DIFF ID

RICKG · Post by **RICKG** » Thu Aug 01, 2013 9:32 am

What have I got here?? Powr-lock or?? It's sure not the stock rear diff.

Am starting to get an audible CLUNK when transitioning from forward to
reverse. U-joints are new. More investigation needed, will spend more time
this weekend. Rick

Post by **wesk** » Thu Aug 01, 2013 10:28 am

Looks like a Powr Loc. The later Trac Loc is much different looking.

Bretto · Post by **Bretto** » Thu Aug 01, 2013 10:32 am

Look like a Power Loc.

Look like you discovered a treasure.

Wes beat me.

Thunderbird712 · Post by **Thunderbird712** » Thu Aug 01, 2013 10:44 am

I was just thumbing through a copy of the TM 9-2320-208-20P Jan 1966 and it has a good illustration of it on page 73. Not sure if it is in any other documents but I believe you can get it here on the site.

RICKG · Post by **RICKG** » Thu Aug 01, 2013 11:26 am

Thx TJ, found and printed Powr-lock pg 73 fig 47 from the TM.
Characteristics I've noticed:
1. Wheels spin same direction when both off ground.
2. Can't spin lifted wheel when one is on the ground.

Can't say how this rear diff got into my M-38.
Pros/Cons for Powr-lock vs std diff??
Gotta find the source of the CLUNK..

Bretto · Post by **Bretto** » Thu Aug 01, 2013 11:40 am

I think you can imagine the pro's

Cons are it can put the full load onto one axle if you lift a tire.
A locker is essentiall a spool when it comes to snow pack and ice.
They can be interesting on short wheel based vehicles.

I dont think you will have any issue concerning breaking anything, these vehicle aren't heavy weights.

Post by **wesk** » Thu Aug 01, 2013 6:20 pm

The USMC contracts from 58 thru 64 came with Pwr Locs. Any of the older M38A1's that went through the depots at Albany & Barstow got them installed as well.

If you have been using regular Hypoid gear oil in the diff then the clunk is from the clutch plates.

The pwr loc is covered on page 223 & on on this page in my album for the SM-1002.
http://www.willysmjeeps.com/v2/modules. ... _album.php

BullRun · Post by **BullRun** » Thu Aug 01, 2013 11:20 pm

Looks like a Power Lok Check your front diff too. Sometimes they are installed on both axles on M38A1's. Pretty rare find.

Maybe your axles have been swapped at some point from an M38A1?

My 1962 USMC M38A1 has Power Lok's on both axles. The clunk is probably the Power Lok doing it's thing. When driving my M38A1 the front axle clicks when turning. I think odd noises from these is normal unless crazy loud.

When driving over a freshly graded gravel road once I could hear the Power Loks engaging and disengaging. You could feel it too as the jeep just plowed ahead. The grader driver was pretty impressed!

idiocrates · Post by **idiocrates** » Fri Aug 02, 2013 7:05 am

If you decide you want to get rid of those ugly lockers just let me know.....I can always use a new set of trot line weights........and yes, I know I'm a worry wart....but am I right in saying that you don't seem to have any locking plates under the bolts that hold the ring gear to the carrier? That would worry the bejeezers outta me wondering if that clunking was the locker plates or the ring gear coming loose.

RICKG · Post by **RICKG** » Fri Aug 02, 2013 8:12 am

Bull, curiosity got the best of me last nite so pulled the front diff cover
and sure enuf the front diff is powr-lock too.

Wes, I was using GL5 approved for limited slip diffs.
Thx for the link, I've printed it and will study it.

Jim, good eye.. no lock plates just hex bolts and lockwashers.
I wonder where a guy could get a set of lock plates..

The noise seems to be coming from the rear u-joint/yoke area.
I'll get under there this weekend and poke around some more..

Post by **wesk** » Fri Aug 02, 2013 8:59 am

The GL5 is approved for modern lockers. The fluid that belongs in those is still available under it's jeep part number from Chrysler dealers. Get the right stuff and preserve those rare diffs.

RICKG · Post by **RICKG** » Fri Aug 02, 2013 9:36 am

wesk wrote:The GL5 is approved for modern lockers. The fluid that belongs in those is still available under it's jeep part number from Chrysler dealers. Get the right stuff and preserve those rare diffs.

I called the Chrysler/jeep dealer. He says what they have is a 4oz
bottle of limited slip additive to add to the GL-5.
Part #04318060AB
LIMITED SLIP ADDITIVE
"Reduces wear, noise and chatter in limited slip (Sure-Grip, Trak-lok
Power-lok) differentials. Should be added whenever the gear oil is
changed or improper limited slip operation is detected".

Bretto · Post by **Bretto** » Fri Aug 02, 2013 12:38 pm

Thats a pretty neat discovery, 2 fold. Now you just need the metal ID tags to put on the diffs to identify they are installed. Otherwise they will never work.

Now don't go getting over confident and try climbing rock walls.

I bet those would fetch a pretty penny.

MODIFIED · Post by **MODIFIED** » Fri Aug 02, 2013 3:45 pm

Bretto wrote:Thats a pretty neat discovery, 2 fold. Now you just need the metal ID tags to put on the diffs to identify they are installed. Otherwise they will never work.
Now don't go getting over confident and try climbing rock walls.

I bet those would fetch a pretty penny.

Rick, they'll also work better if you re-paint w/ "Forest Green"- USMC

jimm · Post by **jimm** » Fri Aug 02, 2013 4:03 pm

[quote="RICKG"
Jim, good eye.. no lock plates just hex bolts and lockwashers.
I wonder where a guy could get a set of lock plates..[/quote]

I got mine for my front axle from Surplus City, but I remember a few other vendors carried them.
Fronts and rears are different:
Front WO-A-792 STRAP, locking, axle drive gear screw 4 req'd $1.95 ea.
Rear WO-802561 PLATE, lock, drive gear screw 4 req'd Price on Request, so may not be readily available. DeBellas has 'em listed as $3 ea NOS
You could always make them from sheet steel - that's something that Bretto would do!

IIRC, the spacing between screws is closer on the front than the rear.