Quote:
Originally Posted by 1976gmc20
So ... does that mean an SM465 would just drop into a 1989 GMT400 with the NV3500 ?
(I know you're asking "Why?" but I use it more off-road than on the highway so the granny gear would be more useful than the overdrive)
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If you can find an aluminum-top sm465, yes. The aluminum tops had the rearward shift position and the low passenger side slave. You'll want to definitely get the correct bellhousing to go with this sm465.
The squarebody iron-tops will need floor modifications, custom slave cylinder plumbing, and possibly exhaust rerouting to clear the slave.
Also look for the 1992-1994 nv4500. These years had the granny gear and the overdrive. The granny isn't quite as deep as the sm465, but it's close. These should drop right in, but you might have to change the transfer case input shaft. Again, you'll want to purchase an nv4500 complete with a bellhousing.
I might be winging it a bit here. I'm confident in my information regarding the nv4500. I'm less certain about my knowledge of the nv3500. Keep that in mind with the following paragraph.
The R/V trucks continued to offer the iron-top sm465 as the only manual option through the end of their run in 1991. The gmt400 trucks started out with the nv3500 in 1988 on the half-tons. The heavier trucks got the aluminum-top sm465's with the rearward shift position and passenger side slave. This shift position and slave position were identical to the nv3500. In 1992, the sm465 was dropped for good, and the nv4500 showed up on the scene. This was the same length, the same shift position, and the same slave position as the lighter nv3500 and the now-discontinued aluminum-top sm465. My knowledge of the nv3500 drops out at this point. The nv4500 continued in the granny-low configuration through 1994. In 1995, it was rearranged to match the Dodge nv4500 ratios. Granny low was dropped, and all the gears were spaced better for daily driving. In 1996, the bellhousing to trans bolt pattern was changed to match the dodge bolt pattern. At the same time, a new internal slave bellhousing was introduced. A few more minor changes followed in 1997 and 2001, but those don't affect fitment much.
In summary, any manual transmission from a gmt400 should be interchangeable with any other, until you get into the mid-90's with the internal slaves. The aluminum-top sm465, the nv3500, and the nv4500 can all be switched. Just make sure each one comes with it's respective bellhousing. The bellhousing has to stay with the respective transmission. Also, the spline counts on the t-case input shaft might change between the lighter weight trucks and the heavy weights. The input shaft on a np241 is a very easy and cheap swap, though.