Is this normal for a driveshaft?

Justglkn

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Oct 9, 2019
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Just recently bought another fox and I noticed that on the highway at high speeds above 65mph there is some vibration. I will say, though, it needs new tires - they’re bald. Anyways I got up under the car to inspect my u-joints and they look good, but I noticed when I spin the driveshaft and stop spinning it makes a clunking sound. Is that normal? Here is a link to the video of the sound: View: https://youtu.be/TSffwbOjvUk
 
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Justglkn

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Oct 9, 2019
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I also have noticed that the car “bucks” when driving slowly in gears. If I’m in lower rpms and I let off and on the gas you can hear it. Obviously I need to downshift but I’ve never heard it this loud in any of my other cars. It sounds similar to the sound in the video above. I have 3.73 gears and a limited slip differential. I also have a torque arm, but don’t know if that’s relevant. Here’s a video of that sound:
sounds like it could be loose backlash?
View: https://youtu.be/HADA59b6sCc
 
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Habu135

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My drivetrain sounds identical when I spin the driveshaft under my car. I also have a aluminum driveshaft. Additionally, I have the same drivetrain play in my car in high gear at slow speed. A big cam multiplies the problem.
 

Rdub6

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My drivetrain sounds identical when I spin the driveshaft under my car. I also have a aluminum driveshaft. Additionally, I have the same drivetrain play in my car in high gear at slow speed. A big cam multiplies the problem.
Why would you run in high gear at low speed? That’s just asking for trouble.
One of the first things i was taught when driving a stick was to not “lug” the motor, and make sure I was in the right gear at the right speed.
 
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Steel1

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The lugging at low speeds is usually more of a tune thing.
Is the engine modded , i.e. cam ?
I had quite a bit of low speed lug when I first built my 393w w/Pimp XS, had to tune it out
actually not totally gone but much improved.
 

CarMichael Angelo

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1. Your hearing the ring and pinion clanking together.
2. Stop driving the car in such a high gear at such a low speed.
3. Return to class in common sense school.
 

Justglkn

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Oct 9, 2019
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Well let me be clear, I don’t drive it like this. But when I first got the car, obviously I noticed this as I was becoming familiar with it. I’ve never had to be so mindful of it before or let my car reach such high rpms before shifting. But I think @Steel1 is right, it probably needs a better tune. The engine does have upgraded heads and an e cam. Thank you guys for the responses, I wanted to know what this technically was, which sounds like the ring and pinion.
 

Habu135

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Jan 10, 2019
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Why would you run in high gear at low speed? That’s just asking for trouble.
One of the first things i was taught when driving a stick was to not “lug” the motor, and make sure I was in the right gear at the right speed.
I don't drive my car like that. I was simply answering the man's question.
 

General karthief

wonder how much it would cost to ship you a pair
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The low speed bucking is a by product of the e cam.
there is a chance the tps has a bad spot in that rpm area but it would do it in every gear at the same low rpms.
avoid the low rpm in high gear bucking obviously,
 

jrichker

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First, do some diagnostic work to make sure you don't have some unknown engine problem or problems....

Assuming that you didn't buy some trashed out EFI to carb conversion, the stock EFI is pretty good at finding engine tune and drivability problems.

Cylinder balance test: use this to find dead or weak cylinders:

Revised 09-Sep-2017 Added reminder to write down the stored codes and engine running codes.

The computer has a cylinder balance test that helps locate cylinders with low power output. You’ll need to dump the codes out of the computer and make sure that you have the A/C off, clutch depressed to the floor and the transmission in neutral. Fail to do this and you can’t do the engine running dump codes test that allows you to do the cylinder balance test.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Be sure to turn off the A/C, have the clutch depressed to the floor, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.


Here's how to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

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583776.jpg


If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

583777.gif


The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

583778.gif


The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.
This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and drivability problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you dump the codes and then you start the engine with the test jumper in place. Be sure the A/C is off, clutch depressed to the floor and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10
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Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see www.midwayautosupply.com/Equus-Digital-Ford-Code-Reader/dp/B000EW0KHW Equus - Digital Ford Code Reader 3145.
It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
Order it at Walmart for a better price and free shipping
583780.jpg


Write down the codes that the computer outputs since they will give you information on problems that are stored in the computer's memory


Cylinder balance test


If you have idle or IAC/IAB problems and the engine will not idle on its own without mechanically adjusting the base idle speed above 625-750 RPM, this test will fail with random cylinders pointed out every time it runs. The IAC/IAB must be capable of controlling the engine speed to run in the 1300-1500 RPM range. Playing with the base idle speed by adjusting it upwards will not work, the computer has to be able to control the engine speed using the IAC/IAB.

Warm the car's engine up to normal operating temperature. With the test jumper in test position, start the engine and let it stabilize. It should flash a 10 and then a 4 and maybe an 11. If no 11, then there are other codes that will be dumped.

Write down the codes that the computer outputs since they will give you information that the computer found when it is running. These are often different from the stored codes.

