Brown aux transmission advice needed

Son has 48 chev one ton pick-up with 9 foot stepside bed. We are refurbishing , not restoring, just want some changes. Rear ratio is very slow, 5 to 1 range. I have a brown-lipp light aux transmission with straight 15 % and 45% reduction. I used this box pulling goose neck loaded well over wolf-creek pass with ford 460. Transmission is in good shape. What we are thinking is to reverse the transmission to step up the effective ratio. We do not want to change the rear axle nor change ring and pinion. Question is have any of you folks ever reversed one of the boxes. Spicer bought the Brown-lipp company years ago . Many may know of this as a spicer box. It is the light series as was couenly used on one and a half to two ton trucks in the 40 to 50 decades. I have copies of the engineering drawings where oil slingers and shift linkage and be carefully reversed. As I understand the 9 foot box is rather rare, also it has lock ring rims with 17 inch rubber. We will change to one piece rims. Yes I know 2 piece lock rims are not the so called widow makers, however I watched a similar rim with a leaking tire blow apart and cut a wood fence post in two parts. Ok Advice please. Who has ever reversed one of these transmissions??

A few comments here....
While I have never reversed one of those transmissions, I have worked on repairing transmissions my entire life. Mostly automatics, some stick. First thing I see is the 45% reduction. Using that ratio, it will give you nearly 2:1 in reverse. Much too high for your application. Might give you a top speed rivaling NASCAR if you have the power to pull it, but not a lot of pulling torque. Next thing is the whole Spicer thing. In my experience, Spicer transmissions are not the strongest. Saginaw is also not really robust for heavy applications. I would want to look at Dana or Borg-Warner if it were me....or even Fuller/Eaton or Rockwell.
Another possible consideration would be to look for an older overdrive unit from an antique car. Every make used them at one time or another, and they should be readily available.
Also, are you sure about the 5 to 1 ratio in the rear?? Sounds very high to me. In direct it would give you a top speed around 35 miles per hour on 15-inch rubber. I would think that such a ratio would be used with BIG tires/wheels. Bigger than would likely be found on a 1-ton pickup.

I have a 51 GMC 3/4 with 17 inch split rim Michelin tires that stand about 31 inches tall. My axle ratio ratio is 4.57:1.
From an id application chart: 1946-1972 - Corporate "drop out" style (similar to a Ford 9"). 4.10, 4.57, 5.14 ratios available. Full floating. 8 lug. My truck with a 270 inch 6 will keep up at 65 mph no problem. Jim

Speed calculator: http://www.apexgarage.com/tech/gear_ratios.shtml
Tire Size Calculator: http://tire-size-conversion.com/tire-size-calculator/

Assuming tires around 29" diameter (your's may be a little bigger)

With 5:1 in the rear and 1:1 in the trans, 3500RPM would give you 60MPH
With 5:1 in the rear and .5:1 in the trans+OD, 1750RPM would give you 60MPH

What engine is in it? If it's still the 216 CI, there is a reason it's geared so low. Very much decrease in gearing and it won't be able to pull it's self empty.

I had a 71 GMC 3/4 ton 4x4 with 4 speed and 4:54 rear and a 307ci. It had MPH at the bottom of the speedometer, P was about 1 1/4 to 1 1/2 inches past 100 and I had the needle there a couple times.

Thanks guys it does have the late 235 6 the aux transmission has another stick , As far as reverse simply shift to straight . No problem just using the 15 per cent only would use the 45 percent on interstate, This box gives 3 speeds, easily shifts same as regular transmission

That is a fairly rare bird these days. Lots of half tons and plenty of 2 tons but the 1 tons not so much.

I don't think the browny will care which way it turns but have you fleshed out a location to install it?

Using the first stage of your "new" double over the roughly 5:1 will be roughly 4.25:1 which I think would be fine for a 235, not sure though for a 216.

Other option is an adapter plate and an NV4500, but that will be more $$$.

turning a trany backwards might not be a problem but you loose the support the clutch and pilot bearing gave to one end -- how you gonna get that back? I dont see how it will work-- most old style gears can turn either way -- trust you me a couple of those gears will be turning faster than they should and it wont last -- do what you want- but wasting time and money is not an option in my neck of the woods -- good luck -- Roy

I'm lost with all that math, but I am wondering about running the rear end input above its usual speed. All of the transmission options from GM give your rearend the same input speed and the rearend changes it to the best ratio. What you are going to do is leave the rearend and speed up its input. I wonder if you won't be putting seals in it frequently. Only reason I wonder is I dollied home my old grain truck at about 60 mph with the driveshaft out. The truck is geared to run about 50 balls out. That trip trashed the pinion (input) seal.

Aux transmission not connected to original transmission Has its own front and rear bearings.

(quoted from post at 14:26:46 08/18/15) I had a 71 GMC 3/4 ton 4x4 with 4 speed and 4:54 rear and a 307ci. It had MPH at the bottom of the speedometer, P was about 1 1/4 to 1 1/2 inches past 100 and I had the needle there a couple times.

Click to expand...

A very optimistic speedometer!