I have an 86 Nissan 720. This was apparently an early "changeover" model as it has the Z24 with 8 plugs but still has an OEM Carb. It does not appear to have been altered from new.
This is an Automatic (L3N71B) with the HF38 rear axle.
Correct me if I mis-read the articles in the forum posts but I believe this should be an H190A rear axle?
At any rate, I have verified the actual gear installed and it appears to agree with the 3.889/1 ratio as expected.
I have not completely found all the posts about the auto transmission but I believe from what I have read is that is is supposed to be a 3 speed box. I have not read anything about any kind of torque converter clutch or overdrive.
(Sometimes during acceleration it appears to seem to be trying to find an extra gear between 2 & 3.....almost as if it were actually a 4 speed but skipping 3rd and shifting 1,2,4).
Still, I believe from all I've read that it is indeed a standard 3 speed automatic.......possibly it has some other minor shifting defect that leads to this strange small hiccup at times.

My issue...like many others I've seen here is that at freeway speeds....the little engine sounds like it's about to come apart at 75mph. Living in Arizona......the rural speed limit is 75 and most folks regularly run 80 - 85.
In my opinion, this vehicle desperately needs another gear to run high freeway speeds. I believe it produces sufficient power to easily pull a taller gear as it is only lightly loaded.
I understand that other rear axle 3rd members available for a direct bolt in would be an HF37 (out of a similar year 5 speed truck or possibly a 3.364/1. Would that be an HF33 or an HF34??????
In my opinion, changing up to an HF37 would barley be a large enough gear change to warrant the cost/labor involved.
I would think that the 3.364/1 would be a better option. Is there a particular model I should look for to find a direct bolt in pumpkin in the 3.364 ratio?
Please help me clarify what my actual gear options are. I've read all the related posts and I'm still not clear on what to get.
I understand that I could get taller rear tires to increase the effective ratio but that would be in direct conflict to my plans to lower the truck.
Thanks in advance for helping me learn what my practical options are, keeping in mind that I wish to change only the 3rd member, not the whole rear end assy.
Last, if you have a source for the part I need - used. Let me know.
As far as I know, my HF38 is working perfectly with no bearing noise or gear whine. If I can find a better highway ratio unit.......my take out HF38 may be available for trade if anyone should need it.
Please let me know.......Regards, Ibjman
PS: I did read the posts showing the OEM part numbers for new gears in most all the ratios.....not sure if those new parts are still available.
I have the resources & knowledge to change the actual new gears if required but I'd prefer to buy a used unit for obvious reasons.

I would agree that going from 3.9 to 3.7 gears is kinda a waste of time unless you are changing out the rear end because it is toast, they also have a 3.5 and the 3.3 that you already have referred to, they are a lot harder to find.
The 720 came with all the H190 gears above and more, but the 3.3 and 3.5 gear sets will take getting used to, especially the 3.3 as it will be like starting out in second, almost.
I have 3.5 gears in my Datsun 521KC diesel(SD25/71hp), I am going about 80mph at 3000rpms, I have normal tires(P195/75R14), it was strange starting out in 1st gear at first, but I don't even notice it anymore.

Thank you for that!!!
Since I have 3.88 now I think even 3.5 might not be a huge change. I would probably opt for 3.3 if I could find a good set already installed in the pumpkin.
Remembering of coarse....that I have an automatic with all the advantages of a torque converter....so I'm thinking that starting out from a stop would not be such a noticable issue.
Does anyone have opinions on which models I should look around for to locate a 3.3?
As for the H190 configuration.....I understand that H190A's had a bigger pinion bearing. I'm hoping that the one that I have in the 86 now is an A.
Although I have verified that my actual ratio is the correct original 3.88......the tell tale yellow paint markings on the outside rear of the housing indicate that it's a junkyard used unit....so someone before me has already replaced it at some time. Maybe it's an A.....maybe not.
I really want to make a fast trip to Los Angeles soon....so I'd really like to find one.
No one else has yet piped up yet offering to sell me one.

