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Is it possible to swap out the rear diff from an M38/CJ2 and drop it in the floating axle dif in an MB/GPW?

...asking for a friend....

(Truth is - I donated a newer front dif to the project, and the tech didn't check the ratios as I suggested.
Now when it goes into 4wd, it winds up tighter than a bulls ass in fly season.

hoping that the easy fix is to drop in a read diff, too..)

I think you can put M38 diferentials in an MB if both front and rear are from the M38.

Thanks - that"s what I'm trying to confirm...the front was already done, I'm hoping he can match the rear..

Charles are you asking about swapping the entire axle assembly from an M38 to an MB or just the differential.

M38:

Front: Spicer Model 25 5.38:1 Floater No steering bellcrank on it.

Rear: Spicer Model 44-2 5.38:1 Semi-floater. (axle retained in diff by outer bearing retainer)

MB:

Front: Spicer Model 25 4.88:1 Floater. Steering bellcrank mounted on axle housing.

Rear: Spicer Model 23-2 4.88:1 Floater (axle retained by flange bolts)

If you are only swapping the diffs then there should not be an issue so long as you truly have a Spicer 44-2 with 10 spline axle and not a later CJ spicer model 44 with the 19 spline axle. There is a slight difference in the inner axle bearing sizes and I do not recall what effect if any that has on the swap.

The side bearings at the diffs that support the inner end of the axles are:

MB Spicer 23-2: ORD# 705438, Timkin 24780

Timkin Brg 24780
https://cad.timken.com/item/all-product ... 4780-24720
Specifications
Series 24700
Cone Part Number 24780
Cup Part Number 24720
Design Units Imperial
Bearing Weight 0.4 Kg0.9 lb
Cage Type Stamped Steel
Dimensions
d - Bore 41.275 mm1.6250 in
D - Cup Outer Diameter 76.2 mm3 in
B - Cone Width 23.020 mm0.9063 in
C - Cup Width 17.463 mm0.6875 in
T - Bearing Width 22.225 mm0.8750 in

M38 Spicer 44-2: ORD# 705440, Timkin 25577

25577 Brg Timkin
https://cad.timken.com/item/category-15 ... 5577-25520
Specifications
Series 25500
Cone Part Number 25577
Cup Part Number 25520
Design Units Imperial
Bearing Weight 0.6 Kg1.3 lb
Cage Type Stamped Steel
Dimensions
d - Bore 42.875 mm1.6880 in
D - Cup Outer Diameter 82.931 mm3.2650 in
B - Cone Width 25.400 mm1.0000 in
C - Cup Width 19.050 mm0.7500 in
T - Bearing Width 23.813 mm0.9375 in

Thanks - I was thinking that just the diff assembly would do it - should I ever try a job like that.

now I need to confirm that the diff did actually come from an M38, and not a CJ2 or 3.

Surprised to see that the ratio is actually higher on the M38, I expected it to be the other way round..

f

The WWII jeeps used 6.00-16 tires and the M38 used 7.00-16 tires. The tire diameter dictated the gearing change.

The 19 spline axles came much later than the CJ2A & 3A. Just look inside the diff's spider cage and count the receiver's splines. If they are 10 per side your good to go.