4th gear 2800--3K rpms

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MAPS

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Hello Everyone

I just got over my 6 pack issues (thank you Brian) and today driving to the shop to have something looked at, I realized (on the highway) that when I shifted into 4th gear and the car reached around 2800 to 3000 rpm there was a wicked vibration on the shifter,car.... I let go of the gas back to 2500 no problem at all.
This is a new rebuilt engine (150 miles only). So the car is still going thru the break in process, it's not being abused (for now,lol ) but I never had this problem before.
Yes the front tire is off a little as I have new rims for the car with tires but haven't put them on yet as I am waiting for the front tires to arrive and then I'll do a wheel alignment one shot, new rims, new tires, etc.... But like I said I didn't have this problem last yr before the rebuild all of a sudden I have this problem.
The mechanic said I may need a driveshaft balancing.. First time I hear of this happening from one day to the next.
Any help will be appreciated.
Thanks.
MAPS
 
Hello Everyone

I just got over my 6 pack issues (thank you Brian) and today driving to the shop to have something looked at, I realized (on the highway) that when I shifted into 4th gear and the car reached around 2800 to 3000 rpm there was a wicked vibration on the shifter,car.... I let go of the gas back to 2500 no problem at all.
This is a new rebuilt engine (150 miles only). So the car is still going thru the break in process, it's not being abused (for now,lol ) but I never had this problem before.
Yes the front tire is off a little as I have new rims for the car with tires but haven't put them on yet as I am waiting for the front tires to arrive and then I'll do a wheel alignment one shot, new rims, new tires, etc.... But like I said I didn't have this problem last yr before the rebuild all of a sudden I have this problem.
The mechanic said I may need a driveshaft balancing.. First time I hear of this happening from one day to the next.
Any help will be appreciated.
Thanks.
MAPS
Might want to double check those universal joints while your under there.
 
Go put 30 or 40 miles on it and them come back, jack it up and put your finger on all the u joint. They should be cold to the touch. If you find a warm or burn you finger on one.........Well you have found your problem.

Also if you slide the yok off and didn't put it exactly back the way it came off, they well be out of faze and cause a lot of vibration.
 
You might try taking the driveshaft out & rotating it 180* & see if the vibration gets better, or worse.
 
Try pushing in the clutch and putting it in neutral at that speed. Does anything change?

Once the motor has been brought up to temperature for 20 minutes, cooled down and rechecked for proper torque on everything accessible, I drive the car like I use it, hard, and I only rev it hard once it is fully warmed up though, at least 15-30 minutes.

Do you have a wide band on the car? Curious if it is a flat tappet or roller cam?

Grab the driveshaft yoke and see how much play there is in your tail shaft bushing. The yoke should not have any noticeable free play. I've put new ones in and still had excessive free play with brand new yokes. Seems to be an issue that most of us just live with, and never get ride of the resultant vibrations.
 
Try pushing in the clutch and putting it in neutral at that speed. Does anything change?

Once the motor has been brought up to temperature for 20 minutes, cooled down and rechecked for proper torque on everything accessible, I drive the car like I use it, hard, and I only rev it hard once it is fully warmed up though, at least 15-20 minutes.

Do you have a wide band on the car? Curious if it is a flat tappet or roller cam?

Grab the driveshaft yoke and see how much play there is in your tail shaft bushing. The yoke should not have any noticeable free play. I've put new ones in and still had excessive free play with brand new yokes. Seems to be an issue that most of us just live with, and never get ride of the resultant vibrations.
 
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Try pushing in the clutch and putting it in neutral at that speed. Does anything change?

Once the motor has been brought up to temperature for 20 minutes, cooled down and rechecked for proper torque on everything accessible, I drive the car like I use it, hard, and I only rev it hard once it is fully warmed up though, at least 15-30 minutes.

Do you have a wide band on the car? Curious if it is a flat tappet or roller cam?

Grab the driveshaft yoke and see how much play there is in your tail shaft bushing. The yoke should not have any noticeable free play. I've put new ones in and still had excessive free play with brand new yokes. Seems to be an issue that most of us just live with, and never get ride of the resultant vibrations.


Wow how someone can be educated here is unphukkenbelieveable .. Thank you guys.
I want to' also ask if I press the clutch when it's vibrating at that time what should happen ?

Now I will still have my floor on the gas right? Cause once I let go at that remit stops that wicked vibration.
Sport at on the gas when it starts vibrating just dump the clutch and wait for what to happen?

Ok also going to check the joints answer it the drive shaft needs to be balanced ...

