Chasing a Vibration - Flex Plate?

[barnett468 418]

5 hours ago, MikeStang said:

Nope... My vibration is not engine or trans related.... I can hold any RPM in neutral and its smooth... my engine is also Zero balanced so it's not a balancer or plate issue and vibration was there b4 and after I had motor freshened up.

In case anyone wondered what 4.5 Leaf Mid eyes with 275/40/18 looks like in terms of ride height..here it is

 

its most likely caused by driveshaft angle then.

 

[RPM 1,190]

1 hour ago, barnett468 said:

its most likely caused by driveshaft angle then.

 

Miiike! Until just now, the only angles I've measured on my 69 were the crank and pinion, to make sure they were close,  <1°.  I've got a triangulated 4 link on the rear. I measured the drive shaft to pinion, and found the ds is 2.85° up. A quick search found 3 different answers for the acceptable degree difference. Should it be closer to 1°? What say you Mike?

[RPM 1,190]

On 6/22/2018 at 5:51 PM, bigmal said:

Thanks Barnett, it's cyclic. 

Hey Mal, I just re-read this thread and watched your video. Seeing your steering wheel shake sure looks to me like a constant vibration. Am I wrong, again?

On my vibration, I'm going to check the radial and lateral run out of the rear axle hubs. 

Best of luck. 

[bigmal 225]

1 hour ago, RPM said:

Hey Mal, I just re-read this thread and watched your video. Seeing your steering wheel shake sure looks to me like a constant vibration. Am I wrong, again?

On my vibration, I'm going to check the radial and lateral run out of the rear axle hubs. 

Best of luck. 

Hi Bob, to be honest it's now a few months since I have run the car so I am not sure if it was cyclic or constant at 1600 rpm.

[bigmal 225]

Another question as I am pulling the last little bit of my hair out. I started the engine today and it starts fine but the starter was not disengaging so I removed the inspection plate and could see that the pinion was retracted but just touching the flex plate gear. I removed the starter and it shows that the flex plate gear has been contacting the starter housing as well as the pinion. 

This is the original starter and flex plate so nothing should have changed. I did make a fundamental error when bolting the transmission to the engine before installing. I bolted the torque converter to the flex plate first and after tightening the bell housing bolts the engine was locked as the torque converter was not lined up correctly with the transmission shaft. I removed the transmission and aligned the torque convertor correctly, installed the transmission and then bolted the torque convertor to the flex plate as I should have done in the first place.

Is it possible I have bent the flex plate enough to fowl with the starter or is there another possible reason?

Feeling like an idiot and swearing a lot.

 

[barnett468 418]

12 hours ago, RPM said:

Miiike! Until just now, the only angles I've measured on my 69 were the crank and pinion, to make sure they were close,  <1°.  I've got a triangulated 4 link on the rear. I measured the drive shaft to pinion, and found the ds is 2.85° up. A quick search found 3 different answers for the acceptable degree difference. Should it be closer to 1°? What say you Mike?

Your driveshaft goes uphill 2.85 degrees from the trans?

What is the angle from the pinion to the driveshaft?

Ideally, the amount of driveshaft angle at the trans and pinion should be exactly the same but in opposite directions. For typical street use, anywhere from 1 1/2 to 3 degrees seems to be fine in my experience. The higher the speed, the straighter the shaft should be providing it is never exactly parallell to the trans and pinion for a prolonged period because the u joints will not "rotate" in this position which can cause premature u joint wear.

One of the major issues with setting up the driveshaft angle, is that on a leaf spring suspension that does not have a torque bar like a old SS Camaro has, the springs will flex (develop a slight S shaped bow) under load, which allows the pinion to rise.  The greater the load, the higher the pinion will rise, which of course changes its angle relative to the driveshaft. This means that the angle of the shaft will change the harder one accelerates and the faster one goes. The pinion can rise several degrees in some cases, but I typically allow for around 1 - 1 1/2 degrees in rise at freeway speed on standard leaf spring type applications. Some others do it differently but this is the method that has worked for me.

 

 

 

 

 

 

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[RPM 1,190]

1 hour ago, barnett468 said:

Your driveshaft goes uphill 2.85 degrees from the trans?

