9 inch traction lock issue

Hello, I am having an issue and hope the fix is easy, but who knows.

I bought a freshly rebuilt 9” traction lock center section. I put it in the car with proper fluid and friction modifier. It worked great for a short period then just suddenly started spinning one wheel :huh:  Is there anything besides the S spring breaking that would cause sudden loss of limited slip? Has anyone ever heard of one of thes springs breaking? Thanks for any help.

Probably the spring. I never had much luck with traction lock (limited slip) differentials. Even when new it's too easy to over-ride the clutches. If one tire is on the pavement and the other on gravel the tire on gravel will spin. They only work when both tires have similar traction.

Detroit lockers are the only positive engagement differentials, other than electrically or air locked differentials.

Interesting info there. I say that because over winter, I am taking the rear axle out of my 71 Mach 1 and sending it to a local specialist just for a refresh. It's the only part of the drivetrain that has not yet been totally serviced. Currently it is an open 3.25:1 dif and for what I do with the car, I'm happy with that. However, Brad suggested swapping in a new Trac-Lok center section that he just happens to have on the shelf, keeping the 3.25:1 ratio if I want. Now, I don't know much at all about differentials, so I'm open to all information available without overstepping on the original poster's toes here. 

A friend of mine has a 73 Torino with a 429 swapped in. He was having problems with the rear end. He had the center section replaced with a Dana and still had problem with whining. Finally he sent it to Brad who suggested a "True-Trac" I believe it's called and has had zero issues since. For me, too much money for that, but it might be a suggestion for our poster.

Geoff.

Truetrac still depends on friction against the sides of the helical gears to provide some torque to the spinning tire. However, at most it provides only about 20% of the torque to the spinning tire, which is better than an open differential. The design of the helical gears can be changed to increase the torque bias, but at the expense of differential action and driveability.

Theoretically, If the spring in traction lock is strong enough it can provide a 50/50 torque split, but at the expense of driveability. In NASCAR jargon it would be too tight in the corners, wanting to go straight ahead, especially if the roadway is slick. The differential action depends on the clutches slipping.

Detroit lockers provide full differential action in corners, until one tire spins, then it locks up like a spool and wants to send you straight forward. Plus the clicking around corners is objectionable to some.

So, they all are compromises.

Never had an issue with a Ford Trac-lok unit in my Mustang's in 40 year's... Great units is done properly.

Hello, I am having an issue and hope the fix is easy, but who knows.

I bought a freshly rebuilt 9” traction lock center section. I put it in the car with proper fluid and friction modifier. It worked great for a short period then just suddenly started spinning one wheel :huh:  Is there anything besides the S spring breaking that would cause sudden loss of limited slip? Has anyone ever heard of one of thes springs breaking? Thanks for any help.

Click to expand...

What "S" spring? Perhaps not enough preload and initial break in made it worse. You do have a Traction-lok and not an Equa-lok right? Chuck

EDIT: Just to be clear, neither one of the vintage factory differentials I mentioned above have an S spring. The Equa-lok had a belleville spring and the traction-lok used 4 coil springs, along with a shim, to set preload.

I believe he is talking about the pre-load spring.

Hello, I am having an issue and hope the fix is easy, but who knows.

I bought a freshly rebuilt 9” traction lock center section. I put it in the car with proper fluid and friction modifier. It worked great for a short period then just suddenly started spinning one wheel :huh:  Is there anything besides the S spring breaking that would cause sudden loss of limited slip? Has anyone ever heard of one of thes springs breaking? Thanks for any help.

Click to expand...

What "S" spring? Perhaps not enough preload and initial break in made it worse. You do have a Traction-lok and not an Equa-lok right? Chuck

EDIT: Just to be clear, neither one of the vintage factory differentials I mentioned above have an S spring. The Equa-lok had a belleville spring and the traction-lok used 4 coil springs, along with a shim, to set preload.

Click to expand...

What's an "Equa-lok? Never heard of that one. Just thought I'd ask the question

Truetrac still depends on friction against the sides of the helical gears to provide some torque to the spinning tire. However, at most it provides only about 20% of the torque to the spinning tire, which is better than an open differential. The design of the helical gears can be changed to increase the torque  bias, but at the expense of differential action and driveability.

Theoretically, If the spring in traction lock is strong enough it can provide a 50/50 torque split, but at the expense of driveability. In NASCAR jargon it would be too tight in the corners, wanting to go straight ahead, especially if the roadway is slick. The differential action depends on the clutches slipping.

Detroit lockers provide full differential action in corners, until one tire spins, then it locks up like a spool and wants to send you straight forward. Plus the clicking around corners  is objectionable to some.

So, they all are compromises.

Click to expand...

Thanks for the explanation Don.

 For me, I'm wondering if it would even be worth the extra money to put in the True-trak and stay with the open dif.

Geoff.

Hello, I am having an issue and hope the fix is easy, but who knows.

I bought a freshly rebuilt 9” traction lock center section. I put it in the car with proper fluid and friction modifier. It worked great for a short period then just suddenly started spinning one wheel :huh:  Is there anything besides the S spring breaking that would cause sudden loss of limited slip? Has anyone ever heard of one of thes springs breaking? Thanks for any help.

Click to expand...

What "S" spring? Perhaps not enough preload and initial break in made it worse. You do have a Traction-lok and not an Equa-lok right? Chuck

EDIT: Just to be clear, neither one of the vintage factory differentials I mentioned above have an S spring. The Equa-lok had a belleville spring and the traction-lok used 4 coil springs, along with a shim, to set preload.

Click to expand...

What's an "Equa-lok? Never heard of that one. Just thought I'd ask the question

Click to expand...

It was in production from about 1964 through mid year 1969. Instead of 4 coil springs and a shim for pre-loadT, the Equa-Look used a belleville spring. It was a flawed design that would not stand up as well as a traction-lok. Not a great write-up but, will give you an idea.  http://automotivemileposts.com/autobrevity/equalok.html

Back to the original post does dohsvct really know what he has? If it is a Equa lok than it sounds like the S spring as explained would cause the problem. If it is a trac-lok than to me it sounds more like a preload issue with the clutch pack. If not loaded right once worn just a little it will start slipping. Can't imagine any way that the springs would cause the issue unless they were already shot when it was rebuilt and they weren't replaced.

What "S" spring? Perhaps not enough preload and initial break in made it worse. You do have a Traction-lok and not an Equa-lok right? Chuck

EDIT: Just to be clear, neither one of the vintage factory differentials I mentioned above have an S spring. The Equa-lok had a belleville spring and the traction-lok used 4 coil springs, along with a shim, to set preload.

Click to expand...

What's an "Equa-lok? Never heard of that one. Just thought I'd ask the question

Click to expand...

It was in production from about 1964 through mid year 1969. Instead of 4 coil springs and a shim for pre-loadT, the Equa-Look used a belleville spring. It was a flawed design that would not stand up as well as a traction-lok. Not a great write-up but, will give you an idea.  http://automotivemileposts.com/autobrevity/equalok.html

Click to expand...

 Thanks for your knowledge and insight on this. Coming from the UK, I had never heard of that differential set-up.

 Now I know.

Geoff.