Transmission Issues

[Tracy Bowman]

I would be asking for a retraction. Quoting people out of a forum for an article is BS.

Incidentally I have no shudder or transmission issues. Love the truck.

No shudder or transmission issues here either. Great truck!

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[DavidR]

That article didn't appear to be terribly well written. Making some very oversimplified, generalizations, saying there is a "growing chorus of discontent" - it reads like clickbait to me.

And quoting Phil like he was a current part of the Ranger engineers when his signature CLEARLY says he is retired.

I totally agree. I posted it mainly because I thought it was amusing rather than informative in any way, though maybe I should have stressed that more. I'm not too surprised at the omission of Phil being retired, because people tend to gloss over "second-order" things, but it is definitely bad journalism to have not have noticed that.

Unfortunately, many titles are now click bait, to the degree that sometimes they say exactly the opposite of what the article text says.

 

[CompDude]

Just start looking for a ranger I definitely want this resolved before I make a purchase

 

[DavidR]

Very interesting, Phil! The same sort of complicated interactions occur in electronic systems, but usually at much higher frequencies (but not always). One time I solved a problem by noticing that a finger placed on a certain node stopped a problematic oscillation we were having. It's a common enough thing to try that it's got a name - a "finger farad" -- a bit like loosening the bolts to decouple parts of the system from each other.

My question is whether sometimes actual damping is used to solve some of these problems. The reason I ask is because our '93 Ranger has what appears to be a damper attached between the engine and the frame. I have always assumed that was to allow the use of softer engine mounts without generating oscillations/vibrations.

I've also been curious if this kind of thing might be why the same '93 Ranger has a 10-lb weight bolted to the transmission (or maybe the transfer case, can't remember right now) that seems to have no obvious other use?

Hi Ron,

Phasing is reallly getting all the U-joints singing the same song in the same key. U joints are 2nd order excitation sources. Driveshaft speed is first order frequency generator and the U-joints are double the driveshaft frequency. Driveshaft rpm divided by 60 seconds per minute gives driveshaft frequency. Simple example is 600 driveshaft rpm which is also expressed as 10hz and U joints are putting out 20 Hz. Now you can feel 20Hz, but not 10Hz for example so the U joints can be a very big offender of being an excitation frequency. In the world of NVH, you have excitation generators, engine, driveline, tires.

Now on the other hand the vehicle is full of responders, Floorpan/seats, Steering wheel/column, brake and gas pedal and so on. So lets say the seat with you sitting in it coupled to the floorpan has a resonant frequency of 20hz and you have a very nice excitation force at 20hz of the U Joints...so you sitting on your calibrated assometer feel this vibration. The rule of thumb is to separate resonance responders from excitation forces by 10% or more or in the case above by at least 2hz or below 18hz or above 22hz. This is not always possible but if you can reduce the excitation force (amplitude of the vibration at a certain frequency) then your calibrated assometer can't feel this (called numb ass?) and this is done by isolating the excitation frequency....Body mounts,, engine mounts, Driveline center bearing rubbeer mount), spring eye bushings and so on. So the tools of the trade are to reduce excitation forces, move responder resonant frequencies and if all this failes, isolate the excitation.

All the above is and can be a real headach to do, especially since the resonant frequency is the square root of the stiffness (spring rate) over the mass. The damn square root radical is the killer as large changes in stiffness or large changes in mass produce little change in resonance frequency. Whew! Stilll with me? So since the center bearing is mounted in rubber, you have mass of the center bearing and the spring rate of the rubber mounting, So you have a driveline resonance...because the driveline system only resonates at a fixed frequency, as you launch the vehicle and the driveline rpm increases, you effectively drive through this resonance quickly but your assometer perceives this as a shudder.at the lower frequency of a two piece driveine. One piece driveline have such a high resonance frequency that it is outside the operating range, but there is a critical speed where the driveshaft starts to look like a jump rope which is not good.... You move the critical speed by reducing the length of the shaft, use lighter materials than steel and increase diameter of the driveshaft. That is why in some cases shortening the driveshaft via a two piece design is necessary.. Okay? still with me???

Back Story...

