motor swap question

[hashsdatsun]

Hey everyone wat is the easiest motor swap to go 5spd the 4spd is unbareable also would i need to change my diff if i go ka anything helps thanks

[datzenmike]

Run on sentences are hard to read and could result in misunderstanding.

 

 

You can run your L16 with a 5 speed. Why not?

 

If you drive on the highway a lot and it seems buzzy then swap the differential for a 3.90. This wil drop the RPMs just like a 5 speed and is both easy and cheap

[MikeRL411]

It would also help to say just what vehicle / engine / transmission you currently have.

[DanielC]

This post is in the 521 section, so I am going to assume, knowing the dangers of assumptions, that it is a 521. 

It takes some getting used to the fact that the L-16 engine in a 521 is turning around 3600 RPM at low freeway speeds, (55 MPH)  the engine is happy doing this, in fact, the torque peak of a stock L-16 in a 521 is at around 3600 RPM.  This is the RPM the engine is most efficient.

 

A L-16 is not like a typical American engine.  It likes to run at high rpm.  Do not run it below 2000 RPM.  In a 25 MPH zone, I suggest running third gear, it is really easy to creep up above 30 MPH in fourth.   As you drive you 521 and get used to it, you may find you can actually climb some hills by going faster, because the engine is running closer to it's torque peak, than by going slower.  By the way, the "yellow" zone for RPM on a L-16 is around 6500.  Red line is 7000.

 

The easiest engine swap, an L-18.  You get a little more power.  But that does not help the engine RPM.

A five speed swap is not difficult, ANY L transmission will bolt on to ANY L engine.  There are more than a few transmission swaps detailed in 521 trucks in this and probably other forums.   Basically, different rear motor (transmission) mount, relocate the shifter, longer speedometer cable, shorten the drive line, get a different U-joint flange on the front of the drive shaft.

 

The first gear ratio in a stock 521 four speed is around 3.6 to one.  Most other transmissions that bolt on to a L-16 have a 3.3 or even higher, (lower numerically, "faster" or less starting torque) than a stock 521 four speed.  This makes it a little harder to get rolling from a dead stop, especially up a hill, or carrying a load.  But even carrying a load, that is not a big deal, and with almost any five speed, you lose the huge jump between second and third gear.  

Do not expect that going to an overdrive ration will improve the gas mileage as much as the overdrive.  It takes the same amount of power at the rear wheels to push the truck through the air at the same speed.  If you slow the engine down, RPM wise, at the same speed, you need more throttle to get the power back you lost from the lower RPM.  Additionally, if you do a five speed swap, you lose the efficiency of the one to one fourth gear ratio, at freeway speeds.  You will need to downshift more.

 

Changing out the rear axle ratio will have the same problem, harder to get rolling, as a five speed swap.  But it will lower the RPM, in fourth.   You will gain a little more fuel mileage.  But you will have to downshift more.

[hashsdatsun]

Wat about cruising 65 is that to much

[datsunaholic]

65 isn't too much.  You can cruise at 70 and the engine won't care.  Loud, but the engine is fine with that.  You can easily exceed the 521's safe operating speed with the engine (due to the 4-wheel non-power drum brakes).  The utter lack of soundproofing makes it sound like it's gonna come apart, but unless you're crusing at 70 MPH in THIRD gear, the engine will be fine.

[saveacivic]

So this 3.9 rear end you speak of... What is it off of and what do I need? Just a rear end? I come from the FWD world so rear end ratios are new to me. I can swap it out, just want to know what is the easiest to cross over from. Thanks. I have a 72 521

[datson4life]

I believe a datsun/nissan 720 diff should swap right in

[wayno]

So this 3.9 rear end you speak of... What is it off of and what do I need? Just a rear end? I come from the FWD world so rear end ratios are new to me. I can swap it out, just want to know what is the easiest to cross over from. Thanks. I have a 72 521

 

What engine do you have in your 521?

[datzenmike]

Hey everyone wat is the easiest motor swap to go 5spd the 4spd is unbareable also would i need to change my diff if i go ka anything helps thanks

 

Get ear plugs. You won't like the acceleration of 3.90s.

[ggzilla]

Waueno, 521 comes with the L16 engine.

 

It lives to rev. Keep the 4-speed and let it rev. The 521 was designed back when the usual speed limit was 65-75 MPH.

[mikeanike99]

Should my 620 have the same tranny in it? I have a l16 with a 4 speed.

[ggzilla]

Yes, 521 and early 620 use same transmission series (63) with same gear ratios. The output flange differs though so they are not exactly the same, but almost.

[mikeanike99]

Cool

[datzenmike]

It's the exact same gearing as the 510 goon 4 speed. A same length (although car ratio gears) 710 4 speed will also swap into the early 620.