One of the first tests it does is to open the EGR all the way, this will cause the engine to stumble and almost die. If the engine dies here then you have EGR problems.
To start the cylinder balance test, briefly floor the accelerator past 2500 RPM and let off the accelerator. The engine will stabilize at about 1300-1450 RPM and the cut off the fuel injectors one at a time. The engine speed will drop briefly and the computer will turn the fuel injector for the cylinder under test back on. Then it starts the process for the next cylinder. When it has sequenced through all 8 injectors, it will flash 9 for everything OK, or the number of the failing cylinder such as 2 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures.
Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure

See View: https://www.youtube.com/watch?v=HDXrkKS4jTE
for a visual tour through the process. There is no voice narration so you have to listen carefully for the engine sounds. I posted the link for the benefit of Stangnet members who had questions about how to do a cylinder balance test. I do not own that video and I am not the creator.

Do a compression test on all the cylinders.
Take special note of any cylinder that shows up as weak in the cylinder balance test. Low compression on one of these cylinders rules out the injectors as being the most likely cause of the problem. Look at cylinders that fail the cylinder balance test but have good compression. These cylinders either have a bad injector, bad spark plug or spark plug wire. Move the wire and then the spark plug to another cylinder and run the cylinder balance test again. If it follows the moved wire or spark plug, you have found the problem. If the same cylinder fails the test again, the injector is bad. If different cylinders fail the cylinder balance test, you have ignition problems or wiring problems in the 10 pin black & white electrical connectors located by the EGR.

How to do a compression test:
Only use a compression tester with a screw in adapter for the spark plug hole. The other type leaks too much to get an accurate reading. Your local auto parts store may have a compression tester to rent/loan. If you do mechanic work on your own car on a regular basis, it would be a good tool to add to your collection.

With the engine warmed up, remove all spark plugs and prop the throttle wide open with a plastic screwdriver handle between the throttle butterfly and the throttle housing. Crank the engine until it the gage reading stops increasing. On a cold engine, it will be hard to tell what's good & what's not. Some of the recent posts have numbers ranging from 140-170 PSI. If the compression is low, squirt some oil in the cylinder and do it again – if it comes up, the rings are worn. There should be no more than 10% difference between cylinders. Use a blow down leak test (puts compressed air inside cylinders) on cylinders that have more than 10% difference.

I generally use a big screwdriver handle stuck in the TB between the butterfly and the TB to prop the throttle open. The plastic is soft enough that it won't damage anything and won't get sucked down the intake either.

A battery charger (not the trickle type) is a good thing to have if you haven't driven the car lately or if you have any doubts about the battery's health. Connect it up while you are cranking the engine and it will help keep the starter cranking at a consistent speed from the first cylinder tested to the last cylinder.
 

General karthief

wonder how much it would cost to ship you a pair
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Nope, no adjusting the tps, just set it at or near like about .98, the thing to look for is a steady rise in numbers as you open the throttle, it works like a rheostat, the higher the numbers (up till like 4.25 or something like that) the more rpms.
 

TOOLOW91

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Nope, no adjusting the tps, just set it at or near like about .98, the thing to look for is a steady rise in numbers as you open the throttle, it works like a rheostat, the higher the numbers (up till like 4.25 or something like that) the more rpms.
The old mythical .98-.99 setting .....

You can set it anywhere from like .60-.99 and the computer is ok . It sees this and won’t throw a light.
If I had a dollar for everytime someone said a tps was bad or had a flat spot I’d be rich. 10 years playing with these cars now and not one have I ever actually seen with a bad tps that had a flat spot .
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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I said 'set it at or near about .98' only as a reference point. I know about 'setting it as close to' whatever bs and the .60 to .99 thing too. Look, my tps had a dead spot, the car would buck and bitch between 1100 and 1600 rpms in any gear. I tested it and found that in that rpm area the tps would jump around from 1.6, 1.8 back to 0 very rapidly. So I replaced it with another I had (used) and the bucking and bitching went away except tip in (the first movement of the throttle blade) was dead, like a badly adjusted accelerator pump on a carb, I loosened up the tps and it acted as it should at tip in, locked it down then measured with a volt meter and it was at .98 and that's that.
I do believe that the tps does not have to be as close to whatever the latest rumored volt reading is, I also believe that it is not a bad thing to check the voltage readings of the tps and if it works at .68 or .98 then don't fix it. I also tested my tps several times over several days to see if it changed and it always tested between .96 and .98
That's my story and I'm sticking to it.
 

TOOLOW91

If you're the village idiot what's that make me?
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The back lash in that rear does sound excessive . Easiest way to see what’s going on is to get a dial indicator and pull the cover and check it . I want to say the ford spec was .008-.012 . It’s been a long time since I messed with the one in my car so don’t quote me there .
 

74stang2togo

NERD!
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Last edited:

Steel1

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Aug 18, 2017
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Thanks for the "education" but that scenario is not what I'm referring to.
I never purposely lug my car...lol
I should have worded it better , what I'm talking about is more of a low speed bucking and
thought that was what the op was experiencing.
Here's a link to "educate" yourself on what I'm referring to, not my car but same idea.
 

74stang2togo

NERD!
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Mar 7, 2002
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Thanks for the "education" but that scenario is not what I'm referring to.
I never purposely lug my car...lol
I should have worded it better , what I'm talking about is more of a low speed bucking and
thought that was what the op was experiencing.
Here's a link to "educate" yourself on what I'm referring to, not my car but same idea.
:dig: