I need help with my rear

-
furyus2

furyus2

Well-Known Member
Joined
Oct 30, 2010
Messages
2,419
Reaction score
907
Location
weeki wachee fl
The problem is, When the car has been driven for a while, I can hear a clunk clunk clunk when making slow turns. I have changed the fluid, and put in the Ford friction modifier, but it still does it. It's a 742 case 3.55 gear sure grip. Any ideas from experienced rear end guys?
Thanks.
 
furyus2 said:
The problem is, When the car has been driven for a while, I can hear a clunk clunk clunk when making slow turns. I have changed the fluid, and put in the Ford friction modifier, but it still does it. It's a 742 case 3.55 gear sure grip. Any ideas from experienced rear end guys?
Thanks.
Click to expand...
Are you running the adjustable axle bearings or the green bearings?
 
Hmm my rearend made a clunk noise on turns with a suregrip and green bearings. I had to remove the thrust button out of pumpkin. Have you given your rear of vehicle a good shake check the axle bearings?
 
furyus2 said:
Tapered . all stock. possibly never been rebuilt.
Click to expand...

Any vibration? Have you checked axle end play?

The last time mine did something like that in a Dana rear, it was the ring and pinion coming apart, it was real bad in reverse.
 
Yes, I did set axle end play.
Have you given your rear of vehicle a good shake check the axle bearings?
Not sure what you mean. The axle bearings felt fine when I pulled the axles a while back.
 
furyus2 said:
Yes, I did set axle end play.
Have you given your rear of vehicle a good shake check the axle bearings?
Not sure what you mean. The axle bearings felt fine when I pulled the axles a while back.
Click to expand...
I’ve had some bearings so bad I could shake the rear of car while on ground and here them clunk. If you said they seemed fine I’d be more incline to remove your 742 for a closer look
 
Hello All,
I just had to.....
Stay Save......
Happy Mopar :)
Arron.
 
Dartsun said:
I’ve had some bearings so bad I could shake the rear of car while on ground and here them clunk. If you said they seemed fine I’d be more incline to remove your 742 for a closer look
Click to expand...
I'm thinking I will need to pull the rear AGAIN, and have it rebuilt, or get one from one of the rear end specialists. And have new axle bearings installed.
 
If it's not in the U-joint;
Ima thinking there might a tooth or more broke off the spider gears.
The other thing that happens is the cross-pin saddles "waller" out. Then you get a clunk going into gear, and also from forward to reverse.
But that clunk, is hard to differentiate from spider-gear endplay.
In any case if the clunk originates inside the diff, it has to come down.
 
AJ/FormS said:
If it's not in the U-joint;
Ima thinking there might a tooth or more broke off the spider gears.
The other thing that happens is the cross-pin saddles "waller" out. Then you get a clunk going into gear, and also from forward to reverse.
But that clunk, is hard to differentiate from spider-gear endplay.
In any case if the clunk originates inside the diff, it has to come down.
Click to expand...
There's no clunk going into gear. Only when turning left, or right. U joints as well as the drive shaft are new. I'm wondering if it's the clutches.
 
My clutches have never clunked and I have been using various Mopar SGs almost continuously since 1970, Daymn I'm getting old.
I have experienced a shudder, on a new build before the SG additive worked in.
Try this, run the car in a circle ~10 times and then reverse directions for another 10; Lessee what happens.
 
AJ/FormS said:
My clutches have never clunked and I have been using various Mopar SGs almost continuously since 1970, Daymn I'm getting old.
I have experienced a shudder, on a new build before the SG additive worked in.
Try this, run the car in a circle ~10 times and then reverse directions for another 10; Lessee what happens.
Click to expand...
What does that do, besides make me dizzy? All I know, is it clicks/clunks while im turning. I was hoping someone could help. It only happens after I drive for a while.
Not trying to be a jerk. Im just frustrated
 
furyus2 said:
What does that do,
Click to expand...
It forces the clutches to rotate inside the case, Cone-type clutcges have a spiral groove machined into them. The groove on the now-spinning clutch picks up the oil and smears it all around the friction surfaces. This action agitates the oil and homogenizes it,thoroughly mixing the oil and the friction modifier.
Now; if the clunk WAS being caused by the clutches, it should be gone.

It might not take 10 turns each way, maybe only 4, but I erred on the side of too many .
If the clunk does not go away,is not end-play, and it absolutely originates inside the differential; then it's more serious business, and the sooner you get a peek at it ,the better.
As mentioned several times above, you can check for loose axle end-play clunk by standing at the back of the car,and pushing the body to one side and pulling it back, in a push/pull shaking motion. If there is too much endplay, it makes a very distinctive clunk.
Setting the end-play is a bit of an art, and the wheels need to be off the ground, and hanging free. Sometimes the bearing races stick in the axle tubes and give a false reading. I have a 5pound sledge hammer I use to tap the axles home.
Sometimes when you pull an axle out, on the clutch-type SG, the Thrust-button will fall out. Then when you set the end-play on the one side, if you are not cognizant of this possibility, the side without the button is still loose.
Also, pinion nuts have been known to loose their torque, and it doesn't take much play for the diff to get noisy.

