Ramblings about doubler options (2 Viewers)

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DangerNoodle

DangerNoodle

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Right, before I get laughed off this forum, I really have no clue if this would be possible to do, or practical. It is just a random idea bouncing around in my limited number of brain cells. My current build does not have a crawl ratio that I am satisfied with (60:1). It is in an FJ40, WB is roughly 98". Not much room for a long drivetrain. The current drivetrain I have is a SBC ->NV4500->AA 16 spline adapter->16 spline T-Case. I know I have some options just to lower the ratio, like the Orion, but I don't want to always have a 4:1 low as soon as I shift. To me, a doubler would be the best option, as I can double the low when I need it, while still having a very useable low for hopping between obstacles. Plus, it's cool. I have a 38MM split case to use for a blackbox, my only problem is driveline length at this point. I'm thinking the blackbox would be around 7"-8", but I'm not really sure. Since the BB to NV needs to be attached to the long tailhousing of the NV, adding another ~8". My NV output shaft has been trimmed for the AA adapter, and I am wondering if It would be possible to make a new, stubby tailhousing that replaces my AA adapter, and then allow the BB to bolt on.

Anyway, that is my incoherent rambling for the day.

Thanks,
-Noodle
 
It already exists. The blackbox/ecobox will bolt straight up to the NV4500 assuming you have the correct input shaft on the blackbox. The NV4500 4wd tailhousing has the 6 bolt round pattern that's common to everything else.

 
GLTHFJ60 said:
It already exists. The blackbox/ecobox will bolt straight up to the NV4500 assuming you have the correct input shaft on the blackbox. The NV4500 4wd tailhousing has the 6 bolt round pattern that's common to everything else.

Click to expand...

The problem is I can't really use the long NV tailhousing for the added length. I'm looking at making a custom, shorter tailhousing/adapter to the blackbox.
 
What's long about the 4wd tailhousing? Much shorter and you'd lose 5th gear. Most of the spline in the output shaft is used by the mating gear, so you might be able to gain 1/2" or 1" with a custom tail housing?

Just to make sure we're on the same page, this is the NV4500 4wd tailhousing I'm talking about:

1605799456489.png


NV4500 with tail housing removed. There's very little room to make that tail housing shorter.

1605799529677.png
 
GLTHFJ60 said:
What's long about the 4wd tailhousing? Much shorter and you'd lose 5th gear. Most of the spline in the output shaft is used by the mating gear, so you might be able to gain 1/2" or 1" with a custom tail housing?

Just to make sure we're on the same page, this is the NV4500 4wd tailhousing I'm talking about:

View attachment 2500170

NV4500 with tail housing removed. There's very little room to make that tail housing shorter.

View attachment 2500172
Click to expand...

Yep, you are right. I didn't remember the gears taking up that much space.
 
i think the tailhousings are already as short as they practically can be because you need the room to thread nuts onto the doubler/Tcase mounting studs.
 
It's an interesting idea. Would need a CNC mill to make such an adapter easily, with a pocket for the 5th gearset, a bolt pattern, and a sealing surface for the transfer (or doubler) input gear. Your space to gain would be dictated by how long the snout is on the mating gear in the transfer (or doubler) and how much spline you have left on the output shaft.

The big constraint though is that you still need room to get to the studs or bolts to bolt the transfer (or doubler) to the transmission. Most of these things like the blackbox have threaded studs that stick through the tailhousing where you thread nuts on. Can't make the mating surface flush with the pocket for the gears. Could make it tighter though.

EDIT: Matt beat me to it.
 
cruisermatt said:
i think the tailhousings are already as short as they practically can be because you need the room to thread nuts onto the doubler/Tcase mounting studs.
Click to expand...

I'd think so. I'm just really looking for a way to stuff a doubler in here.
 
GLTHFJ60 said:
It's an interesting idea. Would need a CNC mill to make such an adapter easily, with a pocket for the 5th gearset, a bolt pattern, and a sealing surface for the transfer (or doubler) input gear. Your space to gain would be dictated by how long the snout is on the mating gear in the transfer (or doubler) and how much spline you have left on the output shaft.

