Transmission vibration, I sure could use some help.

[Mick40]

I haven’t driven the car in a year while I was undertaking the bodywork. However, today I took it out with the body on for the first time and now have a transmission vibration. This only occurs when in gear, ( any gear), but, disappears once the clutch is pushed in. I did move the motor to allow for better alignment of the side pipes. I also needed to adjust the free play in the clutch. Other than these two tweaks I have done nothing else to the driveline. With the clutch in, the car coasts very smooth so the brakes are not dragging. It's definitely a transmission issue.

A little more background, the car has IRS so pinion angle is not an issue correct? When I moved the motor I put the same spacers for the transmission support back in place. I guess that is the first place I should look but, not sure what to look for.

The only thing I noticed was mice made a nest in the transmission. I have Forte’s hydraulic clutch so there is no cover. I remove the debris but, could this have caused some damage?

I’m at a point of installing the doors latches and I’m ready for paint. Hopefully, this will not be a huge setback.
Suggestions?



Thanks,
Mick

[GoDadGo]

If you moved the motor you may have inadvertently created an out of phase condition with your IRS differential.
Your transmission output shaft and differential pinion angles must be in phase.
I'd check that first since the vibration lessens when you are coasting when you depress the clutch.

https://youtu.be/Idk3BVDVHq4

Good Luck!

[Mick40]

GoDadGo,

What an excellent video to explain the pinion angle and vibration. As I watched and listened, it's exactly what I was experiencing. Hopefully, I can move the transmission and not have to adjust the motor.

Will report back tomorrow.

Thank you!!!!
Mick

[edwardb]

If I'm understanding your post correctly you're saying you drove the car enough before to know whatever vibration you're feeling now was not happening before. I have a hard time understanding how a transmission was not vibrating before but now is. I wouldn't hesitate to consider all possibilities, but the transmission itself wouldn't be the first thing I'd think of. You said you adjusted the clutch, and you can turn the vibration on and off by pushing the clutch. I'd start there. Doesn't completely fit what you're describing, but any chance you're dealing with flattening on the tires from sitting for an extended time? My BF Goodrich Rival S tires develop flat spots if sitting only a week or two. But smooth back out within the first mile or two.

But mainly reacting to your statement "...the car has IRS so pinion angle is not an issue correct?" No, that's not correct. Pinion angle has to be considered and correct in all cases. No matter the rear suspension type. The only difference is the IRS diff doesn't move. So what you measure is what it is all the time. With a solid axle the diff may move under hard acceleration, so is typically compensated for.

[GoDadGo]

Steve's Stupid Questions:

1. How much did you move the engine to make your pipes look right?
2. Would that change create more than a couple of degrees?
3. Do you have an old school angle gauge available?

NOTE: Home Depot has them for about $10.00.

Unlike Edwardb, I know nothing about Ford Clutch Adjustments since I'm from the Dark Side.

Steve

[NAZ]

You do realize that pushing in the clutch with the trans in gear does not stop the trans gears and shafts from turning? It only decouples the engine from the trans. My money is on a drive shaft / u-joint vibration. It doesn't take much shimming of the trans or engine mounts to make a significant angle change when you're dealing with a short driveshaft.

My advice is to always start with the basics, and in this case since you moved something that can affect the drive shaft angle, start with the pinion angle set-up. Drive shaft vibration is sensitive to load -- accelerate and you add load, pull in the clutch and the load is removed.

[Mick40]

First and foremost, thank you all for the help.

I moved the engine quite a bit so that is likely the culprit. Edward, the car sat on jack stands the entire year so no flat spots on the tires. If that were the case the vibration would not significantly reduce once the clutch is pushed in. The vibration is evident the most when accelerating. Just like video GoDadGo shared the faster the rotation of the driveshaft the more vibration. Naz, I too learned to start with the basics. So, given it ran fine prior to moving the engine, I'm going to start with the tailstock on the transmission. Edward, you mentioned in another post about a 1.2-degree pinion angle. When I originally installed the driveshaft I made it visually level with the differential. I hope once I get under the car it will be obvious that it's no longer the case. If not, I will look to change the angle regardless and see if there is a noticeable difference.