Going from the 3.9(3.89) to the 3.5(3.54) was a big difference to me, it was like starting out in second(5spd.), but my diesel engine has the torque to pull it off.
I also have a 720 with a turbocharged SD25/5spd. with 3.364(3.3) gears, it also has the torque to pull it off.
Nissan made several gear ratios for the H190 if that is what you actually have, they are,
4.875(4.8)
4.625(4.6)
4.375(4.3)
4.111(4.1)
3.889(3.9)
3.70(3.7)
3.545(3.5)
3.364(3.3)
The late '83 to '86 720 with the 'Mileage Option' package which included the Z20 engine has the 3.364 rear H-190 diff, check the engine tag under the pass side hood hinge and look for the Z20(S) motor, the axle # will be on the lower right corner and will read HF 33 for the 3.364. That's the only 3.364 ratio H-190 I know of.
It would likely be a good idea to post a good photo of the axle you have to be sure it's in fact a H190, I am sure someone on here could ID it if the photo is good enough.
The later 720 4X4 trucks came with a C200 differential, it is easy to ID because access to the gears is a rear cover instead of dropping the gear set out the front.

ibjman wrote:Thank you for that!!!
Since I have 3.88 now I think even 3.5 might not be a huge change. I would probably opt for 3.3 if I could find a good set already installed in the pumpkin.
Remembering of coarse....that I have an automatic with all the advantages of a torque converter....so I'm thinking that starting out from a stop would not be such a noticable issue.
Does anyone have opinions on which models I should look around for to locate a 3.3?
As for the H190 configuration.....I understand that H190A's had a bigger pinion bearing. I'm hoping that the one that I have in the 86 now is an A.
Although I have verified that my actual ratio is the correct original 3.88......the tell tale yellow paint markings on the outside rear of the housing indicate that it's a junkyard used unit....so someone before me has already replaced it at some time. Maybe it's an A.....maybe not.
I really want to make a fast trip to Los Angeles soon....so I'd really like to find one.
No one else has yet piped up yet offering to sell me one.

Thank you for all the good answers.
I'm reasonably sure it's an H190 since it has a removeable 3rd member. I not sure if its an H190A, however but for my situation it really has no bearing.
It does not have the mileage option. It has an H38 and a carburated Z24.
The only question now is trying to assemble a list of possable vehicles to look for to find a 3.3.
Am I to understand that you are telling me that the only vehicle made with the 3.3 was the 720 pickup with the 2.0 engine.
I read somewhere that some 200xs may haxe had at least a similar high gear option???
I continue to remain hopeful that some member here on the forum will have what I need to sell me.

As far as I know, that statement is true, the only 720 that came with the 3.364 gears is the mileage option package 83-86 Nissan 720 with the Z20s engine.
I used to search the wrecking yards every weekend, I have only seen 2 720s with the 3.3 gear set, and I bought one of them, I have seen several 3.5 gear sets, I even found a 3.5 LSD in a 90 hardbody one day, but the 3.3 is a rare find even around here where there are usually several 720s in the wrecking yards around here on any given day.
I don't have any idea what the 200SX had for gearing, all I know about them is that I believe that the 1980?? 200sx had an H190 rear end with disc brakes.
As I said before, I have a 3.5 gear set in my 1969 DatsunKC diesel, it turns 3000rpms at 80mph with P195/75R14 tires, can you live with a 3.5 gear set, they are easier to find for sure, although I don't know how easy it is to find anything Nissan in your neck of the woods.

ibjman wrote:Thank you for all the good answers.
I'm reasonably sure it's an H190 since it has a removeable 3rd member. I not sure if its an H190A, however but for my situation it really has no bearing.
It does not have the mileage option. It has an H38 and a carburated Z24.
The only question now is trying to assemble a list of possable vehicles to look for to find a 3.3.
Am I to understand that you are telling me that the only vehicle made with the 3.3 was the 720 pickup with the 2.0 engine.
I read somewhere that some 200xs may haxe had at least a similar high gear option???
I continue to remain hopeful that some member here on the forum will have what I need to sell me.

Thanks to all for the help on this issue.
I was able to locate a 3.364 at an auto parts dismantler in the Midwest. $125 + $38 to ship it here.
Kind of pricey for my pocket but the only other 2 that came back on the online parts locator were $150 +.... so maybe I did ok? Now....just hoping it's a good one that doesn't whine like crazy or have a growling bearing in it!
I guess there's little to lose by just flopping it in, filling it with 85W90 synthetic and givin it a spin down the freeway!
By my calculations changing the old 3.889 to a 3.364 will give me a 14% change. Wish me luck!!!!
Regards, Ibjman

According to the prices at "PNP" in my area it would cost me $106.00 plus the environmental fee to walk out with one if I were to pull it myself, and as I recall I have never walked out with one for less than $120.00 except on a half off holiday, which it still costs over $80.00 out the door.
But when I pull it myself, I get to check it out first, I don't buy anything with more than an eighth inch slop/play at the pinion flange, I prefer less than a sixteenth inch play, and I get to look at the color of the fluid also, there is always a little fluid left even after they have drained it.

