[CJunk]

I posted a few weeks back about a grinding noise coming from the rear end. I changed out the fluid and the noise mostly went away.
Now what is happening is a couple of things.
Once in while, when I gas it after a turn it will feel like the clutch is slipping. Engine revs up, and its slow going. When this happens I let off the gas, and things seem to be normal again.
Also, only once this happened- I made a turn, and it felt almost like a posi rear end, and kind of shot me forward.
So, the question is, how do I check to see if it is the trac-loc failing. I figure it also could be the rear two piece axle failing.
How can I check out this stuff without taking too much apart? Or, should I plan on getting messy.

 

[gosupes]

I would plan on getting messy. The Belleville spring inside the Trac-Lock has been known to crack and clutches wear, but it sounds to me like you might have spun one of your axle hubs. A bad Trac-Lock will just act like an open differential (which is not much difference than a good Trac-Lock), but it will not free wheel thru a corner like you are describing. Rent a hub puller from the auto parts store and pull the hubs off both sides. If the keyway is missing or sheared and the splines are flat, get some good one piece axles. It's a weak link anyway, time to upgrade.

 

[only in a jeep cj]

Yes, I have heard/felt what you described and it was a spun hub that was spinning and binding. To check it, lift the rear and remove the wheels so you can remove the center caps (if stock). Re install the wheels and now the axle ends are exposed. Use a black sharpie marker to draw a straight line on the axle shaft end and hub . Drive it around till the symptoms happen again. Check the lines and if theyre not lined up, that is the trouble axle end.

 

[80cj]

So, the question is, how do I check to see if it is the trac-loc failing. I figure it also could be the rear two piece axle failing.
How can I check out this stuff without taking too much apart? Or, should I plan on getting messy.

If the Trac Lok has high mileage on it (say over 50K) It's probably not working enough to make a difference and is pretty much an open diff). Even new ones are relatively ineffective.

 

[CJunk]

I have a feeling it may be the two piece axle. Thanks for the tips, and I'll repoet back with what I find.

 

[80cj]

I have a feeling it may be the two piece axle. Thanks for the tips, and I'll repoet back with what I find.

That's my guess also.:thumbsup:

 

[JeepHammer]

OK, lets start with the obvious...

When was the last time you took the back cover off the diff and cleaned it out?

Did you use posi additive (Friction Modifier) when you changed gear lube?

Friction Modifier wears out, and it needs to be replaced occasionally.

Did you do the backwards circles after changing lube or adding friction modifier?
It takes about 5 backwards circles in each direction to work the friction modifier into the clutch plates when you change gear lube or add new modifier.

--------------------------------------

Do you have stock 2 piece rear axles?

If the engine revs up and the speed doesn't increase, then you have drive line slippage somewhere.
There is NOTHING in the rear differential that will allow the RPM to increase without turning the tires...
If the 'Posi' clutches fail, you simply get power to ONE wheel instead of both,
And if the clutches lock up, you get power to BOTH wheels instead of just one.
There is NOTHING that will allow the engine to rev without increasing the speed of the vehicle in the differential.

If you have 'Slippage', it's probably an axle flange slipping on the axle shaft and you just spun it hard enough to gall the metal onto the flange and get some traction.

----------------------------------

Without the 'Friction Modifier' in the rear gear lube, you will get the clutch plates galling to each other and you will occasionally pull BOTH rear wheels when you shouldn't.

You will also notice a 'Yanking' or 'Popping' as the clutches stick, then break loose, then stick again.
All signs you need new lube and friction modifier, and some laps in a backwards circle to work it into the clutches.

-----------------------------------------

If the Trac Lok has high mileage on it (say over 50K) It's probably not working enough to make a difference and is pretty much an open diff). Even new ones are relatively ineffective.

Actually, The 'Track Lock' type clutches last a LONG TIME if they are PROPERLY MAINTAINED!

