Thud from the rear after quick acceleration, now I have issues...

[Sdgg91]

Good evening,

Last night I went for a drive, and as all things happen I was just under a mile from my house when after a quick 1st to 2nd shift I heard a thud from the rear of the car. I let off and then was met with more popping/thud type of noise when giving the car some throttle and letting off. I limped home trying to give as little power to the car to get home and avoid anymore noise from the drivetrain.

I have checked the rear sway bar and bushings, everything is in tact and there are no rubbing marks on the transmission or sway bar itself. ( I read this could be a potential suspect)

There is play in what seems to be the CV or transmission area. I did recently rebuild my CV joints so I am wondering if something is worn inside there or potentially the inner splines are worn??

I marked all of my 6 inner cv bolts on each side with red paint to keep an eye on any movement as those bolts have occasionally backed out on people. Everything is still in place but there is definitely some type of play in the wheels when twisting the rear wheel back and forth with the other wheel of the car on the ground.

I have attached a YouTube video below. First question, should there be any play in the rear wheels when rotating them back and forth with the car jacked in the air?

What do you think this could be? I have a bunch that whenever I assembled the CV joints after rebuilding them I went wrong somewhere and caused some wear to inner spline or CV itself.

https://www.youtube.com/watch?v=nCB28__41MY&feature=share



https://www.youtube.com/watch?v=nCB28__41MY&feature=share


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[agfours]

Open the decklid and check that the bushings on the top of the shock are still there/in place. Same thing happened to me, and sounded like something heavy was really loose when the car went over bumps... was a quick fix with new Bilsteins. (of course, you could replace the bushings alone, but if they are worn, the shocks probably are too...)

[Sdgg91]

Here is the same noise when rocking the car back and forth - gently.

It almost sounds sort of like marbles rattling around.


https://youtu.be/QftgQ85Y7A8

[Sdgg91]

Originally Posted by agfours

Open the decklid and check that the bushings on the top of the shock are still there/in place. Same thing happened to me, and sounded like something heavy was really loose when the car went over bumps... was a quick fix with new Bilsteins. (of course, you could replace the bushings alone, but if they are worn, the shocks probably are too...)

I checked both shocks, everything is solid. New Bilsteins are only about a month old on the car as well.

Thanks for the suggestion.


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[Mahler9th]

How much experience do you have with CV's, axles and tranmissions?

I listened to all three vids. The sound from the first two was very concerning to me. I do not like that loud click. I do not like it at all.

Is that just turning the wheel/tire with the suspension unloaded and the transmission in neutral??

I have trouble envisioning any type of inner spline or CV damage, especially if you have experience with proper ways of refreshing and/or replacing CV joints.

If you have a more experienced friend or shop owner nearby, I might suggest asking them for help.

One thing I can think of is to disconnect the inner CV's from the stub axles. Move them out of the way and try to rotate the stub axle on each side by hand. Again in neutral. They can be kind hard to turn since you only have about a 4 inch wheel as leverage-- gloves can help. See if you get that same click.

If not, again, try carefully turning the wheel tire and turn the axle/cv. The cv's can usually handle the angle just hanging there, but of course it cannot hurt to suspend it with string, rope or wire from the crossmember. The idea in all of this is to determine wehther the click is in the CV /axle world or in the transmission world.

[Mahler9th]

I am wondering if something broke in the tranny.

[Sdgg91]

Originally Posted by Mahler9th

How much experience do you have with CV's, axles and tranmissions?

I listened to all three vids. The sound from the first two was very concerning to me. I do not like that loud click. I do not like it at all.

Is that just turning the wheel/tire with the suspension unloaded and the transmission in neutral??

I have trouble envisioning any type of inner spline or CV damage, especially if you have experience with proper ways of refreshing and/or replacing CV joints.

If you have a more experienced friend or shop owner nearby, I might suggest asking them for help.

One thing I can think of is to disconnect the inner CV's from the stub axles. Move them out of the way and try to rotate the stub axle on each side by hand. Again in neutral. They can be kind hard to turn since you only have about a 4 inch wheel as leverage-- gloves can help. See if you get that same click.

If not, again, try carefully turning the wheel tire and turn the axle/cv. The cv's can usually handle the angle just hanging there, but of course it cannot hurt to suspend it with string, rope or wire from the crossmember. The idea in all of this is to determine wehther the click is in the CV /axle world or in the transmission world.

I don’t have a ton of experience on trannys or axels. I’ve done a good bit of DIY and it seemed pretty straightforward.

The car is not in neutral, it is in first gear in these videos. When in neutral everything spins freely.

The car rolls fine and makes no noise at all when I’m in neutral or not under load.

Really a bummer if it’s something big, I just got this thing all sorted to be a nice driver.

[Sdgg91]

Originally Posted by Sdgg91

I don’t have a ton of experience on trannys or axels. I’ve done a good bit of DIY and it seemed pretty straightforward.

The car is not in neutral, it is in first gear in these videos. When in neutral everything spins freely.

The car rolls fine and makes no noise at all when I’m in neutral or not under load.

Really a bummer if it’s something big, I just got this thing all sorted to be a nice driver.

Also it’s a 1987 Targa with the G50 if that helps...


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[mikesarge]

LSD? Sounds to me like a CV joint blowout. It wouldn’t leave you stranded if you have an LSD so it may be harder to diagnose. I’d remove both axles and inspect.

[Sdgg91]

Originally Posted by mikesarge

LSD? Sounds to me like a CV joint blowout. It wouldn’t leave you stranded if you have an LSD so it may be harder to diagnose. I’d remove both axles and inspect.

