Swapping in a Brownie box

[nchinca]

Hi,

New to the forum, and it is time for my first post. I have a 85 K2500 with a BBC, SM465 bolted to an NP205, sending power to the axles which are stuffed with lockers and 4.56 gears. The truck has a 6 inch lift and rides on 36's.

My latest project is putting in a Spicer 5831, which I picked up last Saturday. I was going to mount it behind the transfer case for now for ease and cost effectiveness. I was wondering if anyone has put one of these or something similar into their trucks, and what else was needed. I know I will need shafts, a shifter (which I will use an old SM465 top modified with shift rails welded together to come out the back) and I will be buying and modifying crossmembers to make the mounts. Can I mount the box to the rear of the transfer case with a U-joint, or do I need to have a short shaft? I am probably going to mount the parking brake to the back of the Brownie. My question is, is there an easier way, am I forgetting anything, and should I do anything different?

Thanks for the help,

Nick

 

[dremu]

Welcome to the forum, btw, and it sounds like you're having fun.

For the uninitiated, I'm assuming from a little Googling that this thing is an overdrive? The phrase "auxiliary transmission" kept coming up, maybe two speeds, namely 1:1 and a 1.27:1 gearing?

Actually I'm thinking that should be 1:1.27, as otherwise it's an underdrive, right?

By putting it after the transfercase, you should realize that your front axle could be spinning at a different rate than the rear, which will break things in short order. Presumably you'd only use this thing on the highway in 2WD?

Seems to me that coupling the thing to the t-case with a U-joint (and two yokes) would work IF you could keep it and the t-case exactly parallel. Just mounting them both to crossmembers with rubber feet prolly wouldn't be enough and you'd snap the coupling in short order (especially 'cuz a bigblock can put stupid torque through a '465 in low )

If you could rigidly couple the two, though, like with fat channel on a coupla sides, might work...

Why a parking brake on the driveshaft? Do your rears (be them disc or drum) not have provisions for a parking brake?

I've occasionally contemplated putting some kind of extra gearbox on my tow rig; the TH400 could use one more gear for highway runs ... and yeah, I could do a 4L80E, could do lots of stuff. ::shrug:: Never done anything about it, in any event. Too many other projects.

-- A

 

[nchinca]

It is the B series with 2.35 low, 1:1, and 0.85 over. As for putting the brake on the back of the box, I converted to discs years back, then upgraded to the 3/4 ton front calipers, so I have not had a parking brake on it for years (Except for a rubber wheel chock). It will probably be too much of a pain to get it to line up perfectly, especially since I was going to give it a slight angle for a better rear d/l angle. I was expecting to only use it in 2wd (or 2lo) to take advantage of the overdrive.

Thanks for the answer, I am staring at this thing, and wondering where the hell to even start and just looking for some guidance on it.

 

[dremu]

It is the B series with 2.35 low, 1:1, and 0.85 over. As for putting the brake on the back of the box, I converted to discs years back, then upgraded to the 3/4 ton front calipers, so I have not had a parking brake on it for years (Except for a rubber wheel chock). It will probably be too much of a pain to get it to line up perfectly, especially since I was going to give it a slight angle for a better rear d/l angle. I was expecting to only use it in 2wd (or 2lo) to take advantage of the overdrive.

Thanks for the answer, I am staring at this thing, and wondering where the hell to even start and just looking for some guidance on it.

Ahhh, interesting. Never heard of the things, but the fact that it's got both over and under drive is sexy ... it's like a doubler, but BOTH ways.

Is your truck a longbed? if so, you have enough wheelbase you could switch to a 2WD tranny and do this thing right on the ass end of the tranny ... then do a divorced 205 xfer case, say. Makes for a boatload of intermediate shafts but you'd have NO problems with the *front* driveline angle! =))

I've heard of folks wanting to flip a 203 rangebox backwards and do like an anti-doubler to do what you're talking about ... but it means custom machining the adapter to connect them, or else crazy intermediate shafts or couplers like you're facing.

Sorry I'm no actual real help ... but maybe we'll get people talking or thinking. Hell, I remember years back, NP203/205 doublers were hand-made welded gizmos, and even a few years ago (when I did it ) putting 52" springs up front was an exercise in custom fabrication. Now the doublers are one machined piece and there are kits to do the spring swaps. Point being that as knowledge and ideas spread, cool stuff comes of it.

And I'm *liking* the under/passthru/overdrive thing. That is SECKSAY ... I could have 3.73:1 gears in my towrig for topend economy AND still pull in low if needed.

Would the thing shift okay behind a slushbox, or would I have to pop into neutral like you pop in the clutch?

-- A

 

[nchinca]

Ideally, it would be a 2wd trans to the 5831 to the transfer case - but I am already hearing how I spent too much money, and this way, the fairly new front shaft stays, and I can modify the existing 2 piece rear to make one of them into the intermediate and the second piece into the now 1 piece rear.

I told the wife about the overdrive as a selling point, but am digging the low gear for the creepiness - even if it is 2wd. I might even go back to the factory 3.73's for economy, and go from 7 to now 8 mpg! On second thought, screw it, 4.56's are too fun!