Locking rear axle

Bill D · Mar 8, 2016

First, I'm pretty much a "newby" when it comes to Jeep mods. In the past it was always "buy it and drive it" but my last aquisition came with a couple of items that just may not be optimum for the type of off-roading that I want to do. The Jeep in question is a 1980 CJ5 Renagade with a 4.2 six, 176 transmission, 300 transfer, and an AMC20 rear axle with factory installed trac-lock. The tag on the differential cover says that my axle ratio is 3.07:1. I'm also running BFG All Terrain 32" tires. I know that the 3.07 isn't the best ratio for anything even remotely associated with rock crawling. I think I probably know the answer to this problem (changing out both front and rear ring gears and pinions to something closer to 4.11:1) or having lower gears (Tera-Flex) installed in the transfer case. The former probably has advantages over the latter so I'll probably go that route at some point in time. The problem that I would very much appreciate help with is the "trac-lok in the rear. Right now, in low range four wheel drive, the trac-lok seems to bind and build up pressure until it lets loose with a bang. I've been told that the cure for this condition is probably an overhaul of the differential but I would rather go to a locker. Problem is, this whole thing is running into serious cash in a hurry. ARB makes nice lockers but they go for about $1,150 plus install and an additional $275 for an air compressor. OX makes a locker for about $850 plus install but again a shifting method puts another $150 + on the bill. Also, I can't seem to find an OX that works with the 3.07 gears. Detroit Lockers were suggested but my conversations with folks that have used them suggest that they have some characteristics that I probably don't want to deal with.

I know this is getting wordy but I want to describe my conditions accurately. Anybody got any good advice for me?

mriplaybass · Mar 8, 2016

I guess it depends on what you are looking to do. You are right, 3.07 gears are not exactly crawler gears, especially with 32" tires. Your thoughts on 4.11s is a good all around gear for on/off road. Are you getting the "bang" in low range on loose ground? or does this occur only when you are on hard ground or pavement? I had a J10 that did this only when I had too much traction to be using four wheel drive. It almost felt like a giant spring was being wound up, then releasing.
Variety of lockers are many. You can go with something like a Spartan which is a simple matter of replacing the spider gears in your stock carrier with the locker, and is fairly inexpensive I believe this is referred to as a "lunch box" locker. If you want something with an on demand feature, then lockers like OX, Eaton Elocker, and such are the way to go. The OX requires extras like an air compressor or other compressed air source like a CO2 tank. The Eaton just requires a connection to the battery. I have only used the Eaton's, and am very happy with them, but others swear by the other lockers. Either way, you are going to have to do some major work on your differentials to get them set up right. Also, if you decide to stay with the AMC20, you may want to consider welding the tubes to the differential case, and trussing the axle to strengthen it. I just decided to switch to a Dana 44. Less work than modifying the 20.

mriplaybass · Mar 8, 2016

Just saw Posi's post about the lunch box locker in a Trac-lock 20. So this pretty much limits you to the more expensive lockers, or doing a Dana 44 switch where you could use a lunch box.

HackFabrication · Mar 8, 2016

As was posted, you would be better off with the 4.10 gears for overall performance. Putting lower gears in the transfer case isn't going to help on the highway. But certainly will help on the trail. LoMax makes one heck of a set for the Dana 300.

Lockers. AMC20. Lots of info on upgrading the 20. At a minimum, I'd go with Moser 1 piece axles and weld the tubes. Your going to have to swap the diff carrier out to go to 4.10 gearing, so MAW get as much locker as you can afford. A full Detroit, is pretty much bulletproof. But it does have it's 'quirks'. There are a fist full of 'soft' lockers out there. Others, hopefully, will chime in with their recommends and experiences.

My CJ5 has ARB's:

I wanted open diffs for the pavement/street. When they are activated, they turn the diffs into basically spools. You get true 4 wheel drive with no differential action. And yeah, they were expensive. But there doesn't seem to be many inexpensive parts anyway....

BusaDave9 · Mar 8, 2016

Are you sure you have a Trac Lok and 3.07 gears?
If someone put in a locking differential it will bang as it unlocks.

Torxhead · Mar 8, 2016

BusaDave9 said:
Are you sure you have a Trac Lok and 3.07 gears?
If someone put in a locking differential it will bang as it unlocks.

Yeah, like my old style Detroit locker has a "Bang" to it. When I got my rig it had the oem trac loc and it was quiet and useless. 4.10 gears is a bit low for freeway use for me also. So maybe more research is needed.

