Tcase gears D1 axle swap questions

[formercruiserhead]

I have seen you can change out the tcase high range gear in the LT230 cases. How come there isn't more guys doing this? It would be easier and cheaper than new diff gears.

Also do the D1 axles have the swivel type ends and the D2's have the booted open knuckle cv's? Would swapping the D1 axles into the D2 be beneficial or stronger? Thinking you could mod the swivel ball to compensate for caster on a bigger lift and maybe not doing the arms. Seems like an easy inexpensive way to get things dialed in.

 

[Devildog01]

If your going to do an axle swap you might as well just go with Toyota axles.

 

[fishEH]

Oh boy. Swapping TC gears only helps your high range. Diff gears help you in Hi or Low.
Clocking your swivel balls helps your castor but does nothing for your pinion. To be done right a D1 needs cranked radius to adjust pinion for a DC driveshaft AND clocked swivels for castor correction.

 

[Buddy]

If your going to do an axle swap you might as well just go with Toyota axles.

If you're going to do an axle swap you might as well go with 35 spline.

 

[Mongo]

You can get 35 spline toy stuff...stupid to do all that work for a D1 axle

 

[formercruiserhead]

Oh boy. Swapping TC gears only helps your high range. Diff gears help you in Hi or Low.
Clocking your swivel balls helps your castor but does nothing for your pinion. To be done right a D1 needs cranked radius to adjust pinion for a DC driveshaft AND clocked swivels for castor correction.

Yes I understand that that's why I said you can swap the high range. That is not an option with other brands. Kinda cool and can help on the road gearing. The low range is lower than most other brands already.

 

[Mongo]

you're right about the t-case...just a lot of work for very little gains. The HD D2 stuff is pretty good

 

[Leadvagas]

Oh, I don't know, I really like my 1.4 Defender case. Of course I live in the middle of the Rockies, so I go up hills a lot. It makes life with a 2.5 litre diesel more livable. With that said, it is a nitch item.

 

[Timmy!!!!!!!]

I have always enjoyed my 1.4 ratio Tcase also.

 

[Trevor]

The issue with swapping to a lower (higher number) t-case high range is that the difference between high range and low range is less. So your "lower low range than most" is not really true. I want to put 1:1 high range gears in mine, so when I gear the Dana 60s going into mine the low range will truly be a larger difference.

 

[Mongo]

If you want real low gearing get a Ashcroft Underdrive

 

[mgreenspan]

The issue with swapping to a lower (higher number) t-case high range is that the difference between high range and low range is less. So your "lower low range than most" is not really true. I want to put 1:1 high range gears in mine, so when I gear the Dana 60s going into mine the low range will truly be a larger difference.

???

You're gaining on low range by re-gearing the diffs. Lower low range than most stays the same because all the t-cases only change high ratio. Not low ratio. Your low to high ratio difference is less but compared to other brands' low ratios it stays the same. The ratio of your high range has zero bearing on the ratio of your low range. They are set gears and do not affect each other. The diffs affect the final ratio so they affect both.

I would wait to put that 1:1 in until you actually re-gear your Dana 60s. The stock diff gears with that ratio will not be enjoyable at all. I have a 1.003 t-case and it only works because of the super torquey at a very low rpm 3.5 liter mazda diesel. It doesn't work as well in the mountains at all with 31-32" tires. It was a struggle bus for the day I tried it with 255/85s.

 

[Trevor]

???

You're gaining on low range by re-gearing the diffs. Lower low range than most stays the same because all the t-cases only change high ratio. Not low ratio. Your low to high ratio difference is less but compared to other brands' low ratios it stays the same. The ratio of your high range has zero bearing on the ratio of your low range. They are set gears and do not affect each other. The diffs affect the final ratio so they affect both.

I would wait to put that 1:1 in until you actually re-gear your Dana 60s. The stock diff gears with that ratio will not be enjoyable at all. I have a 1.003 t-case and it only works because of the super torquey at a very low rpm 3.5 liter mazda diesel. It doesn't work as well in the mountains at all with 31-32" tires. It was a struggle bus for the day I tried it with 255/85s.

I think you maybe taking me wrong. The 3.32 low range of the lt230 is killer for a stock t-case. the thing no one looks at is when you change to a lower hi range gear set you no longer have the 3.32 ratio difference. The lower low range will not stay the same. if we use a 3.55 axle ratio for an example and a NP241 case for a comparison:


1.003x3.55=3.56
1.2x3.55=4.26
1.4x3.55=4.97
1.6x3.55=5.68
3.32x3.55=11.786


now the difference between:
(1.003)11.786-3.56=8.226
(1.2)11.786-4.26=7.526
(1.4)11.786-4.97=6.816
(1.6)11.786-5.68=6.106


NP241:
1.0x3.55=3.55
2.72x3.55=9.656


difference of:
6.106


So using a 1.4 ratio hi range is about the same as a t-case with a 1.0 hi, and a 2.92 low range. And using a 1.6 hi would be the same difference as a stock np241 with a 2.72 low.


I am just saying I would rather have that difference and gear the axles to what is needed/wanted with the 1.003 ratio, so then when I drop in low I have that greater ratio difference. a 1.4 hi just closes that gap and makes it less of a difference. Though if you don't plan on re-gearing axles I can see your point. I hope that helped. I am building from scratch when it comes to gearing so I have my options open. Mine is going to be off road 90% of the time, so when I re-gear it will be with plenty low gears. but all my money is getting tossed into my house remodel so my dana 60s are just sitting next to the disco waiting for attention right now

 

[Trevor]

If you want real low gearing get a Ashcroft Underdrive

If that is directed at me, yes that's my plan. As a doubler. I want my t-case to be 1.003, 2.7, 3.32 , 8.93. my last two rigs and different doublers and I liked having the choices

 

[Mongo]

Just a comment in general...

