Rear end vibration
Thread Starter
4th Gear
Joined: Jul 2002
Posts: 4
Likes: 0
From: St. Sauveur Quebec
Rear end vibration
Does anybody have a suggestion? I just changed both of my rear trailing arms, replaced them with a set of Van Steel rebuilts. Also changed the rear leaf spring for a fibreglass 330lbs. version. Had the usual problems getting the trailing arm bolts out, had to cut them. Anyway, did the alignment, front and back, balanced the wheels and took it out, and I have a vibration at 65-72mph. Definitely a driveshaft type vibration, but it was not there before doing the job. Anybody have a clue?
Advanced
Joined: Jun 2002
Posts: 60
Likes: 0
From: Tacoma WA
Re: Rear end vibration (jimbb72454)
Theres a few things that could cause that.
U-joints in the prop shaft, and the halfshafts is my first guess. The yokes that hold the u-joints can wear and cause a bit of vibration too. A wheel bearing that is about to go can cause a vibration feeling, especially the inner, that supports the weight of car, but since youve had the just redone, i doubt thats it.. A brake rotor that isnt exactly true can be another cause, and can quickly wear out a caliper as all 4 pistons will be pumping in and out as the warped area passes thru the pads (at freeway speeds, when your tire rpm's are in the 1000's those caliper pistons are moving like crazy).
For me, eliminating rear end vibration has been a bit of a crap shoot.
I recommend starting with the cheaper parts to swap out, and moving up the foodchain from there. Perhaps ujoints -->brakes-->yokes-->whatever is left. :smash:
good luck!
U-joints in the prop shaft, and the halfshafts is my first guess. The yokes that hold the u-joints can wear and cause a bit of vibration too. A wheel bearing that is about to go can cause a vibration feeling, especially the inner, that supports the weight of car, but since youve had the just redone, i doubt thats it.. A brake rotor that isnt exactly true can be another cause, and can quickly wear out a caliper as all 4 pistons will be pumping in and out as the warped area passes thru the pads (at freeway speeds, when your tire rpm's are in the 1000's those caliper pistons are moving like crazy).
For me, eliminating rear end vibration has been a bit of a crap shoot.
I recommend starting with the cheaper parts to swap out, and moving up the foodchain from there. Perhaps ujoints -->brakes-->yokes-->whatever is left. :smash:
good luck!
C6 the C5 of tomorrow
Joined: Nov 2000
Posts: 6,665
Likes: 2
From: Twin Cities Minnesota
Re: Rear end vibration (mnow)
You may have overtightened your U-joints, if they are too tight they will bind.
You may have caused the pinion angle to become misaligned or maybe the new stuff is just stiffer so you can feel the misalignment.
I spent about a year trying to eliminate a driveshaft vibration which turned out to be a pinion angle misalignment problem.
Don't ask me how it got misaligned, it is all factory stuff!
I eventually measured the front and rear pinion angles and found that the trasnmission tailstock was too far towards the passenger side by about 3/4 inch! That was all it took now I can see out my rear view mirror again! WhoooHooo!
You may have caused the pinion angle to become misaligned or maybe the new stuff is just stiffer so you can feel the misalignment.
I spent about a year trying to eliminate a driveshaft vibration which turned out to be a pinion angle misalignment problem.
Don't ask me how it got misaligned, it is all factory stuff!
I eventually measured the front and rear pinion angles and found that the trasnmission tailstock was too far towards the passenger side by about 3/4 inch! That was all it took now I can see out my rear view mirror again! WhoooHooo!
Parrothead
Joined: May 2002
Posts: 48,231
Likes: 289
From: Margaritaville Embassy
St. Jude Donor '08-'09,'13, '14
Re: Rear end vibration (jimbb72454)
I had a terrible shimmy and vibration in the back end of an MGB once. couldn't figure it out until the tire came apart at 50 MPH
Thread Starter
4th Gear
Joined: Jul 2002
Posts: 4
Likes: 0
From: St. Sauveur Quebec
Re: Rear end vibration (mnow)
Thanks for your answer. The bearings and rotors are new, and the rotors are supposed to be matched. I think that it is driveshaft related, and maybe the new fibreglass spring misaligned the main driveshaft. That is where I am going to look.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: Rear end vibration (427V8)
427V8. How did you measure the pinion angle? I have thought of running a string down the center of the motor and the center of the rear end and eyeball the driveshaft. At 90 mph my mirror starts to get the shakes. With the old T5 I had an alignment tool but with the tremec I have never checked it.
C6 the C5 of tomorrow
Joined: Nov 2000
Posts: 6,665
Likes: 2
From: Twin Cities Minnesota
Re: Rear end vibration (norvalwilhelm)
Norval,
With the body on it's near impossible to get any tool on the driveshaft as you can imagine.
I used a piece of wire, wound it around the threads of one of the transmissions tailstock bolts, then tightened the bolt down on the wire, and pointed the wire towards the diff and another one on the diff pinion.
You need the U-joint angles to be as close to identical ( but oppisite sign ) as possible so the vibration in the front U-joint is canceled out by the rear U-joint.
