What is the better solution: super deep gears, doubler, or tcase gears

Lil'John

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Short: one of the three is available; super deep gears (5.86), doubler, or tcase gears. Why would you pick one over the other?

Long:
Setup: Big block cady(472), SM465, and 34mm split case in FJ55. Axles are Dana 60s with 3.54 gearing and rear steer. Front is getting Spartan locker, rear will get selectable locker(leaning toward OX) Tires are 35" and may go 37". Virtually zero highway miles. ~35 miles of Wentworth Springs to get to Rubicon(windy mountain roads).

I have a single set of 5.86 gears and an open carrier to go with them. I have to buy a selectable locker for the rear so cost of 'carrier split' will be a wash.

Use: Rubicon rock crawling. Snow plowing the yard. From previous wheeling with similar drivetrain(5.0L TBI, SM465, one piece case, 4.1 axle gears, and 35" tires), I found it not to be geared low enough. :(

In actuality, the doubler is off the plate since I've already got the SM465 to split case adapter but I would like to hear some logic on picking that. Last time I priced the Blackbox for split case, it was ~$1800. Not 100% certain it is available for 35 spline SM465. Which possibly puts getting another SM465. Length in an FJ55 isn't a concern nor is there a gas tank in the way issue ;)

The 'super deep' gear of 5.86 puts a pretty good limit on top speed; 3000 rpm gets me to about 55mph. But if I call the locker a 'wash' cost, I have to setup gears(~$300 each end) and cost of quality gears(~$250). So relatively speaking, it is a cheap fix to gearing. But it is a 'lot' of up front costs.

Going to AA gears takes out one gear setup and cost of gears. But it adds in cost of tcase gears(~$1k) and requires a new split case housing($300) plus machining of case(~$300 I think). The requirement of a new case is based upon the thinner casting of the 34mm case being a strength concern(transmission guy recommends 38mm) Side benefit is it gives a 10% underdrive so it brings the 3.54 gears to similar 'feel' as 4.1 gears.

I will temporarily run the 3.54 gears since they are setup but looking for some opinions.
 
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Short: one of the three is available; super deep gears (5.86), doubler, or tcase gears. Why would you pick one over the other?

Long:
Setup: Big block cady(472), SM465, and 34mm split case in FJ55. Axles are Dana 60s with 3.54 gearing and rear steer. Front is getting Spartan locker, rear will get selectable locker(leaning toward OX) Tires are 35" and may go 37". Virtually zero highway miles. ~35 miles of Wentworth Springs to get to Rubicon(windy mountain roads).

I have a single set of 5.86 gears and an open carrier to go with them. I have to buy a selectable locker for the rear so cost of 'carrier split' will be a wash.

Use: Rubicon rock crawling. Snow plowing the yard. From previous wheeling with similar drivetrain(5.0L TBI, SM465, one piece case, 4.1 axle gears, and 35" tires), I found it not to be geared low enough. :(

In actuality, the doubler is off the plate since I've already got the SM465 to split case adapter but I would like to hear some logic on picking that. Last time I priced the Blackbox for split case, it was ~$1800. Not 100% certain it is available for 35 spline SM465. Which possibly puts getting another SM465. Length in an FJ55 isn't a concern nor is there a gas tank in the way issue ;)

The 'super deep' gear of 5.86 puts a pretty good limit on top speed; 3000 rpm gets me to about 55mph. But if I call the locker a 'wash' cost, I have to setup gears(~$300 each end) and cost of quality gears(~$250). So relatively speaking, it is a cheap fix to gearing. But it is a 'lot' of up front costs.

Going to AA gears takes out one gear setup and cost of gears. But it adds in cost of tcase gears(~$1k) and requires a new split case housing($300) plus machining of case(~$300 I think). The requirement of a new case is based upon the thinner casting of the 34mm case being a strength concern(transmission guy recommends 38mm) Side benefit is it gives a 10% underdrive so it brings the 3.54 gears to similar 'feel' as 4.1 gears.

I will temporarily run the 3.54 gears since they are setup but looking for some opinions.
With you using the 465 transmission, I personally would go transfer case gears, and the 5.86's. I'm not a huge fan of doublers (although, if it's the only option, I would take it) and prefer the deep single case gears.
I would also plan a larger tire with dana 60's. I found 37's to not have enough clearance in the rocks.
 

Lil'John

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With you using the 465 transmission, I personally would go transfer case gears, and the 5.86's. I'm not a huge fan of doublers (although, if it's the only option, I would take it) and prefer the deep single case gears.
At this time, I can only go with only one. Plus, I'm not sure I see the point of going both or all three in this case ;)

This project is my 'ultimate giggles' build.

I would also plan a larger tire with dana 60's. I found 37's to not have enough clearance in the rocks.
I've heard a little bit of both. If I find it to be an issue, I'd clean up the bottom of the 60 first.
 

