Technical 1950 Chevrolet 2 dr. styleline vibration

can't do right now have the u bolts off

 

Funny that's the same kit the owner of the car said it needed, that looks like the most fool proof option

 

Well the crank angle is more then close enough. Maybe making the pinion parallel with the tail shaft will help. Maybe checking the balance on the drive shaft will help. Could be that you are using the wrong flex plate too. GM used internal and external balance flex plates. if you are running an internal balance motor with an external balance flex plate or vice versa you are going to pick up some vibration.

 

Have some pictures above. its a 1973 chevelle station wagon rear end with the mounts welded on from the original 1950 rear end to use the original springs etc,

 

How do you check to see the difference flex plates and no which balanced motor you have

 

How do you tell if flexplate & damper match engine? The 350 is a 1971

 

The external balance flex plate with have a little weight welded to it out near the ring gear. It will just look like apiece sheet metal with a couple of tack welds. the '71 motor should be internal balance if it is a 350.

 

Your engine is older, it is internally balanced. The key is the rear main seal. After 1987,8, or 9, they have a one piece main seal that is visible on the rear of the engine and use different flywheels and harmonic balancers on the front. Your flexplate & front balancer should not have added balancing weights added to them. The weights show up as welded on chunks on the flywheel/flexplate and the harmonic balancer on the front.

You say it doesn't shake when revving the engine when standing still, these are probably not part of your problem.

OOOS, sorry ******, I print slow & the magic marker messes up the screen

 

Something is't right here! First of all, that is not a 73 Chevelle Station Wagon rear end; it is from a Pontiac or Oldsmobile, as evidenced by the "scallops" in the cover of the rear end housing (I'm not sure an Olds/Pont style cover will fit the Chevrolet style, but it's possible). It does't appear the rear end is even bolted to the springs (???), but you unbolted them before the photos, and what's with the upper control arm (not needed/used with a leaf spring setup)? Is the front end of the upper control arm connected to anything?
I would removed the entire rear end, torch off ALL the brackets and finish grind the remnants, get a leaf spring mount kit (like has already been suggested), and WELD the spring pads in (don't use the pivots front the original leaf spring setup), being sure to have the angle set up correctly. I'm surprised the pivots even bolted in, IN LINE with the lower trailing arm brackets. The rear end looks to be tilted down at the front (unbolted causing this?); I can understand a vibration. The car looks good, but the rear end is a mess and needs to be straightened out before anything else is done. Is the front suspension stock? I'm having some difficulty wrapping my mind around what was done. Looks nothing like the conversion we did on our 51 Bus Coupe. JMO. I am Butch/56sedandelivery.

 

you can not have a leaf spring rear with the upper bars from the original Chevelle rear in use. you need to unbolt those upper bars and get new spring pads and weld them to the rear and mount the rear end like a normal open drive car would have. whoever put that together just was not thinking.

 

From what I have leaner here with this post and all the posts, I would be better off to get a new leaf spring kit and get rid of the set up I have now. Thanks for the posts

 

Update on post. I ended up take the car to a custom shop. They used the original springs, attached new perches and removed the stabilizer braces, set the pinion angle to 1 degrees up, the ****** output shaft is at 3 to 4 degrees down as close as I can gauge with angle meter. Drive shaft is 5 degrees. This fixed the vibration fairly good but there is still some, more noticeable when accelerating . So to rule things out I have had tires balanced, reset one rear brake(dragging some) checked wheel bearings, checked rear end, had new driveshaft fabricated and balanced at Fleet Pride. I don't heard any strange clinking, t******* ,etc coming from the flex plate area, however I do get a squeal for a second very occasionally on start up from the starter. I contacted the previous owner who had the transmission professionally rebuilt . The owner installed it and was sure he installed the correct flex plate( who knows??) .Anyone with suggestions things I'm over looking. The car has 450 miles on rebuilds.

 

If that one degree is honestly what it is, and the trans output is 3-4 degrees, this won't work. The two joints need to be equal degrees, but opposing.

