Question Regarding Cj2a's Differentials

Now that I have true 4WD in my intermediate, I was wondering what were the OEM differentials & axles in the Willys CJ2a's ?

 

I think the front was a Dana 25 and the rear was a Dana 41. These are not much different from the later Dana 27 and Dana 44 that was used until ca 1970 for the CJs and Jeepster.

 

Thanks Tim,
Do you know if they had open differentials or was there some sort of OEM production type lockers used ?

 

AFAIK an LSD was available, the Dana PowerLock.

 

The early 2A's used D25/D23 (full float) front/rear axles. The D41 replaced the D23 at sn 13453. I'm not aware that the Powr-Lok was available in any of these during production. And there wasn't ANY Kaiser associated with these!!!!!!

 

And they would be 5.38 gears. A lot of Dana 44 parts can be used in the 41 like bearings, seals, brakes, and axle shafts. However, the pinion, ring gear and case are different. The 41 can be identified by a round rear cover without the flats a 44 has.

From the factory, early CJ2-As used either Bendix, Tracta or Rzeppa CV joints in the front Dana 25. Most ended up being replaced by regular cross-jointed axles through the years.

 

FWIW, the D41 has a larger ring gear, which makes it stronger than a D44, but the 10 spline axle shafts are the downfall of it.

No factory traction devices came in the stock 2A axles.

 

I have heard you can put 19 spline Dana 44 spiders and axles into a 41. Dana 44 Lunchbox lockers will also work, but you're limited to 19 spline max.

 

So ...... The US Army did not have 4WD in their Jeeps ?

 

Is this a riddle?

 

Naw..........Should have asked " Diid the US Army have open case's in their differentials " ?

 

Yes, the military jeeps had open diffs.

 

It was the US Military who initiated the development of axle traction devices.
It was developed specifically for the M38-A1.
The Thornton designed Spicer "Powr Lok" rather soon became a civilian option.
The very first axle to get it was the 10 spline Dana 44 and this quickly initiated the switch over from 10 spline milled axle shafts to become stronger 19 spline involute shafts due in part to increased minimal diameter.
That change occurs late in the 1956 model year when they first became a civilian option.

 

This

 

You can. I’ve done it several times for customers. You must also change the axle thrust block at the same time. The 10 spline thrust block has too large a diameter and can make contact with the side gears. Switching to the smaller diameter 19 spline unit will allow it to fit inside the side gears if necessary.

 

yup. The 10 spline Powr lock side gears are extremely hard to find. I’ve come across a few sets and all had worn out splines. I looked for many years for a good set for a customer in Belgium who was restoring a Marine Corps M38a1 and never did find him a good set. Correct me if wrong Ken but wasn’t it the Marine Corps that ordered the a1 with Powr Locks?

 

My memory now is old but that certainly sounds correct to me.
You're right Nick about the scarcity.
I've never even seen one of the early Powr Loks, just some old publications.
The very early production of the D44 Powr Lok units had cone type clutches in lieu of the later mass produced disk type clutches.

 

Many years back, I had a '64 M38a1 (Marine Corps) that had PowrLoks front and rear. I don't think they were added as both diff covers had about 10 layers of OD green so thick I couldn't get a socket on the bolt heads. I wish I still had that Jeep today!
-Donny

 

The D44 Powr Lok clutch disks were standardized long before 1964.
I'd have to check the exact date on that but it was in the late 1950's.
I'm thinking it was 1957.
Also the D25 Powr Lok was developed after the D44 Powr Lok was perfected or standardized and that relatively rare unit was first used in 1962.
The D25 Powr Lok unit was the 2nd Jeep traction device to be developed.
Unlike the D44 Powr Lok it underwent no further changes since it merely mimicked the perfected D44 unit.

 

Limited slip differentials predate the M38A1 by a bit. The original Torsen differential (geared) patent was issued to Gleasman in 1951, and applied for in 1949.

Ferdinand Porsche commissioned ZF to develop a torque bias design differential as early as 1935 for his racing cars. This didn't lock the axles together, but sent the power to the tire with the greater traction.

I haven't found a date on when the first clutch type differential was patented, but it may precede the Torsen.

Mike