620 rear axle vs 720

[TimmyG]

Could someone confirm that the 620 rear axle is narrower than the 720? I'm talking total width between wheel mounting surfaces, left to right. 

 

Also, what gear ratios came in the 620 rears? Honestly, the search function on here isn't great. Sorry.

[wayno]

What are you trying to do?

I know the later 720 Nissan trucks have wider axles than the early ones, I do not know if a 79 Datsun 620 axle is the same or different than a 1981 Datsun 720 axle(front disc brake versions), I also don't know if the 1973 Datsun 620 axle is any different than the 1979 axle.

I do know I am barely able to fit a 1986 Nissan 720 axle under my lowered 1966 Datsun 520 using the 1979 Datsun 620 disc brake rims/wheels, but the right tires have to be used, p195s will not work.

Just about any gear set will bolt into your 720 or the 620 axles as long as they are H190s, everything from 4.8 to 3.3, I have a set of 3.3 gears in my 1969 Datsun 521KC turbodiesel as it has the torque to turn them gears, I have 4.6 gears in my 521 work truck right now(used 4.8 gears once).

What are you trying to do?

[TimmyG]

1 hour ago, wayno said:

What are you trying to do?

I know the later 720 Nissan trucks have wider axles than the early ones, I do not know if a 79 Datsun 620 axle is the same or different than a 1981 Datsun 720 axle(front disc brake versions), I also don't know if the 1973 Datsun 620 axle is any different than the 1979 axle.

I do know I am barely able to fit a 1986 Nissan 720 axle under my lowered 1966 Datsun 520 using the 1979 Datsun 620 disc brake rims/wheels, but the right tires have to be used, p195s will not work.

Just about any gear set will bolt into your 720 or the 620 axles as long as they are H190s, everything from 4.8 to 3.3, I have a set of 3.3 gears in my 1969 Datsun 521KC turbodiesel as it has the torque to turn them gears, I have 4.6 gears in my 521 work truck right now(used 4.8 gears once).

What are you trying to do?

 

In the near future I would like to lower the truck and be able to tuck the rear wheels/tires. I don't want the tires to rub the bed sides or bed cut into the tires... I will static drop it at first, but later I may do airbag suspension and really slam it low. At that point I would for sure need the wheels/tires to tuck all the way behind the bed sides. 

 

Now I know you're gonna say just get the proper wheel offset/back spacing. Yes, but if I want to run 20+inch wheels they will likely be too wide no matter what offset. So I need to know my options on a narrower rear axle assembly. If a 620 is narrower and bolts right in, then awesome. Next question would be what gears ratios were available. So you're saying the 620s have an H190 housing like 720s? 

 

A whole-nother conversation is if I can't find acceptable 6 lug wheels I may also decide to swap to 5 lug toyota front hubs and address the rear somehow. Not sure if I could re-drill for the rear studs or need to swap in an actual toyota axle assembly. Then your talking fabrications for leaf mounts or 4 link. This would be worth considering when deciding if it's worth it to swap in a narrower datsun/nissan rear axle or not. 

 

Any idea what year 720s had the narrower rear end? Mine is an 84 2wd. 

[datzenmike]

620s are narrower than 720s, not much (maybe inch a side) but narrower. 

 

620 differentials...

'73-'74 automatics 4.625

'75-'79 automatics 4.375

'73-'78 4 or 5 speeds 4.375*

 

*'79 4 or 5 speeds have 4.11 but with optional 4.375

 

 

Datsun 6 lug is common to Chev, Ford, Mazda, Toyota, Trooper...... a lot more

[TimmyG]

45 minutes ago, datzenmike said:

620s are narrower than 720s, not much (maybe inch a side) but narrower. 

 

620 differentials...

'73-'74 automatics 4.625

'75-'79 automatics 4.375

'73-'78 4 or 5 speeds 4.375*

 

*'79 4 or 5 speeds have 4.11 but with optional 4.375

 

 

Datsun 6 lug is common to Chev, Ford, Mazda, Toyota, Trooper...... a lot more

 

This helps a ton. Thanks. Do you know if the 620 H190 axle housing bolt right up to the leaf springs and driveshaft yoke on the 720? And I'm assuming drums are the same. 

[wayno]

As far as I know all axles made from 1966 thru 1986 have the same spacing for the leaf mount perches, but the narrower axles have perches so close to the back plate that the leafs will become an issue with certain offset rims as the inside of the tire/rim could rub on the leaf springs.

This is likely why a lot of guys go to 4 link, they likely could run really wide rear rims/tires and still have them tucked inside the rear fender wells.

If you went 4 link you could also use the 1962 thru 65 Datsun 320 H190 rear axle which is 4 inches narrower, the leaf mount perches are also closer together but that would not matter if you were 4 linking it.

Edited September 18, 2019 by wayno

[TimmyG]

18 minutes ago, wayno said:

As far as I know all axles made from 1966 thru 1986 have the same spacing for the leaf mount perches, but the narrower axles have perches so close to the back plate that the leafs will become an issue with certain offset rims as the inside of the tire/rim could rub on the leaf springs.

This is likely why a lot of guys go to 4 link, they likely could run really wide rear rims/tires and still have them tucked inside the rear fender wells.

If you went 4 link you could also use the 1962 thru 65 Datsun 320 H190 rear axle which is 4 inches narrower, the leaf mount perches are also closer together but that would not matter if you were 4 linking it.

 

Thanks, Wayno. I had not thought of this at all with the leafs and wheel offset. Plus I dont know much about datsuns older than 720s and 620s 😁, not yet.

[datzenmike]

720/621/521/520 have the same frame and leaf spring spacing and all leaves may have different  camber and spring rates but same length.

[TimmyG]

6 hours ago, datzenmike said:

720/621/521/520 have the same frame and leaf spring spacing and all leaves may have different  camber and spring rates but same length.

That's pretty cool. Never knew this.

[Shasta Ratsun]

1983  720 wheel spacing ???

 

[Charlie69]

Centering pin holes in later 720 leaves are 2 1-4" farther back if I remember correctly.

[datzenmike]

720 4x4 springs have been put in 620s and it's never been mentioned. Interesting though.

[wayno]

Every once in a while someone talks about the pin holes being in the wrong place on the leafs, Mrbigtanker was one of them as I recall.

Edited October 19, 2019 by wayno

[datzenmike]

Never noticed. You could drill the top spring hole and shift the bottom leaves to match.

 

The 11/'82 and on 4x4 used a larger C200 differential that the earlier H-190. Maybe the spring perch was altered?

[Stoffregen Motorsports]

You should never drill a hole in a leaf spring. It will crack.

 

Better way is to have a spring shop make new main leaves and you can build the remaining leaf pack around that.

[wayno]

That leaf certainly is not the one you want cracking especially on a lowered truck where leafs may be removed to get even lower, that is the point of using these leafs on a 2wd truck after all, could lead to a very bad day.

 

[Charlie69]

I redrilled 2 bottom leafs on 85 4X4 sprin packs to center the axle in the wheel wells on my 66 520 that sits on a 80 720 2wd frame.  This just for building purposes and transporting around for various work to be done. Once I get to the point of driving this truck it will go to a local spring shop and have new leaves made to set the hieght of the truck where I want it.  The spring shop will set the pinion angle at the same time.