Originally Posted by 38 coupe

I have been interested in smaller auxiliary transmissions for a while. When I got interested I hoped to find a nice web page or forum thread that gave a lot of information on the smaller auxiliary transmissions. This thread has been very helpful with gathering information, but the information is still scattered. This post is my attempt to put together the most useful information I have in a consolidated format. If anyone notices a mistake or omission please contact me so I can correct it.




The history of smaller auxiliary transmissions is a bit confusing. Once you are dealing with trucks newer than the Model T era, three names are prominent: Brown-Lipe, Spicer, and Watson. The cause of the confusion is that at some point all three companies were combined. I have a 5831 and the data tag has all three company names on it. As near as I can figure out most of the Watson transmissions were designed for 1½ ton through 2 ton trucks and most of the Spicer transmissions were designed for 2½ ton trucks and larger. The exceptions are the Watson 2021 and the Spicer 4800, both which were designed for ½ ton pickup trucks. Also designed for ½ ton pickup trucks was the Warn Auxiliary. If you are planning on installing an auxiliary transmission in your truck you should do some careful measuring to make sure you can make everything fit. I also need to make a huge disclaimer at this point; I have not installed one of these yet. My current plans are to put a Spicer 5831 into a ¾ ton pickup. I am still in the planning stages.




I'll start with a table of gear ratios. I included the transmissions in this list for two reasons: first these are small enough to use in a 1 ton or smaller truck, and second I could find some information on them.




The Watson transmissions most frequently mentioned in online discussions are models: 31M, 39M, 41, 42, 43, 44, 45, 46, 47, and 48. I have seen pictures of these Watson transmissions used in ¾ and 1 ton trucks. Watson used a basic design and changed the model number to designate different gear ratios. The 31M and 39M were side loaded transmissions and did not have cast in mounting locations. The 41 through 48 transmissions are top loaded with four cast in mounting holes.
The 31M and 39M transmissions look like this


The Watson 41 through 48 transmissions look like this




The Spicer transmissions most mentioned are the 5531 and 5831 models. The 5831 series transmissions were the updated replacement to the 5531 series. Both series were available in several ratios. These are top loaded transmissions with the shifter rods and forks carried in the top cover. The 5531 has cast in mounting holes at the rear of the transmission. The 5831 does not have cast in mounting holes. I have seen pictures of these Spicer transmissions used in ¾ and 1 ton trucks.
The Spicer 5531 transmissions look like this


Here is a Spicer 5531 parts manual






The Spicer 5831 transmissions look like this


Here is a Spicer 5831 parts manual












Here is an excerpt from a GMC shop manual that covers the Spicer 5831










Warn, the company of Jeep winch manufacturing fame, made an auxiliary transmission at some point in the 1960s. Unlike all the other transmissions I am writing about the Warn Auxiliary has a planetary gear set. I include it here mostly because I lucked into a NOS unit a while back. These were designed to fit between the main transmission and a married transfer case. I'm not sure how well one of these would hold up to 1 ton truck use. I think it looks like a great unit for a vintage ½ ton pickup with a stock gasoline engine.
Here is an add for the Warn Auxiliary


I also have scans of the owners manual / parts list / instruction guide






Here is a picture of a Warn installed between a main box and a transfer case




If you want to save copies of any of these pictures you can find them on photobucket in my Auxiliary Transmission folder: Auxiliary Transmissions by Fred_Mills | Photobucket


Respectfully,
Fred

Originally Posted by weldordude

i have a 97 f super duty i use for my welding truck, i need more speed and less revs my grandad use to restore model t fords and he rebuilt ruckstell axles andmessed around with moore overdrives and underdrives. i was looking at 2 speed rear ends not practical so here i find this thread i need a Brownie i drive interstate and that rear end is just too dam low geared for todays speeds i got the five speed standard what kind of nightmare am i looking at to change this im a welder so i have the ability to cut grind and weld? any info from yall would be awesome. oh i need to buy a brownie so lmk