My rear TracLoc works almost as well as a locker without the issues of a posi... and it has quite a few miles on it.

Stacking in an extra plate or steel, making the clutch pack 'Tight' will get you pulling on both tires MUCH faster, while leaving them loose in the housing will delay the locking...

What wears out the plates are people NOT putting in the friction modifier ('Posi-Lube') and the clutches welding themselves and galling each other until there is no friction surface left and they have clearance themselves to the point of uselessness.

There is also the '$1.98 Locker' modification,
Which is an extra shim in the clutch pack locking things up MUCH more solid and much faster,
With the extra shim in place, both rear wheels pull MUCH harder before one unlocks.

Now, remember, BACKWARDS Circles turn the tires at the highest differential speeds, so it works the lube/friction modifier into the clutches faster,
And REMEMBER! Not all gear lubes work well with 'TracLock'...

The biggest issue I have with Track Lock in Jeeps is the AMC 20 axles.
When the friction modifier wears out/evaporates, the track lock can lock hard enough to break the drive flange loose from the axle!
So if you intend to keep your two piece axles with a 'Posi', you NEED to keep up on that posi maintinance or you will be changing a LOT of axles/flanges!

 

[80cj]

Actually, The 'Track Lock' type clutches last a LONG TIME if they are PROPERLY MAINTAINED!

My rear TracLoc works almost as well as a locker without the issues of a posi... and it has quite a few miles on it.

I had an 76 CJ-5 that I purchased at around 35K miles and the Trac Lok didn't even work even while applying the parking brake at times. I had the unit rebuilt and there was practically no difference. Fast forward to 1989. I purchased a supposedly rebuilt rare AMC Power Lok unit for my 80 CJ-5. Turns out the rebuild was defective so I sent it back to the dealer I bought it from. Not wanting to stick the stock open diff back in and not wanting to go to a Detroit locker, I opted for a brand new Trac Lok. It sorta worked for a while and the more mileage I put on it, the less it worked. After about 30K miles on the unit, I pulled it out and replaced it with an Auburn. A big improvement. If yours works almost as well as a locker, it's a very rare Trac Lok unit. I seem to remember that you purchased a Trutrac. Does it perform any better than your Trac Lok?

 

[only in a jeep cj]

Ill second JH to the point that when mine started making noises, I took it to an off road shop. (Many years ago before I knew how to do all this stuff). One new disc kit later and it was chirping tires in sharp turns as I left the shop. Off road was a HUGE difference. Climbs I wasn't making the weekend before, I found myself walking right up. Yes, with mileage they do wear out. The most common failure I see when servicing them is spun carrier plates where the tabs dig into and around the carrier.

 

[Renegade82]

When the friction modifier wears out/evaporates, the track lock can lock hard enough to break the drive flange loose from the axle!

What length of time do you think it takes to "evaporate"? I know mine hasn't "worn out" since last change, due to lack of use (maybe 300 miles per year), but I never realized it evaporates as well.

 

[twoscooterz]

The most common failure I see when servicing them is spun carrier plates where the tabs dig into and around the carrier.

To eliminate my welded gears & 3.54 gearing, I just bought a '70 Scout Dana 44 w/ 4.27's & Trac-Loc. Without complete dis-assembly, Is there some way to check the condition of the Trac-Loc before putting it under my CJ?

The seller said it was posi-traction - which is what I wanted. After opening it, turns out to be different - it will still chirp in corners?

 

[Gregg79CJ7304]

If the Trac Lok has high mileage on it (say over 50K) It's probably not working enough to make a difference and is pretty much an open diff). Even new ones are relatively ineffective.

I have 115,000 mile on my CJ7 with a 304, and my factory trac lok works perfect. No noise and works almost like a posi off road.

 

[Cutlass327]

To eliminate my welded gears & 3.54 gearing, I just bought a '70 Scout Dana 44 w/ 4.27's & Trac-Loc. Without complete dis-assembly, Is there some way to check the condition of the Trac-Loc before putting it under my CJ?

