i am experiencing a vibration with my new 5 speed...
in another thread i am being told about Optimal Pinion Angle and aparently this is what is causing the vibration... http://forums.corvetteforum.com/zerothread?id=713758

aparently the difference in lenght between the two tranys has changed the angle of the drivshaft in relation to the trany as well as the differential, causing this vibration...
if this is the case...wouldnt the same thing apply to our cars that have a 4 speed vs an automatic??? are they not different lenghts too? of course they are...

in that thread "yellow 72" posted a link to a very helpful page...
heres that link... http://www.carcraft.com/howto/91758/
it is helpful because it explains the phenominon but because they demonstrate on a Mustang, so it dosnt tell me EXACTLY how to make this adjustment on my C3...
can anybody here tell me how to make this adjustment?
i mean EXACTLY how? where are the adjustment points etc?
did any of yall out there that did the 5 speed swap experience the same ting too?

i have another question...if this is true then why does Keisler only say...

"If you experience a vibration at cruising speeds, it may be necessary to adjust the rear end angle to acheive the correct driveshaft angle. Please refer to the factory manuels for measurment and ajustment methods."

and this they say in small, inconspicuous type near the back of the instructions...
if this IS true then i would think it would apply to EVERY 5 speed install in every C3 and be a part of the main instructions so that you can do it during installation of the trany, AND know how to do it!

i have forwarded this message to Kiesler in hopes of finding answers...

 

I ran into this exact problem about 2 or 3 years ago. I ended up running a string down the centerline of the motor and used the little stud hole in the rear of the housing as my center of the housing.
1st pinion angle. I removed the driveshaft then with a good magnetic protactor read the down angle of the output shaft of the transmission and I got about 1 degree down, something like that, the number is not important the valvue is. I then read the angle off the pinion using the yoke and got another number. These 2 numbers must agree but be opposite in sign.The transmission points down so the rear end must point up and exact same amount.
Driveshafts can travel in jerky motion , a universal speeds up and slows down. If the 2 universals have the same angle up or down they add up the speed up slow down. If the angles are exactly the same but opposite they cancell.
To change the transmission is hard but the rearend can be shimmed up or down with the donut on the front of the pinion.
I will get into stringing the drivetrain later. It is late and I have to be someplace in 15 minutes.

 

thanx so much...i will stay tuned...

while we're on the subject of alighnment...
my shifter sets a lot further to the left than centered...hense when pulling it left, through the gate to go into 1st gear, it hits my console...
could it be out of line left to right too?

 

Remember that the side to side pinion angle is just as critical as the up and down angle!

I chased a vibration in my '69 for a couple of years untill I finally moved the trans almost an inch towards the drivers side.

No more vibration!

 

Keith, what was required to move the tranny to one side. I thought mine looked like it was to one side when I finished my install.

 

All I did when doing the 700r4 install in place of the Muncie was to take the mounting shoeoff, keep the same centerline, obviously, and bend it down and slot to the rear a good bit.....

put the trannies on the kitchen floor (well before even meeting wife)...and then measured with my framing square all the offsets and length differances to make the new mount....somethig like 2 inches to the rear, and 2 inches lower.....whatever....so I figgered if I hit that target, things be ok....
U joints still ok, no apparent vibration, and I looked at the shaft and it seemed ok, but never made any high effort to actually measure it....

GENE

 

The simplest solution is to determine the driveshaft angle, then use a como protractor with a bubble to align the driveshaft to to meet that angle.

 

im goning to assume that because they said...
"it may be necessary to adjust the rear end angle"...
that i am not going to screw with the trany angle at all, but instead, i will be adjusting the rear end to match the angle of the trany...
and i also assume that i will achieve this adjustment at the bushing in front of the rear end...
it just so happens that i have a brand new bushing on the shelf that i was going to put on soon anyways... :D

 

Remember that on solid axle cars it's easy to adjust the angle of the diff, just use shims. Near imposible on our cars!

 

OK...so how is it done?
im callin Kiesler tomorrow and see what they say... :yesnod:

 

Keep us posted on this. I'm very curious about his now. I have a Tremec on the way next week and need to know about this. I am going to take all kinds of measurements now before removing the Muncie.

 

Remember that on solid axle cars it's easy to adjust the angle of the diff, just use shims. Near imposible on our cars!


Why is it impossible. We have this rubber donut on the front of the pinion with a spacer, I don't remember exactly but I had no trouble shortening my spacer to raise the front of the pinion.
Our transmissions point down so the pinion must point up, reduce the spacer thickness and it raises the nose of the pinion.
I had vibration between 62 and 70 and agian at 90.
After adjusting my pinion height and direction I have absolutely no vibration in the shifter handle right up to 130 mph where I chicken out.

 

im goning to assume that because they said...
"it may be necessary to adjust the rear end angle"...
that i am not going to screw with the trany angle at all, but instead, i will be adjusting the rear end to match the angle of the trany...
and i also assume that i will achieve this adjustment at the bushing in front of the rear end...
it just so happens that i have a brand new bushing on the shelf that i was going to put on soon anyways...

Your right about this. A magnetic protactor set on a cleaned up yoke, take the yoke and make sure there are no burs , paint or anything else, install in the back of the transmission and put the magnetic protrator on here and take a reading. If it reads 1 degree down you know the rear pinion must be 1 degree UP. Clean up the pinion yoke as best as possible and put the magnetic protractor on this, use a mirror if necessary to get a reading, then move the pinion nose up using a thinner reduced spacer on the front getting the angle the matching but opposite angle.
I have avoided the left to right adjustment because it is not easy.
I will post on that right.

