Oh, decisions, decisions..........

[Camarogenius]

Went "junking" today, and hit the jackpot/ mother lode, and the lottery as well.

I found two auxilliary boxes. one is a 3 speed, and one is a 4 speed. Both are in 60's model GMC 5500 series trucks.

One is $350, and the other is $450. I'm willing to bet thatthe lowest gear in that 4 speed would pretzelize a driveshaft without even straining.

 

[Diesel JD]

Hey good scores. You could probably grab them both and sell which one you don't want. Are we talking Spicer Brownie boxes here? The 4 speed would have to be a 6000 or 7000 series I think, the 3 speed I think would be a 5831B. RLDSL just did the same install on his F350 and if you read the mileage thread the results were really good!

 

[RLDSL]

If you can clean off the id tags on them and get the model number I can look up the gearing specs for those boxes. I have the manuals and specs for just about every spicer box ever made.
The low range in that 4 speed would be pretty similar to the low range in my 3 speed , it's REAL low . It makes it REAL nice on the left leg when pulling the 5er into a tight campsite , no feathering the clutch needed. Just dump that puppy and let it crawl , gives you lots of time to see what you're doing Only difference in the 3 and 4 speed is the 4 gives you 3 splittable gears to each mainbox gear and the 3 speed only gives you 2. In the low range you cant split the gears, It's super low reduction, you just run through the gears in the main box with it in 1 but it is possible to get a 3 way split on each gear with the others theoretically ( in reality, you might only do it in 5th or 4th to find a sweet spot when towing heavy to maximize fuel mileage or to pull a hill . Once in a while I split 3rd or 2nd in the mountains)

 

[RLDSL]

As far as driveshafts, you should see the driveshafts my guy built me they cost me a fortune but are built stout enough for a semi ( Heck, I could barely lift the front one when he heard diesel I guess he thought I had some modern torque monster and he built it to handle anything , so I'm not too worried about the things . Only weak link is the rear U joint to the diff since it's factory size, the ones on the aux are 1550

 

[flatlander]

Check the numbers. If the 4 speed is a 6041 then if I recall it has .20 under, 1:1, .20 over and double under. I considered this in my truck but then my 1 3/4" thick envelope of receipts that are already in the truck changed my mind.

Maybe the model number is a 4061. I've slept many times since then.

 

[Camarogenius]

I didn't get the boxes, yet. I just have their location carved inside my skull, and a pretty strong assurance that they're not going anywhere.
They're in a way-back corner of a junk yard, still in the trucks. He won't pull them out, or lift up the trucks for me until they're paid for. (Wasp hell).
How bg and heavy would that 4 speed box be? And how much of a night mare to get the speedo to work properly?

 

[RLDSL]

I didn't get the boxes, yet. I just have their location carved inside my skull, and a pretty strong assurance that they're not going anywhere.
They're in a way-back corner of a junk yard, still in the trucks. He won't pull them out, or lift up the trucks for me until they're paid for. (Wasp hell).
How bg and heavy would that 4 speed box be? And how much of a night mare to get the speedo to work properly?

Lets see if this file can be blown up big enough to be read

 

[RLDSL]

If yours has the electronic speedo with the tone ring in the diff, no changes needed, but if if has the speedo in the tranny, you would need a brownie with the speedo out in the tailshaft. luckily it is standard spicer speedo stuff so it is fairly easy to get parts for and calculate. Any good driveline shop should be able to get the parts. The outlet cable is a standard size. I didn't need the speedo so I bought a cable for a chevy 4x4 pickup and pulled the cable out of the casing and just routed the casing up to the frame as an extra case vent.