I very much appreciate everyone's help.

[GoDadGo]

If you don't have an angle finder you can grab one of these, or a similar unit at any ACE Hardware, Home Depot, Lowes, Etc.

https://www.homedepot.com/p/Johnson-...-700/100161689

Hopefully the angle of the dangle is off and some simple shimming will have you grinning and vibration free once more.

Good Luck From The Dark Dart Side!

Steve

[Mick40]

Hi Steve,

I have a magnetic angle gauge somewhere in my toolbox. If not, I will look to download an app. The more I read about pinion angle the more I believe this is the problem. A good place to start. Thanks for the support!

[RJD]

TREMEC has an easy app - TREMEC TOOL BOX, Driveline Angle Finder. You use your smartphone to take three readings - transmission output shaft, driveshaft, and rear axle, and it determines whether your driveline angle is within acceptable limits.

40AC85C2-3557-44E7-8EB0-C2643F23914C.png

[wallace18]

I had the same issue on a MK4 IRS customer build. Raising the rear of the trans fixed it 100%.

[Papa]

TREMEC has an easy app - TREMEC TOOL BOX, Driveline Angle Finder. You use your smartphone to take three readings - transmission output shaft, driveshaft, and rear axle, and it determines whether your driveline angle is within acceptable limits.

40AC85C2-3557-44E7-8EB0-C2643F23914C.png

Plus 1. This worked better than the cheap angle finder I bought.

[wareaglescott]

No one else has mentioned it but are you sure you got everything out of there from the mice? The access hole isn't that big. The mice can certainly get farther up in there that your hand! If you didnt have any problems before the mice but do now that is certainly something I would give some consideration to.

[Mick40]

Update-

* The driveshaft was in phase but, was out of alignment by at least 3 deg- Corrected.
* There was a ton of insulation on in in the clutch plate- Removed but, concerned it is stuck to the springs especially after driving it. Curiouos if anyone thinks this should be replaced?

The car vibration is much less but, still present. I'm not sure the clutch ( which is new), needs to be broken in or the mice really did a number with insulation. Under acceleration, the car has no vibration now. However, at idle in neutral when the motor is reved i can feel a vibration. Regardless if the clutch is in or not. I don't recall this but, it could have been present before. I installed a new mild heavy clutch. I recall reading that maybe the harmonic balancer needed to be upgraded? Yeah, I'm guessing here but, moving in the right direction.

I have little seat time in the car. What I may have thought was fine a year ago may not have been the case. Curious about anyone's thoughts on the harmonic balancer theory.

Thanks, everyone!
Mick

[GoDadGo]

Darn; I was really hoping your engine move was the culprit.
You're Definitely Outside Of My Area Of Expertise!
Maybe if I had slept at a Holiday In Express last night I'd have the right answer for you but I don't.
Good Luck!

[Railroad]

Vibration with trans in neutral rules out drive line issue.
Clutch break in will not cure a vib.
Harmonic balance is weight matched to your flywheel, or zero balance.
No way to tell what the rats put in there.
I would have someone turn the engine over by hand, watching inside the clutch fork window for debris.
Remove what you can and drive it. Centrifugal force will work for you.

[NAZ]

Sounds like you have solved the drive line vibration.

All engines vibrate to some degree and may seem worse at different RPMs. You may be more sensitive to it after the drive line vibration experience. Using urethane motor and trans mounts can add a bit of harshness as the durometer may be harder than a typical OEM rubber mount that tends to dampen vibration better. Engine vibration can also resonate with the natural frequency of chassis, body, and sheet metal parts making it seem worse. And while mice debris may have some effect I think that's not likely as when the engine is running there is a great deal of centrifugal force working to throw soft debris out into the bell housing.

Have fun with your build.

