Chasing a Vibration - Flex Plate?

[bigmal 225]

11 minutes ago, smh00n said:

It might be worthwhile pulling the housing and having it checked for straightness? More of a make sure nothing else is going to stuff you up step.

Worth considering. I'll see how it goes with the straightened axles first. Thanks

[bigmal 225]

I got to test drive this morning after straightened axles, new wheel bearings, rebalanced tailshaft, new universals, new yoke and new transmission extension housing bushing.

While I feel there is an improvement it definitely still has a vibration. 80 and 115 kmph is the most noticeable. While it is no longer severe, it's still not right. I keep feeling like it's the tail shaft. I can see the vibration through the shaker when driving which continues when I put it in neutral and engine returns to idle.

Running the engine in neutral and moving through the rev ranges the engine is smooth.

I would like to try a different set of rear wheels for a test drive and see if that makes a difference. I may swap front to rear for a start. It's a good thing I drink! (not while driving).

[det0326 179]

Bigmal If it wasn't for bad luck u would not have any luck. lol  This is so disappointing I know. 

I know you have been over this a thousand times and you may have answered this before, I just missed it but I do have one more question about it. The drive line angles u say are 0 that they more or less canceling each other out.  I  think you said you were getting your transmission angle from front engine pulley while this should be fine the transmission yoke I feel would be more accurate. I would get all four wheels up on blocks doesn't have to be perfectly level and try to get the trans angle directly from the yoke, it should be pointed down toward ground by some degree and the front of the  pinion yoke should be pointing up by some degree. I know that you know all this but if you decide to try this again please post these angles for us. Some people use a cell phone to find these angles my phone has throwed me a curve before. An inclinometer has always served me well.  

 

 

 

 

[RPM 1,190]

"I think you said you were getting your transmission angle from front engine pulley while this should be fine the transmission yoke I feel would be more accurate."

Man, if those two aren't the same angle he's got bigger problems. 

 

[rwcstang 201]

RPM could it be the transmission housing wasn't indexed? 

[RPM 1,190]

I not know. I've only used stock bellhousings.

[bigmal 225]

5 hours ago, det0326 said:

Bigmal If it wasn't for bad luck u would not have any luck. lol  This is so disappointing I know. 

I know you have been over this a thousand times and you may have answered this before, I just missed it but I do have one more question about it. The drive line angles u say are 0 that they more or less canceling each other out.  I  think you said you were getting your transmission angle from front engine pulley while this should be fine the transmission yoke I feel would be more accurate. I would get all four wheels up on blocks doesn't have to be perfectly level and try to get the trans angle directly from the yoke, it should be pointed down toward ground by some degree and the front of the  pinion yoke should be pointing up by some degree. I know that you know all this but if you decide to try this again please post these angles for us. Some people use a cell phone to find these angles my phone has throwed me a curve before. An inclinometer has always served me well.  

 

 

 

 

Hi mate, I am using a digital inclinometer that has a zero function. I have been setting it to zero on the harmonic balancer to compare with the angle at the diff universal.

I have experimented with shimming up and down from zero to see if it helped. zero had the least vibration.

[bigmal 225]

4 hours ago, rwcstang said:

RPM could it be the transmission housing wasn't indexed? 

What is transmission housing indexing? It is a stock FMX on the back of a 351 Cleveland.

[RPM 1,190]

I've not heard of it being done on OE early Mustang bellhousings and their manual trannys, nor an automatic. But, it's where you attach a dial indicator to the flywheel, rotate the motor, and check to see if there's any runout on the trans hole. 

https://www.moderndriveline.com/proper-bellhousing-alignment-indexing/

[det0326 179]

On 4/7/2023 at 12:55 PM, RPM said:

"I think you said you were getting your transmission angle from front engine pulley while this should be fine the transmission yoke I feel would be more accurate."

Man, if those two aren't the same angle he's got bigger problems. 

 

2 words Bob "bent pulley"

[bigmal 225]

6 hours ago, det0326 said:

2 words Bob "bent pulley"

Hi mate, I used the balancer rather than the pulley to get the measurement. With the engine running the balancer and pulley are true, so it will be in line with the centerline of the engine. Thanks

[smh00n 87]

I would spend some cash with another driveshaft place and have them check the shaft. If it is at 2 different speeds it's definitely harmonic. Thinking out loud below;

Have you tried changing gear when you feel it? So keep to 80k but increase engine revs; try both second and first gears. Does applying the brakes change it? If you drop it into neutral is the vibration still present? Can you swap wheels front to back, or if not, side to side to see if that changes it? 

Does it feel more towards the rear or the front? Could it be a wheel? Is the vibration a constant rattle or does it cycle from minor to major? Does it do it when cornering or just straight line?

Perhaps take off both rear brake drums, spin it up and see if the axles are true. I still suspect there may be housing damage. A 9" is a big sucker and if you had bent axles it's had some sort of hit in the rear so maybe the tubes are out of alignment?

[bigmal 225]

6 hours ago, smh00n said:

I would spend some cash with another driveshaft place and have them check the shaft. If it is at 2 different speeds it's definitely harmonic. Thinking out loud below;

Have you tried changing gear when you feel it? So keep to 80k but increase engine revs; try both second and first gears. Does applying the brakes change it? If you drop it into neutral is the vibration still present? Can you swap wheels front to back, or if not, side to side to see if that changes it? 

Does it feel more towards the rear or the front? Could it be a wheel? Is the vibration a constant rattle or does it cycle from minor to major? Does it do it when cornering or just straight line?