 

First I made a number of strings, each about 18 inches long with large nuts tied on either end. These I put over the front of the crank behind the damper, one on the yoke at the back of the transmission , one on the pinion yoke and hung a string straight down from the hole in the rearend cover where the spring center bolt use to be.
I then run a string from front to back tying it to the sway bar and making sure it went right between the 2 strings hanging down from the front damper and used the string hanging from the center of the rearend cover tied to a stool that I could adjust.
Nothing ligned up, nothing. The pinion pointed hard to the right of the transmission.
Something was out of alignment, Moving the transmission was out because the shifter fit perfectly and any movement would run me into the tunnel.
Next I remove the driveshaft and cut a heavy 1/2 inch plate that had the dimensions of the yoke, about 2 inches by 4 inches, In the center I drilled a reamed a hole for a 1/2 steel rod. I then cut a steel rod about 26 inches long, sharpened both ends and pressed it into the plate, sticking out the back by about 1/2 inch, I then carefullp placed it on the pinion seeing if the pointed end fit in the drilled hole in the end of pinion, I would tap the rod deeper into the plate until i got the end of the rod into the center drilled hole in the pinion at the same time as the plate mated to the surface of the pinion yoke.
This was my pointer for the pinion and it pointed about 1 or 2 inches off on the passengers side of the rear of the transmission. Couldn't push the transmission over this amount.
I then remove the rearend and slotted 3 of the 4 holes in the crossmember leaving the one on the left front alone and only this bolt holding the rearend in, I made it really tight. I then reinstalled the rearend and after checking alignment carefully pushed the pinion until the pointer pointed to the center of the output shaft on the transmission.
I then remove the rearend and put the other 3 bolts in tightening them down.
I reassembled the rearend, checked with my homemade checker, restringed the whole car and made sure everything was right.
I know it is alot of work, more then most will even consider but to me it is a labor of love and nothing is too much trouble.
If you really want to get to know your vet take a part like the swing arm, remove and reinstall it every day for a week until you have it down pat then once a year remove for inspection.
Other then the motor I do this all the time, rearend out, calipers off, rear bearings out for inspection, trailing arms off, everything and it only takes a little time after you get good at it.
All bolt holes are taped,all bolts new and antiseize of everything.
This is a poor picture of the tire but you can see the stings under the car if you look close.

I know this sounds extreme but go with the pinion angle down for now and see if that makes a difference, Done right the shifter will have no vibration.

 

Hey sign guy, I have been wondering when guys were going to be putting the tremec (Keisler) in their c2-3's and start complaining about a vibration. The main problem is that the tremec is to tall and as a result you have to lower the rear of transmission so you have about 4.5 degrees angle at the slip yoke. When you leave the rearend in its stock location , your rear pinion angle is at about 1 degree.

I installed a converted tremec a few years ago in my 63. I had the same vibration until I went to work on the angle of the third member. You need the front and rear angles of the u-joints to be equal and opposing each other, there is alot of info on the net explaining all of that.

Norv has some good ideas on string lining your driveline , but I was able to go to the local hardware store and buy a magnetic angle finder for about 10 bucks, which will stick to the u-joints and the drive shaft.

I built 1 inch spacer for the rear of the third member and then used large washers at the pinion so I could have a fine adjustment to get the angles exact. They ended up at 3 degrees each, and the car is nice and smooth.

Another thing that has to be straight is the front to back angles because you have so much angle on a 30 inch drive shaft. Since I had already built a removable cross member, I just slotted a front motor mount and moved the rear of the transmission to the drivers side. It has been my experience that they are closer to the passenger side from the factory, but sinc they only have about 1 degree u-joint angle I don't it mattered.
I am putting a 5spd tremec in my sons 73 and instead of all the rearend work , we are going to try and remove some of the tunnel under the console and build a patch over the hole.
You can also pull the transmission out and take the other shifter location plates off and grind down the raised edges and put in some buton head allen screws, then you can shim up the back transmission mount, its worth about half a degree. Hope some of this helps SSS

 

Well, I been driving this so much like it is.....I haven't noticed any vibrations...

not to say maybe they are there though....used to hit a harmonic in the shifter that made it rattle....used leather washers in the setup to stop that, never thought of driveshaft angles being any cause.....

something else to check out....

oh well....

GENE

 

Well, I stand corrected !

 

Pro Stock chassis builder Jerry Bickel assures us, "there is no mystery to pinion angle." Setting the pinion angle is the final step in driveline alignment. The goal is to create a straight line from the back of the crankshaft through the transmission, driveshaft, and the pinion of the differential-under load. Due to the tendency of the pinion to rise under load, some angle must be present at rest.

When I installed my 700R4 I shimmed the back of the tranny cross member mount. In effect lifting the rear of the tranny to get a straight shot at the pinion. I later had the rear end out for replacement and I bought the poly front pinion snubber. It came with large aluminum shims to set it correctly.

If you read the car craft article - The tranny and the pinion should end up parrallel

I've never had problems with my drive shaft or it's U-Joints. I just replace them periodically every 2-3 years.





[Modified by gkull, 2:25 PM 12/22/2003]

 

Damn good thread going here, when I replaced my rear snubber bushing with a poly one I experienced a bit more vibration and this might be what is causing it. Will be going to a 5 speed at some point and this discussion will help when fine tuning it. :thumbs:

 

Great info here. I just got my magnetic angle finder today. I am going to check everyhting before I disassemble. Should be interesting.