Zombie Slayer: DNE2 Overdrive Install

[UMR_Engnr]

So I decided this box was too far gone, and instead of putting the money towards new bearings, fixing the shift fork, etc I decided to pick up a new box. I ended up snagging a US Gear Dual Range overdrive for a TH400. This new box appears to be pristine, has the speedo gear as well as the full wiring harness. I think I'm going to be making a manually switched harness, so I might be selling the original at some point. I also pulled a Bronco BW1356 transfer case with a flange output from the local pick n pull. The plan will be to use the flanged 1356, add a small stub shaft, replace my carrier bearing with the US Gear unit, and then run a new driveshaft.

 

[UMR_Engnr]

I just picked up another US Gear dual range box for a c6 with 4x4. So now I have a few options for this project. Here's the breakdown.

Option #1:
C6 --> BW1356 (flanged) --> new stub shaft --> US Gear --> new rear driveshaft
The US Gear would replace the carrier bearing in this setup.
Advantages:

• If the US Gear breaks I can easily remove it from the drivetrain.
• The TH400 2WD US gear boxes seem to be the most common, so it would theoretically be easier to get a replacement.

Disadvantages:

• Since it is after the transfer case I can't use it in 4WD mode.
• When in 4WD low mode it could be stressed more.
• Lower ground clearance (poorer breakover angle). It would hang about 5" below the frame right where the carrier bearing is now.

Option #2:
C6 --> US gear --> existing BW1356 --> shortened existing stub shaft to carrier bearing
Advantages:

• I can use the US Gear in 4WD mode to split my low gear.
• Less stress on the US Gear box in low mode.
• The BW1356 will get pushed back about a foot, which means that the lowest point on my vehicle (the t-case skid plate) will get pushed back, but it is still about 2 feet forward of Option #1.

Disadvantages:

• I think the BW1356 is going to hit the cab so I'll need to notch it or figure something else out.

Option #3:
C6 --> US gear --> NP205 --> new stub shaft to carrier bearing
Advantages:

• The NP205 is much shorter than the BW1356, so I don't think it will hit the cab.
• I can twin stick the NP205 and gain front dig capability. Not sure how useful this is (maybe @Dieselcrawler knows).
• The NP205 being a smaller case looks like it would actually improve the ground clearance on my truck.

Disadvantages:

• The NP205 has a gear ratio of 2:1 vs the BW1356 2.69:1.
• The NP205 input to front output distance appears to be about 3" shorter than the BW1356 which would put the front drive shaft out of alignment with the front diff. I'm not sure how much of a problem this would be.

 

[laserjock]

So here’s my 2 cents. 205 is a much stronger unit than a 1356. Several guys have used them. The one that jumps to mind is @junk So I don’t think there is an issue there. It’s a good idea to utilize the extra mount point because it’s much heavier.

There’s really no reason I can think of to be using overdrive in 4x4. So to me that’s a non-issue/ neutral item in the decision tree.

I like the idea of being able to use the more plentiful divorced parts. At least it sounds like that’s what you said.

Unless you are crawling the thing, the low range ratio probably also not an issue especially with the auto. You will in theory have full speed control with the brake pedal.

Don’t know if any of that is helpful.

 

[riotwarrior]

A bronco 1356 has a fixed flange rear yoke btw if that helps your decision making....

Psrsonally i would go C6/1356/OD because who really needs OD in 4x4....really..slow down drive in direct....

 

[UMR_Engnr]

I've already got all the parts for any of the options. I got the US gear for c6 4x4 pretty cheap on Friday. Figured they don't come up that often and I could always use it for parts. Although it could also show up and be completely trashed.

I've honestly not heard many complaints about the 1356 except the oil pump wearing through the case. I would mod that when I rebuild it.

Decisions, decisions.

 

[junk]

I'd skip the NP205 for a street rig. I've since removed my 205 and went to a 1356. The NP205 jams up in gear on icy mix type roads which is where I use 4x4 the most in my truck. The chain cases are easier shifting and don't jam up as easy.

Now if it's an off-road rig then sure use the NP205. And I'd definitely twin stick it. Low range independent of 4x4 I always thought would be super handy.

 

[hesutton]

I have a US gear UNDERDRIVE on my '86 F350. It is between the ZF5 and the NP208 transfer case. Underdrive and 4-low are really good combo for backing up the camper. But, with an OD US gear, it'd be really rare to need OD with the transfer case in 4x4. Not that there is anything wrong with putting it between the trans and t-case, but it wouldn't have a ton of functional advantage there.

Heath

 

[Dieselcrawler]

as for the front digs like you asked, my toy is twinsticked, i RARELY need to do front digs. unless you have a truck locker in the front, it really wont do much other than spin a tire with the least traction.

now for utilizing it as a 2 low, i never saw the need in a street rig. i put it in 4 low and dont lock the hubs..

 

[UMR_Engnr]

as for the front digs like you asked, my toy is twinsticked, i RARELY need to do front digs. unless you have a truck locker in the front, it really wont do much other than spin a tire with the least traction.

now for utilizing it as a 2 low, i never saw the need in a street rig. i put it in 4 low and dont lock the hubs..

Do you have a doubler or just the 205?

 

[UMR_Engnr]

I'd skip the NP205 for a street rig. I've since removed my 205 and went to a 1356. The NP205 jams up in gear on icy mix type roads which is where I use 4x4 the most in my truck. The chain cases are easier shifting and don't jam up as easy.

When you say jams up, do you mean it is hard to shift or somehow the driveline binds?

 

[Dieselcrawler]

203 box has been sitting on the shelf for years. Maybe onday I will build my doubler

 

[UMR_Engnr]

Turns out the box I just got was an underdrive even though I explicitly told the person how to turn the shafts and identify them.

Any idea on how much the underdrive boxes are typically worth? The box itself looks to be in good condition. Trying figure out what to do.

 

[junk]

My 205 wouldn't shift out of 4x4 if you weren't on pure ice or deep snow. The drive line would bind up the tranfercase pretty quick if it had too much traction.

 

[UMR_Engnr]

The seller and I came to an agreement on price, so I'm going to keep it for parts or to sell later. Looks like I'm back to option #1