Naf

iTrader: (1)

Ok, i recently ran into a problem with my ds carrier failing. I then frankenstiened my own carrier and ran into alignment issues.

So to get everything right once i installed a laser on the tranny output shaft.

My findins are unwelcomed. The laser is hittin the lower half of the diff flang. 43mm below the center of the pinion. And i raised the transmission by 7mm already.

The angle in reference to the rear diff of the transmission output flange is -1.5°. So if fhe diff is angle is l, as in 0° , my tranny output flange is 1.7° in / direction.

I have a full set of revshift poly diff mounts. As well as revshift engine and tranny mounts. And specters rear cradle bushings. The gap between my dry sump and the sway bar is roughly 9 mm so reducing the motor mounts buy anything more than a quarter inch is asking for trouble.

I centered and leveled the tranny output flange and carrier so they are now in parallel, but my ds is angle upwards instead of downwards.

After a long discussion with a few engineers here i shouldn't be too concerned. For lowerin the rear cradle 45-50mm is a lot...

Anthony Toal

wont the carrier pick up the two piece ds? such that from tranny to carrier there is a positive slope and from the carrier to the diff a negative slope. I know this is a conversation that us 1pc ds users are having

ls1247

iTrader: (2)

From all I can come up with, you align the transmission to be straight and in line with the carrier bearing so as not to put the flex disc in a bind. The less the flex disc has to work, the smoother it will be and this was pretty much the case in my car working with the voodoo carrier upgrade and stock diff. It worked well this way and IIRC, it took 4 standard 3/8 washers and a little offset to the passenger side of the trans to work align properly using CS soft motor mounts and a filled stock transmission mount.

IIRC, voodoo pretty much told us that the engine/transmission sits lower in the car than the diff does so I'm not surprised at your results.

I would also take note of what AAIIC found and posted in a video in the 8.8 vibration thread. He basically rotated the shaft with the carrier bearing loose and got tons of runout which I'm not sure he ever figured out.

If you can get the front part of the shaft as straight as possible, keeping the flex disc as straight as it can be, then the CVs will do all the compensating for the rear part of the shaft. They are designed to work at differing angles unlike U-joints and should be able to work well without too much concern for their operating angles.

I'd be leery of changing the trans angle too much for fear of what that does to the shift linkage. I imagine of all things in the drivetrain, this would be one thing you'd want to keep as straight as possible...

Of course none of this is published or anything and is simply my opinion. I'm all ears if anybody has other suggestions.

voodoochikin04

iTrader: (3)

Engine and transmission sits lower in the car than the diff. The back half of the driveshaft runs an upward angle to mate with the diff. You need to alignment trans output with the carrier mounting location. When you get the poly carrier installed in the oem bracket, then install just that and put your laser on the trans side. See how close to center it is. In AAIIIC case, it feels to me like a bent trans or driveshaft flange, only thing that makes sense.

Naf

iTrader: (1)

Ok, so i am not completely wrong...

I have the tranny and center bearing lined up.

I will try it out, if my clamp on fails, i will go with voodoos poly route. But i will center it out before installin it on the shaft and makin it more difficult to line up.

jmilz28

iTrader: (13)

For goodness sake, make sure to not let the CV joints fall out when you replace the center support! What a PITA...

Anthony Toal

hey Naf, can you share how you installed a laser on the output shaft? I would like to do this and see how my alignment is

Naf

iTrader: (1)

The carrier i have is clamp on, no need to dissasemble the ds. So no runaway cv parts

ls1247

iTrader: (2)

Creative Steel machined a sleeve that slides over the output shaft on one end and accepts a gun bore scope on the other. They'll rent it to you I believe..

Naf

iTrader: (1)

Made my own from a 12ga bore sight and an alu sleeve that will fit over the output shaft on the tranny.