At the time of the Aerostar, I had Econoline and Areostar NVH. My engineers were gone for the day when my phone rang and it was our executive engineer who directed me to catch the next flight to St. Louis, the Aerostar plant...The plant identified an absolutely horrible moan in the vehicles they plant evaluated as part of their quality initiative. Puzzled and perplexed, I headed home, packed my suitcase and headed to the Airport to see about catching a flight to St. Louis. I called our travel company and they got me a seat and a rental car on an asap basis. Arrived at the St. Louis plant about 10pm. Plant personnel were waiting for me. First order was to drive one of the new vehicles and they were spot on.. 55mph the moan was so loud converstaion was impossible unless you screamed. WTF???? Day before, everything was going well...
I had to determine what was causing this so we had the repair mechanics loosen the engine to transmission bolts to finger tight and we drove the vehicle and there was no moan...PLant folks were amazed...I had solved the problem! Not quite...as we cannot ship vehicles with loose trans to engine bolts, but it did tell me it was 2n order powertrain bending...yes the powertrain has microscopic flexing. So the question to the plant was what changed...what new parts were put on line yesterday...Only chassis parts, not trim and body parts. The plant had the answer in about an hour...It was now about 1am... There were new rear suspension springs put on line yesterday.. I suspected this was the problem and asked if they had any of the original part number around the plant...Answer was no! Drat...Did they have any older Aerostars around...No! However the plant manager said his Aerostar was out in the lot....So into the plant repair area we swapped the springs between the two vehicles. The offending vehicle was now quiet at 55mph and the plant managers vehicle exhibited the terrible moan. Now i understood the problem...the new springs resulted in a rear suspension resonance excited by second order power train bending. Now the only thing I could do was to see if we could isolate the springs. I asked if there were any parts in the plant that we could make rubber washers about 4" in diameter. Again the plant said no...I told them to pull a mudflap off a trailer and we would use that to make some rubber isolators. Crude cutout but but up to the job, we put thiese round pieces of mudflap into the plant managers vehicle and drove it. The vehicle was quiet, so now we had a fix and mudflaps are pretty durable, so the Plant Manager has the power to make design changes and the plant was directed to make up these spring isolators. and start fitting then to vehicles so they could be shipped and the line restarted at 6am... it was now after 3am, so I got about 3 hours sleep and back to the plant...We verified the isolators were working and there was no moan. So hopped a plane back to Dearborn and we started immediate desiign of spring isolatores. We also proved out in the test lab that the mudflaps had excellent life, so there would be no need to recall these vehicles... Whew....I took the rest of the day off to just sleep.... Still with me???? If you see any Aerostars on the the road, you can bet their rear suspension is running in resonance, but they cannot feel or hear it.....This is the world of vehicle NVH...

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

 

[RedlandRanger]

Just start looking for a ranger I definitely want this resolved before I make a purchase

Well, it is either only present in some vehicles or some people are more sensitive to feeling it (maybe like the "bounce" issue - I don't know). I have never felt this in my Ranger and I just passed 10,000 miles.

 

[DavidR]

Well, it is either only present in some vehicles or some people are more sensitive to feeling it (maybe like the "bounce" issue - I don't know). I have never felt this in my Ranger and I just passed 10,000 miles.

I finally got out on the highway where there was no snow to worry about and tried many different acceleration rates in both D and S, and neither my wife nor I could feel it despite specifically looking for it. Along with others who can't feel it, it doesn't seem like every vehicle has this problem. You might just need to be very aware to check for it while test driving.

 

[P. A. Schilke]

Very interesting, Phil! The same sort of complicated interactions occur in electronic systems, but usually at much higher frequencies (but not always). One time I solved a problem by noticing that a finger placed on a certain node stopped a problematic oscillation we were having. It's a common enough thing to try that it's got a name - a "finger farad" -- a bit like loosening the bolts to decouple parts of the system from each other.

My question is whether sometimes actual damping is used to solve some of these problems. The reason I ask is because our '93 Ranger has what appears to be a damper attached between the engine and the frame. I have always assumed that was to allow the use of softer engine mounts without generating oscillations/vibrations.

I've also been curious if this kind of thing might be why the same '93 Ranger has a 10-lb weight bolted to the transmission (or maybe the transfer case, can't remember right now) that seems to have no obvious other use?