Perhaps take off both rear brake drums, spin it up and see if the axles are true. I still suspect there may be housing damage. A 9" is a big sucker and if you had bent axles it's had some sort of hit in the rear so maybe the tubes are out of alignment?

I'm definitely thinking of taking the tailshaft to another place to get it checked.

It doesn't feel like wheels, but I am going to swap front to rear when I can get motivated. Hopefully the 8" 245s will fit on the front.

I've used a large T square on the axles and there is no alignment issue with the axle housing. Applying brakes doesn't change it and placing in neutral doesn't change it. Stright line or slight bends on the highway is the same.

As I have found so many small things causing vibration and I'm getting close, I'm definitely thinking something already replaced during troubleshooting may still be the problem. It feels like center of the car. I keep feeling like tailshaft but as its the third I'm not confident.

When I overhauled the engine and damaged the flex plate by doing a dumb ass thing during transmission installation, I am wondering if I've possibly damaged the new torque converter. Is that possible?

[smh00n 87]

I think the torque convertor would manifest in an engine vibration.

I don't know the answer, it sure sounds like a rotating issue but exactly where is the question. 

[det0326 179]

8 hours ago, bigmal said:

When I overhauled the engine and damaged the flex plate by doing a dumb ass thing during transmission installation, I am wondering if I've possibly damaged the new torque converter. Is that possible?

Just can't believe that a converter would be causing vibration going down the road and not at engine riving in neutral but I guess stranger things have happened.

 

[det0326 179]

Big mail how bad is this vibration, do you really feel it or is it something like you just hear? Could it be a muffler/exhaust drone.

[smh00n 87]

I just realised this has been converted. Was the vibration there before the conversion? Maybe something is not aligned?

[bigmal 225]

14 hours ago, det0326 said:

Big mail how bad is this vibration, do you really feel it or is it something like you just hear? Could it be a muffler/exhaust drone.

I'm not seeing muffler or exhaust. Have changed mufflers and fitted headers and no change.

It is definitely a lot better than when I started chasing it. I think most passengers wouldn't notice unless you pointed it out, but I can definitely tell.

[bigmal 225]

1 hour ago, smh00n said:

I just realised this has been converted. Was the vibration there before the conversion? Maybe something is not aligned?

It was there before I did the conversion, but nothing was changed as far as alignment goes. Using standard mounts, but all replaced.

[Shep69 149]

Hi Mal, 

I haven’t been on here in a long time and can’t believe you’re still chasing the vibration issue. 
Is it worth throwing it on a dyno and getting it up to speed and crawling around to see exactly we’re it’s coming from. 

 

[bigmal 225]

On 4/18/2023 at 10:40 PM, Shep69 said:

Hi Mal, 

I haven’t been on here in a long time and can’t believe you’re still chasing the vibration issue. 
Is it worth throwing it on a dyno and getting it up to speed and crawling around to see exactly we’re it’s coming from. 

 

Good idea. I've had it on stands and been under it but can't identify where it's from. In the car it feels to be central. When parked and running it in neutral through the rev range the engine is smooth and nothing visible from the shaker. When on the road I can feel it and see the shaker vibrating. I keep feeling like its tailshaft or transmission. Third tailshaft and it's been checked three times (I'm still dubious). I keep getting told that there is nothing in an FMX that could cause the vibration.

While it doesn't feel like it's coming from the rear end I wanted to swap the rear wheels to eliminate them. Unfortunately the rear tires do not clear the front guards so I'm trying to borrow a pair of wheels. It has also been suggested that it could be the rear drums. The problem I have is that trouble shooting like this has me spending money each time. Not like you can easily borrow drums or wheels.

[bigmal 225]

An update on my saga of the vibration. Decided to put a dial indicator on the tail shaft at the front, middle and rear and it is good. 

Ran it again on the stands and definitely speed related, not RPM. Did a runout on the axles, all good. The right hand rear tire seems to be a little out of round. Could be just from sitting. I swapped the RH front and rear and ran on the stands again. NO VIBRATION!!!!!!. 

I was thinking a needed a new tire (BFG 245/55/15) so happy to do that. Turning the wheel by hand it appears the drum is out of round. I had a look at the drum and the bolt holes are larger than the studs so can be installed slightly off center. I replaced the original rear wheel and di my best to keep the drum centered. Did another run on the stands and NO VIBRATION. 

Took it for a drive and its a different car. I will be ordering two new drums and shoes this week. 

I am very happy!!!!

[RPM 1,190]

That's certainly outstanding news. I ain't going back to check, but was rotating tires never mentioned? Cuz it's one of the first things that should be done when a vibration is found. 

 

[bigmal 225]

31 minutes ago, RPM said:

That's certainly outstanding news. I ain't going back to check, but was rotating tires never mentioned? Cuz it's one of the first things that should be done when a vibration is found. 

 

Hi Bob, you're correct, it was a previous suggestion. Unfortunately I've had multiple sources of vibration. The rear wheels and tires have been replaced. I have also had the rear wheels balanced three times and was told they were fine. More recently I have been wanting to borrow some wheels to try them out but haven't been able to locate any. Yesterday I used a front wheel but couldn't drive it on the road because the rear wheels won't clear the front guards. Running it on the stands has been avoided more recently because of issues with the neighbors shouting at me. Weird bastards don't like the sweet note of a V8. Yesterday I though I'd ignore them anyway.

While I suspect a tire as well, I'm confident it's the drums holes enabling them to be off center. So new drums coming.

[smh00n 87]

That deserves an extra cuppla beers tonight bloke