Posi · Mar 8, 2016

Bill, you have a good setup with the T-176 and 300, IMO your good there for what you want to do.
The first thing I would do is pull the cover and see what you have then take it from there.
The 1980 was offered with 3.07 with optional 3.54.
Typically the trac-loc doesn't make any noise they just don't work, unless they are rebuilt which is an option, and adding a locker in the front.
If you do have 3.07 with trac-loc the "least expensive" way to go is to rebuild the trac-loc and move up to 3.54. This way there is no carrier change and used 3.54 are close to free, likewise with the open carrier.
I bet there is a few members here with 3.54 and a open case sitting on the shelf from a gear change.
If the trac loc is to be rebuilt you can then add a front aussie or spartan to the front.
Or get a set of low priced used 3.54s, open carrier, and add a aussie or spartan to the rear.
IIRC you have one piece rear shafts?

Lumpy Grits · Mar 8, 2016

The 3:07 is an odd one

IMHO-The trac-loc is a joke.
I run a DL front and rear in mine, and as long as I keep the rear tire psi the same. The 'banging' is minimum on the street, and nonexistent off-road at either street tire psi or aired down to 'play'.
IF-you do go to a real lock'n diff. Upgrade to Moser 1 piece axles. W/32" tire and your 4 speed. I would look at either 3:73 or maybe 4:10 if you think you'll go to 33's.
OP-A DL in the snow and ice is not the best. Look at a good LSD(Limited slip)for your needs.
LG

Hedgehog · Mar 8, 2016

I have to add one/a couple things. The OX locker is a selectable locker with either a manual engagement, like a little shifter or an electric version. No air is required. ARB lockers use air as an E-locker uses electricity. This is an expensive option, but If I had endless monies there would be an OX locker in my CJ. As it is now I have an E-locker in the rear and a tru-track in the front.

Bill D · Mar 8, 2016

OK!
Well, where to start? Lunch boxes were what I carried to school in the 2nd grade with my PBJ and apple inside. A locker is what I put my lunch box into along with my coat. Apples are different now than they used to be. I'm using an IMac to type this.
What I know for certain is this: My rear diff has a round cover that my reference photo says is an AMC20. My '80 Jeep Technical Service Manual tells me to look on the housing boss for a stamped code letter. Mine is stamped with a "Y" which the Letter Code Chart - AMC/Jeep axle says is a Trac-Lok with a 3.07 Ratio (14/43 Pinion/Drive Gear teeth). I am at least the second owner of this beast and who knows what someone further up the food chain might have done to it. The front axle appears from my reference photos to be a Dana 30 and it has a tag under one of the cover bolts that is stamped "5359600 with 3 07 43-14 in two lines.

When I put the transfer into 4Low and drive it, in between places where I really need the compression braking, it seems that something "back there" loads up and then periodically (every 50-75 yards or so) releases with a real BANG! If the Jeep Trac-Lok is as worthless as most of you seem to think it is, I probably should not be hearing this commotion "back there".

As to whether this Jeep has one or two-piece axles, I haven't a clue. My TSM says it went off the factory floor with two piece axles but I wouldn't know how to tell. Posi was around the Jeep this past summer but was having so much fun with his "Barbie Jeep" that I'm not sure he had time to examine mine. Is there a way I might be able to tell without removing parts? I do like Posi's suggestion of moving up to 3.54 gears. I like the 3.07 on the freeway - it's just the compression braking aspect of using 3.07 off road that I would really like to change. If I went to 3.54's could I go with one or two e-lockers?

Please, enlighten me - why do I need to weld the axle tubes? I can kinda understand trusses but welding tubes doesn't compute.

Lumpy Grits · Mar 8, 2016

IF your in 4-lo on hard ground. Your torque binding the driveline.
The 'bang'--When was the last time you lubed the u-joints and slip splines on both driveshafts?

The weld'n is done to keep the center section from turn'n on the tubes. The 20 rear was a VERY weak axle.
My bet-You still have the 2 piece axles and they are a big problem area.
I would make sure those rear axle nuts are TIGHT, 250+ ft/lbs of torque.
LG

Hedgehog · Mar 8, 2016

If it were me ... remember I put in a set of 3.31 gears on purpose .... I'd pull the transfer case and install a set of terralow or lowmax gears. Lowmax has the best low gears at 4:1's. Tat would be your cheapest and fastest route to an off road CJ. I have a T-20 and Terra lows are all I can get for mine. These transfer case gears are becoming expensive, but well worth the price.

