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H190 Differentials (w/Pictures)


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#1 Dime Dave

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Posted 27 November 2009 - 07:42 PM

The H190 solid (live) rear ends used in the Datsun cars and trucks had at least 3 different axle spline sizes/configurations and 2 different alloy center housings.


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The Datsun 320 pick-up uses an H190 rear end that is slightly different than the later Datsun 510 wagon, Roadster and 520/521/620 pick-up centers. The alloy case is lighter in construction with fewer ribs. I have been told (unverified) that the pinion gear shaft is smaller in diameter than the later H190 gear sets. This is a 4.875:1 ratio and weighs 31.5 lbs, as pictured above.



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Above is the alloy case center section used in the later Datsun 510 Wagon and Roadster. This is the same case as used in the 520/521/620 pick-ups and with a swap to the proper spline side gears it can be used in either a truck or car. This unit is a 3.889:1 ratio and weighs 35.5 lbs. as pictured.



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The 320 axle splines are unique to the axle splines in the later H190 differentials. The 320 axle splines are square in shape and have only 13 teeth.



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The Datsun 520/521/620 truck and the later model 200SX car H190 rearends used the large spline side gears shown here. The axles used with these side gears have 30mm diameter x 29 tooth splines.



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The Datsun 510 Wagon, Roadster and the some later model car H190 rearends used the small spline side gears shown here. The axles used with these side gears have 24mm diameter x 23 tooth splines.



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The drive flange on the 320 Pick-up center section is round as opposed to square on the 510 wagon and later P/U centers. The flange counter bore and bolt patterns are the same as the later H190 centers so there are no issues with drive shaft bolt up when swapping center sections.



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This is the drive flange for the later alloy case center section used in the Datsun 510, Roadster and 520/521/620 pick-ups.



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The alloy case center section used in the Datsun 320 pick-up measures 8 3/16" from the face of the drive flange to the mounting flange surface at the axle housing. This is 5/16" shorter than the later alloy H190 centers (8 1/2" long). I have used the 320 center with a drive shaft sized for the later H190 alloy center without any problems.



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These are the internal pinion gears, side gears, pinion shaft and differential case from a Datsun 320 Pick-up center section. The side gears on the 320 are course and square cut, not "V" shaped like the later small or large spline side gears.



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These are the internal pinion gears, side gears, pinion shaft and differential case from a Datsun 510 wagon center section. The side gears on the 510 wagon have the smaller diameter, "V" shaped spline. By swapping the side gears with those from another differential the center section can be reassembled and used that axle housing.

I swapped the side gears, pinion gears and pinion shaft (basically all the loose parts in the 2 pictures above) from the 320 center section with the parts from a 510 Wagon differential carrier to make a 4.875 rearend ratio center to go into my Datsun 1200 racecar with a 510 Wagon rearend. It worked slick and the 3.889 ended up with the the 320 side gears for highway use in a 320 P/U.

Mike Klotz did a great video on swapping side gears, which I watched before doing it myself. Very nice work Mike!
Link: http://tinyurl.com/yctus3l

Mike also has a thread on doing the side gear swap here on Ratsun.
Link: http://tinyurl.com/ykh5pss

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#2 datzenmike

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Posted 27 November 2009 - 07:49 PM

Dave, I seem to remember that some early H-190s also used non metric fasteners in them. Did you find this?
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#3 Dime Dave

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Posted 27 November 2009 - 07:58 PM

The ring gear bolts on the two differentials I swapped between were both the same thread. I assumed they were both metric, but they could have been both standard.

I didn't have any issues using metric tools to do the work, but again this isn't any guarentee of size where several wrenches are close enough to cross over like 13mm & 1/2" or 19mm & 3/4".

Mike Klotz may have the answer here.

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#4 yello620

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Posted 27 November 2009 - 10:59 PM

Very nice write up, thanks.
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#5 mklotz70

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Posted 28 November 2009 - 04:24 AM

Great write up Dave. I put a link to this thread on the other thread :)


As for the metric/sae bolts....I'm not positive, but it doesn't really matter....all the bolts stay with their corresponding parts. If you swap ring gears, I think there is an issue with bolt size. If I remember right, you have to drill out the holes depending on which way your swapping....ie, sae ring gear onto a metric carrier. I'm pretty sure it's info that datsunaholic has posted in the past.
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#6 Z-train

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Posted 28 November 2009 - 05:48 AM

Thanks for the write up.I'm looking to drop to a high 3 series gear in the 620 and go to a 3.36 in my 810 Wagon.I have a 79 810 coupe center section with 3.73s if someone has a trade in mind.
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#7 datzenmike

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Posted 28 November 2009 - 09:28 AM

So you have the 3.364 from a 720 for your goon?
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#8 Z-train

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Posted 28 November 2009 - 10:28 AM

So you have the 3.364 from a 720 for your goon?


I'm looking for a 3.36 gear(has 3.54s now) for the goon.AND i'm looking for a 3.89ish gear set for the 620.
The 3.73 810 coupe gear is mentioned as a possiible trade with a yet to be determined 2nd party.
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#9 datzenmike

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Posted 28 November 2009 - 11:02 AM

Find a late '83 to '86 720 with the 'Mileage Option' package which included the Z20 engine and 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. Thats the only 3.364 ratio H-190 I know of.

