Quote:
Originally Posted by norvalwilhelm
I agree with this. I feel it is drive train alignment problem. Both up and down and side to side. I had a similiar problem and did nothing but align the drivetrain and now it is dead smooth up to 130 or so where I quit.


I'm considering doing this and am curious how you modified the motor mounts to properly align and center the motor/tranny in the car. My T5 yoke hits the side of the tunnel because of the offset and angle of the motor/tranny, and the load to get the tranny somewhat close to straight is way too much. My vertical angle is good, 3 degrees. The drivetrain is offset 1 1/8" and the only measurement that seems to be off is from the front framerail to the driver's mount. The rack interferes with the plum line so my measurement is not accurate (nor is the actual spot to measure from it on the dimentions diagram in an earlier post) but it seems to be off by just over an inch, which coincides with the tailshaft off just over an inch from the center of my line from the hub to the rear.

Norval or anyone else who's done this please chime in. I'm assuming some sort of adjustable motor mounting plate welded to the factory mounts would do it? Either that or some method of pulling forward the driver's mount to at least get the front to rear angle correct? I have Energy suspension poly bushings...

Thanks all.
__________________

 

This may be a bit pre mature,since I haven't yet installed the th400 trans,but may help getting a bead on the alignment.I baught two lazer pointers off the internet and fabbed a plate of 1/2" Lexan to hold the pointer as close to centered on the pinion as I could.The Lexan bolts to the pinion flange with the lazer pointed forward to the tailshaft of the trans. I taped a piece of paper on the tail shaft and rotated the piniion flange while plotting the lazer on the paper for a full rotation. At first I ended up with a 1" circle,but with some minor shimming,I got a dead on alignment for the full rotation of the pinion.My theory is this will locate the pinion shaft centerline exactly.Now I can align the tranny tailshaft to the lazer.

I'll do the same check from the tranny mounted lazer pointing back to the pinion flange ,and this time measure the distance between the lazer beams at both ends.If they are not parallel,I'll raise or lower the tailshaft,or pinion mount untill they are.

Cost me something like $12. for both lazers,and an hour with the drill press to make the Lexan plates.

The lazer beam is about 1/16" diameter,and with the length of the driveshaft being around 30",I should be within fractions of a degree to dead on.

 

This is what I found. The rear of the transmission was pointing towards the rear Passenger tire. The tranny yoke also was very close to the passenger side of the tunnel and actually hit with the larger 3 inch drive shaft.
I run a string down the centerline of the damper and the center of the rearend and found the tranny didn't point down this straight line.
I wanted to move the transmission yoke towards the drivers side but that put a twisting moment on the drivers motor mount.
I know many guys have problems getting the bolts started in the motor mounts if the tranny mount is done up.
This is how most do the motor mounts. Do the passengers side, then the drivers side then pry the tranny mount over until you can start the bolts.
This puts a tremedous twist in the drivers motor mount.
This is how I did it.
I went to solid mounts. I was agianst them at first because I thought the car would idle with a vibration but found I really don't notice a difference at idle or running speed. I do notice that the motor feels more solid and when you blip the throttle it feels alot better and I don't have to watch the blower torque over and worry about tearing another set of poly mounts.
You can remove any mount of my motor or tranny and reinstall and the bolt holes all align without prying anything.
I took a solid mount, cut off the ears that connect it to the block.
I then took the plates that come with the poly mounts, they are flat plates that bolt to the block, I bolted these to the block and the cut off motor mounts to the frame and let the 2 lay together where they were comfortable. No twist in them, the tranny poly mount was centered so the yoke lay directly over the string down the centerline.
I then just welded the plate to the motor mount, removed each mount, finished welding, painted and then put it back.
All bolts started effortlessly and there is no side loading on anything.
This is how I did it, works for me and took very little time. I also feel the solid mounts actually use the block as a stress member and it supports the frame where the steering box is bolted up.
Solid mounts are also suggested in the chevy power manual for preping a vet

 

This is what I found. The rear of the transmission was pointing towards the rear Passenger tire. The tranny yoke also was very close to the passenger side of the tunnel and actually hit with the larger 3 inch drive shaft.
I run a string down the centerline of the damper and the center of the rearend and found the tranny didn't point down this straight line.
I wanted to move the transmission yoke towards the drivers side but that put a twisting moment on the drivers motor mount.
I know many guys have problems getting the bolts started in the motor mounts if the tranny mount is done up.
This is how most do the motor mounts. Do the passengers side, then the drivers side then pry the tranny mount over until you can start the bolts.
This puts a tremedous twist in the drivers motor mount.
This is how I did it.
I went to solid mounts. I was agianst them at first because I thought the car would idle with a vibration but found I really don't notice a difference at idle or running speed. I do notice that the motor feels more solid and when you blip the throttle it feels alot better and I don't have to watch the blower torque over and worry about tearing another set of poly mounts.
You can remove any mount of my motor or tranny and reinstall and the bolt holes all align without prying anything.
I took a solid mount, cut off the ears that connect it to the block.
I then took the plates that come with the poly mounts, they are flat plates that bolt to the block, I bolted these to the block and the cut off motor mounts to the frame and let the 2 lay together where they were comfortable. No twist in them, the tranny poly mount was centered so the yoke lay directly over the string down the centerline.
I then just welded the plate to the motor mount, removed each mount, finished welding, painted and then put it back.
All bolts started effortlessly and there is no side loading on anything.
This is how I did it, works for me and took very little time. I also feel the solid mounts actually use the block as a stress member and it supports the frame where the steering box is bolted up.
Solid mounts are also suggested in the chevy power manual for preping a vet