OldRocDoc

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I have run Dana 60, 5.86 gear sets for a number of years (15 actually), early with a doubler (203-205) and then lately with a TH400 and Atlas 3.8. As I am sure you know, the down side of the D60 5.86 is the incredibly small size of the pinion gear and the resulting minimum gear-tooth contact with the ring gear. After going through 5 R&P sets in 10 years in the rear, I finally gave up and switched to a GearWorks 10 in the rear. The original 5.86 in my front finally gave up last spring and has been replaced with a fresh 5.86.

If your goal is running the Rubicon and similar trails on 37's you should be able to keep the Ring & Pinion intact for a number of years. My driving style is, should we say, a tad bit more aggressive, and I use larger sticky tires:cool: As long as you realize the weakness in the 5.86 gears, that might be your best option.

And if you choose to go with the 5.86 gear sets, it is extremely important to have them set up correctly, with minimum backlash.
 

Lil'John

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I have run Dana 60, 5.86 gear sets for a number of years (15 actually), early with a doubler (203-205) and then lately with a TH400 and Atlas 3.8. As I am sure you know, the down side of the D60 5.86 is the incredibly small size of the pinion gear and the resulting minimum gear-tooth contact with the ring gear. After going through 5 R&P sets in 10 years in the rear, I finally gave up and switched to a GearWorks 10 in the rear. The original 5.86 in my front finally gave up last spring and has been replaced with a fresh 5.86.
Thank you for the experience. I knew the pinion got a little small. I hadn't read too many issues of blowing up sets.

I was giving some thoughts to running a Jana 76 setup in the rear(Dana 70 guts in a 60 housing) But the lack of an Ox locker option is somewhat giving me a pause on that route. I haven't talked to my gear guy yet to see if he does the Jana 76 work or if he would recommend the Ox locker. I do like the theory of a 'trail fix' lockability.

If your goal is running the Rubicon and similar trails on 37's you should be able to keep the Ring & Pinion intact for a number of years. My driving style is, should we say, a tad bit more aggressive, and I use larger sticky tires:cool: As long as you realize the weakness in the 5.86 gears, that might be your best option.
I'm an overly technical wheeler with an occasional 'giver-hell' moment. My 'rule' is three bounces and stop ;) I had no problem with stock mini-truck birfiends and course spline FJ40 pinions surviving behind a 5.0L and SM465 back in the day.

And if you choose to go with the 5.86 gear sets, it is extremely important to have them set up correctly, with minimum backlash.
My axle guy is Sean at River City Diff in Rancho. He's done me well for 20 years so I'll trust his work.
 
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I personally like dual cases for the gearing options it provides, which is why one is going in my current rig over deep axle gearing and the stock case. With the old rig, it was easy with Marlin dual cases and 4.7’s in the rear case. Stupid amounts of gear and low range options, but necessary with the little 4 bangers. When I ran the rubicon, I usually just used the 4.7 low range and left the first case/rangebox in 1:1. Cruise around in 2nd or 3rd, slow stuff used 1st. Anything more was just too slow for most of the trail. But at Johnson Valley, there were a lot of times when that real deep gearing came in handy.

With my current junk, i’m keeping the 3.73’s I have and running duals with an SM465, which should give highway-ish speeds and still a good crawl 1st gear with the small block. When I first got the truck, it had an SM465 with a 3 speed FJ40 case, and I felt like it wasn’t slow enough for what I wanted to eventually do with it. I then found a one-off Np203 - 19 spline split case adapter, so I got lucky but they’re still out there used if you look around and are patient.

Sounds like in your case the highway speed need isn’t there, so i’d go with the low geared axles since you’re already gonna be in them for lockers. If thats no bueno, look for the doubler or t-case gears.
 

Lil'John

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Cruiser Outfitters shows gear sets for the 34mm split case. Problem solved!?
When you machine out the 34mm case for 4:1 gears, it gets very thin or will peek thru :( My transmission guy doesn't recommend doing it at all.

I personally like dual cases for the gearing options it provides, which is why one is going in my current rig over deep axle gearing and the stock case. With the old rig, it was easy with Marlin dual cases and 4.7’s in the rear case. Stupid amounts of gear and low range options, but necessary with the little 4 bangers. When I ran the rubicon, I usually just used the 4.7 low range and left the first case/rangebox in 1:1. Cruise around in 2nd or 3rd, slow stuff used 1st. Anything more was just too slow for most of the trail. But at Johnson Valley, there were a lot of times when that real deep gearing came in handy.
Sort of what I experienced.

With my current junk, i’m keeping the 3.73’s I have and running duals with an SM465, which should give highway-ish speeds and still a good crawl 1st gear with the small block. When I first got the truck, it had an SM465 with a 3 speed FJ40 case, and I felt like it wasn’t slow enough for what I wanted to eventually do with it. I then found a one-off Np203 - 19 spline split case adapter, so I got lucky but they’re still out there used if you look around and are patient.
I already had one of the split case adapters ;) And I've gone through a few of the SM465 adapters/input gears. By the time you track down both, you are quickly into the price of a blackbox doubler.

