Clunk in 5th Gear only....WTF....HELP

[totheduals]

This just seem to happen the other day.
Driving along in 5th gear and let off for a car in front of me and then easd back on the throttle and got a CLUNK! The girlfriend looked at me and said "what did you do" Not a F'ing thing I said.
Crawled under to check what the movement of the driveshaft was in neutral with the E brake on and it seemed ok.
Had the guy that put my gears in come take a look ( he's a FORD tech ) and he said it seemed weird that the clunk was only there in 5th gear. No clunk in any of the other gears! My car only has 12,000 miles on it so I don't really think anything is wore out just yet.

Why only clunk in 5th gear and no others??? He said we could check the backlash in the diff, and also see if maybe a bearing went but I only have 1000miles on it since he put it in.
U Joints are all good and can't find anything else loose?

PLEASE HELP FELLA'S I DON'T WANT TO SHELL OUT ANOTHER 400 BUCKS TO TAKE THE DIFF OUT FOR NO REASON!
:rockon:

 

[Un4GivN]

The "clunk" is fairly common with our cars. Do a search.

 

[totheduals]

I did search and all I found were ppl talking about always having the clunk in every gear. And also the clunk going into 1st.
I just can't see why it would only be 5th and no others. Some other techs say I should pull out the diff and check it but I thought I would ask so opions on here before doin it!
And with only 12000 miles I don't think anything is wore out.

 

[carnut726]

5th gear clunk is driveline slack.... most of us have it. easy fix,,,,, dont stomp on the gas in 5th, thats what 4th gear is for. LOL

 

[totheduals]

5th gear clunk is driveline slack.... most of us have it. easy fix,,,,, dont stomp on the gas in 5th, thats what 4th gear is for. LOL

Its not when I stomp on it!!! Only when i let off and slowly get back on the gas there is a CLUNK!!
Its never been there before and just showed up now. Its not a normal thing!
And I will not drive the car until I find out WTF it is.

So unless you have some input for me don't ramble on in my thread!
:nono:

 

[Adam01Snake]

I have experienced the "Clunk" in first gear on all the mustangs I've owned at some point or another, don't remember ever hearing it in 5th gear though, but thats not to say it didn't happen, most of my time in the car I have the radio up so loud, except for when I had my 95 GT, I couldn't hear the radio for roar of the 5.0 with the E303, shorties, and full O/R exhaust...It's probably normal like one of the other guys said driveline slack. Drive it around some more and see if it does it in any of the other gears or does it again, it could have just been a fluke.

Good luck,

Adam

 

[totheduals]

Yes it still does it!
Yes only in 5th gear!
Its not just a sound you can feel it in the seat of your pants like someone kicked the back of the seat!
It is not a common problem! Not like what everyone is talking about. For get what year the car is and what make. Then tell me what you think it could be.
PS. It also has nothing to do with the first gear clunk everyone wants to refer to!

 

[Un4GivN]

Yes it still does it!
Yes only in 5th gear!
Its not just a sound you can feel it in the seat of your pants like someone kicked the back of the seat!
It is not a common problem! Not like what everyone is talking about. For get what year the car is and what make. Then tell me what you think it could be.
PS. It also has nothing to do with the first gear clunk everyone wants to refer to!

If it only does it in 5th gear, I seriously doubt the differential is the problem. If it were, it would happen in any/all gears. Does it do it every time you shift into 5th?

 

[totheduals]

Only when I let off and then slowly get back on the gas. There is a very noticeable bang or thud. And again only in 5th. You can feel it in the seat. You can hear it come from behind. Thats why i think it has something to do with the diff.
If I shift normally or hard into any gear there is nothing. In 1 - 4 if I hit it or just get on and off the gas really quick there is no clunk, bang or thud at all.
I talked to some other techs and they said that with 5th being OD it will magnify any loose play in the driveline.
If you put a mark on the bottom of the driveshaft (6 oclock) you can turn it to 7 oclock. That seems a little much to me.
I've pulled the plug on the back of the diff and the oil is perfectly clear and there was no filing at all on the magnet. Thought maybe a bearing was going out?? Since I had the FRPP 4.10 gears put in I have only put 1000kms on the car. I also bought the FRPP install kit with all new bearings and shims.
I had another guy under the car right when it happened and he said he could move the driveshaft from the 6 oclock position all the way to 9 oclock. But I backed the car out of the garage a bit and jacked it up and cannot get it to do this again.

WTF
Think I am just going to have the diff pulled and checked and while its out put in ACCobra's kit and a diff gurdle. Then I know everything is ok back there.

 

[99cobra09]

Maybe your 5th gear syncro is going bad that it causes the clunk.

 

[Bite Me]

The cobra clunk. I get it in first gear and 5th if I let off and get back on.

 

[totheduals]

Well its booked in next week to go to a driveline shop and run thru the gears up on the hoist. Hopefully we can narrow it down!
I have a hard time believing its the tranny but I guess you never know.
I think its in the diff but I will keep you posted on what I find!

 

[Adam01Snake]

Good luck bro! I hope it turns out to be nothing major!

 

[carnut726]

Its not when I stomp on it!!! Only when i let off and slowly get back on the gas there is a CLUNK!!
Its never been there before and just showed up now. Its not a normal thing!
And I will not drive the car until I find out WTF it is.

So unless you have some input for me don't ramble on in my thread!
:nono:

WTF is that all about. I had input, and gave it to you. you asked for help bacause u had NO IDEA WHAT THE NOISE IS :nonono: For some one who says they have no idea what the problem is you sure do know a lot about what is ISN'T. Good luck, and for the record even your tech said it was.
I talked to some other techs and they said that with 5th being OD it will magnify any loose play in the driveline.

 

[Orange Stang 04]

Why would it be the diff if it does it only in 5th gear?? I'm thinking whatever your problem is, it doesn't have anything to do with your differential.

 

[4a7191a]

yeah, ive put an 03 cobra setup on the 99 and even put 390 gears in it, started clunking a while back. wish i would of done a straight axel.

 

[Boostin01Slobra]

its common. mine does it and my gears are jus fine. just ease on/off the throttle more gently

 

[droptopcobra99]

i have a 99 Convert and when i took it for a test drive at 74000 miles it had a clunk when id shift into 5th let off and the touch the gas. now at 106000 it will clunk in any gear if i coast and touch the gas. feels like a tranny mount or something in the rear ive never found out what it is. but im sure a set of 4.10's are on the way. post back what you find if anything

 

[Bart7279]

Yeah I would like to hear what you find out about this...

 

[realitygt]

in my 98 i have a clunk in every gear if I let off the gas and then get back on it even somewhat quickly.... been doing it since i bought it 20k miles ago... :/