Driveline vibration.....Help!

[AUSSIEVETTEMAN]

Ok, here is the list of new parts and still I have a vibration in the driveline.
I am thinking if it is not the trans mount, then it must be the harmonic balance of the fresh engine. There is a vibration at 110 km/h or 2700 rpm. the vibration is there at the same rpm regardless of the speed, but only from 90 km/h and up. When you do higher speeds, say 160 km/h the vibration comes in and out depending on the engine rpm.
When you hold the car in drive (auto) and apply gas the rear sits down under the torque as it is supposed to and the vibration comes in and shutters the steering wheel.
The vibration seems to come from the trans tunnel.

1 New aftermarket steel rallye wheels and tyres - BF's 255/60/15 - all stud balanced
2 New trailing arm bearings and seals
3 New Rear suspension bushings - Graphite Poly (no difference noticed in ride, handles like it is on rails) (Trailing arm, strut rods and new Koni shocks)
4 New Diff carrier bushings - Graphite Poly
5 New Diff yoke bearings and seals - new LSD keepers
6 New universal joints in the input and half shafts and all have been balanced
7 Rebuilt T350 Trans
8 New trans mount
9 New balanced engine + 20 thou over, roller rockers, LT1 Corvette valve springs, new cam, high volume oil pump.
10 New engine mounts

The only other thing I can think of is the front seal is starting to leak a small amount of oil. I have bad feeling the vibration is engine harmonics.

What do you guys think?

I have spent $25000.00 Aussie dollars on the driveline and don't expect any vibration after spending that kind of cash. ad
Probably the smallest part causing the head ache.

Cheers

Tony

 

[Chiller]

You might want to check your main drive shaft. One of my buddies had a universal joint that was bad enough to make the drive shaft out of balance.
Chiller

 

[AUSSIEVETTEMAN]

...You might want to check your main drive shaft. One of my buddies had a universal joint that was bad enough to make the drive shaft out of balance...
Chiller

Good point Chiller, I'll check the trans end of the main shaft for play.
Trouble is that when you are driving and take the load off the driveline and pop her into neutral, the vibration goes away. The shafts are still turning, but not under load. I can only hope it is that simple and I have a crook uni.

Cheers

Tony

 

[AUSSIEVETTEMAN]

Chiller, I think you may be onto something here.
I just went out to double check on the drive shaft and the front uni has sideways play in it. Don't know how that happened, I had them replace uni's and balance the shafts, looks like all they did was charge me for them!

I'll keep you all posted, what brand of uni's do you guys suggest?

Cheers

Tony

 

[1981corvette]

Had the same problem 4 years ago on my 81 w/automatic.
Had all the rear end stuff changed. Still vibrated at 24-2800 rpm's.
Finally had a NEW engine installed.
No problems now.
I also thought driveline, mounts, harmonic balancer, etc.
Something in the engine.
Good luck. It only cost me for the new engine and whole undercarraige
front to back $8900.00 USD.

 

[waterboy1976]

We had a 79 Camaro Z28 with a turbo 350 and replaced almost everything init and had the same type vibration. WE finally traced it down to the torque convertor....it had gobs of bad welds on the one side...almost like the machine that welds it got stuck in one place for 10 minutes. It was on the inside of the convertor so we could nt see it when we installed it...Good luck....

 

[Bob Chadwick]

Tony,

I've got the same problem with a post going as well. Please post what you find and I will as well.

 

[AUSSIEVETTEMAN]

...We had a 79 Camaro Z28 with a turbo 350 and replaced almost everything init and had the same type vibration. WE finally traced it down to the torque convertor....it had gobs of bad welds on the one side...almost like the machine that welds it got stuck in one place for 10 minutes. It was on the inside of the convertor so we could nt see it when we installed it...Good luck....

I thought about this, but would that kind of vibration be there all the time?
I had the trans guys take a look and he ruled it out. I haven't though, wait until we do that uni today.

Cheers

Tony

 

[waterboy1976]

Ours occured only in select RPMs also.....not all the time.....good luck....

 

[AUSSIEVETTEMAN]

Ours occured only in select RPMs also.....not all the time.....good luck....

No worries, I will keep an eye o it and if the vibe is still there after we replace the crook uni, then that will be next.
Thanks for the heads up.

Cheers

Tony

 

[AUSSIEVETTEMAN]

I thout that Trick was Only Pulled in USA!! gmjunkie!!

Yep, they also do things like when you ask them to put the good stuff in, they put the crappy Jap stuff in and then you wonder why you are breathing down their necks when it all goes sour.

Sometimes you get the other side as well. You ask them to do something and they don't do it, they adjust something else or replace it and say that your first item was OK. Then you return, they say that this item is cactus. I get this a lot on my Holden Commodore.

I do it this way now, I go in and ask them to do something and say that if they do not do what I have asked, I am not paying you!

If I had more big boys garage toys, then I would do the lot myself, another thing I have started to do, get more big boys garage toys that is.

I do not know what the neighbours would say about a hoist though!

Cheers

Tony

 

[AUSSIEVETTEMAN]

Tony,

I've got the same problem with a post going as well. Please post what you find and I will as well.

No worries Bob, will do.
So far I am ruling a crook uni, but if the vibe is still there, then I'll keep looking at the trans mount, even though it is new or the torque converter. I had the tranny rebuilt around 18 months ago, but can't remember if the torque converter was an exchange or not. I don't think so, they waited for mine to come back from memory, but it did have a leak when it heated up. They could not pick it in the testing phase, but when the it heated up, the metal expanded and the tranny fluid ran out.

