Bad clutches or no locking diff?

[DC_Gearhead]

I got my bronco out of my uncles barn 5 years ago and have been working on it ever since. I will have it done this spring and start driving it this summer for the first time in 30 years. My uncle said the rear diff was a locker, but when I do all the tests I have read online it doesn’t appear to be one. Uncle died 4 years ago, so I can’t go back to him. I spinned the yoke and it is 3.50 gearing and that is stock matching the little metal tag. I plan to replace it with 4.11 or 4.56, but I would like to think the clutches are bad and I don’t actually need a new locking. I’m in the process of painting, but have taken a break because of the low temperatures and I’m thinking I may do my gears.

Is there anyway that I can tell if I just have a unit with bad clutches vs no locking diff......other than pulling the 3rd member out?

Tests I have done: Lifted both wheels and when one tire is turned the other turns reverse. I lifted one wheel with the other on the ground. The lifted wheel turns fine.

Any advice on how to figure this out without pulling the pumpkin?


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[SP73]

If you’re going to re-gear, the 3rd member HAS to come out. Just see for sure what you have then.

 

[ared77]

You mentioned the little tag on rear end. From my years of Mustangs (and I'm assuming Bronco might be same) there should be a "L" on the tag if it came as locking.

For example on a Boss 302 Mustang from '69 , '70 the rear end tag for the 3.91 Traction Loc would be 3L91.

 

[langester]

I have always gone off of the same tests that you performed. With those results I would say it is an open differential. I was told this years ago and assumed it was the way to check. I would love to hear from others to confirm that this is a fool proof test.

 

[Timmy390]

What I thought was an open diff was a T-loc with no clutches left.

My advice if you want a traction locking rear, Go Eaton TrueTrac No clutches no special oil and tough as nails.

Tim

 

[jamesroney]

I got my bronco out of my uncles barn 5 years ago and have been working on it ever since. I will have it done this spring and start driving it this summer for the first time in 30 years. My uncle said the rear diff was a locker, but when I do all the tests I have read online it doesn’t appear to be one. Uncle died 4 years ago, so I can’t go back to him. I spinned the yoke and it is 3.50 gearing and that is stock matching the little metal tag. I plan to replace it with 4.11 or 4.56, but I would like to think the clutches are bad and I don’t actually need a new locking. I’m in the process of painting, but have taken a break because of the low temperatures and I’m thinking I may do my gears.

Is there anyway that I can tell if I just have a unit with bad clutches vs no locking diff......other than pulling the 3rd member out?

Tests I have done: Lifted both wheels and when one tire is turned the other turns reverse. I lifted one wheel with the other on the ground. The lifted wheel turns fine.

Any advice on how to figure this out without pulling the pumpkin?


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Well, this is an interesting question. And the answer is "yes, you can."

The problem with the Ford traction lok (a clutch type limited slip) is that it is not a locking differential. As it wears, or even better, when it breaks the case halves, the amount of slip makes it behave like an open diff.

If your choices are factory open diff, or factory traction lok, you can remove the left rear axle shaft, arrest the right rear wheel, re-insert the left shaft into the side gear about 1/8 inches at a time, and feel if there are two side gears, or just one. If the clutches are as worn as you say...it will be easy to tell.

But the more interesting question is "why do you care?" If you can't feel any torque bias between the left and right...you either have an open diff, or you have a junk traction lok. Both answers lead to the same solution. You need to buy something new.

 

[Timmy390]

The problem with the Ford traction lok (a clutch type limited slip) is that it is not a locking differential. As it wears, or even better, when it breaks the case halves, the amount of slip makes it behave like an open diff.

Mine went snap......Maybe 50 miles after rebuilding it......

Tim

 

[DC_Gearhead]

Well, this is an interesting question. And the answer is "yes, you can."

The problem with the Ford traction lok (a clutch type limited slip) is that it is not a locking differential. As it wears, or even better, when it breaks the case halves, the amount of slip makes it behave like an open diff.

If your choices are factory open diff, or factory traction lok, you can remove the left rear axle shaft, arrest the right rear wheel, re-insert the left shaft into the side gear about 1/8 inches at a time, and feel if there are two side gears, or just one. If the clutches are as worn as you say...it will be easy to tell.

But the more interesting question is "why do you care?" If you can't feel any torque bias between the left and right...you either have an open diff, or you have a junk traction lok. Both answers lead to the same solution. You need to buy something new.

Good point. My main reason for the question is was money. If I didn’t need to replace the locker, then I’m looking at $300 in parts. If it’s a locker as well, I’m over $1k. The wife is getting touchy about my “problem”. Haha. I was hoping I could just replace gears and fix some little something on the locker. BUT it sounds like I just need to plan on buying both....so that means I need to delay a bit....maybe until I earn my way off the couch. Haha.


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[DC_Gearhead]

What I thought was an open diff was a T-loc with no clutches left.

My advice if you want a traction locking rear, Go Eaton TrueTrac No clutches no special oil and tough as nails.

Tim

TrueTrac is the direction I have been heading. Seems to be the favorite for my use (cruising around in the city and dirt roads with only a few true off-road situations a year)


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[DC_Gearhead]

You mentioned the little tag on rear end. From my years of Mustangs (and I'm assuming Bronco might be same) there should be a "L" on the tag if it came as locking.

For example on a Boss 302 Mustang from '69 , '70 the rear end tag for the 3.91 Traction Loc would be 3L91.

Apparently it is an open diff. No “L”


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[jckkys]

Agreed. The Ford tag says it's an open differential and if someone put a traction device in there they wouldn't have put the same Ford tag back on. Even if they just replaced bearings and seals, they wouldn't have bothered to replace the tag. I've yet to see any rear end shop does that. I have to add that I did have a limited slip Ford rear end that was so worn, it worked exactly like an open differential. I now have TruTracks front and rear. I only sense them when one wheel spins in snow or ice.

 

[Rustytruck]

if you must use a trac loc get the aftermarket billet steel side plate so you have some hope of keeping it together. the thing I don't like is one axle is driven by a narrow spline section on one axle. once that strips you have no power transfer by the rear axle whether in 2 wd or 4 wd. a very weak link especially on the primary axle.