New zippy gears in L320

[ol' 320]

Earlier this year I bought a 1965 L320 ... a Lilliputian truck that is big on style. I usually don't mind low horsepower, pedestrian vehicles with micro motors. But that's because I'm used to driving pre-WWI cars where 40hp under the hood means you have a real tiger by the tail! But this time when I went shopping for a collector car I was looking for a "newish" truck that could be a pre-smog daily driver, yet modern enough to have great brakes, taut steering and better electrics. SOmething that would drive 70mph all day, too, preferably loaded up with the crap one takes on out-of-town trips.

 

The 320 I found had a nicely warmed over A-12 and dogleg five speed, making it a solid freeway runner, albiet at higher rpms. I did some research on Ratsun, the Wikipedia of all things Datsun, and soon learned who are the chosen few folks throughout the country who seem to care about these little 320s. Pretty soon I was focusing on posts by DatsunMike, Wayno, and MKlotz. I cruised around the driveline and made some posts to a few foiks, focusing on people who seemed to have personal experience with re-geared 320s and 521s, as opposed to opinions. I found lots of opinions about installing 3:90 gearsets, but not much else seems to have been tried in 320s ... at least that I could find.

 

I plan to use this truck mostly as a driver, meaning me, the wife or a buddy, and/or my car buddy Mr Maples or his new pal Parnell. Mr Maples is a real heavyweight, a 12 pound Dachsund who thinks he's a Doberman whenever he sees a cat. He hates cats, even the very sound of cats sets him into a frenzied fury. Parnell is a younger, dumber version of Mr. Maples, who bears no ill will against anything except chew toys. But Dacshunds in Datsuns aside, I do occasionally use the 320 to haul a lot of heavy stuff.

 

Note to 320 owners: Your truck will easily haul 2,000 lbs of gravel and sand, or other assorted lumber and stuff if you need to. Ask me how I know;) The fellas who drive the forklifts at Lowes know this truck well ...

 

So back on point: I wanted to regear the 320 for higher top speeds and lower rpms, but maintain the little truck's ability to take off and pull a load. Wayno had the best input. He's run 320s with 4:88s, 3:90s, and 4:37s .... and has run 320s with both 4 and 5 speeds. Wayno advised that he found the 3:90s were great for highway cruising even with the old EL motor, but he definitely knew when he hit a hill or tried to haul a load that the 3:90s were less than ideal. When he switched to 4:37s there was a noticeable improvement over 4:88s but he could still pull a load. I wanted all the drop in rpms at freeway speeds I could get with good load handling, thinking I would always drop from 5th to 4th on a highway grade. I wanted 4:11s, but those turned out to be hard gears to find in good shape.

 

After months of looking for 4:11s and posting on Ratsun with no replies, Wayno, whom I had previously never met, offered to crawl around in haul the junkyards in the PNW looking for 4:11s. While other Ratsun members were probably enjoying their warm homes and watching football, or shopping for big screens, Wayno spent Black Friday lying in the mud somewhere in the Far North. He scored me a decent set of 4:11s! He rejected a couple sets found over a two month period as "less than perfect" in favor of his Mud Day Friday score, and then even found another 320 rear end so he could harvest and pre-install the 320 differential side gears in the 4:11 pumpkin.

 

The Wayno drove 14 hours and stopped off at my house to install this gearset while on his way down to LA. How cool is that?

 

I still need to calibrate my speedo, but I know my tach is dead nuts accurate. I spent last Saturday cruising up Highway 99 to Sacramento and back to check out an all-Datsun swapmeet, and boy, what a difference! On the way back as I neared Fresno I passed one of those roadside radar speed displays at 3,500 rpm in fifth. 70 mph. Very nice, Wayne!

 

Seems like I used to have to hit over 5,000 rpm to do the same speed with the 4:88s.

 

In conclusion: I'm very happy I kept looking for 4:11s. With the 720 front clip and all new balljoint suspension, my 320 should be comfortable to drive up to about 80-85mph. That's about fast enough for Mr. Maples' wild ride on narrow-stock width tires, I think.

 

As a side note: I can also tell you that with the 4:11s installed, the 320 is much more comfortable to drive at freeway speeds with about 700 pounds of sand in the bed ... Tracks really well with some weight in the back, and the 1-ton stock springs smooth out a LOT. It's a cushy ride in this configuration ... even on a rough section of Highway 99 at 70 mph.

 

I did get a strange look for the dude driving the big Kenworth pulling a load of milk when I pooped out from behind his semi and passed him in a little 320 pickup that's about the size of his rearview mirror. Especially when I wound out that A-12 and shifted up into fifth! The Weber Matt put on this engine sounds really good when your foot is in it:)

[ggzilla]

Good on ya. 4.88 is more zippy than the 4.11, but the 4.11s will lower RPM for a given speed, and give it a higher top speed. 320 is RPM limited with the stock gears.

