Compatibility....

[Shuboxlover 474]

I was wondering if the axles, differential, and main gears from a 1974 C-120 Auto would swap right into a 1978 C-161 Auto

Thanks

[953 nut 51,969]

Since they are both Sundstrand the axles should be interchangeable.

[Shuboxlover 474]

Thanks Richard,  I thought the axles might work, but what about the diff and other main gears?

[stevasaurus 22,243]

I looked at the IPL manuals, and the part numbers are different between your 2 transmissions.  That doesn't mean they will not swap.  If those were 8 speeds, I give it 98% probability.  I'd say go for it...you may find that the whole differential and mushroom gear have to be swapped as a pair.  It is worth a try. 

[953 nut 51,969]

Like Steve said, strong likelihood that all differential and axle parts will interchange. The '73 C 120 has a 90-1136 and the '78 C 161 has a 90-1173. The '78 probably is a bit stronger differential but the axles, although the part numbers change over the four years, should swap. The '74 C 160 and C 120 used the same part number axle even though the transmissions had different numbers.

[stevasaurus 22,243]

Actually Richard...those numbers (90-1136 & 90-1173) are for the Sundstrand pumps.  The transmission numbers for the transaxles are C-120 has either the 5088 or the 103903 depending on the Model number of the horse, and the C-161 has a #106457.  I still think the guts will inter-change though.