When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'm in the process of designing and fabricating a brace/mount for the NP231 in my XJ. I'm motivated to add this brace/mount as I'm installing a Northwest Fab 231 based Doubler (Eco box) in front of my "built" (6 pinion, wide chain and 2 low) the NP231. This is also needed as I'm relocating my parking brake up to the transfer case.
As I'm fully aware that the NP231 isn't a particularly strong transfer case, I analyzed NP231 failures and they all seem to be case related (almost never due to the internals failing). What I noticed was all of the failures seem to be at the "joint" of the planetary and chain sections of the case.
What this leads me to believe is that the failure comes from the rear of the case "torquing" over and cracking. With this in mind, I am of the opinion that by adding a steel brace which "sandwiches" the front and rear of the case together and removes this torsional load, the NP231 "should" become much more reliable. It certainly won't ever be an Atlas or Dana 300, but good enough for what I do.
I ordered the doubler with a mount/support which mounts between the doubler and transfer case:
In order to mount the doubler support, I will be building a new transmission/transfer case crossmember and transmission mount. I plan to us a single GM poly mount on the crossmember. On top of the poly mount, I will make a single plate which connects the transmission, doubler and transfer case as one "unit". The idea being that by tying all three together, there can't be any "twisting" occurring over their length.
As far as the transfer case brace/mount, here is what I've go thus far (have to get steel tomorrow):
- rear of transfer case:
- brace/mount template:
- template on case:
As you can see, the concept is to mount the brace using the case bolts. The brace will then extend down to the trans/doubler/np231 mount making everything a single unit.
My inspiration for this brace comes from the C5 (corvette) differential braces which are used on high HP C5s to keep from cracking the transaxle:
Just as I'm attempting to do with my brace, the C5 transaxle brace bolt to the exterior of the case and prevent the case sections from twisting, thereby preventing them from cracking.
I'm not interested in replacing the NP231 at this time (not willing to spend several thousand dollars on an Atlas), just looking for suggestions on my design/plan and would appreciate any input on how I might improve my concept.
Thanks,
Chris
Last edited by CLSegraves1; 01-01-2019 at 06:15 PM.
Engine: 4.3L with headers and full 3" exhaust system
A good idea I think, that 231 will hang out quite a ways from the trans. What are your plans for the ebrake. A guy named Parts Mike has one for the Advance Adapters SYE kit.
A good idea I think, that 231 will hang out quite a ways from the trans. What are your plans for the ebrake. A guy named Parts Mike has one for the Advance Adapters SYE kit.
I'm using Parts Mike's parking brake, but have to build my own caliper mount. As you stated, his kit is designed for the Advance Adapters SYE. The Advance Adapters SYE "case" has a "lip" that Parts Mike mounts his caliper bracket to. I have the JB Conversion's "Super Short" SYE which does not have the mounting "lip" like the Advance Adapters SYE. So I got from him the caliper, disk, flange hub and a new output seal which worked with his hub and the JB Conversions case.
It only took me 3 months to get this project done (along with doing front and rear axles). Got it done middle of the week and went wheeling yesterday (Saturday). Man it works like a champ. The doubler makes switching from high to low easy (one shift vs. 4 clicks for the NP231) and low/low (transfer case and doubler in both in low range) is SLOW!!!!!!!!!! Like 3/4 MPH at 1000RPM. It makes negotiating tight, rocky spots easy.
I also did a transfer case mounted parking brake at the same time and it's much better than the axle mounted version. Because it is before the axle, it gets the 4.88 torque multiplication to help make it hold better with next to zero effort engaging it.
So, to the NP231 brace/mount point. As you can see, I used a single piece of 1/4" plate to tie the transmission, doubler and transfer case together. The brace on the transfer case is also 1/4" plate and it's welded to the horizontal plate. As a result, in order to "twist" the transfer case, the 1/4" plate would need to twist first. This also supports my parking brake.