No. It goes uphill 2.85° from the third member pinion, and down 3.4° from the trans. 

What is the angle from the pinion to the driveshaft?

2.85°. 

Ideally, the amount of driveshaft angle at the trans and pinion should be exactly the same but in opposite directions.

I agree, mine are .55° apart.  

One of the major issues with setting up the driveshaft angle, is that on a leaf spring suspension that does not have a torque bar like a old SS Camaro has, 

I don't have leaf springs. I installed a triangulated 4 link. 

 

 

[1969_Mach1 333]

14 hours ago, bigmal said:

Another question as I am pulling the last little bit of my hair out. I started the engine today and it starts fine but the starter was not disengaging so I removed the inspection plate and could see that the pinion was retracted but just touching the flex plate gear. I removed the starter and it shows that the flex plate gear has been contacting the starter housing as well as the pinion. 

This is the original starter and flex plate so nothing should have changed. I did make a fundamental error when bolting the transmission to the engine before installing. I bolted the torque converter to the flex plate first and after tightening the bell housing bolts the engine was locked as the torque converter was not lined up correctly with the transmission shaft. I removed the transmission and aligned the torque convertor correctly, installed the transmission and then bolted the torque convertor to the flex plate as I should have done in the first place.

Is it possible I have bent the flex plate enough to fowl with the starter or is there another possible reason?

Feeling like an idiot and swearing a lot.

 

I don't know about bending the flex plate.  With the starter removed I rig something to check the runout of the flex plate while rotating the crank from the balancer bolt.

You did remember to install the separator plate between the engine block and the trans?

[bigmal 225]

42 minutes ago, 1969_Mach1 said:

I don't know about bending the flex plate.  With the starter removed I rig something to check the runout of the flex plate while rotating the crank from the balancer bolt.

You did remember to install the separator plate between the engine block and the trans?

I nearly forgot the plate and remembered at the last minute as it was on a different shelf in the garage. I also thought that the small 3 1/2" plate with the 6 holes may be meant to go between the flex plate and the crankshaft but have confirmed that it is in the correct position between the flex plate and the bolts. 

I will try doing a runout on the flex plate later today. Thanks.

[1969_Mach1 333]

41 minutes ago, bigmal said:

I nearly forgot the plate and remembered at the last minute as it was on a different shelf in the garage. I also thought that the small 3 1/2" plate with the 6 holes may be meant to go between the flex plate and the crankshaft but have confirmed that it is in the correct position between the flex plate and the bolts. 

I will try doing a runout on the flex plate later today. Thanks.

With your auto trans, measuring through the starter opening, it should be 3/4" ( or very close to it) from the surface the starter seats against on the separator plate to the face of the flexplate teeth.

[det0326 179]

Sorry Bigmal      

You sure are having your share of problems. If I am following your earlier post it seems you have bent your flex plate. If you have to take transmission back out I would give a close inspection to the transmission pump also. 

[bigmal 225]

27 minutes ago, 1969_Mach1 said:

With your auto trans, measuring through the starter opening, it should be 3/4" ( or very close to it) from the surface the starter seats against on the separator plate to the face of the flexplate teeth.

I did a runout (rudimentary with a Vernier) and not good. In metric it's 11.5mm to 13.5mm or 14/32 to 17/32 and nothing like 3/4". I think it's a forgone conclusion that I have damaged the flex plate so I will replace it. Thanks for trhat.

[bigmal 225]

14 minutes ago, det0326 said:

Sorry Bigmal      

You sure are having your share of problems. If I am following your earlier post it seems you have bent your flex plate. If you have to take transmission back out I would give a close inspection to the transmission pump also. 

That has been concerning me as well. I don't know how easy they are to damage. As I don't know anything about autos I don't how to check or what to look for. And being the Christmas New Year period nothing is open in Australia for a few days/weeks. Maybe I'll go fishing. Thanks.

[bigmal 225]

Also, thoughts on the starter pinion?? Need replacing or can I get away with just dressing it?

I bought a high torque starter a few months ago but it won't fit with the RRS steering rack so I need to keep the old style.. 