Most 720 2wd standards are 3.70 and autos 3.889 (3.90) H-190.
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#10 Z-train

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Posted 28 November 2009 - 12:15 PM

Find a late '83 to '86 720 with the 'Mileage Option' package which included the Z20 engine and 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. Thats the only 3.364 ratio H-190 I know of.

Most 720 2wd standards are 3.70 and autos 3.889 (3.90) H-190.


Hmmm,sounds like i'm looking for a 720 in a haystack.:mellow:

Just did some research.The 620 & 810 both use a H-190 rear.So.....I should be able to put the 3.54s from the wagon into the 620 housing.Correct?

Edited by Z-train, 28 November 2009 - 12:45 PM.

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#11 fisch

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Posted 29 November 2009 - 07:10 AM

Thanks so much for this info guys! I know it will come in handy when I deal with the 5.125 rear end in the '59!

#12 datzenmike

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Posted 29 November 2009 - 09:35 AM

Just did some research.The 620 & 810 both use a H-190 rear.So.....I should be able to put the 3.54s from the wagon into the 620 housing.Correct?


The wagon H-190 should long as the side gear splines match to the truck axle splines and the drive shaft flange bolt pattern is the same. The diff can be broken down and the side gears swapped. (see Mklotz's excelent write up)
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#13 benzo

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Posted 29 November 2009 - 09:40 AM

This is a very informative post. I had a question. so the roadsters rear diff is interchangeable to a wagon? also what are the gear ratios choices for roadster diffs and wagon diffs? I wanted to get more acceleration. I am using a zx trans currently with a stock rear end on my wagon and can get a center section from a roadster and I hear that can help with acceleration.

Thanks

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#14 Z-train

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Posted 29 November 2009 - 11:08 AM

The wagon H-190 should long as the side gear splines match to the truck axle splines and the drive shaft flange bolt pattern is the same. The diff can be broken down and the side gears swapped. (see Mklotz's excelent write up)


Cool.Now i need to decide if i want to go as low as 3.54s in the 620.WIth a LZ-23 and a truck 5-speed,it should still have some grunt left.
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#15 datzenmike

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Posted 29 November 2009 - 11:32 AM

Compared to a higher ratio 3.90 rear end, a lower ratio 3.70 diff will give poorer acceleration, highest top speed and the best mileage economy by having lower RPMs at the same speed.

Compared to a lower ratio 3.70 rear end, a higher ratio 3.90 ratio will have better acceleration, lower high speed and least mileage economy because of higher RPMs at the same speed.

Example

You have a stock standard tranny goon with stock 3.70 rear end ratio and you swap an automatic goon 3.90 rear end in. You are out for a drive and come up beside an identical standard tranny goon with 3.70 rear end in it. You both drive up to a speed of 75.289 MPH and look at your tachometers. The other car with the 3.70 rear end reads 4,000 RPMs while yours reads 4216 RPMs.

If you both were to accelerate hard, you would have the advantage of your motor already revving slightly higher and presumably making slightly more horse power and torque at the same speed. Going from 3.70 to 3.90 isn't that much of a change and would be most noticeable in first gear take offs.

Lets look at changing to a 4.10 rear ratio. Same scenario as above but you have a 4.10 rear ratio and are going 75.289 beside the other goon. While he is revving exactly 4,000 RPMs, you are revving 4,433 or over 400RPMs higher with a resultant greater increase in power and torque!

Same speed as above but with a 4.375 ratio rear end. You will be revving 4,730 RPMs or over 700 RPMs higher. Big performance difference.

Edited by datzenmike, 29 November 2009 - 11:47 AM.

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#16 Z-train

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Posted 29 November 2009 - 12:26 PM

If i remember correctly,the truck 5-speed has a .8 something OD.So some calculations are in order to see where that put RPMs at 80 MPH.I'm trying to split hairs here and get a happy medium.Being able to run at freeway speeds(80 MPH) and still having some grunt to pull things with.
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#17 datzenmike

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Posted 29 November 2009 - 12:43 PM

Sorry Bill that was for a benzo's 510 goon, stock tires with 4 spd.

I can work out the 620 speeds/RPMs if you know your tire size and year tranny used. There were two different o/d ratios used but very close.

Edited by datzenmike, 29 November 2009 - 12:47 PM.

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#18 Jason

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Posted 29 November 2009 - 12:46 PM

Mike, I wasn't aware that the auto and manual 'goons had a different ratio for the rear end. Are you sure about this?
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#19 benzo

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Posted 29 November 2009 - 01:22 PM

thanks Mike for the info. that helps a lot and confirms what I have been reading and understanding.

#20 datzenmike

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Posted 29 November 2009 - 01:49 PM

Ah, maybe not in N AM. For 510 I'll defer to someone who has one. I have an old manual from the '60s and it lists 3.70 and 3.90 for the goon. I always thought the strange wording was a translation thing. So... 3.90 then?
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