black00ssFL

iTrader: (24)

I have a MWC fab'ed 9", ford posi, strange center section, strange 31 spline axles, richmond 4.11 gears, PST 3.5" aluminum shaft, and six speed with ls7 clutch. Since I put my car back together (blew engine in Nov. '10) with an LQ4 I've noticed a vibration that starts at 75-80mph and feels like the car is trying to shake itself apart at 130ish. Before the LQ4 I just had bolt ons and ran a best of 12.09@114mph. Didn't notice a vibration then...but I also didn't bring it up to near 130mph as far as I remember....so it could've been happening before new engine. Seen a best of 1.6 60' on new setup and 1.7 on old. I've used m/t et streets, m/t et radials, and street tires on old setup. Only used m/t sportsman pros on new setup. I launch anywhere between 4500-6000 rpms with a quick clutch let out. I just had PST rebalance the shaft since I thought that could be it, but still vibrated.

I've done the normal tear down and testing with car on jackstands (idling in 6th at about 40mph) and this is what I've discovered. With wheels on I noticed BOTH wheels wobbling. Took wheels off and noticed some studs were slightly bent (stock replacements...will be going to arp 1/2" after this)! Tightened down rotors and noticed both still wobbling. Took off rotors and still noticed wobbling. Took out axles and found flat surface. Axles definitely have a slight bend in them! With the axles out I still get a vibration in the same speed. Driveshaft removed...no vibration. Also tried multiple pinion angles and no difference.

I pulled the center section out today and everything looks good. Spins smoothly with no abnormal noise. Gears have a good wear pattern. Bearings look good and have no play in them.

What's troubling me is that it's obvious that the bent axles would be causing the vibration, but why would it still vibrate with the axles out of the car? Could something still be wrong with the center section even though it looks good?

It still troubles me that these axles bent as well. I know they are "only" 31 spline axles, but I'm only pushing 400whp and I'm fairly certain they probably bent before the new engine since this has been doing it before I went to the track on the new setup. I've already sent an email (since it's the weekend) to MWC about the axles to see if they can help me with Strange about it.

Any thoughts?

black00ssFL

iTrader: (24)

Another thought, could driving it on the bent axles cause damage to the posi, and be the reason for the vibration even without axles in?

ssvert99

iTrader: (26)

Axles and things like this need to be fully mounted and checked for runout measurements with a dial indicator before anyone can help. Check it all out and let us know.

black00ssFL

iTrader: (24)

Thanks Eric! I sent a reply to the email I got from ya. I'll put things back together and get a real measurement this week.

A.R. Shale Targa

iTrader: (2)

I chased a vibration issue in an old 78 chevy pick-up which had nine different
engine/trans combos in it over a 3yr period. I even broke several 350/400
transmission bellhousings. I replaced the worn factory 2 piece driveshaft
with a single 4" steel unit from an industrial truck service so all along I told
myself there's no way that things broke/bent. After I scrapped the rusty hulk
I saved the driveshaft for like 8yrs. before giving it to a freind who needed
one and was willing to shorten it for his application. He called me about a
week later and laughed when saying "man that banana was F@#ked". The
only engine I can think would have done that was a warmed over 68' 472"
caddy that dynoed 306hp/604tq at the wheels.

black00ssFL

iTrader: (24)

Got new axles from Strange a couple weeks back and finally got them in last week. Vibration is gone!