As you rotate the driveshaft you can measure the u-joint angle with a little trig. I measured both the up and down angles and the side to side angles.
It was hard to measure accuratley but easy to see that the transmission was too far to the passenger side about 1 to 2 cm so I split the difference and went 1.5 cm. The up and down angles seemed OK.
It made a world of difference, but could probably be tweeked a little more ...
With the body on it's near impossible to get any tool on the driveshaft as you can imagine.
I used a piece of wire, wound it around the threads of one of the transmissions tailstock bolts, then tightened the bolt down on the wire, and pointed the wire towards the diff and another one on the diff pinion.
You need the U-joint angles to be as close to identical ( but oppisite sign ) as possible so the vibration in the front U-joint is canceled out by the rear U-joint.
As you rotate the driveshaft you can measure the u-joint angle with a little trig. I measured both the up and down angles and the side to side angles.
It was hard to measure accuratley but easy to see that the transmission was too far to the passenger side about 1 to 2 cm so I split the difference and went 1.5 cm. The up and down angles seemed OK.
It made a world of difference, but could probably be tweeked a little more ...
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: Rear end vibration (427V8)
The angles you are talking about unlike a normal drive shaft is not the up and down angles but the side to side angles. The transmission is not pointing at the rearend. With my T5 I thought the anlge was way off since the passengers side of the tunnel was being rubbed by the driveshaft and the drivers side had lots of clearance. I made a tool to slide in the back of a dummy transmission with an extendable pointer that was a precision fit but could be pulled out to extend to the rear pinion nut and found it was right on. I never tried this with the tremec but this weekend want to try checking this out.
I do get bored and look for things to prove or disprove.
I will try the string down the middle of the car and see if I can see any miss alignment problems. I want this car totally smooth regardless of speed. Right now at 90 mph I start to see a slight vibration. I do regularly take it past this. Infact most times I am out.
I do get bored and look for things to prove or disprove.
I will try the string down the middle of the car and see if I can see any miss alignment problems. I want this car totally smooth regardless of speed. Right now at 90 mph I start to see a slight vibration. I do regularly take it past this. Infact most times I am out.
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Burning Brakes
Joined: Oct 2001
Posts: 860
Likes: 40
From: Woodforest
Re: Rear end vibration (427V8)
You may have overtightened your U-joints, if they are too tight they will bind.
You may have caused the pinion angle to become misaligned or maybe the new stuff is just stiffer so you can feel the misalignment.
I spent about a year trying to eliminate a driveshaft vibration which turned out to be a pinion angle misalignment problem.
Don't ask me how it got misaligned, it is all factory stuff!
I eventually measured the front and rear pinion angles and found that the trasnmission tailstock was too far towards the passenger side by about 3/4 inch! That was all it took now I can see out my rear view mirror again! WhoooHooo!
You may have caused the pinion angle to become misaligned or maybe the new stuff is just stiffer so you can feel the misalignment.
I spent about a year trying to eliminate a driveshaft vibration which turned out to be a pinion angle misalignment problem.
Don't ask me how it got misaligned, it is all factory stuff!
I eventually measured the front and rear pinion angles and found that the trasnmission tailstock was too far towards the passenger side by about 3/4 inch! That was all it took now I can see out my rear view mirror again! WhoooHooo!
As always, this forum rocks :cheers:
Advanced
Joined: Jun 2002
Posts: 60
Likes: 0
From: Tacoma WA
Re: Rear end vibration (Woodstoc)
what would cause all these trannys to be offset like this? i went out and checked mine, and sure enuf im set to the passenger side a little.. is this an effect of torque over time? or a monday at the assembly line? :confused:
Thread Starter
4th Gear
Joined: Jul 2002
Posts: 4
Likes: 0
From: St. Sauveur Quebec
Re: Rear end vibration (mnow)
Geez, I didn't think that I would start so much yakety yak for a rear end vibration, but, what I failed to tell you guys and only realized after was that I had the tranny rebuilt two weeks earlier and sho nuf, the tranny was not in line. Problem fixed. Thank ye, thank ye, thank ye.
C6 the C5 of tomorrow
Joined: Nov 2000
Posts: 6,665
Likes: 2
From: Twin Cities Minnesota
Re: Rear end vibration (norvalwilhelm)
Norval,
Even if the transmission pinion is pointing at the diff the angles can be wrong ( the diff would not be pointing at the transmission... )
Everyone else;
I can't believe that three other people have fixed the same problem with the pinion alignment!
I'm starting to wonder if the cars are built wrong or something?
I wonder if the transmision crossmember was installed backwards sometimes or something! ( like on mondays! :crazy: )
Even if the transmission pinion is pointing at the diff the angles can be wrong ( the diff would not be pointing at the transmission... )
Everyone else;
I can't believe that three other people have fixed the same problem with the pinion alignment!
I'm starting to wonder if the cars are built wrong or something?
I wonder if the transmision crossmember was installed backwards sometimes or something! ( like on mondays! :crazy: )