ibjman wrote:Thanks to all for the help on this issue.
I was able to locate a 3.364 at an auto parts dismantler in the Midwest. $125 + $38 to ship it here.
Kind of pricey for my pocket but the only other 2 that came back on the online parts locator were $150 +.... so maybe I did ok? Now....just hoping it's a good one that doesn't whine like crazy or have a growling bearing in it!
I guess there's little to lose by just flopping it in, filling it with 85W90 synthetic and givin it a spin down the freeway!
By my calculations changing the old 3.889 to a 3.364 will give me a 14% change. Wish me luck!!!!
Regards, Ibjman

Yes, I agree, 1/8" freeplay (backlash) would be a great deal more than acceptable especially if the post above is referring to an approx. at the pinion flange as I might guess.
Once the unit arrives I'll do my best to check it out before putting it in.
I would hope the backlash measured at a ring gear tooth would not be much more than .012"....certainly not. More than .016"?
And....one can tell very little about the condition of the pinion bearings untill it's installed and running, assuming of coarse that there's no side to side play at the flange and it doesn't obviously growl while turning by hand. I seriously doubt if it will have any preload torque left.
I might even consider tightening the pinion flange nut a very "wee" bit to add a tiny amount of crush to the collapsable sleeve within, but most likely not as that can be way overdone much too easily.
So, I'll check the backlash and run a tooth pattern on it and if it's anywhere near "good", I'll flop it in & give it a whirl. If I find a bad bearing, I'll just replace them all and then try to set it up as close to "correct" as I can.
Although I would prefer for it to be totally silent like the one installed now, I would not be too concerned about a light whine, assuming I had the knowledge that it was well put together and wouldn't be likely to explode a long way from home.
News at 11........
Regards, ibj....

Everything depends on the color of the fluid left inside the housing, if it is amber(golden) I can live with a small amount of play(backlash), it is very rare to find one with less than a 1/16 inch of backlash.
I hope since they are selling the gear set, that it is a good part.
I talk more about used parts like a backyard mechanic, I don't get all that technical sounding, I have had gearsets that had over a 1/4 inch slop at the pinion flange, and they didn't make a noise, and the fluid looked like crap, but they still lasted a long time, considering what I put them thru, I have worn out quite a few rearends over the last 25 years, this is just one example below of what I use my truck for, and I did this to non-dually axles also, I wore out at least 3 H190 gearsets, but I so far have never lost an axle bearing, there is such a thing as a miracle.

ibjman wrote:Yes, I agree, 1/8" freeplay (backlash) would be a great deal more than acceptable especially if the post above is referring to an approx. at the pinion flange as I might guess.
Once the unit arrives I'll do my best to check it out before putting it in.
I would hope the backlash measured at a ring gear tooth would not be much more than .012"....certainly not. More than .016"?
And....one can tell very little about the condition of the pinion bearings untill it's installed and running, assuming of coarse that there's no side to side play at the flange and it doesn't obviously growl while turning by hand. I seriously doubt if it will have any preload torque left.
I might even consider tightening the pinion flange nut a very "wee" bit to add a tiny amount of crush to the collapsable sleeve within, but most likely not as that can be way overdone much too easily.
So, I'll check the backlash and run a tooth pattern on it and if it's anywhere near "good", I'll flop it in & give it a whirl. If I find a bad bearing, I'll just replace them all and then try to set it up as close to "correct" as I can.
Although I would prefer for it to be totally silent like the one installed now, I would not be too concerned about a light whine, assuming I had the knowledge that it was well put together and wouldn't be likely to explode a long way from home.
News at 11........
Regards, ibj....

The Junkyard unit arrived via UPS today.
The markings on the unit from the dismantler indicate that it is a 3.364 and I checked that out as true.
I'm thinking that I may have come out ok on this one.
I measured the ring gear backlash at the outer edge and the unit appears "like new" with only .005" lash.

Next, I counted the axle splines found in the planetary pinion axle gears and I came up with 29.
Since I don't have my truck apart yet I don't know what spline count my axles are.

Last question is: Since it's out of an 83, can we assume it's an H190 rather than a later H190A? Is there any way to tell without disassembling the pinion bearings???
I'll post again when mine is out tomorrow. In the meantime I'll be happy to hear your comments.
OBTW: my truck is never loaded it's just a daily driver with a 2.4 and automatic. I may eventually use it to transport a motorcycle once or twice.....but that's it......so I don't anticipate any rear end probs. within my foreseeable future.
I'm almost 69 years now so not that many miles left in me.
Regards, Ibj...

