Motown Cad

I'd appreciate any guesses, thoughts or comments. All welcome as I'm stumped.

I noticed an increase in vibration 2 weeks ago in driveline only when engaged and accelerating. It grew and then last weekend the noise (coming from right header area) turn into a tang, tang, tang, tang that matched the engine acceleration when i started out in first, and stays through till 3rd gear if decent amt of gas is applied. Upon inspection, I had the lower rt bolt missing from the trans to bell housing and the upper right bolt just above it backed out almost all the way. I replaced and had to tighten and retorque 3 more and thought I had found the problem. I did the LS7 swap with bearing 13 months ago. That wasn't it. It really sounds like the pressure plate is hitting something but what ???? Any ideas are welcome and I hope all are doing well. Thanks!

AAIIIC

iTrader: (19)

Way back in '08 I had an issue with a speed-related cyclic noise that turned out to be an issue with the driveshaft. I don't know if the shaft has internal balancing weights or something like that? Anyway, the driveshaft was replaced under warranty. It's been so long ago that I honestly don't recall exactly how the noise manifested itself, but the fact that yours only occurs when engaged and accelerating, and only at low(er) speeds, kind of reminded me of what I had experienced.

You said yours is coming from the right header area, but I've found that noises can be pretty hard to really pinpoint from the driver's seat. If you're confident your noise is up front, though, then my suggestion is probably out to lunch.

voodoochikin04

iTrader: (3)

I had a similar instance on a previous vehicle.. I had recently replaced the clutch.. Torqued everything. And few months later similar experience as yours.. Turned out it was a flywheek bolt had backed out and the bolt head was hitting the clutch disc springs... Considering you had your bellhousing bolts backing out.. It's possible something similar is happening.. But then again if it's only when the car is moving...and not constantly with engine rpm...probably isn't pressure plate or clutch.

TheAce

[QUOTE=voodoochikin04;19146036 Turned out it was a flywheek bolt had backed out and the bolt head was hitting the clutch disc springs... [/QUOTE]

Exact same experience and exact same symptoms.

Further more , bellhousing bolts backing out is almost unheard of (but yours did) leading me to be suspect of any and ALL fasteners related to your LS7 clutch install.

Motown Cad

Thanks for the replies! I just returned from garage and found out I had a 2 pronged problem. Much to my horror and relief the vibrations were from the driveshaft because (like the idiot I am), I don't think I torqued the six bolts going into the rear diff. They were all there but everyone loose. So I tightened and TORQUED them this time to the 44lbs required and took it out for a test drive. NO Vibes at all and no "tang, tang, tang". So pull back in clean up and pay and go on my way. And sure as **** no sooner am I a 1/4 mile away and again "tang, tang, tang" while letting out the clutch. So I went back and raised car on the lift and inspected again. I have the voodoo poly bearing and that is still rockin solid. but I do have a 1/4 play in the twist of the DS and the rear portion of the driveshaft has fwd and back movement into diff. I'm pretty sure I lost all the grease in that front portion yoke thing the DS bolts into so I think I need to repack, just not sure how as its all slung on the bottom of the car. (more than normal, TSB). But I agree that it is hard to troubleshoot sounds from driver seat as a rear sound can transmit up the tube and make it sound like it's coming from the passenger header area. I am pretty certain though that when I twist the DS, I hear the normal rear end sound but also a second set of "gear" sounds coming from the middle of the aft section of driveshaft. So then I decide to come home and see what your guys said and "no tanging" on the way home. Arggh. So it's kind of fixed but I'm wonder if its internal and intermittent to the drive shaft. Appreciate the comments as I haven't been on the boards for a long time.

voodoochikin04

iTrader: (3)

To repack the grease in the rear CV properly it needs to be disassembled cleaned and greased with CV grease.

voodoochikin04

iTrader: (3)

Front to back movement is normal plunge.. Twisting there is some.

Motown Cad

Voodoo thanks! Can I do it with the rear installed up in the car? Is there a seal too that would need replacing? Thanks

voodoochikin04

iTrader: (3)

Bare minimum you have to disconnect the rear CV from the diff...
Absolute simplest explanation: remove rear CV plate.. Index star, cage, and outer race.. Remove snap ring. Pull CV boot+cap forward and slide CV joint off the Driveshaft. Disassemble and keep the ***** numbered in order 1-6 as to maintain their original orientation. Clean well, and inspect for wear. Assemble joint dry and install on to Driveshaft.. Pack CV grease into front and rear of joint and put rear cap back on. Now it's much more a pain in the *** than it sounds. If you find damage it may be irreversible, and you probably will struggle with it. I've done so many CV joints and these Driveshaft ones still are a pain in the neck.