[BadAsp427]

You said you had moved your engine for the side pipe install... Do any of your side pipe support brackets touch the body or frame? If so, if you can insulate that area with a piece of rubber you may find that you will not feel that vibration. I had an issue where I did some engine/side pipe adjustments that left the driver's side bracket pushing up against the bottom of the body pretty solid. I then felt a "BAD" vibration at 2100 RPM. Sitting still, driving down the road, etc... any time I was at about 2100 RPM, I had the vibration. Hope this helps.

[Mick40]

A lot goes through your mind when you're trying to diagnose a problem. I believe when I installed the clutch flywheel I may not have installed the correct weight. I started this about 10 years ago so trying to recall specific details is difficult. Heck, I have trouble remembering what I did yesterday. So, I'm going to remove the transmission to just be sure. I'm fortunate to have a lift. From what I have read from others this should take me and a buddy a few hours. At the very least I will have peace of mind.

BadAsp427, I don't have the hangers installed yet, I ordered Gas&Go pipes which should arrive soon.

I really appreciate the help it's a good learning experience none the less. Hopefully, this will be helpful to someone else.

I will provide an update later this week.

Mick

[CraigS]

I forget all the details but SBFs are usually either 28 or 50 oz balanced depending on model. If your engine was stock, or a close to stock rebuild, it is likely one or the other. You may be able to determine which by finding out what vehicle it was sourced from. Then the flywheel and balancer should match which ever it is. If it was built from parts, there is a 3rd choice, zero balance, but I believe that is fairly rare. I 'think' you can determine which flywheel you have by comparing to pics of known flywheels. Also I remember there are some aftermarket flywheels that have a bolt on weight so they can be used as either.

[SJDave]

A lot goes through your mind when you're trying to diagnose a problem. I believe when I installed the clutch flywheel I may not have installed the correct weight. I started this about 10 years ago so trying to recall specific details is difficult. Heck, I have trouble remembering what I did yesterday. So, I'm going to remove the transmission to just be sure. I'm fortunate to have a lift. From what I have read from others this should take me and a buddy a few hours. At the very least I will have peace of mind.

BadAsp427, I don't have the hangers installed yet, I ordered Gas&Go pipes which should arrive soon.

I really appreciate the help it's a good learning experience none the less. Hopefully, this will be helpful to someone else.

I will provide an update later this week.

Mick

As long as you going to all that work, and you want more peace of mind, have the pressure plate assembly balanced. Cost about $50 in California to have an engine builder spin it on his dynamic balancer. I had terrible Vibrations...turned out it was the King Cobra Clutch. Made for Ford by Valeo, purchased from Forte...you never know. After I got the clutch fixed, I still had a minor vibration, that was cured by setting the transmission output shaft parallel to the pinion input gear shaft. (IRS)

HTH,
Dave

[Mick40]

Great advice Dave but, it's too late. Today I replaced the flywheel which was no easy task. If I ever ( let's hope not), need to do this again I'm taking the engine out. I was unable to twist the trans with the bellhousing installed enough to clear the clutch. So, I removed the trans from the bellhousing which gave me the room I needed. I had help and was working with the car on a lift and this still was a huge undertaking.

The flywheel I had installed was not balanced with a 50oz weight so, I'm hopeful this will eliminate the vibration. It certainly will make it better. This along with a properly aligned driveshaft should be a lot smoother. My plan is to test it on Wednesday however, I still have quite a bit of assembly needed.

For those of you that have removed the transmission with the engine in the car, you have amazing talent with a lot of patience no doubt.

I will provide a final update after road testing.

Thanks for all the help. Hopefully, this will prevent someone else from making this mistake.

Mick

[Mick40]

Update - The problem has been corrected!!!! The car is civilized now and drives oh so smooth.

Thanks for all the help and support!

Mick

[wallace18]

Congrats!

[GoDadGo]

Bravo & Well Done Mr. Mick!

Now head down South for Cruising The Coast!