99.9999% of those wheeling a disco will never notice the difference in the t-case ratio when wheeling...and don't take this wrong, either will you. The difference is so minuscule that it doesn't matter either with a 1.2 or 1.4, or even the 1.003. What you will notice is how much of turd your truck will turn into trying to turn 35's with a 1.003 hi-gear. I've driven a D2 with 4.11's, a 4.6 and 35 and it was stupid. What does work is a Underdrive (turns your lt230 into a 4 speed t-case) in that scenario as you can use it when in hi and gives you basically a 1.4 ratio with the 1.003 hi gear. You'd need to put 5.13's in the diff to get anything that resembles reasonable road speed at a reasonable rpm

 

[fishEH]

Isn't most wheeling done in Low, which wouldn't be affected by a TC regear?
I had 4.12 diff gears, stock TC, and 315/75/16's in my 4.0 D1. It was fine. It was actually better than 3.54 gears with 265/75/16's which is pretty common.

Just a comment in general...

99.9999% of those wheeling a disco will never notice the difference in the t-case ratio when wheeling...and don't take this wrong, either will you. The difference is so minuscule that it doesn't matter either with a 1.2 or 1.4, or even the 1.003. What you will notice is how much of turd your truck will turn into trying to turn 35's with a 1.003 hi-gear. I've driven a D2 with 4.11's, a 4.6 and 35 and it was stupid. What does work is a Underdrive (turns your lt230 into a 4 speed t-case) in that scenario as you can use it when in hi and gives you basically a 1.4 ratio with the 1.003 hi gear. You'd need to put 5.13's in the diff to get anything that resembles reasonable road speed at a reasonable rpm

 

[Mongo]

I think Trevor's point was the difference when shifting from hi to low off-road...

 

[Jimmy]

I get what Trevor's doing, it's just not an approach most take. Most folks want to pay for either axle regear, or transfer case regear (and since it hasn't been mentioned, don't forget the pricey 4.3:1 or 5:1 low range gears that are out there) but not both. Not only is he willing to drop the coin on both, he's throwing in the underdrive to boot.

I wouldn't know what it's like to have that much disposable income...

 

[p m]

The issue with swapping to a lower (higher number) t-case high range is that the difference between high range and low range is less. So your "lower low range than most" is not really true. I want to put 1:1 high range gears in mine, so when I gear the Dana 60s going into mine the low range will truly be a larger difference.

And why would you want that, or think there will be any considerable difference?

Here's the compound transmission gear ratios from 1st low to 4th high in stock configuration (3.27low/1.22 high):

8.11 4.84 3.27 2.39 3.03 1.81 1.22 0.89

Your first-high gear is very close to the 3rd low, sounds like a very reasonable range overlap. By the way, 3.27/1.22 = 2.68, a very common range split for most commercial 4x4s.
The same with 1.4:1 high range ratio:

8.11 4.84 3.27 2.39 3.47 2.07 1.40 1.02

First-high gear is still close 3rd low, a little under it. The range split is 2.33 - much closer to the range split in many military-issue 4x4 and 6x6 trucks.

The same with 1:1 high range ratio:
8.11 4.84 3.27 2.39 2.48 1.48 1.00 0.73
Now your first-high is barely beyond fourth-low.

What this means in practice is this - if the trail goes from steep grade to nearly-flat often and your low and high ranges don't overlap, you'll go crazy going between t-case ranges (or start breaking stuff).

It is really splitting hairs as far as drivability goes, but if you are planning to put many miles on high and steep mountain trails (rather than jump a couple of rock piles), it makes a big difference.
And, as others mentioned, extra 15% in high range gearing makes a world of difference on mountain highways.

 

[formercruiserhead]

And why would you want that, or think there will be any considerable difference?

Here's the compound transmission gear ratios from 1st low to 4th high in stock configuration (3.27low/1.22 high):

8.11 4.84 3.27 2.39 3.03 1.81 1.22 0.89

Your first-high gear is very close to the 3rd low, sounds like a very reasonable range overlap. By the way, 3.27/1.22 = 2.68, a very common range split for most commercial 4x4s.
The same with 1.4:1 high range ratio:

8.11 4.84 3.27 2.39 3.47 2.07 1.40 1.02

First-high gear is still close 3rd low, a little under it. The range split is 2.33 - much closer to the range split in many military-issue 4x4 and 6x6 trucks.

The same with 1:1 high range ratio:
8.11 4.84 3.27 2.39 2.48 1.48 1.00 0.73
Now your first-high is barely beyond fourth-low.

What this means in practice is this - if the trail goes from steep grade to nearly-flat often and your low and high ranges don't overlap, you'll go crazy going between t-case ranges (or start breaking stuff).

It is really splitting hairs as far as drivability goes, but if you are planning to put many miles on high and steep mountain trails (rather than jump a couple of rock piles), it makes a big difference.
And, as others mentioned, extra 15% in high range gearing makes a world of difference on mountain highways.

Yes thank you that is what I am wondering. Why not make it so it can still get out of its own way on the road? I understand all about gearing, and swapping diff gears I have done many. Just seems like an easy and cheaper way to offset the bigger tires for the long trips I need to take to get to the good spots (1100 miles away). Dropping the tcase and putting in a $600 gear is much easier and cheaper than the diffs. (Ok everyone start telling me otherwise)