Dual Case Questions

[jkeith.w]

During the short-lived dual-case group buy thread I posed some questions that I never got answered, and since I'm keenly interested in this, I'm revisiting them here:

1. I was told that I shouldn't run 4.7 in the front case. Why is that?

2. There seems to be some lack of confidence in Trail Gear gears - has there been a history of documented failures? (I've read build threads that use these parts with success, I think?)

Feel free to add questions/answers here - I'll certainly have more as I get further into this.

 

[JWaldz]

During the short-lived dual-case group buy thread I posed some questions that I never got answered, and since I'm keenly interested in this, I'm revisiting them here:

1. I was told that I shouldn't run 4.7 in the front case. Why is that?

2. There seems to be some lack of confidence in Trail Gear gears - has there been a history of documented failures? (I've read build threads that use these parts with success, I think?)

Feel free to add questions/answers here - I'll certainly have more as I get further into this.

1) I mentioned not to run 4.7's in a front case with stock 2.28's in a rear case. Regardless, you wont be able to run 4.7's in a front case if you keep your factory case, as it's chain driven and they can't be upgraded. The reasoning to this is similar to running different gear ratios in your front and rear diffs.

2) Trail Gear is known for making parts cheaply, which in return allows them to have such "great prices". Just cus they say a part is chromoly doesn't mean they used the highest (or even mid) quality available.

 

[Sean K.]

During the short-lived dual-case group buy thread I posed some questions that I never got answered, and since I'm keenly interested in this, I'm revisiting them here:

1. I was told that I shouldn't run 4.7 in the front case. Why is that?

2. There seems to be some lack of confidence in Trail Gear gears - has there been a history of documented failures? (I've read build threads that use these parts with success, I think?)

Feel free to add questions/answers here - I'll certainly have more as I get further into this.

1) b/c the torque multiplication is far beyond what the stock case is rated for and it *could* conceivably cause it to break.

2). TG generally sells lower quality at a lower price. Look around on Pirate for more info.

 

[jkeith.w]

1) I mentioned not to run 4.7's in a front case with stock 2.28's in a rear case.

sorry man, couldn't remember who it was after the thread was deleted.

 

[jkeith.w]

so no one runs 4.7/2.28?

 

[Sean K.]

so no one runs 4.7/2.28?

People have.....but none of the manufacturers recommend it in that order.

I ran 2.28 then 4.7 in my 91....and will be doing the same in my new cases in the '99 T4R.....but I'm swapping the whole front end to an FJ80 solid axle....so I'll be able to run gear driven, passenger drop cases.

 

[IBallEngineer]

so no one runs 4.7/2.28?

It's like pushing an egg with a hammer, you "could" do it, but odds are pretty good you are going to break the egg.
Putting the 2.28 first is more like pushing a 8oz hammer with a 12oz hammer. It could still break, but it's not likely.

 

[jkeith.w]

so, stuck with 2.28/2.28 unless one wants to swap Tcases, then?

 

[Tyler James Inc]

1) I mentioned not to run 4.7's in a front case with stock 2.28's in a rear case. The reasoning to this is similar to running different gear ratios in your front and rear diff.

I don't think it's similar to that at all.
You don't wanna run different gear ratios in your diffs, because the tires will be trying to turn at a different rate- causing a constant bind.
It's recommended to run the 4.7 gear set in the rear case, because of the way the lower gear set multiplies the torque output; having the 4.7 gear set in the front case puts more stress on the rear case.

I don't like to support Trail-Gear because they're guys from All-Pro and Marlin that took ideas from each company and started their own shop. Is that wrong? Maybe not. But I'm a Pirate guy, and there was a lot of drama when Trail-Gear started, and it was pretty clear they(TG) stole ideas and designs from Marlin/AP. To add to that, a large percentage of their products are made in China- or from material that comes from China.

For myself, the additional cost to buy Marlin is nothing. His quality is far better, and it's just a shop I would much rather support. Being made 100% in the US is huge to me as well.

From their flame logo to their made in China parts- Trail-Gear is just cheesy to me.

On my 2nd gen 4Runner, I did a 3.0/auto to 3.4/manual swap, and did a flat-belly 4cyl dual case setup behind it.
Inchworm Gear 10* clocked V6 to RF1A case adapter
Marlin 23 total spline 2.28 input
Marlin 23 spline dual adapter
Marlin 23 spline 4.7XD gear set in the rear case
I would have used a Marlin V6>RF1A, but I happened to be ready to buy when Inchworm had a killer sale on it. I have no complaints on the Inchworm either- it was a nice adapter.

The only thing I've bought from TG is the Tacoma PS lines to make the 3.4 PS pump work with the IFS steering box. My buddy is a dealer, and it was just easy.

 

[jkeith.w]

It's recommended to run the 4.7 gear set in the rear case, because of the way the lower gear set multiplies the torque output; having the 4.7 gear set in the front case puts more stress on the rear case.