Here's what I did to the tunnel to fit the doubler and my shifters. I cut the factory "hump" that fit around the transfer case and then moved it back 8" to clear the shifted transfer case. Then knocked a nice dent in the top of it (molded it to the actual shape of the transfer case) to allow the seat to mount back in. I had to move the foot of the driver's seat "out" to clear but overall it looks very close to stock. I'm hoping the carpet goes in and it looks 100% original.
For the shifter, I welded a 1/4" piece of plate into the tunnel to make a mounting base. The shifter then mounts to that with bolts. I then carefully trimmed the transfer case opening of the console to clear and it came out looking very stock-ish.
That looks great......might be a little concerned about mud/grit in the parking brake mechanism where it sits tho.
Also, don't forget, that parking brake will only work if the driveshaft is still connected to the rear axle, and you still have both rear axle shafts (unless you have a locker, then maybe 1 shaft will work).
I looked at similar (the parking brake that is) when I did the np203/np205 lowmax doubler on a previous rig, but decided against that route.
If the driveshaft is toast/missing, or the pinion/ring gear is toasted, or the wheels aren't connected to the driveshaft via a solid connection, it won't stop the vehicle from rolling.
That looks great......might be a little concerned about mud/grit in the parking brake mechanism where it sits tho.
Also, don't forget, that parking brake will only work if the driveshaft is still connected to the rear axle, and you still have both rear axle shafts (unless you have a locker, then maybe 1 shaft will work).
I looked at similar (the parking brake that is) when I did the np203/np205 lowmax doubler on a previous rig, but decided against that route.
If the driveshaft is toast/missing, or the pinion/ring gear is toasted, or the wheels aren't connected to the driveshaft via a solid connection, it won't stop the vehicle from rolling.
I can't see the mud/grit being any worse in this setup than in a axle mounted drum setup. When you drive through mud with drums, mud/grit certainly gets into the drum parking brake and mechanism (those things get NASTY!!!). At least this is a disc and mechanical caliper so the mud/grit can get slung/fall out. I would have liked to mount it "above" the driveshaft (rotated 180 degrees up) but there just wasn't enough room to mount it and run the parking brake cable. So, this is where packaging constraints put it.
Here's what the caliper looks like, it's just two pads floating on bolts with an angled arm pushing one (and thereby causing the other to move) together.
Yes, without a driveshaft/mechanical connection to the axles, there's no parking brake. But, I would think it near impossible to have both driveshafts destroyed at the same time. IF for some reason I lost the rear driveshaft, I could always put it in 4WD and the front would now work (and yes I have lockers in both the front and rear axles). Now sure, it's always possible to come up with a scenario where so many things go wrong that any setup would fail ("well, if you are going down a mountain at 80MPH and both of your axles explode" lol), but personally I'm comfortable with this setup. Heck, I'm a hell of a lot more comfortable with this setup than the stock Dana 35 drums. They would hardly hold on flat ground much less a hill (yes, they were out of adjustment... yes, everything was so rusted up that they needed to be replaced).
Now I have Jeep WJ disc brakes on the front and Ford Explorer disc brakes on the rear. Plenty of stopping power to go around.
With that said, I have always carried rubber wheel chocks with me. Even though my new parking brake works flawlessly, I still always chock the vehicle on steep hills if I'm going to be walking away from it for any length of time (better safe than sorry).
Last edited by CLSegraves1; 03-19-2019 at 10:42 PM.
The big thing tho with drums or discs at the wheels, if if you go thru mud, the wheel is usually spinning the whole time, which makes it harder for crap to get in, and helps sling it out. Yeah, they do still get crapped up tho.
And again, it is very unlikely, but if you happen to lose your tcase and rear D/S at the same time like I did., you're screwed for a parking brake. (np203 chain came apart and bunched up under the front drive gear while doing 40 mph in 4 high....big boom that ventilated the case and trashed the upper u-joint on the D/S......I suddenly had a dead vehicle.
I mention it, as most put those things on, or go with pinion brakes, and think all is good......till they need it to work and it doesn't cuz something else is missing or broken..