The seller said it was posi-traction - which is what I wanted. After opening it, turns out to be different - it will still chirp in corners?

....and my factory trac lok works perfect. No noise and works almost like a posi off road.

Ok, I think there is a little confusion on the whole terminology here...

Tru-Trac, Trac-Loc, Posi-trac... They are Crysler/AMC, Ford, and GM's name for the same thing - a limited slip differential. These either have springs and clutch packs or cones that wedge in the side of the carrier, depending on the design.

A spool, welded spiders, etc are all the ways to have a "live axle" - where both sides are locked solidly together, no differentiation between the wheels on turns or whatever - can and will break axles if used wrong.

Lockers - Detroit, "Lunchbox", OX, etc. all have a ratcheting system that lock the 2 axles together under power, but allow differentiation on turns. Can be selectable like the ARB using air, electrical like the ECTED, or even mechanical (OX?) with a cable.

Then you got the open differential - "the one-wheel peal" design... only power to one side in loose terrain, but the best and safest for ice/snow driving.

 

[JeepHammer]

I have 115,000 mile on my CJ7 with a 304, and my factory trac lok works perfect. No noise and works almost like a posi off road.

Ill second JH to the point that when mine started making noises, I took it to an off road shop. (Many years ago before I knew how to do all this stuff). One new disc kit later and it was chirping tires in sharp turns as I left the shop. Off road was a HUGE difference. Climbs I wasn't making the weekend before, I found myself walking right up. Yes, with mileage they do wear out. The most common failure I see when servicing them is spun carrier plates where the tabs dig into and around the carrier.

I have ZERO complaints with a 'Trac Lock' diff.
They are CHEAP, easy to rebuild, easily modifiable to pull a LOT harder than the factory intended, and they aren't 'RARE', there are a BUNCH of them out there.

Dana did a good job in both design and execution,
The only hole in the plan was the end user, which WILL NOT service the units!

When the 'Popping' and 'Jerking' starts, They WILL NOT add the friction modifier and do the reverse circles!
You can't beat them into it under threat of death!

When the clutches wear (and ALL clutches wear over time/use) you can not make the end users service them!

Nearly every time we go on a Jeep outing there is someone complaining about the "Junk #&@*ing Factory Posi"....

So, just for fun, I dump in a 4 ounce bottle of friction modifier and drive the backwards circles, and PRESTO! About 75% of them start working again!
(I figure the other 25% are just hammered to death or the idiot used synthetic lube that wasn't rated for the clutches...)

A 'Posi' of any kind will break loose at some point, they ARE NOT lockers...

With an extra shim or friction plate you CAN increase that 'Break Loose' point quite a bit... ($1.98 'Locker')
*IF* you do that, expect some 'Chirps' and some 'Plow Steering' out of it since both axles are locked together quite a bit longer until you overcome the friction surfaces!

Many a vehicle has laid down the prettiest set of DUAL black marks on pavement with the '$1.98 Locker' conversion! Don't kid yourselves, we did it all the time when we were young and couldn't afford lockers or proper 'Limited Slip' differentials!
It's hard on the axles and friction plates, but it WORKS!
(REALLY Hard on those drive flanges of the two piece axles! Ask me how I know that! )

-----------------------------------------

Cutlass, YOU missed the terminology.

True Trac and Track Lock are NOT the same thing...
Not even close.

True Trac is a Gear driven "Limited Slip Differential", even though it's not a 'Slip' of any kind...
They call it a 'Limited Slip' simply because there isn't a real category for what it actually is and what it actually does...

The 'POSI' type carriers all rely on FRICTION, and the ability to break that friction and 'Slip',
Either forcing cones screwing themselves into tapered bores,
Or friction from plate and friction discs.

