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Discussion Starter · #1 ·
Greetings, hope you can help....for the background on the car, here goes....
67 Chevy II 2 door sedan, 60,000 original miles
383 12.5-1, on race gas
Mechanical .555 lift cam (valve lash good-triple checked)
Speed Demon 750
Fuel Pressure good, oil pressure good, motor is broken in and seems to run very well

Tranny- TH350 with Cheetah full manual valve body, and 3500 Stall, Tranny rebuilt about 4 years ago, and just now installed, shifts well-firm and prompt....Trans folks felt (at that time) the stall converter was mediocre, but would work "for awhile"

Currie Ford 9 inch, with Detroit Locker and 4.10's, about 3000 miles on whole works, appears to be good......

Ok, got the car back from the exhaust shop and gave it a drive- first time in 10 years.....In general driving, it seems ok, ....when you punch it, I get severe (jarring) vibration, from center of car.....it also feels like only about 50% of the power is actually making it to the pavement under full throttle....skinny tires don't seem to even break loose, car is not accelerating like it should....engine sounds good and seems to run good, but hard to tell with all the shaking and vibration going on....and by the way, THIS IS NOT WHEEL HOP!

I am open to all thoughts, I am wondering if this could be a bad Torque Converter.....but not excited to spend the money on one, just to find the problem is still there......Please Submit Your Thoughts Trav
 

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Discussion Starter · #2 ·
I ahould also mention, driving down the road at 35 or so, i get a fair amount of vibration although not as severe, and when decelerating from 35 it seems to vibrate excessively again, but not near as bad as under heavy acceleration
 

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Discussion Starter · #4 ·
If it hasn't been driven in 10yrs I would jack up the rear in neutral and make sure everything is moving freely.

Could be the brakes dragging or u joints from sitting so long.

Just my 02.
Thanks, but have had it jacked up, run in all gears, and brakes are working properly......U-joints, remote possibility, gonna take out the driveshaft, and check them and have the balance checked, but am leaning toward converter or trans issues......wondering if anybody has had a converter act this way before.......
 

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Discussion Starter · #6 ·
when driving does it go away when you put it in neutral?
if you are asking while going down the road, if i slip it into neutral? That I can't say that I have specifically tried, and I have only driven it a few miles total, out of fear that something will really disintegrate.....when in neutral or in park (stopped) it doesn't seem to do it......
 

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Drive shaft binding?

Plug wires correct? Seen the 5-7 cross do this!


It honestly sounds like a engine balance problem.
Seen a lot of mistakes when building a 383.
Lot of different crankshafts with internal or external balance.

AL
 

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Like Al mentioned, I would drive it down the road. When it begins to vibrate noticably, slide the trans into neutral and see if it immediately quits. Does it intensify as the speed goes up? When you moderately free rev the motor, does the motor shake?

Tiny
 

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I had a B&M converter shake like crazy once. It also caused some tranny issues as well!! Had the converter flushed and went through the tranny a second time and still had the same problem.:rolleyes: I replaced the converter and went through the tranny AGAIN and the problem was solved.

My problem was under a heavy load only. Part throttle and cruise was no problem regardless of speed.

I'd still check all of the easy stuff first. The tires could have flat spots from sitting too long and the u-joints could easily be causing a problem as well but both will be SPEED sensitive, not load sensitive.

Like BigAl mentioned, It could easily be a balance issue in the engine or a firing order swap as well.

Happy hunting...:rolleyes:
Good luck!
 

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I'd check to make sure your drive shaft length is correct. If your yoke is wrong or if not inserting enough or even too much into the back of the trans, that can cause this type of problem.

Another thing to check and perhaps the first thing to check is that the U joint is properly seated in the rear end yoke. I have seen them improperly installed where they did not seat and were tightened slighly offset. Needless to say this will cause a vibration.

It costs nothing to eliminate these items as possibilities.
 

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Discussion Starter · #11 ·
Drive shaft binding?

Plug wires correct? Seen the 5-7 cross do this!


It honestly sounds like a engine balance problem.
Seen a lot of mistakes when building a 383.
Lot of different crankshafts with internal or external balance.

AL
I will doublecheck the first two things,, as far as engine balance, when in neutral it seems ok, you can throttle it and it runs great
 

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Discussion Starter · #12 ·
I'd check to make sure your drive shaft length is correct. If your yoke is wrong or if not inserting enough or even too much into the back of the trans, that can cause this type of problem.

Another thing to check and perhaps the first thing to check is that the U joint is properly seated in the rear end yoke. I have seen them improperly installed where they did not seat and were tightened slighly offset. Needless to say this will cause a vibration.

It costs nothing to eliminate these items as possibilities.
Thanks, I am planning on pulling the driveshaft, and verifying these things as well as the balance
 

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Discussion Starter · #13 ·
I had a B&M converter shake like crazy once. It also caused some tranny issues as well!! Had the converter flushed and went through the tranny a second time and still had the same problem.:rolleyes: I replaced the converter and went through the tranny AGAIN and the problem was solved.

My problem was under a heavy load only. Part throttle and cruise was no problem regardless of speed.

I'd still check all of the easy stuff first. The tires could have flat spots from sitting too long and the u-joints could easily be causing a problem as well but both will be SPEED sensitive, not load sensitive.

Like BigAl mentioned, It could easily be a balance issue in the engine or a firing order swap as well.

Happy hunting...:rolleyes:
Good luck!
I think we are on the right track with the converter, somebody else recommended i check the flywheel, but what you described with your B&M converter sounds just like my problem.....sorry for your troubles, but in a way I am glad to hear somebody else had converter troubles like mine!
 
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