8.8 rear end vibration
03-23-2017, 03:02 AM
#242
Originally Posted by ls1247
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...
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...
I have revshift motor and trans, and find my trans may be 3mm lower than stock.
Am fittin a laser to see where everything is pointin...
03-23-2017, 07:08 AM
#243
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It wasnt hard to me, I had to lower the diff and the trans to put it in, but I am dead center between the tolerance they give you when installing it. To note though, when I first had it installed it was around 80 MPH, but after the motor and tranny mounts were put it, it increased to 85 to 88 MPH, while you still can slightly feel it in 80 MPH, but that could have been my paranoia.
03-23-2017, 08:20 AM
#244
i was was mistaken about the 2nd gen CS mount..it wasn't separating internally just some superficial tearing on the outside..
still, the filled factory mount mount works as good or better than any of the others so it stays.
in other words, I've tried numerous mounts, multiple alignments, clocking and all that and my next move is too shorten this thing.
ive installed my fair share of CV shafts in my time and I've NEVER had to compress one to get it in the car...this is the only shaft I've ever had to do this with.
And on my first DSS shaft, it too fell into the suggested travel limits but the cvs failed within 10k miles and the refunded it completely...that shaft as delivered was almost a full inch shorter than it needed to be and I had to stretch it to bolt it on...
so I've had to DSS shafts...one long and one short...from now on out I'll make my own judgements
theres more on this subject here......
https://ls1tech.com/forums/cadillac-...l#post19579982
Last edited by ls1247; 04-01-2017 at 11:25 AM.
05-07-2017, 05:02 PM
#245
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I put a couple bolts into the rear CV to hold the rear of the driveshaft in position on the pinion flange adapter. At first it appeared the carrier bearing was being driven up into the top of the driveshaft tunnel, so I thought maybe the engine mounts needed to be bumped up a bit. But then I rotated the driveshaft and found that the carrier bearing would move up/down/side-to-side as I rotated the driveshaft.
CTS-V driveshaft vibration troubleshooting - YouTube
As stated at the end of the video, that uneven motion could be due to a number of things. I mentioned the spacers might not be even, or that the transmission output could be bent. The other possibility is that the input flange on the driveshaft isn't square to the driveshaft.
I knew the pipe nipples weren't perfect, so I had spent some time with a Dremel and bench grinder trying to even them up as best I could. However, after shooting the video, I measured the space between the trans and driveshaft flanges at the 3 legs and they weren't the same. So I pulled the pipe nipples out and bolted the flanges back together without any spacers in there, and tightened the 3 bolts to get the 3 measurements to match. I still saw the same movement of the carrier bearing as I rotated the driveshaft.
I didn't really have any way to check the runout of the transmission output flange. I did put a straight edge off the top of the tranny mount, and checked the 3 legs all cleared that straight edge by the same amount as I rotated the output flange, but that's not really a useful check. That maybe gets me 60deg of the 360deg rotation, so I have no idea what the flange is doing for the other 300deg. And with the tools and equipment I had on hand I had no way to check whether the input flange on the driveshaft is square to the shaft. I had to get the car back together, so I didn't really resolve anything.
The way I see it there are 3 options:
(1) My test was invalid. Despite getting the flanges as parallel as I could (using vernier calipers to measure), perhaps it wasn't good enough.
(2) There's runout in the transmission output. I never noted this with the stock carrier bearing because the driveshaft was able to wobble around in the mushy rubber bushing around the carrier.
(3) The input flange of the refurbished driveshaft isn't square to the shaft, resulting in the vibration. I'm not particularly sure how to determine if that's the case or not.
CTS-V driveshaft vibration troubleshooting - YouTube
As stated at the end of the video, that uneven motion could be due to a number of things. I mentioned the spacers might not be even, or that the transmission output could be bent. The other possibility is that the input flange on the driveshaft isn't square to the driveshaft.
I knew the pipe nipples weren't perfect, so I had spent some time with a Dremel and bench grinder trying to even them up as best I could. However, after shooting the video, I measured the space between the trans and driveshaft flanges at the 3 legs and they weren't the same. So I pulled the pipe nipples out and bolted the flanges back together without any spacers in there, and tightened the 3 bolts to get the 3 measurements to match. I still saw the same movement of the carrier bearing as I rotated the driveshaft.
I didn't really have any way to check the runout of the transmission output flange. I did put a straight edge off the top of the tranny mount, and checked the 3 legs all cleared that straight edge by the same amount as I rotated the output flange, but that's not really a useful check. That maybe gets me 60deg of the 360deg rotation, so I have no idea what the flange is doing for the other 300deg. And with the tools and equipment I had on hand I had no way to check whether the input flange on the driveshaft is square to the shaft. I had to get the car back together, so I didn't really resolve anything.
The way I see it there are 3 options:
(1) My test was invalid. Despite getting the flanges as parallel as I could (using vernier calipers to measure), perhaps it wasn't good enough.
(2) There's runout in the transmission output. I never noted this with the stock carrier bearing because the driveshaft was able to wobble around in the mushy rubber bushing around the carrier.
(3) The input flange of the refurbished driveshaft isn't square to the shaft, resulting in the vibration. I'm not particularly sure how to determine if that's the case or not.
I swapped out my driveshaft again today. I was hoping to measure run-out of the transmission output while I was in there, but I had to kind of hustle to free up the lift (was doing this at the auto hobby shop on the local Army/Marine joint base, and there's only so many lifts), so I didn't get to do that. However, I did take a look at the output flange on the transmission and I think it may be the issue.
I have a spare T56 in the basement waiting to be rebuilt. I haven't gotten very far on that yet, but one thing I have done is remove the output flange. When I put a straight edge across any 2 of the 3 "fingers", the mounting surfaces are nice and flat. So, I had that extra output flange with me, and I put it up against the 3 fingers of the output flange on the car. The one on the car is not flat - there were definite, visible air gaps. I did a rough double check with a straight edge (not much room to work with on the car) and saw the same thing.
So why not just remove the "warped" output flange and install the extra one off the spare tranny? Well, there are a couple of issues.
- First, I'm not sure the splines on that extra flange are good. The flange is supposed to be a light press fit onto the output shaft - if you watch this clip, you can see he had to use a 3-jaw puller to get it off, and the FSM also specifies the use of a puller to remove the flange. On this spare tranny I've got, the flange came off by hand (much to my surprise). I don't know if that means the flange is bad, or if the splines on the output shaft is bad, or some combination of the two, nor do I really know how to check one or the other.
- Second, the FSM tells you to use a new drive flange thrust washer when you reinstall the output flange. That's part #19 here. Well, I didn't know that was the case until this morning as I was packing stuff up to head to the hobby shop, so I don't have a new washer on hand. And that site shows part #19 is NLA, anyway. I sent a PM to Luke @ Lindsay this afternoon, so we'll see if he can still source those from somewhere. With that being said, I'm not sure why a new thrust washer is needed. The one that came off the spare tranny appears to have a bead of sealant on it around the inner diameter, so maybe they want you to use a new washer with fresh sealant? If that's the case, I'll just throw some RTV on the existing washer.
- Third, if the spare flange turned out to be a press fit onto the output shaft of the tranny in the car, I wasn't really sure how to deal with that. The FSM doesn't say **** about how to reinstall the flange - it just says to install it. And in the final (reassembly) video in the series that I linked above the guy doesn't say anything about it.
Since I hadn't really done my homework on swapping out the output flange, I elected not to do so today rather than starting into something only to find out that I had fucked myself by not being properly prepared.