And there are several 'Manufacturer Brand Names' for each company that sold the vehicle, even if the axles were all made by the same manufacturer and had exactly the same 'Limited Slip Differential' installed.

GM, Ford, AMC, Chrysler all used Dana axles with exactly the same type of Limited Slip Differential carrier (friction plate type) and called them by 4 different names.

---------------------

The 'True Trac' is Detroit's version of a Thorsen-Gleason type differential.
It's not a 'Limited Slip' at all, so it's mis-categorized badly, but there simply isn't a 'Laymans' category for it.

The Thorsen-Gleason type differential uses a series of gears, SOLID LINKAGES, No friction plates, to split the power between wheels.

The MINIMUM the 'Traction' wheel will get is usually 30-35% of input.
Where every 'Friction Type Limited Slip' will allow ALL the power to go out to a spinning wheel at some point.

Since Formula 1 cars, Indy cars, ect use them, there is a TON of data on them.
They transfer power to the wheel WITH traction seamlessly, smoothly, and without any hint of jerking, popping, or the other power transfer you get with 'Lockers' and LSD type differentials.

It's all gear drive, so there is no 'Slippage' like 'Limited Slip' differentials do,
There is no 'Locking' & 'Unlocking' like lockers do,
It's 100% power distribution, and it works in BOTH directions, where some lockers and some LSD diffs REFUSE to work without tons of complaints & problems.

I have a True-Trac in the front of one Jeep, I have a True Trac in the back of another Jeep, and I can tell you from first hand experience,
They are FLAWLESS FUNCTION in every response!

I've even hung my front tire under an overhang,
Which as anyone that has done it know it's CERTAIN DEATH to the axle or U joint,
And the True Trac balanced the power and I did NOT break the axle or U joint before I noticed the tire was trapped...

The differential sensed the tire stoppage, and transfered the power to the other wheel which spun harmlessly...

My 30% power to the trapped wheel wasn't enough to break the axle or u joint, so I was saved from my own stupidity...

If I'd had a bigger engine, more gear reduction at the transfer case, ect.... Things might have turned out differently, but I couldn't break a D-44 axle/U joint by pounding on it with a 360 engine...

Dana 30 up front, it would have probably borken the axle at the joint...
Putting a True Track (or even a full on locker) into a Dana 30 is a waste of time and money...
A 'Lunch Box' locker up front in a D-30 is marginal since there are so many other weak points in a D-30, but 'Lunch Box' lockers are so cheap and they work quite well if you don't have a full time transfer case and can unlock the hubs...

But a True Track in a D-44/D-60 is a beautiful thing and a joy forever!

They also work great with full time transfer cases where you CAN'T run a full on locker since you can't unlock the front with full time transfer cases...

True Trac presents with NO steering problems,
They present with NO problems when run in the rear either.
All around the PERFECT 'Limited Slip' differential, but VERY pricey...

When you compare them to a 'Selectable' locker, they are about the same price,
More expensive than a well built full time/full size locker,

When you compare them to a 'Lunch Box' locker, there is no contest in price, the 'Lunch box' wins every time, but you can't run a 'Lunch Box' with a full time transfer case...

My FSJ has a True Track in the rear, and open front.
It does NOT PLOW STEER like my rear locker vehicle does, even on ice and snow!
You can turn the vehicle, even on the power, around turns with no issues what so ever...

The True Trac in my CJ-7 does not present ANY steering problems (full time transfer case) unless it's just totally iced over and slick as a gut, then it wants to plow steer a little...

You can run SNOW/OFF ROAD chains with a True Trac.

DO NOT try that with a locker or you WILL wind up in someones living room!
Tire chains and rear lockers are a recipe for NOT steering when it's slick...