"driveshaft angle" means nothing, you must have the cross style u-joints working together, not fighting each other. That fighting comes from the fact that the driveshaft does not have a constant velocity when the shaft is driven by a cross type joint running at any angle other than zero.

so, the driveshaft actually speeds up and slows down as it turns, and if the rear joint has the same angle, then they won't fight each other. You cannot eliminate vibrations if they are different angles.

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I've been thinking about that after everything I have read on pinion ,****** angles have to be parallel. Was thinking of shimming transmission up to 1 degrees. For sure the pinion is at 1 degree up.

 

Might be tough to do if the trans hits or bell hits the firewall or the floor.

one easy option, if you have leaf springs; A spring shop for repairing truck springs should have tapered wedges that are made to do a caster change on solid front axles. These come in different degrees. Loosen the U bolts and slide them in between the perch plate and leaf spring.

if I get to it, I could take a pic of some. They have a long u slot in center, so it can slide past the spring center bolt.

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I started to order shims when I started to fix pinion at beginning of my post, but because the person that installed the 73 chevelle rear end cut and welded the perches off the original 50 rear end and they mount different and pivot so I couldn't use them. I'm going to have to do some measuring but just eyeing it up there maybe room to raise ****** 3 degrees.

 

Disclaimer : I did not read each reply.
'49 to '54 rear is of the TORQUE TUBE variety, the Chevelle is an OPEN DRIVELINE.
If you have a 350 engine with a TURBO 350, you do not have the torque tube rear end.
The DESIRED driveline angle is 3* down, from the ****** and 3* up from the pinion.
The DIFFERENCE between the two angles should be zero to 1*.
Consult a ****er Manual or a Dana Manual for verification to what I have written.

 

The original owner took mounting/perches off the 1950 rear end and welded on the 73 chevelle rear end, that's where the problem developed. I have since had new perches installed but it seems the pinion/****** angles are not quite right. So looking at shims on perches or shimming the transmission.

 

Here are some truck front axle shims I saw on hamb. The two styles at the top make them easy to slide in there, by just loosening the U-bolts. Some have the fat end opposite of these, but they work the same.

 

Don't know if you have seen how the 1950 perches were mounted but they were in front of the axle on a bracket mounted to the axle and pivoted. So when they put the new perches on the axle and used the same 1950 spring to keep the axle center in wheel well they drilled another hole to the front of the perch to anchor to spring centering pin. I could do this also with shims, but with the ****** at 4 degrees down the driveshaft u joint is just about straight out of ****** out put shaft, that's why I'm thinking it would be better to shim ****** up 3 degrees ,with the pinion at 1 degrees up and drive shaft 5 degrees it has some angle to it. There are pictures of the 1950 perches I post on page 1 of this post.

 

I did not know they went with the 50 style perch design,

yes if you have no obstacles, shim the transmission mount.

when you get it moved, you'd not only like to get a matching/(or close) angle on both U-joints, but you need some amount of working angle in the joints to move the grease under the needle bearings on each rotation, for longer life. Internet says 3 is "optimum", but lower is ok if the needles get enough movement. There should be a minimum spec on those web articles on setting driveshaft joints up

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Butch is correct, the rear end attempt is just a mess.
Straighten out the mess already there, then get that pinion to aim upward.

 

The mess is straighten out with the new perches, just don't have the angle quite right.

 

I should of added the upper control arms are gone, will have to post picture tomorrow, and the previous owner who in stalled the rear end said 1973 chevelle station wagon rear end it is.

 

When I put my Ford together I needed an adapter plate to get the Muncie to mate up with the Ford cross member. I used flat steel 4" x 1/2" thick. I also machined up some 1/16" shims in case I had a angle issue.

I took great pains to get the engine 2-3* angled down when I made up the motor mounts. Rear was in the stock factory position. In the end it was perfect with no shims. I would try something at the transmission mount. Try some big flat washers (or fender shims) to see if you can improve the vibration, then make or have a flat steel plate made up the same thickness. Ace Hardware or Lowes should have a selection of flat stock that may help. Drilling a couple of holes should be easy to handle.

