I hate to do this but I've got to ask some newby questions. I'm looking to buy an F150\F250 4x4 for general hauling, towing and winter time use and need to know what to look for. Do all '73-'79's use the same tranfer cases and differentials? If not, what are the better units? Is there a tag or other way to identify the gear ratios? Are all the frames the same from '73 to '79? Are some V8's more durable than others? Thanks.

 

the T-cases were either a NP205 or anNP203 both came in married and divorced versions

NP205's came on trucks with lock out hubs and is a very stong gear driven unit.

NP203's came on trucks with full time 4x4....ie no hub lockout. it is a chain driven unit.

the rear axles were either 28 or 31 spline ford 9" axles on f-100 and f-150's
the rear axles were dana 60 full floats on f-250's

the front axles on all f-100 and f-150's are high pinion dana 44's

f-250's have low pinon dana 44 heavy duty units and devorced t-cases 73-77 (these trucks also have a different frame from all the other 73-79 f-150's and f-250's and are called highboys)

f-250's from late 77 to 79 have a high pinion dana 44 heavy huty unit and a married t-case.

f-350's and some special edition f-250's in 78 and 79 have the really desirable dana 60 high pinion.


engines offerd from the factory in 4x4's included

360 v8
300 I6
351 m
400

each has it's own strengths and weakness....

other engines are frequently swapped in the 2 popular ones are swapping in a 390 or a 460.

other swaps are done also... ie......I swaped a 351w in my 76 4x4.

ratio's are usually 3.50, 3.70, or 4.10's
the easyest way to tell in my opinion is to look ad the door tag on the truck and decifer the axle code... the next easy way is to jack up one side and spin the tire one revolution.....while doing this count how many revs the driveshaft makes and multiply it times 2.

If I forgot something please add to this or correct me.....

 

Wow, thanks for all the info. Can you explain the difference between the married and divorced transfer cases? Is one an advantage over the other?

 

the difference between married and divorced is simple, the transmission is bolted directly to the transfer case in a married t-case config. in a divorced there is a short driveshaft that comes from the tranny to the t-case. they both have there pros and cons, divorced has a strategic weak point that is easy to replace if it breaks, but in this setup the transfer case is lowered and therefor reduces ground clerance. in the married config. the t-case is tucked up in between the framrails, increasing ground clearance, but if the connection point between the tranny and t-case breaks on this, you are in a world of trouble. i've only seen this break one time, and the truck was junked after that. hope this helps.

 

I am not sure where you are located but I am in the rust belt and an important thing that I look for on these trucks is that the front cab mounts are in good shape (not al rusted out) as they are a pain to replace I fixed mine buy using another cab altogether!!!!

also beds for these trucks can be hard to find in the rust belt. And if you do find one it will likely be pricy...I have seen them sold for as high as 1000-1500!!!!!! so make sure it has a decent bed on it

 

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