Also found the relationship between the tranny flange and diff input flange is -2 degrees.

ls1247

iTrader: (2)

the challenge with publishing angles like this is they're relative to your particular combination of motor, trans and cradle mounts...there are any number of part combinations that may or may not yield different angles....

are the revshift mounts exactly the same height as the CS mounts and are they at the recommended installed height that the factory mounts achieved? We'll never know...

what we need is this angle as the car was delivered from GM

Anthony Toal

hope someone find a unused V in some storage bin then

Naf

iTrader: (1)

Fair enough,

I am running full Revshift bushings on motor/trans/diffx3. I raised the tranny by 3mm as well.

I used a digital inclinometer, used the diff as the Zero factor, and then checked the trans output flange. in my case the trans was below level, thus the -2 degree angle, if the trans was pointing upwards i would have given it a positive angle.

In a perfect world i feel the trans output flange and diff flange should have the same angle, therefore all would have less stresses on the CV and donut.

But thats my thought, it could be wrong, and it could be correct.

ls1247

iTrader: (2)

i don't know if anyone ever noted how all this looked when it was brand new and functioning well...

how far did all the factory mounts settle when new...what were the factory angles? And as I got mine with tons of miles on it, I'll never know if these cars were ever smooth in the first place...

there aren't any published standards for any of these angles and now that everybody has different combinations of parts, we'll probably never be able to establish one...

ls1247

iTrader: (2)

that makes perfect sense...let us know how it works!

jmilz28

iTrader: (13)

Bet the guys that make and use these know the proper angles:
https://www.revshift.com/product-p/pfx-cts.htm

ls1247

iTrader: (2)

They publish a procedure for flex disc alignment and if you use that thing, it had better be perfect cause it won't be flexing much. And I quote...

"It is critical to make the alignment angles zero. The factory rubber flex disc is much softer (and weaker) and will absorb some misalignment."

Their procedure actually works pretty good but the challenge is measuring the gaps they refer too with a set of vernier calipers...not enough room to measure the top gap or side gaps.

IIRC....

When i was still running a 2 piece, I aligned the shaft as follows...

Remove the bolts connecting the driveshaft to the flex disc and from the transmission to the flex disc. Rotate the driveshaft until the bolt holes in the driveshaft line up with the transmission and bolt the two together directly through the flex disc. Now, loosen the carrier bearing bolts enough so that the carrier is no longer holding the shaft in place.

As the shaft is bolted directly to the transmission, it will be directly in line with it. Therefore, if you have the carrier bearing bolts loose enough, the carrier bearing will be located where it needs to live to maintain this alignment. Shim the carrier bearing as needed to maintain this position and bolt it firmly in place.

Once you've bolted the carrier bearing down to the position in naturally found when you bolted the driveshaft directly to the transmission through the flex disc, remove the bolts holding the shaft to the transmission, rotate the shaft so it aligns with its original flex disc holes and reinstall all 6 driveshaft bolts.

isis

iTrader: (1)

exactly. Why would any of this be in question if it was all original and working fine?

ls1247

iTrader: (2)

It would be nice if the service manual specified the operating angles the engineers originally wanted for this.

You also think they would have speced acceptable wear/settling limits for the driveshaft carrier and the transmission mount as well as an alignment procedure because none of these items are mechanically indexed from the factory....

You loosen the carrier and you can move it all over the place on the factory bolt holes. How did they locate the thing when the car was being produced or did they just let it fall where it may and tighten it down?

While I know CS and Revshift take pride in their products, it would be interesting to know how they established the heights of all their mounts. Did they buy brand new factory mounts, install them in the car and measure them in their brand new but loaded state? Did they do the same with the transmission mount?

So what happens when you mix revshift and CS products?

I jacked my transmission up until the factory mount wasn't sagging anymore and then filled it with hose and window weld. Wonder how screwed up that is?

isis

iTrader: (1)

I know if you ask Max @ CS he would share that info. I've never talked to Revshift so I can't comment on that. I know I have RS motor mounts, diff bushing and trans insert with CS cradle bushings and diff block. But my diff and driveshaft are 100% stock. I have no vibey issues so far. But that's not much help for this discussion I'm afraid.

honestly with the amount of gooey rubber in the whole drivetrain anything more specified than +\- 2 degrees or whatever was probably not necessary and deemed good enough for GM.