The SM465 input gear/tranny output are one of the weak links of the whole setup. They have a habit of wearing out. I've seen one first hand and read more than a few accounts of the same issue. The other issue is the shifter staying engaged. Takes a bit of finesse to get it right.

FWIW, I got rid of the NP203 setup for a Blackbox ;) It currently sits in the 'hardcore' FJ55 build with 43s ;)

Sounds like in your case the highway speed need isn’t there, so i’d go with the low geared axles since you’re already gonna be in them for lockers. If thats no bueno, look for the doubler or t-case gears.
This is sort of my thought right now.
 
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Interesting on your experience with the split case doublers, good info to know. My NP203-Split case adapter came with a spare input shaft, spare case & internals, almost a spare of everything save the billet adapter itself. I also have a 2nd SM465 complete. I'll keep an eye on it all as the rig gets running, thanks for the pointers.
 

cruisermatt

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When you machine out the 34mm case for 4:1 gears, it gets very thin or will peek thru :( My transmission guy doesn't recommend doing it at all.
You’ve posted this before but it makes zero sense as to why it would be an issue on a 34mm idler shaft case vs 38. I’ve never seen anyone actually show the casting is “thinner”
There’s plenty of people wheeling 80-87 Land Cruisers out there

Other comments:
You don’t need to spend $300 to machine the case, you could spend 20 minutes with an angle grinder
Why do you need to spend $300 a diff to setup gears when you are just driving it an hour to the trail and home? Set them up yourself, it’s not hard
There, $1200 saved.
 

Lil'John

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You’ve posted this before but it makes zero sense as to why it would be an issue on a 34mm idler shaft case vs 38. I’ve never seen anyone actually show the casting is “thinner”
There’s plenty of people wheeling 80-87 Land Cruisers out there
@orangefj45 Would you take a moment here?

Other comments:
You don’t need to spend $300 to machine the case, you could spend 20 minutes with an angle grinder
Why do you need to spend $300 a diff to setup gears when you are just driving it an hour to the trail and home? Set them up yourself, it’s not hard
There, $1200 saved.
I'd rather pay ~$300 for machining than miss with the die grinder and have to spend another $300+ on a case... that is assuming I'm lucky enough to find a case that cheap. In addition, I end up with a clean professional job and a clean case half in hand.

Same as above except on gears. I could buy special equipment then spend hours on gears and pray nothing blows up. Or I can pay my expert to have it done correctly with no worry.
 

GLTHFJ60

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I'm a big fan of a doubler. For a long time I had 4:1 case gears and I found it was either too slow for rolling around on easy trails, or too fast for the big rock gardens. I bought the ecobox and NP205 from @mr jits and I'm a huge fan of of the options I have. I really like 2:1 low for buzzing around on the trails, and double-low is perfect with my 3.73 diff gears in any of the east coast rocks I've encountered. Keeping 3.73 diff gears retains my highway drivability.

There's no special equipment needed to set up gears, unless you don't already have a dial indicator on a mag base. If you don't want to do it yourself, that's fine, no excuses needed, but then the cost of paying someone else can't really be a negative.
 

Lil'John

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There's no special equipment needed to set up gears, unless you don't already have a dial indicator on a mag base. If you don't want to do it yourself, that's fine, no excuses needed, but then the cost of paying someone else can't really be a negative.
Cost can absolutely be a negative... I saw more than just a dial indicator from several videos. It is also time that I don't care to spend. As I noted, it is something I'd rather have 100% done correct and not a concern. The $300 is also a guestimate that I've seen thrown around.
 

HandForged

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Cost can absolutely be a negative... I saw more than just a dial indicator from several videos. It is also time that I don't care to spend. As I noted, it is something I'd rather have 100% done correct and not a concern. The $300 is also a guestimate that I've seen thrown around.
I always looked at it as an opportunity to learn something. Yeah you'll spend money on the tools if you don't have them and yes you'll likely have to do it a few times to get it right. However, it isn't rocket science and when you figure out how to set your own gears and differentials up you'll never have to pay anyone again to do it. Over the past 35 years I'm not sure how many I have done. Still use the same equipment i originally purchased to do it the first time. Knowledge and experience are what a lot of people are lacking these days. All they know is what someone else has told them or they have seen online. Go get the tools, figure it out and you'll be much better off for it.
 

GLTHFJ60

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I didn't mean to distract too much from the original question.

Which gearing solution depends on the intended use, and most importantly your transmission choice IMO. Want highway and big time rock crawling ability with a manual transmission? I think a doubler is the only way to do that. Auto? 4:1 transfer case with or without a doubler. Don't care about highway speeds at all? Super deep diff gears.

They all cost money. In my truck, a doubler is the way to go.
 

HandForged

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I'm building a lightweight rig with a small diesel and I'm going doubler, transfer case gears and a 5 speed with 4.88 gears in the axle.
 
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