Pinion Angle/Tailshaft Bushing

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Yeah that is what I kindof suspected.
I once put a 340 cam and Xheads into/onto an otherwise stock 73 teener. Yeah with 2.76s that was a bit of a disaster. It had great passing power on the hiway, but out of the gate,To say it had"slightly less low end torque" would be too kind. It flat out sucked. The addition of a 2800TC improved things a bit. But when the 4.10s went in well, that was the magic. I won't ever do that again.
When that Dart died, I pulled the powertrain and junked the rusted hulk, which today would still fetch good coin. But in the late 80s who could have known.....
So fast forward 20 years or so, and in 2000 I un-mothballed that same engine.I yanked the 340 stuff in favor of the teener equivalents. I freshened up the rings etc. and plopped it into my FormulaS clone as a winter engine.( I used to pull the 367 every September and go thru it in the snowy season). Some years it had an auto, and some it had a stick. Sometimes a 3.66 low and sometimes a 3.09od and sometimes a 3.09od and a GVOD for a double od. One year it had that 2800TC and 3.55s . Of course it had the TTIs on it and a small-port intake with a TQ on it. It was still the 8point something factory compression.And I put some 360valve springs in it, (or 340, not sure), with the 273 rocker gear. I still have this engine.
Well I'll tell you, that lil teener surprised the dickens outta me.Best lil teener I ever had. It was so sweet, I just hadda mess with it. Every May I pulled it out and stuck the freshened 367 back in. So then,I would contemplate the next winters combo. One winter,I put an A999 in it with the wide ratios and a semi-auto shift kit in it, that allows both auto mode and full manual. And then, Then, I put 2.76s in it.
Now if you have never heard a mellow 4 barrel teener running WOT, in high gear, from 20mph to 65 mph, screaming obscenities at me through full-length dual 3 incher exhaust and Dynomaxers, Man; I can't tell you how sweet that sounds. That is just one long pull at one rpm!
I used to nail it from a stop, get her into 3rd by 20 or earlier, and then, let that TQ moan, for what seemed like forever.65mph was still near 2800.Hyup, that brings me a huge smile just remembering it. The starter gear with the A999 was 7.56, and with a 2800TC, and with the teener top-end back on, she had plenty enough giddy-up for a winter motor.That combo pulled about 75/80 mph still at 2800ish.
I mean imagine the dyno-operator pulling the stick, and keeping the Rs at 2800 for about 14 seconds,lol. That poor teener! I used to torture it so bad.
One winter I had the od/GVOD combo in it with 4.30s I think. That teener pulled the od ratios all by themselves, but I had set the GVOD up as a splitter. The starter gear was 13.29, and double OD was 2.45. Well with that starter gear, the teener hits shift-rpm real quick. I used to shift it at 5000; sometimes 5500, just because.
First topped out at about 30mph,and 1st-over at 39. Second was 56, and 2nd-od was 72. Third was 94, and 3rd-od was 120. But I rarely went past 72@5500; That was 4 ratios........ 65mph was a tic under 2000,lol.
I gotta tell you, a teener with 4.30s, and split-shifting, is pretty neat.
Those winter combos were not fast. Nor quick. But it/they were hands down,the funnest I ever had. They were not about being fast or quick. They were just about being mellow.
I stopped doing that after the 5th winter or so. The 367 was no longer having issues, that I was catching in the nick of time. And she was in her final iteration. I was no longer broke; the kids were on their own, and doing well. I bought a second car, and no longer needed the S for winter. Hallelujah, no more swapping powertrains.
I still miss that teener now and then.............
But 93 in the 1/8 is funner,lol

That all sounds like good fun to me. I've had some good street fun with nice mild 318s. Mines a little rough revving as mentioned, but I think a lot of that is just poor quality replacement motor mounts.

Drove it out to Van Nuys Blvd cruise night tonight and still out right now. Came to conclusion with my phone speedo that 70 mph is 2500 rpm. And actually, the vibes seem to smooth out at that speed and rpm. 2200 is more like 62 mph where it's still a bit rougher on the occelation/resonating vibe.
 
Just wanted to update. Same existing problem still exists. Driveline angles are even closer now. Got brave the past few times and brought the revs up on the highway in 4th/OD to 2600-2700, which is about 72-73 mph. Oddly, the grumbling minor vibration seems to smooth out some at that speed and it is substantially quieter; not gone, but quieter.


With that said, I am beginning to wonder if the newish motor mounts are just subpar at dampening noise and vibration, and/or the same for the trans mount. Other than that, the only other feasible potential cause in my mind for the issue (which is most present from 2100-2500 rpm in 4th/OD) is the tailshaft bushing.


