Diagnose my mustang!

[leos67]

I bought a 1983 GT 5.0 5-speed. The motor in it is freshly rebuilt. I just started driving it a couple of days ago. in the begining the car seemed to be fine but now every time i shift i hear a clunk somewhere near the rear of the car. i know it is not the drive shaft because i check that out and the cuopler bolts weren't loose or anything and the u joints look fine. now either i am not shifting right or i need differential fluid which i haven't check because i can't find the plug? another issue that started is that when i start to drive the car in 1st then shift to 2nd and so on to fifth gear the car seems that it has no go. for example like when i shift from 2nd to 3rd and as soon as it goes into 3rd the car seems to be reving at its max and its time to shift again.even at low speeds like driving it in the streets. i was thinking maybe i need new tranny fluid which i also haven't check. i really don't know what is happening to this car please help????
thanks guys

 

[nito88stang]

teh plug for the differential fluid is on the drivers side of the differential facing the the front of the car. Hard to diagnose without more info.

 

[88GTCobra]

With the clunk sound in the rear of the car, do you have a limited slip diff.? Because if you do then that is most likley the clunking sound. I have an Auburn LSD and when I get on it and shift from 1st.-2nd.-3rd. etc. it makes a clunking sound, not loud, but you can hear it.(People have told me this is what a LSD does) But first things first, cheak the rear diff. fluid. Try to find the plug. (I haven't looked closely at mine so I don't know where to find it, most likely on the rear diff. cover). About the other problem, again cheak the tranny fluid. Maybe you need a new throddle position sensor. I hope I have helped but I have only owned my Stang for about 2 weeks now and I am still learning too. Good luck and keep us posted.

 

[KnowPlay]

Does the "clunk" come right after you release the clutch? Sound like a loud thump as if something hit the floorboard? Fox Bodies are bad about pinion "slap". When you release the clutch, the rearend will roll slightly causing the pinion snout to come into contact with the floor. An inexpensive pinion snubber will solve this problem.

The shifting problem sounds more like a slipping clutch. From a complete stop, put the shifter in third, rev it to about 3000 and dump the clutch. If it stalls the engine instantly, good clutch. If it doesn't, time to invest in new clutch.

 

[DJFox]

i had a problem where i would get that sound when i would get on the gas or let off of it and it turned to be the through out bearing. it was a clunking sound that seemed to come underneath the middle of the car

 

[leos67]

Hey KnowPlay!

i did what you said about putting it in third and then rev it to 3000 and dumped the clutch and the car turned of then i did it again and stall right away. now i still haven't changed any of my fluids put the problems continue that the car really has no take off in any gear. that as soon as i shift its time to shift again. this happens at normal driving speeds. let me know what other info you guys might need to figure what could wrong with my car thanks.

 

[Zero_chance]

Maybe unrelated but check the tranny crossmember. One of my supports on mine was rotted out so the tranny would actually lift up a little and then fall back down on the the support when I shifted. Replaced it with a new FRPP double hump tranny crossmember and Im good to go. Do you know if the previous owner installed gears in your ride? Oh, and itd help to know what RPM you consider is already time to shift again.

 

[91mustangnick]

my stang makes a clunking sound too. i took it to a shop to have a tranny flush and i told them to check the univeral joints. they said they are fine but it was my pinion bearing is bad. a few hunderedth of wear can cause the clunking sound as it moves in the 3rd member.

nick

 

[leos67]

what RPM?

well you see the tac in the car is not working and i don't know where to start to try to fix it. but you can just feel the car sort revved up and asking to be shifted again when i go from gear to gear.

 

[mustang120plus]

Yea it sounds like a pinion issue, unless of course the rear end is going...