Drive train vibration @ 30-50mph - TCCoA Forums
 
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post #1 of 14 (permalink) Old 03-25-2004, 12:18 PM Thread Starter
 
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Question Drive train vibration @ 30-50mph

I have a '96 4.6l T-Bird with 120k that has developed a groaning vibration in the drive train at between 30 and 50 mph. I replaced the differential bushing and it made a slight improvement. I am thinking u-joints or tranny outputshaft bushing may be shot. The car is fine at highway speeds and I do not want to begin replacing more parts without cause. I also get a clunk on coast down, downshifts which is coming from the tranny tail / floor area. Anyone had a simular situation and possible fix?
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post #2 of 14 (permalink) Old 03-25-2004, 05:54 PM
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Quote:
Originally posted by roger blose
I have a '96 4.6l T-Bird with 120k that has developed a groaning vibration in the drive train at between 30 and 50 mph. I replaced the differential bushing and it made a slight improvement. I am thinking u-joints or tranny outputshaft bushing may be shot. The car is fine at highway speeds and I do not want to begin replacing more parts without cause. I also get a clunk on coast down, downshifts which is coming from the tranny tail / floor area. Anyone had a simular situation and possible fix?
-----------------------------------------------------

you've EXACTLY described the symptoms I'm having with my 97 bird (4.6L, 93k miles)

I have both things you've described:

1) groaning vibration, goes away after 50-55 mph. this seems to have "speed-pockets" when it comes on: first betw.30-35 mph, then at 45 mph, then slowly fades with incresed speed. I feel it in the st.wheel, and on the whole frame of the car,too.

2) clunks on downshifts/when letting ff gas sometimes from the tranny-tunnel/ under the floor where the tranny is...exactly:

just like you, i replaced the IRS oem diff-bushings TODAY, the vibe is that I felt in the seat/floor is gone, but the groaning noise is there, although less intense. the ride feels a lot smoother and tighter;
and the clunk is very soft now, not so loud; improved, but still there a bit.

next step for me is: U-joints
then: tranny mount/motor mounts(they're not totally gone, but not in best shape either, and this "groaning" type of noise/vibe can very well come from engine/tranny mounts being bad, IMO. )

However, as we both can see, the IRS diff-bushings also contribute(d) to this...
with new u-joints(IF they're bad), tranny/engine mounts(the BIGGEST contributor, I think) this should be gone...hopefully.

what are your planned modes of attack against this "groaning" ?
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post #3 of 14 (permalink) Old 03-25-2004, 11:22 PM
 
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my guess is you both have bad torque converters. I got the same thing and on here its called torque converter shudder i would change to Merc V if that doesnt work get a new converter
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post #4 of 14 (permalink) Old 03-26-2004, 10:30 AM
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Quote:
Originally posted by Mattscoug94
my guess is you both have bad torque converters. I got the same thing and on here its called torque converter shudder i would change to Merc V if that doesnt work get a new converter
-----------------------------

Thnaks for the reply, Mattscoug.

I think my TC is OK, and I've been using Mercon-V for the last 10k miles or so.
the reason why I think it's not Tc is that it sometimes does this groaning thing also at very low speeds if I punch the gas a little, and it doesn't shudder; this vibe is a very "fine" vibe, nothing that makes antything really shudder/shaker, but fine and is sort of a buzz.

Why I'm leaning toward tranny/motor mounts:
if I put car in R, and hold it with brake, I get this "trrrrr" sound coming it seems from behind the left front dash area, and if I give it a just little gas with brake still held, that noise goes away totally: alls mooth. My guess is that this is the same thing that turns in to the groan/buzz when driving; AND my motor mounts are bad, 'cause they' were inspected, and was found to be in "fair" condition. I stiill have to get somebody to see if the engine moves when I rev the engine with brake held.

what do you think?
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post #5 of 14 (permalink) Old 03-26-2004, 11:24 AM
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I chased a similar sound and finalyy after replacing Rear bearings, halfshafts, IRS bushings etc I took it to the ford dealer and explained everything I had already done. It turned out the driveshaft yoke that goes in the trans was worn. The only main difference....and it's a big one....is that mine got worse the faster I drove

