Driveline Vibration

[philo_beddoe]

No vibe at all under a hard acceleration or high rpm like driving in 2nd gear.  It peaks right at that point between accel and decel.  What does this tell us?


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[VileZambonie]

Excessive backlash does not cause vibration. Incorrect gear tooth contact will as will worn bearings.

[philo_beddoe]

I bet it could be one or both of those. When can we [you] address that? No one else around here seems to know what they're doing.

[gwcrim]

I've been reading this thread with curiosity.  I have a vibration on my C10 as well. I think I know where mine is coming from though.  Ever since I had new 3.73  gears and a posi  installed there's been a vibration around  75 mph.  At this point I've replaced the entire drive train from the radiator back.  Hard to believe that a brand new set of gears or a new posi would cause vibration but that's what has to be doing it.

I'm rarely out on the highway to hit 75 for long periods but last weekend I took a road trip. 300 miles of interstate. The vibration comes on around 73 and goes away around 77. Sometimes it's bad, sometimes not.

I'm 95% sure it's my brand new rear end.  You've checked everything else.  Have someone check that.

[philo_beddoe]

The only thing i have not addressed is the rear diff or rear axle assy.  I have never gone past 65 mph, this vibe can be felt from between 30 and up, i would say peaks at 40-45. I dont feel it in 2nd gear or at hard acceleration. Weird is, sometimes it is so light, i can hardly feel it, but then come to a stop sign and start up again and there it is, or get to a hwy and get up in speed and there it is. It is not uniform and consistant or constant. But generally its always there. I'm seing a shop next week that will not charge unless problem is found 100%. We'll see.

[philo_beddoe]

May have broken a little ground. Jacked rear wheels and found perhaps lots of play turning clockwise and counter and a bit pushing wheels in and out. Also put in drive and gave it gas, and sure enough, felt vibe.

I guess this modern video from chevrolet motor division explains the basics on limited slip.

https://m.youtube.com/watch?v=K4JhruinbWc

[SkinnyG]

I'm keenly interested in what you find.  I've been watching this thread for a long time.

I have a cyclic driveline vibration that peaks at about 48mph.  It is worst when the vehicle is cold.  I don't notice it in 2nd gear, but it's sure there in 3rd.  It's cycle varies depending on throttle position.

[philo_beddoe]

That is similar to my situation. It "appears" to be more present when cold. But then again just the other morning on the way to work it was in its smooth phase, but of course after half way to work i have to stop and go through a small town then when i continue on a 50 mph speed limit road, there it was. I think its somewhere between the rear wheels.

The only area i never addressed was the rear axle/bearings, rear diff. That may be good news, perhaps. I'll keep updating this thread.

[fitz]

Philo_beddoe,
The true mechanics on here that have real trouble shooting skills may laugh at this, but let me through this out there. You make the call.
I have a 10 bolt (6 lug) rear axle (complete drum to drum) you can have.
I also have 2 of the 6 lug rally wheels (with junk tires on them).
You can have it all for free (I'm 30 minutes south of Boston, not to far from you).
Bolt in the 10 bolt (with new u bolts) and buy 2 cheap tires (which you can sell on Craigslist after), and you can play the process of elimination game.
Then again, you can drop the truck off at Vile's house and let him work his magic on it.

[Irish_Alley]

can he swap axle shafts from one 10 bolt to the other so he can keep his tires? but either way it will be cheaper to get a used unit than build another

[fitz]

I thought his truck would have a 12 bolt.
To add to the confusion I think most of my 10 bolts are from 90-91 blazers & suburbans so they would be 30 spline axle shafts.
They all came from running & driving trucks.  If it did solve the vibration it would keep his truck drivable until he gets his original 12 bolt rebuilt.

[philo_beddoe]

I do have a 12 bolt.

[philo_beddoe]

http://forum.73-87chevytrucks.com/smforum/index.php?topic=21074.0

In my case 12 to 10. I am grateful for the offer fitz, let me see what this shop comes up with on tuesday. Could be something simple like bearings. They are a Jasper rear end dealer.

http://www.jasperengines.com/differentials

[Irish_Alley]

i dont know why but i thought it was just said he had a 10 bolt.   

[philo_beddoe]

He did say 10 bolt. I have a 12. That post shows a 10 to 12 swap. My case is vice-versa. Regardless, i'd like to keep my rims and tires. Or is it just me thats confused?