Hi David,

Those mass dampers are tuned devices to counteract a particular frequency. We in the NVH arena used these mass dampers as a last resort when stiffness was not able to correct the problem...Mass dampers were considered a device that hallmarked failure to fix the problem... They are really not damping but counteracting the excitation forces to minimize or counteract the excitation.

best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co, Retired

 

[rdgallo]

Hi Ron,

Phasing is reallly getting all the U-joints singing the same song in the same key. U joints are 2nd order excitation sources. Driveshaft speed is first order frequency generator and the U-joints are double the driveshaft frequency. Driveshaft rpm divided by 60 seconds per minute gives driveshaft frequency. Simple example is 600 driveshaft rpm which is also expressed as 10hz and U joints are putting out 20 Hz. Now you can feel 20Hz, but not 10Hz for example so the U joints can be a very big offender of being an excitation frequency. In the world of NVH, you have excitation generators, engine, driveline, tires.

Now on the other hand the vehicle is full of responders, Floorpan/seats, Steering wheel/column, brake and gas pedal and so on. So lets say the seat with you sitting in it coupled to the floorpan has a resonant frequency of 20hz and you have a very nice excitation force at 20hz of the U Joints...so you sitting on your calibrated assometer feel this vibration. The rule of thumb is to separate resonance responders from excitation forces by 10% or more or in the case above by at least 2hz or below 18hz or above 22hz. This is not always possible but if you can reduce the excitation force (amplitude of the vibration at a certain frequency) then your calibrated assometer can't feel this (called numb ass?) and this is done by isolating the excitation frequency....Body mounts,, engine mounts, Driveline center bearing rubbeer mount), spring eye bushings and so on. So the tools of the trade are to reduce excitation forces, move responder resonant frequencies and if all this failes, isolate the excitation.

All the above is and can be a real headach to do, especially since the resonant frequency is the square root of the stiffness (spring rate) over the mass. The damn square root radical is the killer as large changes in stiffness or large changes in mass produce little change in resonance frequency. Whew! Stilll with me? So since the center bearing is mounted in rubber, you have mass of the center bearing and the spring rate of the rubber mounting, So you have a driveline resonance...because the driveline system only resonates at a fixed frequency, as you launch the vehicle and the driveline rpm increases, you effectively drive through this resonance quickly but your assometer perceives this as a shudder.at the lower frequency of a two piece driveine. One piece driveline have such a high resonance frequency that it is outside the operating range, but there is a critical speed where the driveshaft starts to look like a jump rope which is not good.... You move the critical speed by reducing the length of the shaft, use lighter materials than steel and increase diameter of the driveshaft. That is why in some cases shortening the driveshaft via a two piece design is necessary.. Okay? still with me???

Back Story...

At the time of the Aerostar, I had Econoline and Areostar NVH. My engineers were gone for the day when my phone rang and it was our executive engineer who directed me to catch the next flight to St. Louis, the Aerostar plant...The plant identified an absolutely horrible moan in the vehicles they plant evaluated as part of their quality initiative. Puzzled and perplexed, I headed home, packed my suitcase and headed to the Airport to see about catching a flight to St. Louis. I called our travel company and they got me a seat and a rental car on an asap basis. Arrived at the St. Louis plant about 10pm. Plant personnel were waiting for me. First order was to drive one of the new vehicles and they were spot on.. 55mph the moan was so loud converstaion was impossible unless you screamed. WTF???? Day before, everything was going well...
I had to determine what was causing this so we had the repair mechanics loosen the engine to transmission bolts to finger tight and we drove the vehicle and there was no moan...PLant folks were amazed...I had solved the problem! Not quite...as we cannot ship vehicles with loose trans to engine bolts, but it did tell me it was 2n order powertrain bending...yes the powertrain has microscopic flexing. So the question to the plant was what changed...what new parts were put on line yesterday...Only chassis parts, not trim and body parts. The plant had the answer in about an hour...It was now about 1am... There were new rear suspension springs put on line yesterday.. I suspected this was the problem and asked if they had any of the original part number around the plant...Answer was no! Drat...Did they have any older Aerostars around...No! However the plant manager said his Aerostar was out in the lot....So into the plant repair area we swapped the springs between the two vehicles. The offending vehicle was now quiet at 55mph and the plant managers vehicle exhibited the terrible moan. Now i understood the problem...the new springs resulted in a rear suspension resonance excited by second order power train bending. Now the only thing I could do was to see if we could isolate the springs. I asked if there were any parts in the plant that we could make rubber washers about 4" in diameter. Again the plant said no...I told them to pull a mudflap off a trailer and we would use that to make some rubber isolators. Crude cutout but but up to the job, we put thiese round pieces of mudflap into the plant managers vehicle and drove it. The vehicle was quiet, so now we had a fix and mudflaps are pretty durable, so the Plant Manager has the power to make design changes and the plant was directed to make up these spring isolators. and start fitting then to vehicles so they could be shipped and the line restarted at 6am... it was now after 3am, so I got about 3 hours sleep and back to the plant...We verified the isolators were working and there was no moan. So hopped a plane back to Dearborn and we started immediate desiign of spring isolatores. We also proved out in the test lab that the mudflaps had excellent life, so there would be no need to recall these vehicles... Whew....I took the rest of the day off to just sleep.... Still with me???? If you see any Aerostars on the the road, you can bet their rear suspension is running in resonance, but they cannot feel or hear it.....This is the world of vehicle NVH...

