1 ton 720

[Ratrod720]

I want to build a 720 4x4 with 1 ton axles and 38s. Would the truck be able to handle the loads put on it by such big tires?  Datsun T cases are pretty tough but this is still a really light duty pickup we're talking about. I can stiffen the frame so that shouldn't be a problem. I guess my main question is can the transmission (5 speed) and T case handle the stress of 38 inch tires with 5.38 gears. And no, this thing is not going to be a pavement princess.  

[datzenmike]

The tires don't put any stress on the engine. That would be a combination of how hard the engine works to pull the truck along with any load. T case and differential gearing multiply engine torque and the expense of top speed and a higher RPM. If you are constantly at or near full throttle then the gearing isn't right.  Compared to the 4.375 and 26" tires, 5.38 and 38" is geared a little higher. 6.00 differentials would match perfectly the stock gearing or smaller tires.

 

The Cab/Chassis option (with dual rear tires) is a 2wd long wheelbase frame rated at 1,700 pounds. Frames are good, it's the leaf springs and tires that carry the load and the Cab/Chassis has larger stiffer springs and can come with dual tires.

 

Just don't ever drive through a highway weigh station. No matter how you modify your 720 the GVW does not legally change. 

 

I had to do a Toyota SAS to get 33s on. You'll never get 38s on the front with stock front end.

[Ratrod720]

3 hours ago, datzenmike said:

I had to do a Toyota SAS to get 33s on. You'll never get 38s on the front with stock front end.

I'm guessing you mean stock front IFS. I'm going to put a dana 60 in the front. I'm also going to put spring hoops tied into the frame go through the hood. That is about the strongest suspension setup I could do. That would give me room for about a 48 inch coilover in the front. I'm ditching the leaf springs in the rear and replacing them with coilovers on hoops. I am trying to get a 30 inch coilover in the rear.   

[datzenmike]

Solid Axle Swap

[Ratrod720]

40 minutes ago, datzenmike said:

Solid Axle Swap

I know what SAS means. I just wasn't sure what you meant by stock front end. 

[Stoffregen Motorsports]

On 9/11/2023 at 5:57 AM, Ratrod720 said:

I want to build a 720 4x4 with 1 ton axles and 38s. Would the truck be able to handle the loads put on it by such big tires?  Datsun T cases are pretty tough but this is still a really light duty pickup we're talking about. I can stiffen the frame so that shouldn't be a problem. I guess my main question is can the transmission (5 speed) and T case handle the stress of 38 inch tires with 5.38 gears. And no, this thing is not going to be a pavement princess.  

Lower gears in the axles puts less strain on the t-case. So if you're running 5.38s in the diffs, the t-case takes much less loading than if you had 4.10s in the diffs.

 

Unfortunately the Nissan t-case is a pile of crap. The best way to build a crawler with Datsun/Nissan power is to figure out a t-case swap. I've gone over this a hundred times with my buddy who started Inchworm Gear. We've come up with a couple ways to get a good t-case behind an L or Z motor. One way is to use a T5 bellhousing. The T5 trans was available in the 1983 280ZX turbo, and they are hard to find, but if you had that bellhousing, you could run a number of different transmissions and have a few t-case options.

 

Another way to get a good t-case behind an L or Z motor is a divorced case. OTT in BC used to make a divorced adapter for the Toyota RF1A mini truck t-case, but they are no longer in business. A Sami case is too weak. Then there's the 205 divorced case, but it's massive. If you want double cases, you're going to be limited by wheelbase. Are you going to stretch the wheelbase?

 

It's been many years since we've discussed this, but I think there was an Aisin trans that was similar to the D21 trans. Which would make it possible to use a Hardbody trans and possibly Toyota t-case. You may have to mix/match bellhousings and tailhousings to get it to work, but if I recall, it's possible.

 

@]2eDeYe - you got any ideas?

[Stoffregen Motorsports]

I would figure out the t-case issue before you decide on a front axle. If the drop is on the wrong side, you're screwed.

[bottomwatcher]

4 hours ago, Stoffregen Motorsports said:

I would figure out the t-case issue before you decide on a front axle. If the drop is on the wrong side, you're screwed.

The 720 t case is divorced. Put any trans you want in front of it.

[Ratrod720]

18 minutes ago, bottomwatcher said:

The 720 t case is divorced. Put any trans you want in front of it.

That's what I thought to. Is there any issue with the 5 speed? I just rebuilt it. I don't really want to get rid of it. 

[Stoffregen Motorsports]

Right, it's divorced, but not a very good case. No gearing options and the front output is almost centered so driveshaft travel can be limited.

[datzenmike]

The 720 T case front output is in the middle so not much matter what side the front differential is off set to. It's just over 2:1 ratio

 

The stock 5 speed is more than strong enough for the Z24. If you want something twice as strong the 5 speed from a 240sx or D21 Hardbody KA engine is good. Bolts right up but length is different.

[]2eDeYe]

8 hours ago, Stoffregen Motorsports said:

Lower gears in the axles puts less strain on the t-case. So if you're running 5.38s in the diffs, the t-case takes much less loading than if you had 4.10s in the diffs.

 

@]2eDeYe - you got any ideas?

 

 

This is the way.

You can get low gears for the TX-10 T-case. Not sure if that is the same as the one in the 720.

You can get a hardbody 5-speed if the stock one goes. It is newer bigger better. 

[Stoffregen Motorsports]

15 hours ago, datzenmike said:

The 720 T case front output is in the middle so not much matter what side the front differential is off set to. It's just over 2:1 ratio

 

The stock 5 speed is more than strong enough for the Z24. If you want something twice as strong the 5 speed from a 240sx or D21 Hardbody KA engine is good. Bolts right up but length is different.