I don't know what this H190A is that you speak of, I do know that all the H190 rearends in the trucks from the 1966 520 thru the 2wd 1986 Nissan 720 have 29 spline axles, I call them stump puller axles, I personally have never seen a broken one.
Later 4X4 720s came with the C200 rear axle, it has the rear access plate instead of a drop out pumpkin, the dually axle is also a C200, they share the same carrier.
The H190s in the Datsun cars and the Datsun 320 trucks have a different smaller axle with fewer splines, but these side gears can be changed out as needed, I have sold several 390 gear sets out of a 720 with the 320 side gears in them because 320 owners want better gearing like you do, the 320 came with 488 gears.
I would not have guessed you were 69, I myself am 58 for 2 more days.

ibjman wrote:The Junkyard unit arrived via UPS today.
The markings on the unit from the dismantler indicate that it is a 3.364 and I checked that out as true.
I'm thinking that I may have come out ok on this one.
I measured the ring gear backlash at the outer edge and the unit appears "like new" with only .005" lash.

Next, I counted the axle splines found in the planetary pinion axle gears and I came up with 29.
Since I don't have my truck apart yet I don't know what spline count my axles are.

Last question is: Since it's out of an 83, can we assume it's an H190 rather than a later H190A? Is there any way to tell without disassembling the pinion bearings???
I'll post again when mine is out tomorrow. In the meantime I'll be happy to hear your comments.
OBTW: my truck is never loaded it's just a daily driver with a 2.4 and automatic. I may eventually use it to transport a motorcycle once or twice.....but that's it......so I don't anticipate any rear end probs. within my foreseeable future.
I'm almost 69 years now so not that many miles left in me.
Regards, Ibj...

Thank you all for all the great posts about this axle issue. I installed it today and it all went off perfectly without a hitch. Preliminaey road test indicated that it works great with no abnormal noises.
In a couple of days, I'll get a longer road test while running a GPS to get an idea of how much the speedo needs adjusting. It was about 3% fast originally as is about standard for most factory stock cars....I'm guessing its about 8 - 10% slow now. Hopefully, there's a transmission speedo driven gear available to correct it.
Speaking about the transmission, I don't see many posts about automatics since a lot of "car" people prefer 4 or 5 speeds.
My newest issue is that the trans appears to make the 1 - 2 upshift way early.....changing to second very soon after departing from a stop...while the 2-3 shift appears normally.
I'll be looking more deeply into the exact forces that come into play that time the shift point....something that affects only the 1-2 upshift.......perhaps there's a spring in the 1-2 shift valve in the valve body that can be changed.
I expect I'll have to spend some time learning about the theory of operation on this tranamission before I can see what can be done.
Of coarse there's nothing in the aftemarket service manuals about the internals of the AT.
Wish me luck.
Thx, ibj...

I am happy it turned out good for you.
I don't know a lot about the Datsun/Nissan automatic transmissions, I have a couple for the A series B210/310 engines that I got with an engine, I put one of them in my MGTD, it seems to shift into second real fast also, so now I shift it manually in town, sounds cooler when I rev it up in first.

ibjman wrote:Thank you all for all the great posts about this axle issue. I installed it today and it all went off perfectly without a hitch. Preliminaey road test indicated that it works great with no abnormal noises.
In a couple of days, I'll get a longer road test while running a GPS to get an idea of how much the speedo needs adjusting. It was about 3% fast originally as is about standard for most factory stock cars....I'm guessing its about 8 - 10% slow now. Hopefully, there's a transmission speedo driven gear available to correct it.
Speaking about the transmission, I don't see many posts about automatics since a lot of "car" people prefer 4 or 5 speeds.
My newest issue is that the trans appears to make the 1 - 2 upshift way early.....changing to second very soon after departing from a stop...while the 2-3 shift appears normally.
I'll be looking more deeply into the exact forces that come into play that time the shift point....something that affects only the 1-2 upshift.......perhaps there's a spring in the 1-2 shift valve in the valve body that can be changed.
I expect I'll have to spend some time learning about the theory of operation on this tranamission before I can see what can be done.
Of coarse there's nothing in the aftemarket service manuals about the internals of the AT.
Wish me luck.
Thx, ibj...

Now if I could only find one of you that can sell me the YELLOW transmission speedo "driven" gear that originally cam
with that "high fuel mileage option" truck