How is that expressed mathematically? (math-challenged over here)

 

[jkeith.w]

ok, found this ratio calculator.

(so 2.28/2.28 with 4.10 gives you 21.31:1?)

but that doesn't really tell me what a 4.7 front case presents the factory case in terms of torque..

 

[jkeith.w]

On my 2nd gen 4Runner, I did a 3.0/auto to 3.4/manual swap, and did a flat-belly 4cyl dual case setup behind it.
Inchworm Gear 10* clocked V6 to RF1A case adapter

Does clocking affect the shifter position?

 

[ajordan1975]

Does clocking affect the shifter position?

yes.

 

[IBallEngineer]

How is that expressed mathematically? (math-challenged over here)

2.8:1 Ratio vs 4.7:1 Ratio, with force being equal

With the first, the torque output is 2.8 * the force input. So if you are driving at 100 ft lbs, the output of the first case is 280 ft lbs.

With the second ratio, the torque output is 4.7 * the input. At 100 ft lbs that is 470 ft lbs.

The actual torque is MUCH higher because the input is already multiplied by the transmission gear, say 2.7 in an automatic. So the first case would put 756 ft lbs. into the rear case. with the 4.7 in front that number is 1269!

It's early, hope my math is correct.

 

[JWaldz]

I don't think it's similar to that at all.
You don't wanna run different gear ratios in your diffs, because the tires will be trying to turn at a different rate- causing a constant bind.
It's recommended to run the 4.7 gear set in the rear case, because of the way the lower gear set multiplies the torque output; having the 4.7 gear set in the front case puts more stress on the rear case.

Well, similar in a way that you don't want to run either of these scenarios because of opposing forces. Otherwise, it was a bad comparison lol! :becky:

 

[jkeith.w]

So in my case, we'd need to know max torque of engine, as well as first gear ratio (5 speed), right?


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[Snowy21]

During the short-lived dual-case group buy thread I posed some questions that I never got answered, and since I'm keenly interested in this, I'm revisiting them here:

1. I was told that I shouldn't run 4.7 in the front case. Why is that?

2. There seems to be some lack of confidence in Trail Gear gears - has there been a history of documented failures? (I've read build threads that use these parts with success, I think?)

Feel free to add questions/answers here - I'll certainly have more as I get further into this.

1. I've run 4.7's in my front case for years with no issues as have many other people who want to retain LH drop stock case. Super common, especially in Tacoma circles. If you are going duals, get a 4.7 crawler, you won't regret it.

2. FWIW I have had a TG crawler for a couple of years and no issues or leaks. I think some of the newer inchworm and marlin stuff is better but they used an incorrect bearing for a long time that would strip the input of the rear case because of fretting. I wanted to go inchworm or marlin but I couldn't get a time out of them. Expect to wait close to a year for marlin and supposedly inchworm is better now, but I waited two months and said screw it. Ordered a TG crawler on Monday and had it complete on Thursday.

 

[Snowy21]

1) I mentioned not to run 4.7's in a front case with stock 2.28's in a rear case. Regardless, you wont be able to run 4.7's in a front case if you keep your factory case, as it's chain driven and they can't be upgraded. The reasoning to this is similar to running different gear ratios in your front and rear diffs.

Incorrect, your tcases don't care what the other one is running. You can put whatever ratio you want in front of another case with whatever ratio you want. They operate independently.

Super easy to pick up a top shift tcase from an old 4Runner or pickup, stuff 4.7's in the reduction section and use whatever adapters you please to install in front of your chain drive case.

 

[jkeith.w]

It's recommended to run the 4.7 gear set in the rear case, because of the way the lower gear set multiplies the torque output; having the 4.7 gear set in the front case puts more stress on the rear case.

So my next question, of course, is: what breaks? There is no spreading/exploding of the case with chain-driven (no gears pushing apart), and similarly, the force isn't focused on the meshed gears - so what is the failure mode? Snapping shafts torsionally?

 

[rkntoy]

So my next question, of course, is: what breaks? There is no spreading/exploding of the case with chain-driven (no gears pushing apart), and similarly, the force isn't focused on the meshed gears - so what is the failure mode? Snapping shafts torsionally?

Generally what breaks is the input on the stock transfer case.

And looks like people are mixing and matching transfer case ratios. If you are planning on doing a dual transfer case and retaining your stock chain-drive t-case the gear ratio in the stock case is 2.56:1. The gear drive cases came stock with 2.28:1 gears which can be swapped to 4.7:1. There are no options to regear the chain-drive case that I know of.

I have friends that run 4.7 gears in their reduction box and they have been fine. Most of the t-case destruction I have seen has been triggered by either too much horsepower for setup or shocks to the drivetrain from immediate transition from spinning fast to stopped. I know my 2.7 most likely won't lead to a breakage from too much horsepower and I do not try to skinny pedal/bounce my way through obstacles. So I am considering the 4.7 but it will probably come down to money.