 

Good idea. I was thinking, looks like I should but if I don't have room to bring ****** output up 3 degrees, It would be more work but could raise ****** as much as possible and get the rest shimming rear end.

 

Do this properly. The engine and transmission are already in the right place.

If the pinion angle is actually 1º, then get a pair of 2º wedge shims, put them under the leaf spring perches, and be done with it.

Shimming the engine and transmission up to 1º increases the working angles of the joints, which will enhance vibration, and shorten their lifespan.

From one of my previous posts: The more I think about this, the more I realize that we may be inadvertently be sowing confusion about driveshaft slope and u-joint angles, by the shorthand that we use to describe them.

We all know the old advice: tailshaft 3º down, pinion 3º up (with some caveats).

The trouble is, those two angles are just reference angles to make it easier for us Humans to understand.

The both reference the horizon. We will skip the part that the horizon is not flat, but a curve.

When you measure these using an angle finder, that tool is referencing the center of the Earth, via gravity. We will skip over the part that lines that are perpendicular to the center of the Earth are not parallel to each other.

Neither the tailshaft angle, nor the pinion angle are actually the critical angles, per se.

Imagine these two setups:

Both setups ***ume engine and transmission parallel with ch***is center-line, and axle square in the ch***is.

P***enger car: tailshaft down at 3º, pinion up at 3º, pinion 48" behind, and 3" below the tail shaft.

4x4 truck: tailshaft down at 3º, pinion up at 3º, pinion 48" behind, and 23" below the tail shaft.

The angles are good, so all should be well with both, right? Nope.

The first one will see 200+ at Bonneville, with no issue. The second will shake white off of rice at 55.

Why? The angles of operation between the tailshaft, and the driveshaft, the driveshaft and the pinon are actually the critical angles here, and on these two setups, they are totally different.

In the case of the p***enger car, they are within the acceptable range. In the case of eh 4x4 truck, they are not.

The smoothest operation would be tailshaft 0º, driveshaft horizontal, no pinion offset, and pinion 0º. There are some who would argue that this would lead to premature u-joint failure, due to lack of grease circulation, but I tend to doubt it, as most cars get driven on roads that are substantially less than perfect, and not operated stationary.

The farther the angles get from 0º, the more each pattern of movement of each of the two planes of u-joint movement move from a perfect circle to an ellipse.

Contrary to what many think, u-joints do not move at a constant velocity. Having complimentary angles at each end of the driveshaft helps cancel out that speeding up and slowing down of the shaft at each end, to an extent. Even in the aforementioned p***enger car application, there is vibration, but it is dampened by the motor and transmission mounts, suspension bushings, tires, etc., so you don't feel it. Push the operating angles too far, the ellipse becomes too great, and you will shake your teeth out.

And remember kids, your driveshaft is a dumb chunk of metal, and so are the u-joints. They don't know where the Earth is, where the horizon is. Slope and working angles are relational to the working components, and not external factors. Those are just external reference points to help us to comprehend what is going on.

TL;DR: ONLY WORKING ANGLES REALLY MATTER!

 

OK, on my son's 54 sedan we installed a Olds rear with spring pad like you did setting the angles right and it was ok ...but under hard accelaration (young guy and foot was allways in it) the springs would wind up and the front yoke would hit the floor. Finely it bent the springs. the fix was to make some traction bars and replace the bent main leaves.
I don't know it the tourque tube springs are strong enough for an open drive set up.

 

Something I will have to maybe watch, when I get my angles correct

 

It's true that the springs are "marginal" when used with a V-8, and with any "spirited" driving. The torque-tube itself served as a "traction bar". There are aftermarket spring kits such as Posies and Ch***is Engineering, but simple, ******* type, traction bars, and overload shocks handled everything we threw at the 51 Bus Coupe with a mild 350, built Glide/converter, and 4.88 Positraction. The short answer is traction bars, in my opinion. I am Butch/56sedandelivery.