The big constraint though is that you still need room to get to the studs or bolts to bolt the transfer (or doubler) to the transmission. Most of these things like the blackbox have threaded studs that stick through the tailhousing where you thread nuts on. Can't make the mating surface flush with the pocket for the gears. Could make it tighter though.

EDIT: Matt beat me to it.
Click to expand...

One of my friends has access to a really good shop that could probably do that. I'm just wondering if it would even be practical to attempt it.
 
I may have a lead on an old AA rock box. 5" long, and it would drop into my current drivetrain. Any thoughts? My only worry would be parts at this point.
 
DangerNoodle said:
I may have a lead on an old AA rock box. 5" long, and it would drop into my current drivetrain. Any thoughts? My only worry would be parts at this point.
Click to expand...

Man made parts, man can make more parts
 
Doublers in 40s are always tough unless you're moving the rear axle back a ton.

Move your engine as far forward as you can to make room for the rear driveshaft, and run whatever doubler you can find.
 
GLTHFJ60 said:
Doublers in 40s are always tough unless you're moving the rear axle back a ton.

Move your engine as far forward as you can to make room for the rear driveshaft, and run whatever doubler you can find.
Click to expand...

Pretty much what I am doing. I can move my rear axle back more, but then I have to readjust my fender wells.
 
GLTHFJ60 said:
Doublers in 40s are always tough unless you're moving the rear axle back a ton.

Move your engine as far forward as you can to make room for the rear driveshaft, and run whatever doubler you can find.
Click to expand...

Do you know of any other doubler options? I've heard about people using the minitruck doublers on 40's, but I have no clue how people adapt them.
 
DangerNoodle said:
Do you know of any other doubler options? I've heard about people using the minitruck doublers on 40's, but I have no clue how people adapt them.
Click to expand...

NWF, Titan, Atlas, NP203
 
Personally, I'd look at the Orion since you already have the case. An atlas is obviously another option.
Driveshaft lengths are a serious issue in a 40 with a doubler. I went through 3 iterations of suspension trying to fit a doubler, and finally gave up that idea and went with an atlas.
I think I had some of the same hesitation as you in regards to gearing choices, but there's a reason your transmission has multiple gears. You don't have to be at super crawl speed all the time, as you can simply use 3-4 for normal trail driving, and 1-2 for technical stuff
 
mr jits said:
Personally, I'd look at the Orion since you already have the case. An atlas is obviously another option.
Driveshaft lengths are a serious issue in a 40 with a doubler. I went through 3 iterations of suspension trying to fit a doubler, and finally gave up that idea and went with an atlas.
I think I had some of the same hesitation as you in regards to gearing choices, but there's a reason your transmission has multiple gears. You don't have to be at super crawl speed all the time, as you can simply use 3-4 for normal trail driving, and 1-2 for technical stuff
Click to expand...

I think I can get about a 19" driveshaft in the rear with a doubler right now. I'm not super sure though.
 
Lil'John said:
Look at the Mud tech articles for FJ40 and prototype NP203 by Dan (I forget his last name) He ran a V8, SM465, NP203, and one piece case in a minimally modified FJ40. I got to go on one of the prototype runs with him. I also got to do the same install twice in FJ55s.

Here are some comparisons numbers to get from SM465/NP203 to NV4500/Blackbox:
Bellhousings - same length between the two
Main case - SM465 12.0" and NV4500 12.5"
NP203 adapter - SM465 4.625" and around 6.25" for NV4500
NP203 housing vs Blackbox - NP203 6" vs blackbox of 5.75" with split case adapter
NP203 adapter - ~1" or 1.25"... the longer is for the split case

NP203 number from here:

NP203

www.offroaddesign.com www.offroaddesign.com

The Blackbox is one I physically have measured.

Yes, I've had all of the above in my hands and at various points in rigs.

I would avoid ANY NP203 based doubler like the plague. They add a TON of slop to the drivetrain. The shifter in my experience has problems staying in gear(two different rigs) I swapped out an NP203 to a plain split case behind an NV4500. The split case will be getting a set of AA gears.

My Blackbox is behind a 4l80.

Don't get hung up on "more gear splits" argument on why to go to a doubler. Your NV4500 has more than one gear.
Click to expand...

The only thing I like about the doubler is the lower low. With the Rockbox I'm looking at, it will be right about 200:1 in first, vs an Orion at 115:1 in first.
 
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