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

Thanks for the detailed explanation, Phil. I will have to check the calibration of my assometer. Right there might be my problem. lol I enjoy you back stories.

 

[shred5]

I finally got out on the highway where there was no snow to worry about and tried many different acceleration rates in both D and S, and neither my wife nor I could feel it despite specifically looking for it. Along with others who can't feel it, it doesn't seem like every vehicle has this problem. You might just need to be very aware to check for it while test driving.

It is more from take off... I feel it more in city driving.

 

[shred5]

@P. A. Schilke , you're becoming famous

https://www.motorbiscuit.com/ford-ranger-forums-blowing-up-with-problems/

That is horrible and is not even accurate and seems more like someone just trying to bash the Ranger more than anything.

Maybe it will get Fords attention.

 

[DavidR]

Hi David,

Those mass dampers are tuned devices to counteract a particular frequency. We in the NVH arena used these mass dampers as a last resort when stiffness was not able to correct the problem...Mass dampers were considered a device that hallmarked failure to fix the problem... They are really not damping but counteracting the excitation forces to minimize or counteract the excitation.

best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co, Retired

HI Phil,

Thanks for that candid answer. In electronics, you'll also see things like that, that an experienced engineer will recognize as a similar kind of solution. To be fair to the designers though, the term "failure" can be relative in some contexts. All projects are subject to schedule and cost constraints, so sometimes a more elegant solution, so to speak, isn't practical even if it might be possible.

 

[DavidR]

It is more from take off... I feel it more in city driving.

Yes. My terminology was probably not great. By "highway", I just meant an empty two-lane highway with no snow where I could start and stop several times, looking for the startup vibration under different accelerations and transmission settings. It wasn't a freeway or interstate or anything like that, just a lonely two-lane at a lower elevation.

 

[shred5]

Well it looks like it made it to one of the larger more reputable sites.


http://fordauthority.com/2019/12/2019-ford-ranger-owners-complain-of-low-speed-vibration/

 

[newmantjn]

Have any of you guys tried getting the tires re-balanced? Maybe with a road force balancer?

Switching tire brands perhaps?

 

[shred5]

Have any of you guys tried getting the tires re-balanced? Maybe with a road force balancer?

Switching tire brands perhaps?

I have not but others have had them re-balanced. That is kind of what it feels like though.

I drove the truck for long ways this past week from Milwaukee to Toledo and back. This thing rides so smooth on the highway, what a comfortable ride and the transmission is so smooth for the most part. Honestly it is the smoothest transmission I have ever felt. Automatic transmissions all sometimes have funny things from time to time.

It is just that low speed slight shudder feeling.

The thing is on the way to work today I did not feel any shudder but the first 1000 miles I was babying the truck and driving different. Lets see how it feels today on the way home.

Some people have said it goes away after the transmission learns your behaviors. So we shall see..

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