Bad a833 vibration with rebuilt tranny

General Mopar Tech Discussions

  1. Fran Blacker

    Fran Blacker FBBO Gold Member FBBO Gold Member

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    Rebuild trans did they change tailshaft bushing? Driveshaft vibration started at 3000 rpm. Removed bushing .013 clearance. tb1.jpg
     
  2. 747mopar

    747mopar FBBO Gold Member FBBO Gold Member

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    I had the same problem a few years ago (60-70mph), ended up being the pinion angle. I first tried a 1.5 shim with no change, tried 3 degrees on the next try and voila gone. Not saying this is it but it can definitely cause the problem your having. Like you I started with the tires, driveshaft and yoke with no luck. Something else to check is the universal joint C clips. I had one that had a lot of side to side play, turns out there was a couple options on C clip thickness where using the thinner ones allowed to much play.

    On the pinion angle... If that's what it is you can tell which way you need to go with it by doing a few driving tests. Once your at the speed it does it nail the gas, try again only next time let off of the gas. If it needs shimmed up it will get better while your on the gas and worse letting off because the pinion climbs on acceleration and drops when unloaded. Typically for this to be the problem there's issues elsewhere, poorly made springs, weak fatigued springs, missing leaf clamps, alterations to the spring mounting locations, bad bushings, perches welded on incorrectly to the axle, etc.
     
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    • dvw

      dvw Well-Known Member

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      Nope. I'm going to build another trans and see if that fixes it. A few years ago, well many years. I did a burnout and cracked the tail shaft. It may have bent the output shaft.
      I'll see when it comes apart.
      Doug
       
    • Outlawd

      Outlawd Well-Known Member

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      Interesting, your the 3rd person I have talked to that solved there vibration problem with new tires......
       
    • Meep-Meep

      Meep-Meep дворянин

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      I'm still chasing a vibration at around 3-3500 RPM with a Passon OD gear set. My next move (after all the usual suspects) is to toss in a different tranny.
       
    • DaneBisel

      DaneBisel Well-Known Member

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      Did the engine perform fine before? Are you sure you have the right flywheel? Could be externally balanced with a forged crank or vise versa. Just a thought
       
    • Outlawd

      Outlawd Well-Known Member

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      Well, here's the story of the car I'm helping with. 1968 Coronet with a 440, 4 speed, 8 3/4 open with 273 gears. Drove great no bad vibrations that he recalls, maybe at high speeds but never really drove that fast anyway. The 440 was kinda tired but still ran ok. He installed a beautifully restored complete drum to drum 8 3/4 rear end with suregrip and 373 gears. Shortly after this the car picked up a bad vibration at around 55 mph. Keep in mind this rear end performed perfectly in the car it came from and 55mph now is alot more rpm's than before with going from 273's to 373's. So the goose chase...is it rpm or mph problem.... starts with parts replacement in this order...new harmonic balancer, new tailshaft bushing, new professionally built driveshaft and yoke, pulled the tired 440 and rebuilt high performance now with balanced rotating assembly, new clutch, new pilot bushing. After all this the vibration is exactly the same. only thing left is the tranny but it sounds quiet and shifts great. Honestly don't think its rpm related as it has no problems around town in the lower gears with higher rpms. Because this problem seemed to have started with rearend swap I'm thinking what "747mopar" said, pinion angle issue?
       
      Last edited: Apr 23, 2021
    • Meep-Meep

      Meep-Meep дворянин

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      Tolerance on pinion angle is 1/2 degree. Look at the tailshaft bushing again. I have written extensively on this through another member on moparts. If you have any perceptible up and down motion it will grumble (make that sound). I made my own tail shaft bushings that proved successful.

      I'm fighting a similar thing with my 69 RR and so far have even balanced the aftermarket pinion yoke myself. I rebuild high speed vacuum pumps so have balancing equipment at my disposal. Everything I did helped but the grumble is still there. Final step is to pull the Passon geared 833 and swap with one of my other non OD units. But what I plan to do first is to run the engine at speed with tranny in gear but no driveshaft. Just a slip yoke (while taking steps to make sure it doesn't slide out at speed). I also have vibration monitoring equipment and can really dig deep into this issue.
       
    • 1967coronet

      1967coronet FBBO Gold Member FBBO Gold Member

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      I have to lean towards a tire issue myself.
      Very few tire installers today will take the time or effort to find the (sweet spot ) on a tire , wheel combo.
      Instead of breaking down the tire and moving its location on the rim they just keep nailing / sticking weights on until the machine shows 000.
      Look over your wheels and see if you have much weight in one area.
      Also like posted before try swapping a set on from a buddy for a test run .
      No doubt there are a million things that can cause a vibration.
      I have chased the same animal myself.
       
    • ckessel

      ckessel Well-Known Member

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      When I worked at a shop down south, we had two vehicles with reproduction tires that had vibration issues. Both customers supplied their own so the shop was not liable to cure the issues. On both, they both wanted to use the stock steel rims. The rims were not true due to age and production tolerances from the era. Both sets of tires were not round. They would "balance" but would still vibrate the vehicles. You could see the movement on the balance machines plus it would give you runout measurements. The owners just had to put up with the issue since they didn't want to shell out more money to correct the vibration. That was the only time I've personally been involved with repro tires and I'm not impressed.
       
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