This article is to explain how to make a heavy duty shortshaft 5 speed for a 510 or 521 that will have the shifter in the same position as it came stock with the 4 speed.
First you need the parts, you need a 1980 datsun 720 2 or 4 wheel drive front casing off a 4 or 5 speed longshaft transmission(31" long) with the front cover and the lower cluster gear bearing, it's best to have the whole tranny the first time. Then you need a 1985-86(84?) nissan 720 regularcab shortbox shortshaft 5 speed 2WD transmission(26" long), you need the 2 wheel drive for the speedo drive, but always check all the 4WD trucks in the wrecking yards in case they replaced it with a 2WD tranny. I start with the shortshaft to make sure it is good before I pull apart the longshaft. Side note, once you know how to do this, you can go to the "u pull it" yards, find one with both trannys, pull them apart, put together what you need and buy just the one tranny you need.
First you empty the tranny of fluids, then you remove the front bearing cover bolts, then tap the cover off from the side using the throwout bearing arm mount threw the arm access hole, don't hit it hard, just tap till it loosens.
Once you remove the cover you will see the two bearings, and have 5 bolts, one cover and a shim in your hands. In the photos below you can see the upper bearing with a ring clip holding it in position, that needs to be removed.
This is what you should have now.
Now you take the bolts out of the transmission case to separate the two halves.
Next you put a 2X4 on the floor and set the imput shaft on it holding the tailshaft steady, lightly tap around the base of the casing where it mounts to the engine, it is best I suppose to use a rubber hammer, but we use what we have, tap all around the bottom til the front case separates from the rear.
Now it is apart, you need to check this shortshaft transmission for excessive wear, missing teeth, ect.
You don't want to have to pull it out after you just installed because of bad gears.
More to come.
