help on 73 620

[Craig]

Just got a new 1973 620. It in bad shape. What I want to know is what newer auto trans with OD will bolt up to my L16? And. What can I get it from? also what mods can I do to that motor? Any help would be great?

[datzenmike]

There are none. You have a 5 bolt crankshaft. The only L series automatic with a true 4th gear over drive is the L4N71B from the '83 and '84 Maxima and it is a 6 bolt crank. The flex plate is specific to the L4N71B's torque converter so an older 5 bolt flex plate won't do.

 

I believe that your 620 with automatic has a 4.625 rear axle ratio so it revs pretty high on the highway. Find out for sure and then look at putting any 4.375 standard transmission rear end in to lower the highway revs.

[Craig]

thank you for the information. Is there a 5 speed standard that will bolt up? Or can I bolt it the maximas motor and trans?

[datzenmike]

I believe you have the short 26" tranny in you '73. Any 3N71B from a '72-'73 510 should fit. The maxima motor is an inline six and much too long for a 620. There is a 5 speed called a dogleg that is the same length as yours but this is not a simple thing to do. It is found in the '77-'79 200sx and the '78-'79 A10 (late 510)

 

Grocery list of things needed to install a 5 speed into an automatic 620:

 

one dogleg 5 speed

one set of clutch and brake peddles for 620. The automatic peddle is no good.

one clutch master cylinder and push rod to connect to the peddle.

one clutch slave cylinder with push rod and home made hard line to connect the two.

one clutch arm and rubber boot (if not on the 5 spd.)

one release bearing and collar to hold it. Size dependent on clutch size used.

one 5 bolt flywheel

one pilot bushing for the crankshaft.

one shifter assy. (if not supplied with tranny)

modify the shift lever hole to suit

modify the rear tranny mount to suit the fit.