 

[80cj]

Amazing. I must have gotten a couple of defective Trac Lok units. As I mentioned earlier, I had a rebuild done on the one in the 76 CJ-5 and it was a waste of time and money. Even going to the Jeep gear oil (dark stinking stuff in quart cans) made no difference

I know about the effectiveness of the Trutrac. I installed a couple in my friend's YJ and I have never seen him spin out a tire in conditions when both tires had decent traction. We encounter a lot of slippery clay mud. I was just wondering how it compared to a Trac Lok in your experience. I realize that Trac Lok units are not rare but one like yours that acts like a locker certainly is.


As you say, GM, Ford, Chrysler and Jeep have all used clutch type limited slip units at one time or another and their effectiveness differs mostly because of the number of clutch plates used and the amount of static preload on the plates. The best of the clutch LS units both in effectiveness and strength is the Dana-Spicer Power Lok.

As far as the use of friction modifier goes, I was told by a very knowledgeble mechanic at one of the local auto dealerships that if your LS unit is not chattering, there is no need to add friction modifier as all friction modifier does is make the oil more slippery thus changing the friction coefficient which can lessen the effectiveness of a LS unit. Seems to make sense to me.

 

[CJunk]

Hey this is my thread- no fighting
It turns out, so far anyway, that my two piece axle has failed. I thought it might be the trac-loc (trac- lock?)because, whenever I've had a failure involving something with splines- it's pop and done.
Now I'm off to order up some top of the line Chinease products.


Just kidding, Moser one piece axles seem to be my choice.

 

[mcmud]

I find the Trac-Lok very capable on the road as well as trail driving. Aside from but including good maintenance, in order for it to be most satisfying try not to exceed the breakaway torque, if you do, give it a another try with a bit less pedal.

Having a '82 CJ8 with 160K showing it has never failed me, another, a '81 CJ8 with near 90K can be added to the list.

The one with the higher miles has grated (chatter) while pulling a full sized Ford P/U (bald tires) up a steep road grade.

Depending on which year of production FSM you are relying on to which lubrication to use. For example the '81 manual recommends you use SAE 85W-90 GL-5 where the '84-'86 lists 75W90, grade API grade GL-5. No mentions of adding a friction modifier exist in either manual.

Cleaning procedure is... in short:
The only acceptable way to clean it is disassembling the unit and wiping it clean with shop towels.

If you feel/hear the grating (chatter) as it slips it is indicating that at the very least, the lube is contaminated with particles of the friction plates, a lube change is necessary, as a matter of fact, twice.

First one in an attempt to flush the plates clean of those particles and the other to drive on.

It is mentioned, and I regard this to mean that in order to have any long term effect of having changed the lube, that you first completely warm the lubricant. Drain it, refill it, drive it for at least 10 miles, making at least ten figure eight turns.

While still warm drain that and refill it again. If a slight chatter still exist drive it for ten to twenty more miles.

If the chatter persist after twenty miles of driving, an overhaul may be necessary.

 

[80cj]

Hey this is my thread- no fighting
It turns out, so far anyway, that my two piece axle has failed. I thought it might be the trac-loc (trac- lock?)because, whenever I've had a failure involving something with splines- it's pop and done.
Now I'm off to order up some top of the line Chinease products.

Just kidding, Moser one piece axles seem to be my choice.

Hey CJunk,
sorry for sending your thread off on a tangent. No, no fighting, just differences in experiences and resulting opinions.

Well, seems like most people who have posted here are happy with their Trac Lok units. Makes me wonder if they made a production change some where along the way. The ones I had were older units.

Back to the OP's original inquiry.

So CJunk how far have you gotten in your trouble shooting and what did you find?
Moser is a good choice and most of the people who have bought the Moser product seem to be happy with it.

 

[CJunk]

I took the plastic cover off the rear wheel hub, put the tire back on, and let her have it. I popped the clutch, and leaned out looking at the rear wheel. I got the hub to free spin with the tire remaining stopped. If that wasn't the problem it is now.

 

[mcmud]

You do have a way with the words.

Normally the hub will allow only one, possibly two warnings before it fails.

Nice work.