This has got me wondering about the leak spot and how it was repaired. If it has a bodgy weld on it, then waterboy is right and the torque converter is the source of the problem. I'll quiz old Rex when I take it over today.

Cheers

Tony

 

[Bob Chadwick]

I'm looking at the mounts first as well. I had the tranny mount out last night, the part was only $9 so I replaced it.

I am also going to look at my front differential bushing. Last year I replaced it with a polyurethane bushing. I already had it in when JohnZ posted about the difference in height between the stock and and poly and indicated that it could put a stress on the drive shaft. Well to make a long story short, I already had it in and left it. It's coming out tonight and if that doesn't solve the problem, then the drive shaft will come out and taken back to the shop that balanced it last year for an inspection.

 

[AUSSIEVETTEMAN]

I'm looking at the mounts first as well. I had the tranny mount out last night, the part was only $9 so I replaced it.

I am also going to look at my front differential bushing. Last year I replaced it with a polyurethane bushing. I already had it in when JohnZ posted about the difference in height between the stock and and poly and indicated that it could put a stress on the drive shaft. Well to make a long story short, I already had it in and left it. It's coming out tonight and if that doesn't solve the problem, then the drive shaft will come out and taken back to the shop that balanced it last year for an inspection.

Yeah did our Diff mount as well and it was poly from memory. Our Trans mount is rubber.

 

[Bob Chadwick]

I'll let you know if the change makes any difference. I'll replace it tonight and take the car in for a balance on Saturday on the off chance that the tires are a cause.

 

[AUSSIEVETTEMAN]

Well, the new uni's are in the drive shaft and that seems to have only shifted the problem from 90 km/h to right on 110 km/h. It still happens in the same rev range, around 2700 rpm and you can feel it when you back off from heavy excelleration.

Looks like I may just throw a rubber diff mount in just for an excercise and to eliminate another theory, instead of the new poly one in there now. If this mount doesn't solve it, then the trannies coming out and another torque converter going in. I spoke to the Trans Guys and explained the scenario when we had our trans rebuilt. We had them pressure test the torque converter, but they use water to crack test and the converter is not hot, so when it was full of trans fluid and hot, the crack opened up and the fluid came out. I asked if someone could have botched up the crack site and maybe the weld has put things out of whack, but he ruled it out initially. He has since changed his mind and said it could be possible.

Now we have another problem, but that is in another post.

I'll keep you all posted, when we find the problem, looks like it could be a combination of small stuff.

Cheers

Tony

 

[AUSSIEVETTEMAN]

Alright, where do we start.

Removed the input drive shaft and found a crook uni. Had it replaced and rebalanced. Hmmm......

She still clunks when going from forward to reverse and still has the vibration at that RPM. A couple of Vette buddies of mine came over and one took her for a strap. One felt the vibration and then held her in both neutral and under load in drive and found the vibration without travelling at speed. We all think it could be torque converter problem, possibly a cracked flex plate around the bolt hole connecting to the torque converter. When she gets up to that RPM range 2500 to 3200 RPM, she vibrates as it is off balance.

Mmmmm.......oh well beer'o'clock time!

Cheers

Tony

 

[joe1975]

Did you check for play in the tranny slip yoke,I'm having the same problem your having we jacked mine up each side one at a time and rocked the wheel back and forth their was some noticeable movement I'm hoping thats my problem oh by the way mines a standard also could there be some twist to the splines in the rear of the tranny. when your shaft was balanced was the yoke connected? Please post your progress I'll be following this post

 

[AUSSIEVETTEMAN]

Did you check for play in the tranny slip yoke,I'm having the same problem your having we jacked mine up each side one at a time and rocked the wheel back and forth their was some noticeable movement I'm hoping thats my problem oh by the way mines a standard also could there be some twist to the splines in the rear of the tranny. when your shaft was balanced was the yoke connected? Please post your progress I'll be following this post

Yeah Joe, we had the yoke and input shaft balanced as a complete unit. Our vibration is there when we are moving or stationary, so we believe it is harmonic more than driveline now. Being only really two parts that control balance/ harmonics, it can only be this or the harmonic balancer at the front and after a fresh engine with only 12000 kms on it, I doubt it very much. We had 20 thou over sized pistons installed, lighter units that oil better. Original crank and the whole lot was balanced up. LT1 Corvette valve springs and bigger nostrals to breath through headwise. The block has been decked to bring it back to true. They are out from factory. A set of Roller Rockers top it off, hidden by a set of Edelbrock valve covers not weraring any logo. She goes like a cut cat now!

I recall when the engine went back in that the flex plate had grind marks around the bolt holes that belong to the torque converter. Our guess is that there is a crack around here somewhere and the torque converter is off centre, causing vibration.
While moving at any speed, if you slip her out of drive and into neutral, then all vibration goes from the driveline and it is very smooth. If you rev it to 2500 rpm or a little more, then you can feel it there. If you hold her in drive with your foot on the brake and then apply gas to bring her up to 2500+ rpm, you can feel the vibration and she shutters through the dash a little.
When you are drinving on the highway and come off it doing 110 km/h and back completely off, you can feel vibration while the load is removed.
Every other part in our driveline has been replaced and she is as tight as a drum under there.

Oh well, torque converter $125 AU, Flex Plate $75.00 AU, driving the Vette again - Pricelesss!

I will let you know how I go.

Cheers

Tony

 

[joe1975]

My vibration goes away when I push in the clutch, so mine is probably driveline related.I hope