daz_au

Well..... my dream run so far modifying this car has finally come to an end. I have to admit I have had it good for a while with really no major dramas doing the LS3, suspension and brakes on my 64.

Last month I finally bit the bullet and had a TKO600 shipped over from SST. First of all, SST customer service is great. Apart from two bolts being the wrong size which I just replaced myself, the whole kit was very well put together and complete.

So I get it all installed, again no major dramas, used McRobb offset dowels to get a the bell-housing dialed in and everything bolts up nice. The transmission itself is great, shifts nice, drops RPM significantly in 5th of course and not noisy at all (yet anyway).

The problem is quite nasty vibration at around 65MPH that I have been trying to solve for the past month by getting the driveline angle even close to what it needs to be. The TKO is longer and even though its sitting on the supplied mount and very close to the floor (with supplied pucks installed), it points down at a steeper angle than the M21.

I have tried shimming the transmission up until it basically hits the floor and also tried all combinations of changing the snubber bushing (both thinner and fatter) to get a combination that gives me that close to perfect equal/opposite Z configuration.

I know I am not the only one, this forum is littered with similar situations... I just cant really see how this works for anyone unless they basically "relieve" the tunnel to allow the transmission to come up more.

I have seen at least one person try to shim down the rear of the pumpkin by putting a spacer between it and the carrier/crossmember. I am almost considering trying this as it would allow me to lift the front (pinion) without worsening the transmission to shaft angle which is already bad.

Its a real shame, the whole project is near perfection. Driving around town, this conversion is a dream... and anything up to 65MPH there is no detectable vibration. I have contacted SST and they sent me pretty much the same driveline angle info you can find on google, I guess they know it doesn't work out sometimes

Frankie the Fink

So -- what are the angles and are they equal and opposite at the tranny tail shaft end and the pinion end ?

daz_au

I really need to draw diagrams, but when installed with stock snubber and no shim it was >+2.5 at front and +0.5 at back so they were not opposite and not even close to equal.

Pushing the pinion up (reducing snubber thickness) swings the rear to -1.0, but it makes the front angle even worse... >+3.5. So now you have opposites (Z config), but the difference is still too great and always will be going in that direction while keeping the transmission fixed.

Pulling the pinion down (shimming the snubber) I can get it to +2 and +1.5. Now this is what some people refer to as a W where the difference is in spec but they are equal not opposite angles. This is where it sits now and it has resulted in the mildest vibration to date.

There is lots of debate about the W (equal but not opposite) angles being a valid configuration. People point to its use in off roading and farm machinery, while others say it cancels varying acceleration of the U-Joint, but at the cost of axial load on the bearings at each end.... especially in high RPM cases.

66jack

Heres a Nice description/write up on drive line angle/vibration...

Critter1

I wonder if a CV (constant velocity) joint at the front of the shaft would cancel the varying +/- speed change of the shaft twice per revolution.

I don't know how you would be abla to install the drive shaft in the car though as the separation has to be at the front yoke.

daz_au

I think its been done before, I have pretty much exhaustively searched and read every experience of C2/C3 driveline angles and that is the way at least one person went.

I am fairly certain I have exhausted all the easy stuff like shimming the transmission up as far as possible and playing with the snubber and I am officially now in the "not so perfect fit" category.... from here on none of the solutions are particularly nice or easy to implement .

Evasive

Is this isolated to the LS conversion vs the normal stock small blocks?

Frankie the Fink

I'm wondering that. Original-style small blocks are very amenable to the TKO conversion, I have seen LS-3 with this done but only in custom-built frames/chassis... Maybe someone else has been successful with the combo and will give some thoughts.

Mossy66

I had pretty bad vibrations at around 65 mph also with my TKO installation. I tried new u-joints, re balancing wheels and drive shaft and shimming the rear end. Nothing really helped until I happened to notice that the transmission yoke supplied with the kit was milled incorrectly. It allowed the u-joint to move a bit. Installing a new yoke helped the problem a bit. What really fixed the problem was replacing the Centerforce dual friction clutch. That clutch has a bunch of weights, and the theory is that at higher rpm, the weights spread out and add clamping force. Well, I could see from the wear marks that the weights were "living" off center most of the time.

I never felt any vibration just revving the motor in neutral, so maybe the weights centered themselves in that situation, but maybe while running in fifth gear, the slight vibration from the pinion angle mismatch was causing the weights to move off center and add to the vibration.

I changed to a different clutch, and the vibrations are pretty much gone.


Gerry

cardo0

This reads like you are trying to get the trans tailshaft and the differential to point directly at each other. Yes? That is not parallel! BTW I have always promoted parallel angles though many seem to disagree.

Monster trucks used to have huge driveshaft angles but in no way did the trans tailshaft and differential point at each other. The centerline of the trans tailshaft should continue on and never intercept the differential centerline. You want them parallel as in that link provided above.

