Hello, going to look at a 90 4x4 diesel. Just curious, is the 90 an intercooled truck? Also he says it has the 727. Is that a better choice for automatics verses the 518? Any thing to look for? (problem areas) Thanks

 

90 should be a non-intercooled truck, intercooling came mid 91.

 

hey-Hey!!!,
As noted by a few folks, nearly *ANYTHING* could be lurking under the hood of a 21 y-o truck. Now if it is original it will not be IC'd; there is a short pipe crossing over the motor between the turbo compressor and the intake manifold.

On the 727, it is a stout trans. It can make good use of a better torque converter( this applies to *ALL* the automatics ). Trucks that came with this trans are almost exclusively equipped with 3.07:1 gears. That is a not a bad thing; and I suspect you'll want another gear if you wish to travel with traffic on the highway. Now the 518 has a .69:1 OD v.the .73:1 OD of the manual trans; Getrag G360, NV4500(later), and NV5600( later still ). The 518's pump does not keep line pressure high enough at low rpm to tolerate full throttle in OD. The 3.07 axle housing is dedicated to that ratio, 3.54 and 4.10 get one without as much pinion offset since the pinion head is smaller on the higher( numeric ) gear sets.

Now if you run a 518 with 3.07 gears, 3rd is 1:1 just like the 727 and that ratio served the automatics for 3.5 years( up to 1991-1/2).
cheers,
Douglas