If memory serves me right - and it usually does not......

4-150 150 pto hp and 4-180 180 pto hp (210 engine)

4-175 150 pto hp (much improved version of the 4-150) 175 engine (2-105 rear ene parts basically)

4-210 210 engine and somewhere around 180 pto hp (2-135/155 rear end parts = planetaries) replaced the 4-180 with bull gear rear ends like 4-150, 4-180, 4-175

4-225 improved version of the 4-225 with 225 eng hp (turbo 3208)

4-280???? was that the number? Cat in line 6 engine and one heck of a tractor from what I heard but few sold before White went belly up. Always impressed me at the farm shows.

I bought a 4-175 used and ran it 4 or 5 years mostly on grain buggy and cultivating one year. It was a nice driving tractor and like many tractors an "almost" great tractor. Much like Oliver/White history they made 95% of the tractor a "great" tractor and left 5% designed poorly to relegate it to an "almost ran" status. The 4-175 was what the IH 2+2 always dreamed to be. Light, nimble, manuverable, powerful, able to handle loads much superior to a comparable MFWD, almost unbelievably fantastic visibility. The Cat 3208 engine was a death sentence to begin with although I will say that of the 3 3208's I have owned didn't have a minutes trouble with any of them and they were all bought used (maybe that is why I didn't have trouble - troubles were already fixed). Not that the 3208 was such a bad engine - it just had a terrible reputation by that time and many avoided anything that had one it it like the plague - doesn't matter if they fixed the problems and the engine was ok, if people will not buy it, better not put it in anything if you want to sell tractors. The center hinge was terribly weak in the 4-150 and was resolved in the 4-175 but they left the weak pto/hydraulic driveline design. This is probably the weakest part of the tractor. Some greatly improved it by replacing the original driveline with heavier parts so the ujoints and splines were not regularly going out. If they would have put the hydraulic pump on the front and ran hydraulic lines to the back and then this driveshaft would probably been ok if it only ran when the pto was needed. As it was, running all the time, it was a regular replacement item. Hydraulic pump was typical White of that era good for 1500-2500 hours - not a real big issue, just increased cost of operation, was easy to replace and not terribly expensive.

The 4-175 was a really nice driving, nice handling, as far as I am concerned the answer to a MFWD tractor ever made. If only it would have had an 8.3 Cummins (wasn't made then), fixed the driveline issue, and had something other than White and been painted silver, that tractor should have been where every MFWD is today. It is probably the best kept farm tractor secret ever to not be sold (much). 

John