If it's in the middle, it will run into the engine oil pan or even the trans body at full compression.

 

Having the front output clocked up flat makes a nice clean underbelly without rock anchors.

[Stoffregen Motorsports]

13 hours ago, ]2eDeYe said:

 

 

This is the way.

You can get low gears for the TX-10 T-case. Not sure if that is the same as the one in the 720.

You can get a hardbody 5-speed if the stock one goes. It is newer bigger better. 

So you use the entire Hardbody 5 spd and TX-10 t-case? What gears and where do you get them?

[Stoffregen Motorsports]

Another concern here is horsepower. With 38's and a Z motor this thing will hardly push itself down the road, much less be able to hit the freeway. Trailer queen maybe?

 

The coolest thing about full width axles is not what most people think. Full width axles allow you to run a much lower ride height. Don't be afraid to trim the fenders a bunch, and maybe even the cab corners.

 

Lower is better.

[Ratrod720]

24 minutes ago, Stoffregen Motorsports said:

Another concern here is horsepower. With 38's and a Z motor this thing will hardly push itself down the road, much less be able to hit the freeway. Trailer queen maybe?

 

The coolest thing about full width axles is not what most people think. Full width axles allow you to run a much lower ride height. Don't be afraid to trim the fenders a bunch, and maybe even the cab corners.

 

Lower is better.

Yeah I'm going to cut the rear fenders so there inline with the wheel wells and trim the front fenders 6 inches all around.

 

EDIT: Yeah I know it is going to be pretty underpowered. I think I can drive it a couple miles to local trail heads, but I got a 2500 and a trailer so I can tow if I need to. 

[Stoffregen Motorsports]

Good. Sounds like you know what to expect.

 

Do you know what axles you're going to run? Ford one ton front D60 axles came with bigger brake calipers than Chevy had. Bigger rotors too. Be sure to upsize the brake master to 1" minimum or even 1 1/16". Wilwood has a 1" master that looks identical to the Nissan master and bolts right up too.

[Ratrod720]

6 minutes ago, Stoffregen Motorsports said:

Good. Sounds like you know what to expect.

 

Do you know what axles you're going to run? Ford one ton front D60 axles came with bigger brake calipers than Chevy had. Bigger rotors too. Be sure to upsize the brake master to 1" minimum or even 1 1/16". Wilwood has a 1" master that looks identical to the Nissan master and bolts right up too.

I was planning on using some form of superduty axles. Not sure though. It kinda depends on what I can get for cheap.

[datzenmike]

3 hours ago, Stoffregen Motorsports said:

If it's in the middle, it will run into the engine oil pan or even the trans body at full compression.

 

Having the front output clocked up flat makes a nice clean underbelly without rock anchors.

 

38s remember? It'll be up pretty high to clear them.

 

Other than the added weight of the rubber and the axle, 38s and 5.38 differentials are the same as stock tires and swapping from the stock 4.11 to a 3.70 differential. At 3,000 in forth it's 63 MPH now rather than 57 MPH. A 5.5 differential with 38s would perfectly match stock tires and gears.

[Stoffregen Motorsports]

Yes, but...

 

38's push a lot of air. They also weigh about 200 pounds apiece, mounted up.

 

And guys now days don't want to build them way up in the air. Lower is really the best way to build a crawler and guys now days understand that. Building low rigs is soooo much more difficult than building one that's a mile high. That's how I made my name in the business. Building low crawlers that worked well offroad, but also on the road.

[bottomwatcher]

Well here is my spare T 100 transfer case and C series trans. The current C series trans has had no issues for 19 years and the original transfer case at 250k miles behind the KAE is still going strong. There is zero aftermarket support for these gearboxes but you can get rebuild kits. These were once sought after because it only took 4 grade 8 bolts to make a double transfer case. Due to how rare they are you ar better of finding something more modern with parts support.

[]2eDeYe]

On 9/13/2023 at 8:03 AM, Stoffregen Motorsports said:

So you use the entire Hardbody 5 spd and TX-10 t-case? What gears and where do you get them?

There are a couple 

This is the first that comes to mind. 
https://calmini.com/detail.php?b=1&m=4&t=3&p=916&n=

NW Fab has a kit to put a Dana 300 behind one. Haven't really looked into that though being a Dana 20 guy lol 

Nissan T-cases have a large following outside the US as well so there may be more upgrades out there that I am unaware of. 🙂

[Stoffregen Motorsports]

2 minutes ago, ]2eDeYe said:

There are a couple 

This is the first that comes to mind. 
https://calmini.com/detail.php?b=1&m=4&t=3&p=916&n=

NW Fab has a kit to put a Dana 300 behind one. Haven't really looked into that though being a Dana 20 guy lol 

Nissan T-cases have a large following outside the US as well so there may be more upgrades out there that I am unaware of. 🙂

NW Fab makes some great stuff and I've used them in the past. But a D300 is much harder to find now days than they used to be.

 

3.92 gears would be a great upgrade, especially for a truck on 38s and a single case.

 

Any double case kits for Nissans?

[Stoffregen Motorsports]

Oh, the NW Fab kit is a doubler - https://ruggedrocksoffroad.com/nissan-hardbody-tx10a-to-d300-transfer-case-doubler-by-north-west-fab-30l-v6-4x4-1986-1997-p-36009.html

[Stoffregen Motorsports]

Stolen from the interweb - this guy is running the D300 upside down. Less leaking that way I guess!!!

 

Edited September 14, 2023 by Stoffregen Motorsports