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Driveline vibration/pinion angle?

5K views 10 replies 7 participants last post by  TommyK 
#1 ·
Just looking for suggestions, I feel like it's pinion angle causing my issue, but wondering if there's anything else it could be...Here's the issue: Cruising down the hiway at anywhere from 45 mph on up, I get a weird, "oscillating" type vibration coming through the entire car. It's not a constant vibe, it's kind of on it's own frequency that comes through about every other second or so. If I let off the throttle, the car then vibrates worse on decelleration, and then it's a constant vibe until I stop. It's done this with it's old engine/tranny combo-351 Cleveland/C6, and it does it with the big block/C6 combo in it now (different C6 trannys behind the two engines, obviously). I've had 3 different driveshafts built by 2 different guys in the thing, too. The last one, the fella said "if you've got a vibration, it's not this driveshaft, I guarantee that"....and I'm apt to believe him. U joints have been replaced at same time as driveshaft replacements. Engine mounts for both combos have been stock motor mounts and the same stock trans crossmember used for both. Tires have been replaced and rebalanced, as well. Does this sound like a pinion angle issue to you guys, or am I missing something else? Anything else I should try? I was going to try and shim the trans up to change it's angle in relationship to the pinion and see if it gets better from there. I feel like the pinion probably needs to be angled "up", because it get's worse under decel, when in my mind the pinion would be dropping lower. Does that make sense? And if so, are the pinion angle shims a guy puts between the leaves and axle tubes the best option? Long post, but just wanted to get all my info out there. Thanks for your time,

Lucas
 
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#2 ·
The pinion shaft should be at the same angle as the tranny shaft.
 
#3 ·
Thanks for your reply. I'm with you there, got my angle finder and going to climb under it tonight. Was really just checking to see if I'm missing something else that it might be, something I'm looking over that can do the same symptoms. And, quite frankly, I've never driven a car that had the angles wrong, so I don't know 100% if the pinion angle would do this in the first place.....

Lucas
 
#4 ·
Your pinion angle should be set to the equal but opposite of the angle of the tranny output shaft compared to the drive shaft.

Here is a graphic (thank you Car Craft) to show you what I'm talking about:


And here is the Link to the Car Craft article on how to adjust the pinion angle.
 
#6 ·
Had the gears put in by a younger friend of mine when he was in high school for a shop project, and of course the lash wasn't correct after that. Whined pretty bad. Removed it and had it re-set up by a professional who now works for NASCAR....that was years ago, and the whine never fully went away, which he told me at the time would be the case from the first improper install. I have another known good 3rd member sitting around with 2.75 gears that I was running in my station wagon....I was going to slip that in just for fun to see what the car acts like with highway gears in it. Guess it'll be a good experiment for the vibe issue, too. Thanks for the reply,

Lucas
 
#9 ·
Yes, same yoke. IF, and that's a big if over the last 15 years, I remember correctly, I got a new one when I went to the C6 behind the Cleveland, because it was originally an FMX. I'll check that, too. I do know that I've had the driveshaft in and out about 4 times when I was putting the engine in (long story you can read about my perils in my build thread if you want) and all seemed tight. Haven't gotten a chance to climb under it this week yet-been at work from 7 A.M. till after 8 P.M. all week and just burned out when I get home. Thanks for the help fellas....and can someone that knows answer if the pinion angle being wrong would cause this kind of vibration? Haven't gotten a clear answer on that yet. Thanks again, really do appreciate the help.

Lucas
 
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