Well... how do I know if I have a LSD?. The car is new, too me.


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[Mahler9th]

Happy to hear that you have some experience... and thanks for clarifying that the tranny was in first.

Was the entire rear suspension suspended? And if so, you had it in first and rotated the wheel/tire on one side and heard that clicking? Did you try the other wheel/tire and hear the same thing?

If you disassembled the CVs and cleaned them and re-packed them, did you have and problems or confusion reassembling?

I have long been a proponent of paint dotting--started doing that around 1994. DOn't need to bother with my current car.

I don't have any experiences with G50's except with a 993 so cannot comment on that.

LSD... if the rear suspension is unloaded and you have an LSD or TBD and rotate one wheel/tire, the other one will rotate the same way. Open diff and it will rotate the reverse way.

[Mahler9th]

Ok, I now re-read your original post and see you said that both sides were up.

So now I am curious where that sound is coming from. Can you determine that somehow? Of course getting closer might mean getting under the car, so jackstands, jackstands, jackstands....

Maybe a stethoscope would help.

If that is a normal sound with a G50 set up in rear suspension droop in first gear, I cannot envision what could cause it... but I can envision that someone with the same set up and DIY experience can comment... or maybe an transmission expert like Matt Monson.

Did you her the thud during the shift or afterward?

Have you checked all of the engine/tranny mounting bolts?

For years I had no issues with mine ('75-based race car with a 3.6-3-8L engine and a 915). Then after about 15 years I had an issue with the tranny mount bolts so now I safety wire and paint dot them.

Did you remove the axles as assemblies, leaving the stub axles and tranny output flanges in place?

Has anything else been off of her recently?

[mikesarge]

Originally Posted by Mahler9th

LSD... if the rear suspension is unloaded and you have an open diff and rotate one wheel/tire, the other one will rotate the same way. LSD or TBD and it will rotate the reverse way.

Oops- that’s backwards. An open diff leads to wheels spinning opposite directions. An LSD will force both wheels to spin the same direction.

[Sdgg91]

Originally Posted by mikesarge

Oops- that’s backwards. An open diff leads to wheels spinning opposite directions. An LSD will force both wheels to spin the same direction.

Ok so when the car was up, when turning the wheel the wheel on the other side spun in the reverse direction.

So it sounds like I have no LSD.

[Sdgg91]

Originally Posted by Mahler9th

Happy to hear that you have some experience... and thanks for clarifying that the tranny was in first.

Was the entire rear suspension suspended? And if so, you had it in first and rotated the wheel/tire on one side and heard that clicking? Did you try the other wheel/tire and hear the same thing?

If you disassembled the CVs and cleaned them and re-packed them, did you have and problems or confusion reassembling?

I have long been a proponent of paint dotting--started doing that around 1994. DOn't need to bother with my current car.

I don't have any experiences with G50's except with a 993 so cannot comment on that.

LSD... if the rear suspension is unloaded and you have an open diff and rotate one wheel/tire, the other one will rotate the same way. LSD or TBD and it will rotate the reverse way.

I didn’t really have issues getting things together.

I reused one of the CV joints since it was in good shape, I had to replace the other one since it showed some pitting and wear.

When I put the new CV back on the shaft it was sort of difficult to get on, almost like the splines were not completely lined up. I ended up being able to get everything together with a rubber mallet, but the old CV slipped on no problem.

I still can’t quite make out where the noise is coming from. I am going to take the car for another spin to try and get another feel for things.

[Sdgg91]

Originally Posted by Mahler9th

Did you her the thud during the shift or afterward?

Have you checked all of the engine/tranny mounting bolts?

Did you remove the axles as assemblies, leaving the stub axles and tranny output flanges in place?

Has anything else been off of her recently?

The thud seemed to happen when I released the clutch into second gear, it was a spirited take off probably to 4500 RPM or so.

All engine bolts and tranny bolts looked good when I was poking around in there today.

I removed the Axels as assemblies and then took everything apart from their.


I have done a bunch to her recently,
. In the rear the only thing I have done other than the CV joint rebuild is replacing the shocks, which is really straightforward.



Also I have put about 150 miles on the car since doing the CV joints.


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[Mahler9th]

"Oops- that’s backwards." Yes it it... sorry I was doing too many things at once. Will fix my post.

And I meant to add that another way to tell if the car is fitted with factory LSD is to look at option codes.

[76FJ55]

So just to clarify and make sure I'm looking at this correctly, in the vids in the original post both wheels where off the ground at the same time when you shot the videos?

During the initial rotation causing the click was the wheel on the opposite side moving at all?

once the click has occurred could you continue to rotate that side you were turning and what does the wheel on the opposite do?

Do you get the same result when rotating the opposite side wheel? it looks like both vids are of the same side.

[icarp]

Maybe the center of the clutch has broken , just an idea
ian

[Sdgg91]

Originally Posted by 76FJ55

So just to clarify and make sure I'm looking at this correctly, in the vids in the original post both wheels where off the ground at the same time when you shot the videos?

During the initial rotation causing the click was the wheel on the opposite side moving at all?

once the click has occurred could you continue to rotate that side you were turning and what does the wheel on the opposite do?

Do you get the same result when rotating the opposite side wheel? it looks like both vids are of the same side.

It looks like I posted the same video twice. Sorry about that.

When the car was up, the other side was spinning in the opposite direction until that click happens and both stop. The car is in first gear here, so I wouldn’t expect the wheels to move much at all in gear.

I could then rotate it the opposite direction, wheel movement on both sides was probably a quarter turn of the wheel or so each direction.

Both sides behave identically.


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