Take it or leave it I can't say anymore.

93Polo

Andrew on LS1tech I believe has 2 LS swap cars with a CV joints at the front of the driveshaft.

http://ls1tech.com/forums/conversion...ion-2-0-a.html

Post 368 he really begins discussing it.

Lotsacubes

Our experience was opposite of Mossy's. The vibration was corrected by removing the SST provided PP and clutch and replacing with a Dual Friction. Also used a Centerforce billet flywheel. Stock engine here tho.

Critter1

I like that CV unit from a Porsche. That would elimiate the double U joint and the bulky unit that connects the two.

Direct link to post 368 on the page...

http://ls1tech.com/forums/conversion...-2-0-a-19.html

daz_au

No, not at all, just (close to) equal and opposite angles. I realize I dont want zeros, but it is recommended to keep all angles under 3* for the sake of U-Joint life. If I could achieve +3.5 and -3.5 without vibration and replace UJoints more often, I absolutely would.

Reading the many threads on vibration after TKO, you see a mix of LS3/SBC, but you also see a mix of resolutions from things like brand new tailshafts that came out of balance....

I realize vibration can easily be something else.... although I didnt experience any issues with the muncie so I feel things like half shafts, wheel assemblies etc are ok.

Of course the driveshaft is new, and I did replace the clutch (which is a McLeod dual friction and amazing to use by the way, I love it, but thats another story).

Like I say I have tried all the simple stuff, checking and rechecking the U-Joint seating, verifying no vibration when revved in neutral clutch in and out, have had wheels/tyres rebalanced etc....

The other reason I am quick to blame driveline angle is that I am not able to achieve the equal/opposite Z configuration within the specification required... plus I have been able to improve but not eliminate it by adjusting the snubber.

wmf62

what does SST say?
Bill

DansYellow66

Go to post 25 on this thread.

https://www.corvetteforum.com/forums...gles-c2-2.html

There is another way to align u-joint angles - the "W" configuration. I didn't know about this arrangement until our overseas buddy Alexanderdvr posted about it. You might see if there is a way to adjust things to get to the "W" configuration and see what happens.

Frankie the Fink

You may be on to something

daz_au

As per the last line of my original post above, I have contacted them. They sent me generic articles on driveline angles and some install notes with the things I had already tried.

The reality is, there are some easy things you can change, but the transmission only goes so high due to its size and I already have it sitting higher than it did on the supplied "perfect fit" bracket. I don't really know what else they can say.

There is also mention of "excessive" floor sagging due to crapped out body mounts. I have the supplied pucks installed and it wasn't that hard to get them in so I wouldn't say it was excessively sagged... but yes the body mounts are 50+ years old.

daz_au

Yes the post you are agreeing with here is on one side of that debate and the post that DansYellow66 refers to above is on the other side. This is the Z vs W debate, its all over mustang, camaro, corvette forums. The proponents of W site credible information from Spicer, saying that it works to cancel vibration but at the cost of axial bearing load.

Most people saying that W cant work don't have any evidence other than "I would never do it that way". I would say I have read the majority of information out there on this topic over the past month including the cited Spicer document. The Z configuration is obviously preferred, but the point of my post is that it cant be achieved given the little adjustment available to me.

GearheadJoe

I have a TKO 600 in my '67 with the original small block and I absolutely love it. Following are some suggestions that might help you with the vibration problem:

1) I found that there was one specific point in the transmission tunnel where the TKO-600 hit first as the transmission tail shaft was raised. The attached photos show the place on the transmission and the place in the transmission tunnel where this contact occurs. I removed the lip on the transmission cover to gain an additional 1/8 inch. When I mentioned this later to the Keisler tech guy, he said I could have accomplished the same thing by simply flipping the cover plate over. If I had cut out the "nub" in the transmission tunnel, I could have gained another 1/8".

2) You can gain some more clearance by adding a few shims to every body mount. This has the effect of raising the body with respect to the frame, but it's virtually impossible to see this change by just looking at the car after the shims have been added. Don't forget to loosen the steering column plate at the firewall before you raise the body.

3) Lastly, I seem to recall that the LS engine is actually an inch shorter than the Gen I small block. The engine mount adapters used to put an LS engine onto Gen I engine mounts usually have some fore-and-aft adjustment range. You may want to look at moving the LS engine as far forward as you can, even if that requires a longer drive shaft. That will help with getting the driveshaft angles right.


Using just items 1) and 2) above, I was able to raise the TKO 600 tail shaft enough to get the driveshaft angles equal and opposite. I could have further improved things by adding a shim to the differential snubber push down the nose of the differential, but I did not need to do that.


Personally, I favor the "equal and opposite" method for driveshaft alignment, which worked for me. However, I sort of "get" the so-called "W method" too. You could try that if all else fails, but I bet you can get this fixed using just items 1) and 2) above.