So, you'd have 3.07 gears for eating up the road miles and low/low range good for most all off road work with the exception of the most serious rock crawling.

There are tests for a locker in the rear. Lift the rear, turn one wheel, if both turn in the same direction you have some sort of traction device. Then lift one side, if you absolutely can't turn the lifted wheel without turning the wheel on the ground you have a locker.

Your description of the banging sounds like you've got axle slipping problems.

Posi · Mar 8, 2016

Bill - I had a great time, but I did have time to check out your CJ and from what I recall it had the one piece shafts.

Look at the center of your rear wheel
It will have either a flange or a nut (if it has a dust cover it has a nut).
The flange is the one piece shaft

As you can see, one piece shaft on your left, two piece shafts on your right.

Lumpy Grits · Mar 8, 2016

I run a DL's and can un-lock'em and spin just one wheel. You do hear the ratcheting of the drive cogs.
The 2 spin'n in the same direction is a great way to ck for LSD.
Very good point about 4:1 t'case gears. Love mine.
LG

007 · Mar 8, 2016

I'm starting to think the TC gearing is best bet...IF gearing is needed and IF you're staying with 32's.

IF you need a locker - put a TT in the rear (which replaces your carrier, keep your 3.07's and leave the front alone.

IF you do not need a locker - just swap carrier's and keep your 3.07's and again leave the front alone.

Like in the other thread - it's all about what kind of wheeling you're going to do really. If you are going to do Colorado mountain trails like what we did last summer, I can't imagine spending money on a front locker. Smarter people than me could persuade me, but smarter people than me it's silly unless your are rock climbing. You want to spend a week a Moab, then perhaps it's a better idea.

I have 2.72's and tractor around all day (or in until I vapor-lock

). Posi rode with me and a friend of mine in 2014 and I was never needing more power or more gear with three of us in there. I presently have two-piece axles torqued down tight, and I've welded my tubes but have no trusses.

If you stay with 32's I'd keep the 3.07's because unless you go to 4.10's it's a marginal difference. See the link below...

Gear Ratio Calculator

Bill D · Mar 9, 2016

Hedgehog said:
If it were me ... remember I put in a set of 3.31 gears on purpose .... I'd pull the transfer case and install a set of terralow or lowmax gears. Lowmax has the best low gears at 4:1's. Tat would be your cheapest and fastest route to an off road CJ. I have a T-20 and Terra lows are all I can get for mine. These transfer case gears are becoming expensive, but well worth the price.

So, you'd have 3.07 gears for eating up the road miles and low/low range good for most all off road work with the exception of the most serious rock crawling.

There are tests for a locker in the rear. Lift the rear, turn one wheel, if both turn in the same direction you have some sort of traction device. Then lift one side, if you absolutely can't turn the lifted wheel without turning the wheel on the ground you have a locker.

Your description of the banging sounds like you've got axle slipping problems.

OK, today I break out the jacks and try this. Do I leave the emergency brake off and where should the gearshift/transfer be?

I'm beginning to think that either I have the only Trak-Loc in the world that actually works OR someone further forward than me has installed something in the diff that IS working.

Lumpy Grits · Mar 9, 2016

Tranny in "N" and t'case in 2HI.
You could remove the diff cover and take a few pictures for us.
LG

Hedgehog · Mar 9, 2016

Being a "moron"

my ideas might be suspect. But, removing the diff cover would be the ultimate answer to your question. A CJ trak-loc should be silent in operation. If you don't have a locker the banging you describe is a more serious situation. Besides removing the cover will give you a chance to fully evaluate the condition of your differential. Also, filling with new oil/grease could do it a lot of good, maybe even fix your problem.

Lumpy Grits · Mar 9, 2016

Bill D-Will you PLEASE answer my question about the last time the u-joints and slip-splines on the drive shafts were lubed. :bang:

Have you ck'd the u-joints for play/slop?
LG

Bill D · Mar 9, 2016

Posi said:
Bill - I had a great time, but I did have time to check out your CJ and from what I recall it had the one piece shafts.

Sorry, Posi - it has the two piece axles.

Now, I wonder what to do. Maybe go down to FN Jeep Parts and see if they have a Dana 44 rear end for cheap (Don't laugh - it could happen. : :dbanana:

OR spend $350 + for one piece axles, have the tubes welded, and look for some kind of LS or locker to put in it.

Guess I could leave it like it is and use that 8,500 lb. Warn thingamabob taking up room on my front bumper.

Locking rear axle

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