The thing about the SD22 diesel engine is that it is only 61hp, it has torque, but torque don't get you down the freeway, hp does, the rear end gearing is very important, the 2wd with stock tires needs the 390 geared rearend, the reason is that 411s will rev the engine to high, and 370s are just at the point that the engine doesn't have the HP to push it down the freeway unless you have a very healthy engine.
I have 2 SD25 diesel powered vehicles right now, one is my 521 kingcab with 350 gears in the rear, it goes alright, until recently I thought it was awesome, but now I have come to realize that it goes down the freeway alright, but my heavier 720 with an SD25 turbocharged engine with 330 gears has more torque, it may not go any faster than the lighter 521, but it gets up to speed much faster, I am waiting to see how my fuel consumption is(better/worse?).
Never use any 5 speed transmission made before 1980, the gearing is wrong for the diesel engine unless you are using big tires.
I drove SD22 powered trucks for years before finding my SD25 engines, they did alright, but I don't ever want to go back, the SD22 just doesn't have the power I want.
If you don't mind driving down the freeway at 55/60, then the SD22 engine will likely work for you, but if you try to go 70mph your mileage will go from 35mpg to less than 25mpg in a 2wd, I don't know about a 4wd.
The front 3rd member on a 4wd truck is right under the engine, it has a strange oilpan, some of the oilpan is not even under the engine anymore, it's off to the side(see photos).
Where are you located?
Daniel Conkel wrote:Of course we didn't get the diesel 4x4s; don't want anything to threaten gasoline. I don't want to build a big rig with big wheels. I just want to swap the engine and keep the 4x4 stock. Is the diesel total weak sauce? Can one not solve the slowness problem by using a different tranny and regearing the differentials? Is the custom oil pan necessity due to axle clearance?