Thanks.
Maps
 
Wow how someone can be educated here is unphukkenbelieveable .. Thank you guys.
I want to' also ask if I press the clutch when it's vibrating at that time what should happen ?

Now I will still have my floor on the gas right? Cause once I let go at that remit stops that wicked vibration.
Sport at on the gas when it starts vibrating just dump the clutch and wait for what to happen?

Ok also going to check the joints answer it the drive shaft needs to be balanced ...

Thanks.
Maps

This last post was a bit hard to follow, but by pushing in the clutch and letting the engine speed idle down, you are taking the engine, flywheel and pressure plate out of the equation temporarily. If the vibration remains, it indicates the issue is in the transmission, driveline or rear end.
 
This last post was a bit hard to follow, but by pushing in the clutch and letting the engine speed idle down, you are taking the engine, flywheel and pressure plate out of the equation temporarily. If the vibration remains, it indicates the issue is in the transmission, driveline or rear end.


If it's still the same (vibrating) it's one of these trans, driveline or rear end.. Really is not telling me much as I don't think it can be much more than that, aside maybe a wheel balance issue or front end.
What I was thinking was if it doesn't do the vibrating when the clutch is engaged at least I'll know it's not a trans problem or driveshaft etc...i know it's probably the tranny or driveline most probably.
I was just trying to see thru a process of eliminatio, I would be able to narrow it down batten those 3 main issues. That's all.
Thanks for your input as well, will see if I will get it done on the weekend.
Have a good day..

MAPS
 
You know you may have something there, last week I had the air right out of the front tire and didn't see it when I got in the car (my weight does not help either lol) and drove up my garage ramp and heard the fender touch the tire and I thought I heard the headers scrapping too so I knew something was wrong, as soon as I heard that I stopped and jumped outside as I then saw that the front end leaned to the left and saw the air was gone (almost all of it) left the car exactly where it was and then went back after work and took care of the air in the tire... Maybe it could be that (touched)

I'm going to know on that weekend if I can get time to go to the shop that will look at the driveshaft.

Thanks.
 
If it's still the same (vibrating) it's one of these trans, driveline or rear end.. Really is not telling me much as I don't think it can be much more than that, aside maybe a wheel balance issue or front end.
What I was thinking was if it doesn't do the vibrating when the clutch is engaged at least I'll know it's not a trans problem or driveshaft etc...i know it's probably the tranny or driveline most probably.
I was just trying to see thru a process of eliminatio, I would be able to narrow it down batten those 3 main issues. That's all.
Thanks for your input as well, will see if I will get it done on the weekend.
Have a good day..

MAPS

I always start my process of elimination with the first step, and don't move on to the next step until I've determined the answer to my first step. So, was that a yes, it continues or no it stops?
 
I always start my process of elimination with the first step, and don't move on to the next step until I've determined the answer to my first step. So, was that a yes, it continues or no it stops?


My bad, it continued vibrating.... But what's really baffling is why doesn't do it in any other gear but 4th..
Thanks.
 
My bad, it continued vibrating.... But what's really baffling is why doesn't do it in any other gear but 4th..
Thanks.

No worries. Get the car up in the air on both ends, grab a long thick screw driver or awl type prybar, some gloves and a flashlight. Leave the transmission in gear and use the prybar to try and move the u-joints back and forth while looking closely at them for any sign of sloppiness.

Also, see how much play there is between the front driveshaft yoke by grabbing it and moving it side to side. Can you see any movement? How much? Is it more than a stack of 3 or 4 playing cards?

If that all checks out, pull the driveshaft out, be ready to catch some gear oil out of the trans, and rotate it 180 degrees and reinstall.

Are all your tires and rims the same size? Was the car sitting on them for more than a few months causing them to flat spot? Take them down to a tire shop and have them balanced again. Ask them to let you watch each tire get balanced so you can see any runout will they are spinning.

While the tires are off, check to see if the face of the axle flanges have any excessive runout.
 
Well;
4th gear at 2800 is about 65 mph with 3.55s. Are you saying ;
65mph in third gear does not illicit the vibration?
Or how about 2800 in third gear at ~45mph;
how about if you just lightly back off the throttle, or lightly lay on the throttle?

If no vibration on the; third gear @2800 test; that sorta proves it is not related to anything forward of the slip-yoke. But to be sure, try; up to a couple hundred rpm either way from 2800.

If the vibration originated in the rear tires or rearend, it would continuously increase in both frequency and intensity, directly proportional to speed. Since you don't mention that, it sorta proves that the vibration originates somewhere else.

