Jump to content

320 Diff swap


Recommended Posts

  • Replies 19
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

There are other people who should know this. I do know that a center section from a 520 1300 truck will bolt into a 1970 521 truck with a L-16. It would seem to me very possible that the center section from a 520 or a 521 truck would bolt in.

I believe the 320 trucks came with a 4.875 ratio, I could be wrong. The 520, and 521 trucks with a 1300 engine also had this ratio. The 521 trucks with a L-16 had a 4.375 ratio. I do not know about other ratios that were commonly available.

Be advised that just putting a higher geared rear end in your truck will not make your truck go faster. It will be harder for your engine to move the truck, and it will accelerate slower. You will have to spend more time in lower gears. The actual top speed of the truck may even end up slower, because the engine cannot "pull" the higher speed gear ratio.

Link to comment
Is there a direct rear differential swap for a 320 truck that will make it more driveable?

No there is not. If you are asking about lowering the engine revs at freeway speeds, be aware that 1) high revs won't hurt the engine 2) a 5-speed is what you need.



If you lower the differential gears, then the 320 will have a hard time taking off from a stop. 320 has an H190 diff doesn't it? So you theoretically add a more freeway-friendly gearset from another Datsun vehicle with H190. But again the little 320 engine can't pull it as well.


The other way is to fit larger diameter tires. It's the same effect as higher diff gears.

Link to comment

While the 320 does have an early version of the H190, it's unique in how the gears and splines are cut. So here's no "bolt in" replacement.





13 spline 320 side gears.





29 spline 520/521/620/720 side gears.




23 spline 510 side gears. (goon of course)



Link to comment


The later gear-sets will work as well as the 510 wagons and Roadsters that all use the H-190. If you can score a Raodster gearset that is a 3.89 ratio, you will have free-way gallore (~70 mph) but you will suffer alittle on the take-off. THe factory gears are 4.875. The 620 pu's had a 4.37 gear set. This will give you a more streetable ratio, with out sacrificing take-off torque. The Wagon and roadster gear sets (sae vice metric) you will have to re-use your side gears from the 320 diff, and remove the side gears from the car and disguard. If you use a metric third-member from a later truck (the H-190 was used all the way up to 1989 and was primarily the 3.89 in the latter years), then you can still make it work, but it takes some dismanteling and modifications to work. My 63 NL320 has this particular set-up, and the 1st gear on the column shift 320's is lower than the 1st gear on the later 520/521 and floor shifted 320's. The hybrid uses the case from the later model H-190, but uses the ring-gear carrier from the 320. This carrier needs to be carefully drilled out to the next larger diameter hole to allow the late model ring gear to be bolted to the 320 ring-gear carrier. Then bolt the metric ring gear to the 320 carrier, and reinstall the ring-gear carrier into the pinion housing. Then re-install the assembled thirdmember into the 320 H-190 housing, and you have it made. This is the best I can remember because the truck is in WA and I now live in Alaska. But I have been running the 3.89 gears in my L520 with the J-13 for years as a commuter in San Diego and WA state. A little slow on the take off, but I could cruise at 60-65 no problem (except on the hills ;-).). I have not driven my NL much, but the top end should be the same as my 520, and I know driving around the NL320 at my dads farm, the new gearset worked fine and 1st gear was a definite improvement over my 520 with the same gears and tires. The 520 I was running 255x50x15's and the 320 is running 195x65x15 both were similar in outside diameter.

Link to comment

Any idea if the roadster gear ratio would cause the same loss of low end torque when mated with the A14 engine as opposed to the stock L320 "E" series engine ? The reason I ask is that my 65 L320 has the A14 from a 1977 B-210 but Im still suffering from the same lack of speeds over 50-55 problem ???

Link to comment

no tach, but the damn thing is def revin way up there.....regardless of whether it can handle it, it jus doesnt feel right hearin it reved up that high.....is there anwhere you can reccomend to get the setup, or do you just have to find a donor car ?

Link to comment

Come to the next Datsun meet and ride along with someone and have them show you what is right. Don't go by feeling. Yes, a 5-speed is the most logical solution. If you have the original 320 engine, it will be easier to swap an A14 with 5-speed than to adapt a 5-speed to the 320 engine.

Link to comment

My truck already has the A14 engine installed with the stock rear-end and tranny. With that in mind from what Ive gathered, my best bet for better cruising speeds is the Roadster gears, any suggestion on the easiest 5spd tranny swap ? Lastly I really enjoy the amount of low end torque that the truck has and several people have said that with the A14 I shouldnt experience the same amount of loss in that area as I would if I was still running the E series......that said Im trying to decide If i want to chance losing the low end power......Im moving to Hawaii with my truck in the spring and will be having to deal with a LOT of uphill driving where I think that low end pwr will serve me well, and on top of that the speed limit on the freeway there is 55 so Its not like 60-65 cruising speeds are a MUST, but if I can still obtain that without losig all of my bottom end I would still like to do it before I go ??? As far as a Datsun meet, that would be cool, but Im all the way down in Texas, and my truck is currently in Los Angeles getting service performed and awaiting its shipping date to Honolulu, so probably wont be feasable.



Link to comment

Hands down, install the 5-speed. It directly replaces the 4-speed and uses the same mounts and driveshaft. Get one from a 1979-1982 Datsun 210.

You can use a Datsun B210 5-speed, but they are much larger and also need a different driveshaft than the 4-speed.


This way you keep your differential gears and still get overdrive!

Link to comment

Thanks for the advice Zilla, I guess that will be my next mission then is to find a tranny in the Los Angeles area that will meet my needs. I will have to decide whether or not I want to have the current shop complete that kind of task as well.....blows my mind how expensive it is there per hour to work on the little truck. 80 an hour.....which maybe is normal some places but not down here where Im at to work on something as simple as an old Datsun.

Link to comment

The 5spd may be an option for Wydler, but not G-funk. Either way...I love the 3.89's I put in my NL. I run fairly small tires on it, so factor your tires in when deciding on gear ratios. I love torque and jumping off the line as much as the next guy, but in a rig this old and rare....I'd rather be able to cruise with it. I can easily maintain highway speeds now. Besides...if you put a 3.89 in and decide that you gotta have more pep...you can easily find someone to trade you a 4.11 or 4.39. :) The diff swap is a gasket and a couple of hours. I'm not saying to not do the trans swap, but, as in my case, it's not even an option and I'm thrilled with the diff swap!! :)


As for swapping the spider gears....



  • Like 1
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.