Wrecked my TTB

Ohhh man!

I shattered the ujoint in the strange TTB drive line!

Turns out lockers, and 4Low was to much for it! Also turns out that a two wheel drive, pickup is almost impossible to drive in a Blizzard!

So now I am on the hunt for some new parts but not really sure were to start, can you folks point me in the direction of axel shaft and u-joints. Looking for something that can stand the 4.56 gears and lockers!

Thanks.

I don't have much problem driving in 2wd with 18" of snow on the ground but I have a good amount of weight in the bed.
(Gary can attest that my job boxes are loaded)

You are always going to have problems with a true locker if you have traction.
Any time you are turning, each front wheel is traveling a different arc, with much different distances.

This is why we have differentials to begin with!
https://youtu.be/yYAw79386WI

So, you found the weak link in your setup.
Probably a lot better than splitting your carrier.  

What part do you want to fail?
Because geometry and physics say you can't have both axles turning together.

Man, that is BROKEN!

So, what were you doing that caused it to break?  Or, did the u-joint fail due to lack of grease and take the yoke?

You just did the math in the other thread....

Now look at the tires and factor 4.56 gears into the torque multiplication and ask again how a universal snapped when driving a locker.

ArdWrknTrk wrote

I don't have much problem driving in 2wd with 18" of snow on the ground but I have a good amount of weight in the bed.
(Gary can attest that my job boxes are loaded)

You are always going to have problems with a true locker if you have traction.
Any time you are turning, each front wheel is traveling a different arc, with much different distances.

This is why we have differentials to begin with!
https://youtu.be/yYAw79386WI

So, you found the weak link in your setup.
Probably a lot better than splitting your carrier.  

What part do you want to fail?
Because geometry and physics say you can't have both axles turning together.

Yep, I have always wondered why they even offer lockers for 4wd applications.  I can see a posi but not a out right locker.  But the TTB unit I was looking at they dont offer a truetrack gear posi like I will be running in my 9", only a stock open type differential or a locker type.

There are always people who are into swamp buggies, pulling or some other edge case that could really make use of a spool or detroit.

If you don't have slip across the wheels something has to give the moment you turn.

Maybe the best thing would be to get crappy break-away locking hubs?
They are easier to change than an axle.

I have an electric locker in Big Blue.  That's because there may be a time I need to ensure that both front wheels will pull.  But that's not likely to happen around corners, which is where the problem arises.

Which is why I asked how this one broke.  Looked like he was in snow, so I wouldn't have thought that there could be enough torque to break a yoke.  Maybe he hit dry pavement?

Look closer at the tires...

If you've got snow that packs (like we did a couple of days ago) there is probably better traction than you'd have with those on dry pavement.

I guess I've never realized you could have that much traction on snow.  

When you have snow that packs and ices up under pressure it is amazing how much traction you have with a reasonably open tread pattern.

With 4.56 gears you are doing a fair bit of torque multiplication but it's not so easy to keep the tires broken loose.

I don't know. I wasn't driving.

It's a genuine Spicer U-joint.
I suppose you could get solid cross 'greased for life' universals, but I know nothing about stronger D44 LD axles for 150's.

If it was a 250 with leaves you could use D50 hubs and outers.

stevenscoffee wrote

....  So now I am on the hunt for some new parts but not really sure were to start, can you folks point me in the direction of axel shaft and u-joints. Looking for something that can stand the 4.56 gears and lockers!....

Most of what I'm familiar with comes from rock crawling, and people get rid of TTB pretty quick for that, so I don't know of anything specifically for a TTB.  But the desert race crowd loves the TTB axles, and I'm sure they break stuff too.  So I'm pretty sure something is out there.  (www.gofastbroncos.com is a forum I've heard of but never checked out, it might be helpful to you)

Moser, Yukon, and Strange are the names that come to mind first of companies that make chrome-moly axle shafts.

There are stronger U-joints (CTM I think?).  But I don't know if any are made for the center of a TTB.  Might be, I've just never looked and mostly see them for the steering knuckles.

You can check with some of the on-line parts suppliers too.  Four Wheel Parts Wholesalers is a good one.  And some of the more Ford-specific ones like Wild Horses or Tom's Bronco Graveyard might be more likely to have Dana 44 TTB parts.

ArdWrknTrk wrote

....  Maybe the best thing would be to get crappy break-away locking hubs?
They are easier to change than an axle.

Warn actually made a "hub fuse" for a while.  It was a locking hub with an intentionally weaker part that would break to protect the harder to change axles and U-joits.  The broken hub part could generally be changed in just a few minutes.

Rusty_S85 wrote

Yep, I have always wondered why they even offer lockers for 4wd applications.  I can see a posi but not a out right locker.  But the TTB unit I was looking at they dont offer a truetrack gear posi like I will be running in my 9", only a stock open type differential or a locker type.

Because that's where the biggest market is?  The vast majority of people who would buy a locker already bought a 4WD.  And while the front axle is usually considerably weaker than the rear, most people seem to agree that a locker in the front is more helpful than a locker in the rear in most situations.

And the Eaton TrueTrac is made for the Dana 44 TTB.  I would assume the Eaton posi is as well, but the posi is a clutch-type limited slip, not the gear type like the TrueTrac.

