OK guys and girls,

i got the car a few years ago, (everybody say basket case), w/ the stock LG4, T-5, and 3.73 posi w/4 wheel disc.

it was purchased w/ intent to auto-x (HEAVILY), after an overhaul,
ie...new engine, rebuild t-5, fresh fluids in the butt, and new tires w/ some newpoly bushings.

well 4 years later, I've finally managed to put the new motor in...
GMPP 350 290hp.

everything went pretty much straight forward, a good smooth installation w/ the help of two friends that are otherwise mechanically inclined. i pulled the tranny out from under the car with the intent of moving the speedo gear back into position.
(it wasn't inline any more,my fault don't ask)
any way got it fixed and was putting tail housing back on and had the fifth gear oilernext to the bolts on the ground as i was reassembling everything, and one of my mechanically inclined buddies stepped on it and crushed it into about 16bajillion pieces.
i replaced this peice with one out of a newer model(as the old funnel style isn't availbel any more through GM.)
The new style is a cylinder looking thing w/ an angle cut off the end.

i managed to put everything back together and get everything back in the car, (had to use bolts to pull the tranny backin place.)
(this had never happened w/ the 305)

went for a test drive and now she has more power and torque than she's ever seen.

she'll break tire at will in first and second but when you get on the interstateshe starts vibrating (kinda like an out of phase drive shaft)around 50mph all the wayy up to 80.(kinda scared to take her any faster than that because of the vibration.)

my diagnosis:
its not in the drive shaft or ujoints as i flipped it thinking i may have inadvertantly screwed up and put it in backwards.(no change)

i rebalanced the new 16" tires thinking that maybe that might have been the prob.(no change)

flipped the tires to opposite sides(no change)

i have noticed w/ the clutch engaged that the vib. is almost contained, however if you push the clutch in it gets really bad.

it's not rpm related, and i'm really at a loss here. Normally i'm the guy people call and say "hey, my car/truck is doing this' and i can usually spot on nail it.

this has got me stumped.

...help!

 

It might be stupid but try swapping driveshafts with a good one can't hurt and only takes 10 minutes.

 

ok guys
i'm thinking its in the fly wheel.

on of the guys i work with at the dealership said some thing about going from the lg4 to 350 i would need to counterbalance bla blablah... was about what i heard

they definitly have different cranks

i have narrowed it down to an engine/tranny issue.

if this is a prob any body has run into...let me know.

 

My car is having a similar problem at highway speeds when i get on it 4th gear especially it vibrates real bad like someone is sitting behind u shaken you. Well i was curious just like you and did some searches and saw that cars when they had higher than 3.42's like 3.73 or 4.10's that the stock steel driveshaft reaches a point where it cant keep up and gets all out of whack. When i was reading about it people said they went and bought aluminum driveshaft which are lighter and spin easier they said there problem went away or got signifacantly better. My car is very similar to yours mine is a T5 and used to be a 305 and now is a 350. I think im sold on the driveshaft thing im looking into buying an aluminum one. They say most of the 4th gen Ls1's came with aluminum ones and they are a direct bolt in. Hope this gave u some help.

 

Dumb question but did you install a pilot bushing on the new eng? If so was there any sign of wear on the trans input shaft?

 

ok...

I finally got time to work on MY car this weekend.

first problem that i tackled, was the front half.

I replaced the wheel bearings. I figure at 300,000+ miles this was probably a good idea, and not a moment to soon.

the pgr side wasn't bad but if you do one, do both.

dvr side was BAD!!!!!!!! bearings had actually galled the material on the face of the inner race down to the brassy material. the outer bearing looked like it had worn permant dimples into the race.

This fixed a whole lot of problems.
1.) I don't have to crank my stereo up any where near as LOUD as i used to.
2.) I caould here what was going on in the rest of the body.


Next fix was a set of electric fans that i robbed off a wrecked Toyota. (yes, they work. around town i stay at about 200F)

this fixed:
that nagging flywheel out of balance feeling. (comfort and confidence in one fell blow...THWAP)(fan clutch was toast.)

I wasn't ging to mess w/ the rear of the car this weekend until i noticed/felt this annoying little click/ pop whenever i let off the brakes from the back half of the car on a test drive.

Jack up the rear and LOH AND BEHOLD... the torque arm is loose t the rear end. The bolts could litterally be turned by hand.

This fixed a lot of SLOP in the back. my nagging annoying vibration/grinding noise is gone a 4th and 5th.

Now, you might be saying to yourself "Damn self looks like he doesn't need our help any more."

not so fast.

drive shaft is bent, (had it balanced)

and i need ANOTHER new set of 3.73's(extensive whine on the anystate around 65-70)

any body got any clues which aluminium shaft, from what car, and where i can find one cheaply in the Baton Rouge New Orleans area?

 

Any Fbody aluminum shaft will work. The most common and easy to find will be the cars with LS1's 98 and newer Fbodies. The driveshaft has to be my problem my car is basically a brand new Fbody i have replaced almost every single part on the car from end to end its all brandnew. Except the transmission and the driveshaft. They are both going to get changed soon. My car has had a complete suspension rebuild all new bearings and seals all 4 corners. 4wheel brake job. Complete rearend rebuild. New ujoints i have about 10K on my pilot bushing and it is on of the solid bushings not the stupid bearing. Im convinced its my POS driveshaft. If u throw an aluminum one in post back up and let everyone know how it worked out i will do the same.

 

no prob.

You might want to go have the shaft you have balanced.
i had to do that when i had my ujoints changed out and it made a big difference as the joints i had wheren't installed correctly.