[det0326 179]

10 minutes ago, bigmal said:

Also, thoughts on the starter pinion?? Need replacing or can I get away with just dressing it?

I bought a high torque starter a few months ago but it won't fit with the RRS steering rack so I need to keep the old style.. 

If it was mine I would replace starter pinion. You sure don't need to screw up a new flex plate. 

What transmission do you have ?  Most of the time a situation as this may be forgivable but the gears in the pump I believe are cast and can crack if distorted enough.  Did you start the engine before you realigned the converter?

[bigmal 225]

7 minutes ago, det0326 said:

If it was mine I would replace starter pinion. You sure don't need to screw up a new flex plate. 

What transmission do you have ?  Most of the time a situation as this may be forgivable but the gears in the pump I believe are cast and can crack if distorted enough.  Did you start the engine before you realigned the converter?

Thanks for that. No, I didn't attempt to start it. I was turning the engine over by hand as I bolted the bellhousing up. I have an FMX. 

[unilec 57]

Looking at the back of the pinion, it looks like it has been rubbing against the flex plate, maybe try a space and see if it makes any difference.

[barnett468 418]

6 hours ago, RPM said:

 

"Ideally, the amount of driveshaft angle at the trans and pinion should be exactly the same but in opposite directions.

I agree, mine are .55° apart. "

That is actually such a small amount that it "should" not cause a problem. I have seen them farther apart then that and not cause a vibration. I'm guessing that your link arms are not adjustable. If not you could install ones that are adjustable on the top or the bottom then set the pinon angle the same amount as the trans etc and see if that helps. Some driveshafts can also produce harmonics that can cause a vibration but these are typically aftermarket ones.

 

"One of the major issues with setting up the driveshaft angle, is that on a leaf spring suspension that does not have a torque bar like a old SS Camaro has, 

I don't have leaf springs. I installed a triangulated 4 link."

Yes I saw that, I just added the leaf spring comment for others that might read this that have leaf springs.

 

.

[RPM 1,190]

Thanks Mike. I've got right and left hand rod ends on all 4 rear control arms. 

[MikeStang 247]

Well I am running leaf springs but also have Cal-Trac's which I have tried adding more or less preload to in order to see if that helps any...it does not Lol!!.

 

[MikeStang 247]

On ‎12‎/‎30‎/‎2018 at 4:28 PM, RPM said:

Mike, do you know your best friends 69 crank and pinion angles, or can you get them? Looking at the pic of your 69, ours sit the same. However, my exhaust doesn't scrape speed bumps or driveways. 

I don't know the angles but I can get them the next time I am near his car... His sits just about the same as mine does. 

It may be a little bit b4 I can get the measurements 

[RPM 1,190]

I'm only interested if it's no trouble, like if he knows them without measuring.

[MikeStang 247]

On 1/8/2019 at 2:45 PM, RPM said:

I'm only interested if it's no trouble, like if he knows them without measuring.

No he wouldn't know them since we have never had a reason to measure them.

 

[MikeStang 247]

On ‎12‎/‎30‎/‎2018 at 10:31 PM, RPM said:

Miiike! Until just now, the only angles I've measured on my 69 were the crank and pinion, to make sure they were close,  <1°.  I've got a triangulated 4 link on the rear. I measured the drive shaft to pinion, and found the ds is 2.85° up. A quick search found 3 different answers for the acceptable degree difference. Should it be closer to 1°? What say you Mike?

Yep 1 degree max seems to be the consensus I have read 

[bigmal 225]

Well I finished my rebuild and ran it today for the first time. 

I ended up installing a new correct flex plate which is a different bolt spacing to the original and the torque converter wouldn't fit. As this is the correct flex plate I bought a new torque converter which is substantially larger and 2500rpm stall. Engine was rebuild +.020 with 2V heads (were 4V) and some other bibs and bobs. Spent way more than I wanted to.

……………….It runs like a top. No vibration and more power. I also installed an electric fuel pump and my starting problems are gone.

Definitely a worthwhile venture. Thanks everyone for your suggestions. I wish I could pinpoint exactly what was the cause of the vibration but very happy it's gone.