Do you think the steel bracing of the aluminum case made a difference ??
The big thing tho with drums or discs at the wheels, if if you go thru mud, the wheel is usually spinning the whole time, which makes it harder for crap to get in, and helps sling it out. Yeah, they do still get crapped up tho.
If I go through mud with this transfer case brake, the output shaft of the transfer case is spinning so it's no different than a disc on the wheels (except this one is much higher up than the wheels).
Originally Posted by TRCM
And again, it is very unlikely, but if you happen to lose your tcase and rear D/S at the same time like I did., you're screwed for a parking brake. (np203 chain came apart and bunched up under the front drive gear while doing 40 mph in 4 high....big boom that ventilated the case and trashed the upper u-joint on the D/S......I suddenly had a dead vehicle.
Yes, in such an instance I would lose my parking brake but as I said, I always have wheel chocks with me. While not ideal, I'd stop with the main brakes, "beach" the vehicle against something (a curb/rock/tree/etc.) and then chock it. I've considered putting a line lock in the rear hydraulic brake line which would give me a temporary "hold" (electric line locks don't like to be engaged for more than 30-60 seconds as they get extremely hot) until I could chock the vehicle.
Originally Posted by TRCM
Do you think the steel bracing of the aluminum case made a difference ??
You still running those drop brackets ??
No idea if it made a difference or not. I certainly feel better knowing it's there and it made mounting my parking brake caliper easy (even if I hadn't tied the brace into the trans/doubler mount, I would have ended up making something very similar to the brace to mount the parking brake caliper). Hopefully I never find out if it helped (ie: nothing ever fails).
Yeah, I've been running the drop brackets and heim joint control arms for over a year now. I'm very happy with their performance (I get a full 12" of travel out of my short arm setup) and they ride nice. One day I may long arm the vehicle (though I have little reason to do so), but that certainly won't be until after I swap in a V8 (I have a fully built iron block/forged piston 5.7L LSx sitting in the garage). If I ever do long arms, I want to do double triangulated to get rid of the trackbar. As is, this thing already does everything I want it to do (other than it desperately needing the V8's highway HP), so hard to advocate for changing much at this point.
If I go through mud with this transfer case brake, the output shaft of the transfer case is spinning so it's no different than a disc on the wheels (except this one is much higher up than the wheels).
Yes, in such an instance I would lose my parking brake but as I said, I always have wheel chocks with me. While not ideal, I'd stop with the main brakes, "beach" the vehicle against something (a curb/rock/tree/etc.) and then chock it. I've considered putting a line lock in the rear hydraulic brake line which would give me a temporary "hold" (electric line locks don't like to be engaged for more than 30-60 seconds as they get extremely hot) until I could chock the vehicle.
No idea if it made a difference or not. I certainly feel better knowing it's there and it made mounting my parking brake caliper easy (even if I hadn't tied the brace into the trans/doubler mount, I would have ended up making something very similar to the brace to mount the parking brake caliper). Hopefully I never find out if it helped (ie: nothing ever fails).
Yeah, I've been running the drop brackets and heim joint control arms for over a year now. I'm very happy with their performance (I get a full 12" of travel out of my short arm setup) and they ride nice. One day I may long arm the vehicle (though I have little reason to do so), but that certainly won't be until after I swap in a V8 (I have a fully built iron block/forged piston 5.7L LSx sitting in the garage). If I ever do long arms, I want to do double triangulated to get rid of the trackbar. As is, this thing already does everything I want it to do (other than it desperately needing the V8's highway HP), so hard to advocate for changing much at this point.
True,. the t-case is spinning which would clean the disc, but the level & caliper isn't. I was thinking more drums which is what I have (and you mentioned), and all of that is inside the spinning drum.
I too am waiting for V8 power, but I am trying to find a decent engine...around here, they want $2500 for a 200k engine that needs work. Tempted to just buy new.
01-01-2019, 04:55 PM
NP231 Brace/Mount Build
