Anthony Toal

Watching this closely, got Vibes around 80mph with a 1-piece aluminum, talked to CS and going to try a few things to limit it, but would like to see what else I can do to remedy it.

voodoochikin04

iTrader: (3)

We were never able to eliminate the vibes and harmonics from the aluminum one piece shafts we messed with, even after repeated trips for rebalance and blah blah. Which started this whole poly carrier endeavor...

Aaiiic they may have spun the shaft and called it straight but did that include checking run out on the mounting flange? It could be slightly off on one of the three fingers... Also grease in the rear bolt holes is normal. They seal happens when they are bolted down tight.

ls1247

iTrader: (2)

the output flange fingers on the transmission look scary easy to bend and as heavy and bulky as the t56 is, it doesn't look like it would take much to tweak one during a clutch install.

at least the DSS adapters make a solid surface to check runout on and Iirc, I got .002 or .003 on mine when I checked it. However, I don't know how tight a tolerance I could keep on the rig I was using to measure it cause i was using what I had laying around and it wasn't optimal but I was able to convince myself it wasn't straight.

This is one major reason I thing the cvs need to be loose enough to float...

i honestly think this is one reason GM got away from this design on the V2

Creative Steel

I should say this before this goes further; the 8.8 adaptor is as short as it possibly can be before the pinion threads push into the cover of the CV. Also, the adaptor isn't really "compressing" the CV. Sure, it needs to be fully compressed before installing, but then once you bolt it up you gain back the ~1/2". It isn't the "OEM location", but it is the best possible location with saving the customer money.

Also, they stayed with this design on the ATS-V, Camaro, and V3. I don't know why. We had to put about 0.004 of shim stock on one of the three fingers.

ls1247

iTrader: (2)

glad to see you're still monitoring this and ponying up an answer to the adapter thickness concerns.

i agree the adapters in of themselves aren't compressing the cvs, the shaft is just simply to long based on my past experience with other shafts that slide right in an uncompressed state. The shaft isn't compressing because of the existence of the adapters, it's compressing on itself...imho.

54inches

iTrader: (4)

This is just a shot in the dark, but I think it is the adapter. Not that there is anything wrong with it. I am just thinking that there is more mass at the end of the pinion and it is creating the vibration.

I am running the GForce DS sans any adapter on the Diff side.

Just a thought.

voodoochikin04

iTrader: (3)

Possibly...However it's obvious that the one driveshaft was not rotating true to center nor anywhere near it.. that is definitely causing a nasty vibration.

54inches

iTrader: (4)

I was referring to AAIIC saying that switching up shafts did not remove the vibration.

voodoochikin04

iTrader: (3)

Aww gotcha. Makes sense then lol

vroom_vroom

iTrader: (5)

You couldn't give me anything from dss. Would still like to play with a one piece one day but after doing lots of homework on them gforce is the better company personally

Mercier

iTrader: (15)

Another shot in the collective dark--

Have any of you with nagging vibes thought of taking the axles out(I guess leaving some kind of stub in the diff) and running the car up to speed to see if it's any different?

ls1247

iTrader: (2)

I would if messing with the driveshaft didn't yield some improvement. Based on the fact that I have been able to drastically change the vibes by playing with nothing but the driveshaft, I'm going to stick with it until I don't realize any more change.

ls1247

iTrader: (2)

they're attention to detail leaves something to be desired. They seemed willing to mess with it but only if I pushed the issue.

But the one piece feels way more responsive in the car so I'll keep messing with it.

AAIIIC

iTrader: (19)

Is there anything that can be done to service the front CV?

For the rear CV, do you use any RTV when you put the cover on it?

BudRacing

iTrader: (3)

With all the vibration near 80mph talk, are we sure it isn't just the T56 transmitting the mainshaft vibes down the tuning fork of a 1 piece DS? I've convinced myself that all of the T56s have this issue so I stop throwing parts at it.

Anthony Toal

I will be able to test this out here hopefully soon, I had vibes near 80 MPH. I have only been in 6th at the time and when my transmission was rebuilt they found my 6th gear engagement teeth were worn bad and it slipped off the shaft just by pulling on it. So after my rebuild, I will see if this theory is correct or not. I do have the 8.8 with 1 pc alum DS.

ls1247

iTrader: (2)

Unfortunately there's a lot of directions to point to when dealing with this...

In my case, shimming the front cradle bolts down significantly changed and improved my vibes but after driving the car for 6 months, i finally got it fast enough to find them again....it simply displaced them to another area up the mph range...

Could this still be transmission related?

Possibly...

Even though I originally thought this was pinion angle related, I'm beginning to doubt that and I'm hoping that my issue is more length related. As I had to sandwich the driveshaft into place, I'm think shimming the front cradle bolts simply unloaded the shaft a little length wise and is allowing it to work better....

I'd pursue a trans overhaul if i thought the t56 was really worth the time and effort but I'm waiting patiently for Merciers results on his swap to see if that's the new way to go...

In the mean time, I can have the driveshaft shortened to test my "its too long" theory but as it only vibrates over 110 or so now, i don't have an immediate need to mess with it.

Beyond that, I'm at my wits end with DSS and I've only got one more round of patience left to deal with them...may as well hold out to see how Merciers setup works and only modify the driveshaft once if that swap deems worthy...only next time, i'll measure the length myself instead of depending on DSSs or CSs dimensions...somebody somewhere got the dimensions wrong unless the CVs need to be severally compressed to work properly in this operating scenario...somehow I doubt that.

Is the one piece worth it? Until I've exhausted all other avenues, yes. It feels so much more direct than the 2 piece and is much more responsive....the car feels better with it in my opinion and its worth a little more aggravation to possibly get it right.

There have also been enough positive vibe free reports using the one piece to indicate that it will work in the car so I can only guess that somewhere along the line, the original dimensions got lost in the shuffle or they remembered them wrong or something. Having had too many workings with DSS, this seems extremely possible given their track record of inefficiency and lack of detail with my orders and others...

ls1247

iTrader: (2)

How hard was yours to install?

I had to bolt my driveshaft into the car before installing the front cradle bolts cause I couldn't compress it enough with the cradle fully seated in the car.

pdxmotorhead

Chevy Silverado's had a recall on this at one point, wonder if there is any common components, I think they replaced the AL drive lines with Steel.

It sounds like there are multiple problems, just a dump of stuff I chased on other vehicles in the past...
- Drive line balance
- Alignment of pinion to output shaft (One piece units and 2 piece)
- Harmonics in the AL and CF drive lines (None of the salt flat guys use one piece drive lines, just for this reason.FWIW) Perfectly balance but any vibes from engine or tranny would start it whipping.
- Timing of the CV joints, the ***** in the front and rear need to be in time or they will cause harmonics. Had one shaft with the front CV out by about 3 degrees from the rear rotationally raised hell.. (Same on the diff to wheel drive lines.. )

AAIIIC

iTrader: (19)

I missed this before:
I took measurements (measuring horizontally forward from the upper front diff mount/bushing) and posted them earlier in this thread; as far as I can tell, you don't gain the 1/2" back.
Just to be clear, I'm not complaining about or blaming the adapter. I think it's a smart option, and it definitely saves the customer money. I paid around $100 to have a stock driveshaft shortened 1/2"; compare that to paying $700 for the cheapest of the aftermarket driveshaft options when one buys the CS 8.8" kit. It's a no-brainer, IMO, but I do think it's advisable to shorten the stock driveshaft to account for the play that is lost due to the adapter.