Who knows, maybe in the end, with everything checked off of the list, there might always be some of this noise/roughness present at the noted engine speed in 4th/OD with this A833 OD trans and the associated 3.92 gear. I put 250 miles on the car this past weekend, half being highway miles, and the severity never varied or changed.
 
Just wanted to update. Same existing problem still exists. Driveline angles are even closer now. Got brave the past few times and brought the revs up on the highway in 4th/OD to 2600-2700, which is about 72-73 mph. Oddly, the grumbling minor vibration seems to smooth out some at that speed and it is substantially quieter; not gone, but quieter.


With that said, I am beginning to wonder if the newish motor mounts are just subpar at dampening noise and vibration, and/or the same for the trans mount. Other than that, the only other feasible potential cause in my mind for the issue (which is most present from 2100-2500 rpm in 4th/OD) is the tailshaft bushing.


Who knows, maybe in the end, with everything checked off of the list, there might always be some of this noise/roughness present at the noted engine speed in 4th/OD with this A833 OD trans and the associated 3.92 gear. I put 250 miles on the car this past weekend, half being highway miles, and the severity never varied or changed.

Put it up on jackstands. Run her up into top part of the vibration zone. Put her in neutral and let the driveshaft rpm come back down thru the zone. Still there? You know where to look; not in the tranny.
 
Put it up on jackstands. Run her up into top part of the vibration zone. Put her in neutral and let the driveshaft rpm come back down thru the zone. Still there? You know where to look; not in the tranny.

Yep. Pretty convinced it is one of the mounts being hard or poor quality, something vibrating on something else. Worse case, maybe my driveline angles still aren’t quite perfect
 
The pinion angle is only ever close at one level of power input. Whn you are off the gas it is one number, and when you are launching with maximum traction the springs could be all wound up and the pinion angle is g-o-n-e thru the roof.At all power and traction settings in between, the pinion angle will be between these extremes. With a sprung axle, there can be no one perfect angle
BTW, don't forget, the driveshaft may also not be parallel to the centerline of the vehicle,lol.
 
I don’t see an issue with driveline parallelism to the vehicle centerline. What is more likely is one of the motor mounts sitting higher than the other in my case.


After lots of time to determine exact symptoms, the problem isn’t really noticeable on acceleration or amplified on deceleration (only noticeable on deceleration when coasting down from the speed/engine speed that it is most noticeable at). Definitely most noticeable when achieving a steady speed of 55-70 mph in 4th gear, which is 2000-2600 rpm. If acceleration out of that range, the grumble doesn’t seem magnified. Lastly, above 2600 rpm/70 mph, the grumble from the front is less noticeable altogether, anywhere from the shifter handle, steering wheel, and through the accelerator pedal.
 
and through the accelerator pedal.
the gas pedal is not physically connected to anything vibratory except maybe the firewall. If the firewall is vibrating,could it be that your engine torque-strap is too tight?By that rpm the engine should be dead-smooth.
About the only other thing that can send vibration into the chassis that strongly, would be an out of round tire. But that never gets better. Just worse and worse til you can't stand it anymore.lol.
On thing that does get better is a natural body cadence, which usually gets just noticeable at 55, worsening to mid 60s then getting better again. All my Barracudas have done this, no matter what engine,tranny, or rear-end was in it.The worst was actually a slanty/904 with 2.71s. But is was stimulated by the N50-15s humming along back there. 60mph was dreadful. 55 was bearable,65 better and by 70 it was smooth sailing. AFAIK there is nothing you can do about a vibration like that;except not stimulate it.
 
My '68 suffers from a vibration that begins around 100 mph and gets worse up through 140mph. It's bad enough that I have not exceeded that speed. It's silky smooth at all speeds up to that. Interestingly, if I coast at 100mph and let it slow down to 95mph, it goes away. It also goes away at 100mph to 95 mph, if I put light pressure on the throttle. That indicates it wants a bit less downward pinion angle. I do have slapper bars with the snubber slightly touching the front spring eye to limit the rotation.

I used the special tool to replace the tailshaft bushing in my transmission with it in the car. It took about half an hour with the tool to remove and replace the bushing. It cost about $150 US. Tire balance has been checked several times too.

My trans is at 0 degrees, the pinion is down 2 degrees in relation to that. Driveshaft has been checked for balance and my local driveline guy says it is dead on. The input yoke is a forged Mark Williams unit. I believe the clearance is still excessive between the yoke and the tailshaft bushing as I can move it with a bit of effort.

If I could get an accurate measurement of the inside diameter of the installed tailshaft bushing, there is a local shop nearby that repairs aircraft and production machinery. They could hard chrome plate and build up and surface of the yoke and then finish grind the yoke surface to any larger diameter I spec. Does anyone know what the ideal clearance is?

Once of the problems I have is figuring out how to accuratly measure the bushing with the output shaft of the transmission in the way.
 
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