Posted by Charlie on December 07, 1998 at 22:14:18:
In Reply to: SM540 transmission posted by george bonta on December 07, 1998 at 16:05:53:
Maybe you're referring to a NP540 5spd? Probably a very few were made with a bolt pattern matching a flathead bellhousing, mostly for 1.5-2.5 ton trucks. But if you find one with a different bellhousing, try putting a spare M37 bellhousing up to the front face. Sometimes all you need to do is have a machinist drill some new hole for the bolts, enlarge the center hole to match the bearing retainer, and use a clutch disk with a larger splined hub. All of this is pretty simple. The HARD thing is FINDING a NP540 with good insides (in overdrive configuration). Apparently, the input gear (the weak point in most overdrive 5spds, including this one) is NOT FINDABLE in NOS condition. So if you buy one, make sure the input shaft and countershaft are good. If you can find one, it's the shortest, lightest HD light-duty truck overdrive 5spd. The OD version ratios are: 6.06, 3.31, 1.81, 1.00, 0.821.
Charlie