A click is different from a clunk. If the clicking increases with speed, check your tire treads for a foreign object stuck in them.

Also, just because a U-joint is new, does not preclude it not being noisy. I have seen the cups moving from side to side in the straps, and I have seen the crosses moving side to side in the cups. The driveshaft turns at many times the speed of the wheel, so if the clicking picks up tempo in a hurry, I'd be checking the U-joints for lateral motion.
Also, if you have wire-wheel wheel-covers,lol, they have been known to click in many places.

But having said all that;
inside the diff, the only thing different from driving in a circle to straight-lining, is the engagement of the side-gear/pinions and the SG clutches.
And the only things different between hot and cold is the pinion preload, and the oil-viscosity change, which while turning and at idle, could allow the spiders to be slamming up and down on the crosspin between the case and the side-gears; I've never heard them do that tho. A little throttle will drive them apart and that would be the end of the clunk.
Happy Hunting
 
Last edited:
AJ/FormS said:
It forces the clutches to rotate inside the case, Cone-type clutcges have a spiral groove machined into them. The groove on the now-spinning clutch picks up the oil and smears it all around the friction surfaces. This action agitates the oil and homogenizes it,thoroughly mixing the oil and the friction modifier.
Now; if the clunk WAS being caused by the clutches, it should be gone.

It might not take 10 turns each way, maybe only 4, but I erred on the side of too many .
If the clunk does not go away,is not end-play, and it absolutely originates inside the differential; then it's more serious business, and the sooner you get a peek at it ,the better.
As mentioned several times above, you can check for loose axle end-play clunk by standing at the back of the car,and pushing the body to one side and pulling it back, in a push/pull shaking motion. If there is too much endplay, it makes a very distinctive clunk.
Setting the end-play is a bit of an art, and the wheels need to be off the ground, and hanging free. Sometimes the bearing races stick in the axle tubes and give a false reading. I have a 5pound sledge hammer I use to tap the axles home.
Sometimes when you pull an axle out, on the clutch-type SG, the Thrust-button will fall out. Then when you set the end-play on the one side, if you are not cognizant of this possibility, the side without the button is still loose.
Also, pinion nuts have been known to loose their torque, and it doesn't take much play for the diff to get noisy.

A click is different from a clunk. If the clicking increases with speed, check your tire treads for a foreign object stuck in them.

Also, just because a U-joint is new, does not preclude it not being noisy. I have seen the cups moving from side to side in the straps, and I have seen the crosses moving side to side in the cups. The driveshaft turns at many times the speed of the wheel, so if the clicking picks up tempo in a hurry, I'd be checking the U-joints for lateral motion.
Also, if you have wire-wheel wheel-covers,lol, they have been known to click in many places.

But having said all that;
inside the diff, the only thing different from driving in a circle to straight-lining, is the engagement of the side-gear/pinions and the SG clutches.
And the only things different between hot and cold is the pinion preload, and the oil-viscosity change, which while turning and at idle, could allow the spiders to be slamming up and down on the crosspin between the case and the side-gears; I've never heard them do that tho. A little throttle will drive them apart and that would be the end of the clunk.
Happy Hunting
Click to expand...
I did have the thrust button fall out.pulled the 3rd member, and put them back in with a roll pin. Put new fluid in it with Ford friction modifier. I will try pushing the car side to side, and drive in circles. Can it be bad bearings?
 
I took the car for a ride, and did the driving in circles thing. It was quiet at first, but then it started making a groaning noise, then the clicking noise, then it shuddered, and I didn't think it would make it home. Then, driving normally, it quieted down. When I got home, turning into the yard, and shop, it sounded like it was going to self destruct. So, I guess it's dead.
 
AJ/FormS said:
not likely,
But;you know those wheel bearings have to be packed full of grease before you install them ....... right? They do NOT share oil with the diff. When that happens, the oil runs into the brakedrums and makes a horrible mess.
Click to expand...
I put new inner seals in, and packed the bearings before putting the axles in. Heat has something to do with it, since it's quiet when cold. When it makes the noise, it sounds like the wheel/axle, but it does it turning both ways. I think the rear noise is possibly telegraphing through the axles. Your thoughts?
 
I tried to contact Dr Diff, but the voice mail said he can't answer the phone, but to contact by email, so I did. So, I have to wait to see what he says. Does this sound like it's the differential? and can I just put a new one in, and keep my stock ring, and pinion? Or is that just going to cause more issues?
 
I think yur jumping the gun.
I have never heard a diff make all those sounds. And I don't know of anything else back there that could, unless it's in the brake housings; they can groan when yur riding the brake-pedal. And I have heard noises coming from the backing plates, created by the shoes.
So maybe have a look in there first.
I have heard U-joints groan too.
After that I guess,I'd drop the diff and see what's what.
 
Ok. I'm going to replace the brake shoes, and turn the drums. Then I will see if that's the problem. Dropped the drive shaft, and checked the u joints. They feel great.
 
You must log in or register to reply here.
-

Back
Top