe make sure it is in balance.

Every car is a little different so what works for an a body may not be the same with a B body. I always had good luck with the bars barely touching in my roadrunner. I was running an 8' converter and it was setup to flash between 5200-5,400 in my 499.

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If your angles are good I would say replace the bushing in the rear of the trans and check the pinion. How much does the driveshat pull out of the trans? Also maybe try to let out of it when it is vibrating and see if it stops. That would tell you if it is rear pinion angle needing to rotate down.

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I have been thinking of checking out the rear bushing and thought I would see if anyone suggested that.
To add to my initial post I would say that the acceleration noise is from the front u-joint or tail shaft and the initial deceleration noise is from the rear u-joint, and I believe I read some were when noise comes upon acceleration roll the pinion down a few degrees and when It comes on decel to roll the pinion up? I have tried rolling it up and down a little and the noises stay consistent so very well could be the rear bushing or maybe needs rear roller support for what (speed) the car is going?