1966 4sp vs 1975 ? sp differences.

[vince1]

I saw a transmission in a 75 P/U with the gear shift stick missing so couldn't tell the number of gears or shift pattern. Looking underneath it looked to me that the transmission, as well as the bell housing might be different. It was cast iron case with the PTO plates, one on each side. Any chance they had 5 sp back then, or what would any other differences be to the original one that came as OE in the 66? Thanks.

['63GENIII]

If you are able to post a pic, it could probably be identified here within minutes. It could be a bunch of different transmissions. Yes there were 5 speeds then. The Clark 5 and the NP540 come to mind. Some of the harder to find ones had OD for 5th.

[1963c-10]

I think the SM420 & SM465 were both available with PTO's also.....

[padresag]

the main difference is the input bearing cover is larger in dia on the sm365(75) vs the one on the sm420(66) and will not fit into the earlier bell housing without enlarging the hole or using the later bell housing which means that you will have to install a rear trans cross member to mount the trans.
believe the sm365 is also synchromesh in first
ron

[Captainfab]

The SM420 4 speed was used up thru the '67 model year. Then starting in '68 the SM465 was used into the 90's I believe in some applications. Padresag is correct in the front bearing retainer. The SM420 has a front bearing retainer that measures 4-13/16" OD whereas the SM465 front bearing retainer measures 5-1/8" OD. Consequently a '68-'72 bellhousing would be needed to upgrade from a SM420 to a SM465. Or you could go with a '73+ bellhousing and add a trans crossmember.

The '75 truck you saw more than likely had the SM465 4 speed.

[vince1]

I might go back and take another look. With the stick out there was only a hose clamp left so probably had some problems there. It's behind a 292 that I would also like but don't think I can afford the time to bring all that stuff home and rebuild it.