 

Norval,

I'm not trying to be an *** and I know we had this discussion previously, everyone's gotta do what he wants but I can not stress enough how wrong this is, the engine has to be dead parallel to the vehicle centerline, it's offset 2 inches to the pass side, the diff pinion is offset to the pass side by about 3/4 inch, the engine inclination is 4 degrees down at the back and the diff has to point 4 degrees up at the pinion.

the engine crank axis/ytransmission axis have to be aligned parallel to the pinion axis (from a birdseye view), that means the entire engine & trans stick striaght backwards w/ the 2" offset from crank snout to trans yoke. Then the driveshaft angles in towards the pinion yoke, which is also offset by 3/4" because of the pinion/ring gear alignment and the necessity for the diff to sit absolutely centered from both stub axles (so that both suspension corners & halfshafts are equal lengths)

 

Twin turbo I saw this post a while ago and tried to ignore it but I couldn't with my name on it.
Do what ever but I still believe in aligning everything in the one plane.
Wrong or not my car is absolutely vibration free to any speed I want to push it. No shifter rattle,no nothing.
Roger the cascar builder believes in stringing a car too and aligning everything.
This is my last post on this and didn't want to take heat for what I believe. You really think I don't know about the offset?? My blower hole in the hood quickly points this out.
My driveline is aligned, my motor mounts are not in a twist mod and the car is vibration free.
Hopefully my last post on alignment of the drivetrain, Please guys leave my name off your post title.

 

Ask roger if his cars have offset engines and pinions, most race cars do not.

With our diff we can't have a centered pinion, it's always offset by 3/4 because of ring/pinion setup in an otherwise perfectly symmetrical IRS. that would mean that you would at a minimum have 3/4 offset on the engine too and only then you can stick the engine straight to the pinion.

I guess we'll just have to disagree on this one, I believe you when you say it's all working for you and with no vibration but the problem is, if someone else copies it it may lead to potential problems.

I can't make out from your text if you're pissed about what I wrote but I hope you're not. I'll try to get some info posted to back this thing up. I'm not sucking it from my big thumb

 

TT, I hate to disagree with your information but I will do so because I have seen this 2" engine offset information written (by others) many times. My assumption that this 2" figure is correct caused me problems when I did my Tremec swap (I couldn't figure out why my tailshaft was not off center 2"). The engine in a C3 is offset 1" from center to the passenger side. The pinion (on an early C3) is offset 1/2" to the passenger side.

I totally agree with you about the engine/diff inclination. I still believe that all C3's were built with the engine at about 4 degrees (although Norval is the only person I could persuade to measure his).

 

2"...1"...could be I forgot what it exactly was, the pinion is offset by about 2cm, so that's 3/4th of an inch, not 1/2" but it's somewhere around that.

Either way, we are not talking about inclination here, it's about the alignment from a birdseye view. the 4" inclination is right, all factory installed engines are 4deg. inclined, that's why the carb flange has a 4 deg inclination. Anyone with a factory carb manifold and an angle finder can easily check it.

I'm saying this is the wrong way;


and this the right way:



[img]http://www.clubfte.com/users/jniolon/drivelinephasing/phasing1a.jpg/img]

A = wrong B = right

Here's the old topic

http://forums.corvetteforum.com/show...ight=driveline

I don't have a better screen dump here...I'll have to do a new one from straight looking at the bottom..maybe you can see it but this represents my exact frame and the offsets and alignment. Everything is to scale.

 

Norval Thanks for your illustrated explanation of your technique, and by no means wanted to start a disagreement between board members. I feel you're one of the most knowlegable and helpful people on the forum and saw the old thread on this which is why I included your name in the post.

Regardless if I align the drivetrain or not I need to modify the driver's motor mount so I can adjust the angle. Both you guys agree the motor and tranny need to be straight, and if I'm going to go through all that trouble I leaning towards Norval's approach and the symmetry of an aligned drivetrain.

This type of work is a bit out of my realm so I the final decision will be made with the help of the local pros that will do the work, but even they are looking for recommendations of methods used by those who have done it.

That's the whole point of this section right? You can never have too much information, or be closed minded to not listen to the ideas of others or think 'out of the box'.

If anyone else has experience doing this please share it with us.

Thanks as always,
SD

 

When I replaced my auto with the 5 speed, I ran into the same problem. I installed new rubber motor mounts and found that the tailshaft was extremely close to the right side of the tunnel. I wanted to get the drivetrain as straight as possible so I shifted the rear of the tranny to the driver's side until the drivetrain was straight. I did this before I installed the new motor mounts. The right mount went in with no problems but the left mount took about 2 hours to get the bolts started. They did start without having to pry on anything but I still believe there might be a little strain on the left mount. There is absolutely no vibration in the drivetrain. I feel that if there was something wrong with what I did I would notice something. I do plan on going to solid mounts this next winter and will reposition and reweld the left mount if it needs it. I was first worried that there may be vibration induced into the interior if they were solid but that is not the case. I also believe with solid mounts the front will be stiffer and give a better feel to the car. This worked for me with no problems afterwards. I believe that a lot of the things done with the C3 were compromises between designers and engineers, and most of the time the designers won. I won't agree or disagree to the different theories of drivetrain alignment, but I do know what has worked for me.
Bernie

 

I just made 2 screen dumps, look at the centerlines...everything is aligned straight back, only the driveshaft angles:


from a side view it'll be normal like this, opposing angles @ the trans tailshaft and pinion, engine sloped back at about 4 deg.



hope these pics help.