Birdless

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post #6 of 14 (permalink) Old 03-26-2004, 06:07 PM
 
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Tim,

What does that part run. i am having the same problem. i get the shakes @ about 90 and a year ago I lost a tranny due to this. The front U-joint gave way and took out the bellhousing on my tranny. I am looking to pull the shaft, get the u-joints replaced with upgraded ones and high speed balanced. I am also replacing the differential bushings to correct the pinion angle. if this doesn't solve the problem I will be forced to go back to lower gears and that will suck big time.
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post #7 of 14 (permalink) Old 03-27-2004, 02:38 AM
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Mine is doing basically the same thing, and it's the differential. I know this because I've drained the oil and it looked like glitter. I have a new one coming in the mail. There are some days when I can't go over 40 without considerable vibration, but most days I can go 80 with only a little vibration. If you think you can safely get your rear-end in the air, you can get under it and listen around while someone gives it gas. That's what led me to change the oil.

1994 Thunderbird LX 232
Discarded air silencer. Gutted cats. [email protected] mph at this point. 8.8" Trackloc differential with polyurethane bushings. PA manual valvebody. Sport springs.

1989 Thunderbird SC 5-speed
ESM ported supercharger. Performance exhaust.

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post #8 of 14 (permalink) Old 03-27-2004, 10:36 AM
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The yoke is around $60

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post #9 of 14 (permalink) Old 03-28-2004, 07:22 PM Thread Starter
 
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Many thanks for all of the great replies! It looks like I in the market for a new yoke and may be some U-Joints. I hope that this will get rid of some of the play in the drive train at this high mileage. Keep the info coming.
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post #10 of 14 (permalink) Old 03-28-2004, 10:08 PM
 
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hey roger when it makes the noise does it almost vibrate and groan at the same time and does it do it immedietly when you start driving??
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post #11 of 14 (permalink) Old 03-29-2004, 08:02 AM Thread Starter
 
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Matt, I get the dual combo of vibe and groan at those speeds. If I accelerate at moderate speed than back off quickly, I get a clunk up front. If the car downshifts on a coast down, I can get a clunk out back at the differential. Seems like lots of wear slop due to the mileage. I can believe that the u-joints can be that worn since the drive shaft does have the travel of a live axle, rear driver. The DS remains fairly straight during its useful life.
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post #12 of 14 (permalink) Old 04-04-2004, 08:00 PM Thread Starter
 
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Just got my '96 T-Bird back from the local garage and here are my results in trying to get rid of the groaning vibration. I purchase a new front yoke from Ford ( $140 - ouch!) and had my local mechanic change it and both u-joints. 2.5 hours labor and $36 for the two u-joints and the job was done. They had to drop the gas tank 6 inches to remove the DS so make sure that you run the tank down to 1/4 full. The improvement is dramatic - drive train is much tighter, up shift and coast down clunk is gone, at highway speed, the drive train has a new silkiness / smoothness that I have not seen in years. I still have some groaning with reduced vibration between 30 and 50 mph but the effort was well worth it in my opinion. My front yoke did not look worn at all so I am not sure that this part needed to be changed. But the tighter tolerances in the splines probably helps after 120K. A new transmission mount might be the next step if I want to go to the next step to cut down on more vibration and finances allow. Botton line is change those u-joints to cut the slop!
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post #13 of 14 (permalink) Old 04-05-2004, 07:23 AM
 
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Roger,

In replacing the front yoke, did your mechanic have yo pull the tranny or anything like that? I am going to get my DS balanced and have the U-Joints replaced but is this can be an issuue I would like to handle it while the shaft is out. Thanks.

William
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post #14 of 14 (permalink) Old 04-06-2004, 09:22 AM Thread Starter
 
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The front yoke slides out with the tranny left in place. The splines are inside the yoke. You want to make all of the changes at once due to the gas tank drop down part of the DS removal process. My mechanic said that with only six inches to drop the tank, he did not have to disturb any fuel lines or tank wiring. this is a big plus on an old car!
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