That doesn't leave a lot of other sources. But;
If you can feel it in the steering wheel;
it is usually found in the front tires, like a shifted or blown cord.
If the steering wheel develops a will of it it's own, that would be the alignment, usually in the toe, but could be other, and occasionally it is aggravated by worn parts, altho the worn parts are seldom the cause of it.
After that, I think there are only two other possibilities;
1) the various vibration isolators; like engine and trans mounts, and spring bushings. Again these are not the cause of it, but only allow a pre-existing condition to to be discovered.
2) Or the driveshaft;
If this just came out of nowhere, look for a bent or damaged, one.
If it has been developing over time, look for shifted cups, or a loose X-pin.
If it has always been there, look for U-joint phasing.

Well; I just thought of another; If you have recently installed two different rims on the front with different backspaces, this will cause the left and right scrub radius's to be different, and they will fight for dominance.
Same goes for matching wheels that are offset to the outside, or taller than factory wheels with a non-complimentary offset; which all destroy the factory scrub radius. If your tie-rods are loose in this situation, the front wheels will "shimmy". A loose steering box won't help any either.

Or another one I have experienced ; is a raggedy clutch disc,or sticking flyweights in a diaphragm type. The sticking flyweights is a PITA, cuz sometimes they don't and everything is fine. Then the next time I fly thru the gears, there it is again. I always notice it in 4th gear at hiway speed, because I just got to hiway speed by revving third to 4000, and dropping in at 2870 for me (@65) , so the flyweights were just recently out for a ride. I can usually get rid of it, by hitting neutral and gently blipping the throttle. Sometimes it takes several trys.
If it doesn't go away, for me, that usually spells a fragged disc, so I schedule a replacement.
I like factory 340 discs, and always have a spare in stock. They don't last long in the CenterForce PP, but as a streeter, I like the organic feel and I think the small penalty of replacing them every so often is acceptable; altho I no longer sidestep the clutch; Sidestepping, usually/eventually, busts/cracks the hub and she spits out springs; now I know it's time.
Well sometimes I do sidestep the clutch, but only to show off from ~zero mph, and very low rpm, to show the dump it and go personality of my 367combo.

Happy Hunting.


Some of these things, I see, have already been mentioned.
 
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Hello Everyone

I just thought the least I can do is let you all know what happened.
You all are so helpful answering problems that have nothing to do with all of you yet when we get our shyt fixed we don't say anything?
Not right.

Ok I finally got the car to the driveshaft place and he said something to me that was kind of new (hell everything is new to me lol) after looking at the car he said that he removed the drive shaft and saw that the joints were not greased properly and that if I store the car for the winter (more than 6 months) I should grease them before I store them as they dry up and that could also cause the vibration. Damn simple greasing.
He did also balance the driveshaft as it seemed to be off somewhere on some weld from what I understood

When I took the car I asked him what if it's still vibrating do I come back (200 dollars later) he said no, there is nothing more I can do, it's another problem .
I'm thinking I just paid him 200 dollars to put some grease on the universal joints and driveshaft balanced.
Did either of those things need to have been done if it's still vibrating?

As soon as I left I went on the highway to get home, got into 4th gear and went 2500,2700 2900 and now I'm at 3 k and I'm not hearing, feeling anything,next thing you know I'm up to 5k and I'm coasting.
Finally, done. What a feeling. Been a yr since I felt this...
Thanks to all of you guys as well for your ideas, input and suggestions.

MAPS
 
Hello Everyone

I just thought the least I can do is let you all know what happened.
You all are so helpful answering problems that have nothing to do with all of you yet when we get our shyt fixed we don't say anything?
Not right.

Ok I finally got the car to the driveshaft place and he said something to me that was kind of new (hell everything is new to me lol) after looking at the car he said that he removed the drive shaft and saw that the joints were not greased properly and that if I store the car for the winter (more than 6 months) I should grease them before I store them as they dry up and that could also cause the vibration. Damn simple greasing.
He did also balance the driveshaft as it seemed to be off somewhere on some weld from what I understood

When I took the car I asked him what if it's still vibrating do I come back (200 dollars later) he said no, there is nothing more I can do, it's another problem .
I'm thinking I just paid him 200 dollars to put some grease on the universal joints and driveshaft balanced.
Did either of those things need to have been done if it's still vibrating?

As soon as I left I went on the highway to get home, got into 4th gear and went 2500,2700 2900 and now I'm at 3 k and I'm not hearing, feeling anything,next thing you know I'm up to 5k and I'm coasting.
Finally, done. What a feeling. Been a yr since I felt this...
Thanks to all of you guys as well for your ideas, input and suggestions.

MAPS
Happy Ending !!
 
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