And having had lockers in three different rear axles and two fronts and a TrueTrac in one rear axle, I'll say that a TrueTrac doesn't come CLOSE to the performance of a locker.  Sometimes that's good because it doesn't have the bad manners of a locker.  But if you have one tire getting no traction (common in rock crawling or when ice is a factor) a TrueTrac does very little.  The TrueTrac works best when both tires get at least semi-decent traction.

I think Bob hit on the main point of lockers: extreme circumstances where one or more wheel has 0 traction and anything short of a fully locked system will only spin the wheels you dont want spinning.

E-lockers seem to be the way to go if you can afford it.

Seems like you were having fun when the damage occurred! I love driving in the snow, its the next best thing to mud.

Nothing Special wrote

Warn actually made a "hub fuse" for a while.  It was a locking hub with an intentionally weaker part that would break to protect the harder to change axles and U-joits.  The broken hub part could generally be changed in just a few minutes.

This is what I recall.
If you know you're going to break something, make it cheap and easily accessible.

Good info on possible beefier parts, Bob.
Like I said, I don't know much about the little D44 IFS

Nothing Special wrote

But if you have one tire getting no traction (common in rock crawling or when ice is a factor) a TrueTrac does very little.  The TrueTrac works best when both tires get at least semi-decent traction.

I have considered a posi or Truetrac several times. I’ve read that when in those situations with a Truetrac a little brake will help get more traction to the best side. Do you agree? And I’m not talking rock climbing, but snow, ice, sand, etc.

I think perhaps I’m better off with an open diff on my long wheelbase truck. Then I drive my 92 Bronco with the posi and I like it in the snow and ice. I lean towards the Truetrac because of no clutches to replace and they are tough.

Dane - I've read the same thing about bringing the brakes on slightly to get the Truetrac to come in.  I've not yet had a need to try that, but it is in my bag of tricks.

Bob - Does that work?

Gary Lewis wrote

Dane - I've read the same thing about bringing the brakes on slightly to get the Truetrac to come in.  I've not yet had a need to try that, but it is in my bag of tricks.

Bob - Does that work?

It definitely works with a TrueTrac.  Gear-type limited slips essentially have a multiplier.  As I understand it, a TrueTrac for a rear axle application will send 3.5 times as much torque to the tire with traction as the tire without traction will support (2.5x for a TrueTrac intended for a front axle application).  When one tire is in the air, or on polished ice, it takes 0 torque to spin it, so the TrueTrac send 3.5 x 0 = 0 torque to the other side.

Apply the brakes slightly (parking brake ideally) and now it takes say 50 lb-ft of torque to slip the brake and 0 to spin the tire.  But that's still 50 lb-ft.  Multiply that by 3.5 and it's sending 175 lb-ft to the tire with traction.  Of course it takes about 50 lb-ft to slip that brake too, but you still have 125 lb-ft available to drive that tire forward.  (If you're applying the service brakes you also need to overcome the front brakes, and that might take more than you gained, which is why using the parking brake is ideal).

When I first got the TrueTrac in my pickup I tried that.  I jacked up one back tire and put it in gear (in 2WD).  That tire spun freely and the truck just sat there.  Then I applied the parking brake.  The spinning tire stopped and the truck still just sat there, but the engine rpm had dropped a bit (auto trans).  I gave it some gas and the truck drove off the jack.  So yes, it definitely works.


By the way, this also works to some extent with at least some clutch-type limited slips.  The clutch packs are typically between the side gear and the carrier.  As you apply more torque to the diff the spider gears will apply more force outward on the side gears.  I don't know about the Eaton posi, or any other clutch-type limited slips, but in at least the Powr-Lok differential this force results in more normal force in the clutch packs so they tighten up.  I don't know if it's as dramatic as in a TrueTrac, but at least in the Powr-Lok it can be very significant.


Incidentally, other than using friction clutches which wear rather than gears which don't wear (much), clutch-type limited slips work completely differently than gear-types.  Rather than being a multiplier a clutch-type limited slip is an adder.  If it takes 100 ft-lbs (number pulled completely from the air) to slip the clutch packs it will send 100 ft-lbs more torque to the tire with more traction than it will to the tire with less traction, regardless of how much less it has*.  So if you have a tire in the air or on ice, a clutch-type limited slip will drive you forward better than a gear-type (if you don't use the parking brake trick).  That's a plus for clutch-type limited slips there.  But it's a minus in other situations, like when you are turning with both back tires on ice.  You need to slip the limited slip clutches or else the tires will be "locked" together, so it's easy to spin out when going around a corner on ice with a clutch-type limited slip, even if you are just coasting.  So for me clutch-type limited slips are the worst of both worlds, the traction of an open diff when you need a locker and worse road manners than a locker when you are cornering on ice.


* OK, as I said above, at least the Powr-Lok will send more than my arbitrary 100 lb-ft to the tire with more traction if the tire with less traction gets enough to load up the spider/side gear mate.  But it still adds the torque required to slip the clutch packs, it's just that the torque is now higher.

Bob - Thanks for the detailed explanation.