 

The A12 can run all day at 5000 RPM, I've done it many times going from washington to california and back (and it does not wear out the A12). But with lower RPMs the fuel economy goes way up. The A12 can pull 4.11 gears just fine and is probably best for a 4-speed in a heavy truck with no load. In the lighter Datsun 1200 car, 3.90s are stock.

[datzenmike]

The dogleg 5 speed is an over drive 5th gear and is designed for highway cruise (light load) speeds to reduce RPMs and increase economy. It should never be used when passing, climbing steep hills, towing or carrying heavy loads. Doing so increases the side load on the internal bearings wearing them out sooner. Always down shift to fourth gear. Fourth 'gear' does not involve any gears at all and is a 1 to 1 ratio and transmits power straight through the transmission bypassing the counter shaft and all those bearings.

[Dguy210]

Enjoyed talking with you at the swapmeet ol' 320, this truck is very awesome in person :thumbup:

[ggzilla]

where'd you get the aluminum rocker cover?

[wayno]

The dogleg 5 speed is an over drive 5th gear and is designed for highway cruise (light load) speeds to reduce RPMs and increase economy. It should never be used when passing, climbing steep hills, towing or carrying heavy loads. Doing so increases the side load on the internal bearings wearing them out sooner. Always down shift to fourth gear. Fourth 'gear' does not involve any gears at all and is a 1 to 1 ratio and transmits power straight through the transmission bypassing the counter shaft and all those bearings.

 

Is this statement true on all datsun/nissan 5 spd' transmissions?

[ggzilla]

It's true on ALL overdrive manual transmission, be they Nissan, GM, Ford, etc. You want to put heavy freeway loads (pulling steep hills) in the "direct" gear, which is usually the one below top in a 5-speed. In 6-speeds, usually 5th and 6th are both through the cluster gear, with 4th still being "direct".

 

Nissan made a few (very few) non-overdrives. I've never seen one, that's how rare. Datsun & Nissan competition sold them. Datsun made some factory stock for Japan-market A12s too, a "direct fifth" 5-speed (non-overdrive), which was sold here in USA via Datsun Competition. In this case, use fifth gear, not fourth -- if you have enough power in fifth.

 

For a light car, just keep it in fifth. It won't wear out the transmission. When pulling heavy loads is when to be more careful.

[Stoffregen Motorsports]

Enjoyed talking with you at the swapmeet ol' 320, this truck is very awesome in person :thumbup:

 

That's ceramic coating on steel. If you want aluminum valve covers, there is a guy out there that makes them. I'll think of the name and post it up.

[Stoffregen Motorsports]

Good on ya. 4.88 is more zippy than the 4.11, but the 4.11s will lower RPM for a given speed, and give it a higher top speed. 320 is RPM limited with the stock gears.

 

The A12 can run all day at 5000 RPM, I've done it many times going from washington to california and back (and it does not wear out the A12). But with lower RPMs the fuel economy goes way up. The A12 can pull 4.11 gears just fine and is probably best for a 4-speed in a heavy truck with no load. In the lighter Datsun 1200 car, 3.90s are stock.

 

I worry about them being too numerically low. The motor I built is slightly more than "warmed over" as Eric put it, with a .500 something lift cam and 10:1. It never did have much of anything below 2500 RPM's. I hope Eric doesn't lug it around too much and load it up.

[ol' 320]

I usually run the truck about 3-4k when just cruising on freeway. I know what you mean about lugging it. This engine is a whole different animal over 3k rpm. But it is nice not to drone down the highway at 5k all the time. I will probably run it down the highway a lot harder once I have the new speedo programed. BTW: Matt, I've been talking about coming up to Tom's to tweak a couple of gauge connections possibly Dec. 27 or 28. I'll drop you a note in case we can connect, too.

 

This is getting off the topic of re-gearing the 320 a little, but when I drove the 320 up to Sacto to go to the Pare Composites swap last weekend it was pretty cold out by early evening. I think one reason my heater was not pumping out a lot of heat is that the truck's thermostat probably opens too soon. The running temp on the highway at speed with a very accurate mechanical gauge was only about 150 degrees. Maybe I should have stopped and placed a piece of cardboard over half the radiator or something .... that electric 8" fan you put on this truck sure does it's job, Matt. Engine pulls nice and smooth. With the 4.11s each gear is just a lot deeper. And 4k and up is much nicer in second, third, fourth ...

[Amerikilla]

I put the 3.88 out of a 720 in my 320 by just swapping the side gears. I have an L18 with a dogleg 5-speed.

[mklotz70]

Back when I owned Wayno's NL320, I'd get it up to 70+ on the highway with the 3.89's in the rear. It would take a while to get there, but boy did I love the looks on the faces of the people when I passed them.....it still had the ratty paint on it then. I was kinda hoping I'd get a ticket just to have proof at how fast I was going. lol :)