over/under drive unit

[WOT]

Ok, GV & US Gear are quite pricey. I want an OD unit for cruising empty - no need to use it at all when towing. This is what I would like to see:



A unit that is in the $1000 price range. Don't care if it's synchronized or not. I have 4WD, but would never plan on using it with over/under drive so I would want it behind the transfercase. I plan on putting it in over drive when I am not towing (and going to be on a long highway trip) and leave it there. Shifting only when not moving is fine. It would be perfect if it also had a underdrive to use when jockeying the trailer (say a 4:1 would be great), but not a neccessity. The overdrive should be somewhere in the area of . 75 -. 8.



I'm thinking it would be nice if it were divorced from the trannny/tranfercase. That way same unit could be used on either. I suppose a nice adapter housing would make it work on either too. If divorced it would work on any truck. I don't know that an additional crossmember would be sufficient to handle it, might also need some sort of adapter to attach it to the transmission/transfercase to help resist twisting. Divorced would mean an extra driveshaft too. For us long bed guys we probably have plenty of room, not sure if a shortbed would.



Anyone have any thoughts on this? There has gotta be something out there like this.



I think Range Rover has an OD unit that actually mounts as an "add on" to the transfer case - very cool. Not sure if the transfer case could be modified to allow a 1:1 as well as a . 8:1 2WD mode. That would be nice too!



WOT

 

[Ol'TrailDog]

I put a Warn OD on a 67 LandRover 88. Also put a Warn in a Willys wagon that I dropped a V6 in. Loved the mechanical versus electric shift (GV and US G). Simple to install, since they bolted right onto the back of the transfer case. They are now marketed as Saturn overdrives.



However, the torque ratings for thes overdrives are not near up to snuff for a CTD.



Sure wish I had a LandRover 88 or Defender with a 4bt in it.

 

[cojhl2]

Since you want it behind the xfer case it has to stand the torque of low range.



How about an old 4 speed out of a 2t shev truck turned around bkwards?

 

[Mundgyver]

I seem to remember years ago in my youth, that they made two speed rear ends. That would be the place to put your over/under drive if one did not want it on the back of the transmission.

 

[COWBOYDUALLY]

where could you possibly get a 2 speed rear end for our size of trucks? that would be even better back there vise having to have another drive shaft made and a bracket for the over/under box. that would be the perfect comb for those that tow a wagon for a living!!!! Jeremy

 

[SBledsoe]

What you are describing sounds like the old "Brownie" auxilliary transmission.

This would be a "divorced" setup with a lever (or cable, if you cold fabricate it) type of shifting.



They were made in two series, models 5231 & 5831(weighing in at 150 lbs) and model 8000 (weighing in at 500 lbs).



This product was originated in the '40s and bought by Spicer in the early '60s.

The box had three gears; over, under, and direct. They were generally found in GMC 5000 series trucks (and larger). I'm not sure when they quit making them, but they have, so it's junkyard time! There's probably some source out there who offers this unit as a rebuild. ???



There were seven different models altogether, based on the 5831series.

And obviously, it's the 5831 that would work best for the pickup truck folks.



A - 1. 54U - 1. 00D - 0. 73O

B - 2. 35U - 1. 00D - 0. 85O

C - 2. 00U - 1. 00D - 0. 73O

E - 1. 27U - 1. 00D - 0. 73O

F - 2. 00UU - 1. 27U - 1. 00D yes, this one is "double under"



The "D" and "G" model ratios are unknown. The 5831 holds 4 pints of lubricant and the tag on the unit usually reflects a relationship to General Motors and Dana.



Steven

 

[cojhl2]

Steven,



Where can I find info on the Brownie. Im not so sure they have quit building them cause last year I was driving a 74 359 that had the 4sp brownie.



Also I have friends that have lowboy tractors that use them for the Deep under they need to get started.



Some lowboy tractors have a 2spd axle setup for that reason but that is quite a mess keeping both axles of a tandem setup in the same gear.



Appreciate your help,, thank you.

 

[Mundgyver]

The one I remember using in my long lost youth was on a Mac 5 Ton. The truck had a 4 speed in it and then there was an cable/electrical pull button (I do not recall) on the shifter which would engage the gearing that was in the pumpkin in the rear end. It was an interesting set up. I don't know what the gearing out come would have been with this, but I do know it was very affective.

 

[cojhl2]

What you guys are referring to is an Eaton two speed axle. They are very common in the smaller trucks.



Some were vacum operated but mostly the newer ones are electric.



However, I have never seen one in a 1t. The smallest ive seen them is a ton and a half like a 600 size. .

 

[WOT]

Thanks for the replies - did a little more digging...



Found some nice links... .



http://www.6066gmcguy.org/spicer-5831-b.htm

http://www.6066gmcguy.org/SM420.htm



Looks like there are some out there to be had in the $700-$1000 price range. Sure would be nice to get some dimensional data on these to see if they are even practical in our application.

 

[SBledsoe]

cojhl2 and all,



As for finding the "Brownie", it's junk yard time or... .

as I mentioned before, you may Google it and find

a rebuilder who may stock them.



Good luck.



Steven

 

[TurboFan]

What about another transfer case behind, just for the gearing? Mount it backwards for overdrive, and fowards for under?



Cheap.



Chain part not used so chain strength not an issue.



Neat Links WOT

 

[WOT]

I'm not sure about the stength running backwards. Also, it would be a very steep overdrive (think our transfer cases are in the area of 2. x:1). I wonder if someone could "mod" a transfer case with the correct gearing. Of course by the time you buy a transfer case and change the gearing you might as well just find a brownie.

 

[R.Merritt]

If my memory serves me right, the Brownie was a Brownlite Auxillary Transmission. I don't believe they are in business anymore. Army surplus might have some of these critters.

 

[cojhl2]

There was a company called "Advance Adapters" who built overdrive units that fit between the engine and first transmission.



Maybe they could provide a lead if you could find out where they are.

 

[COWBOYDUALLY]

need more levers to shift

ive been digging around on the internet but havent seen any aux box that would work, im probably looking in the wrong places anyhow. sure would be nice to have a better gear selection to pull hotshot,houses down and d9 dozers outta the mudd :-laf jeremy

 

[NIsaacs]

Like Steven said, the 5831 Spicer will work and fit in pickup sized vehicles. I have one in my CTD powered Ford. Keep in mind, like he said they are not made anymore, so parts are hard to come by and expensive. Also keep in mind, since they were used in old farm sized trucks of years ago, the Cummins has too much power for them. If you use one, stay out of overdrive on third gear and down in the main box, or use light power. I was pulling a heavy load up Wolf Creek in third and over, throttle mashed on the first switch back going east, when overdrive goes bang. It is a cool, fun transmission tho! The bigger, 8000 and 12000 series are still made, but the 7000, 6000 and 5500-5800 series are not.





"NICK"

 

[WOT]

I'm surprised they aren't strong enough. Guess I figured they came on 2 ton trucks they should handle the cummins. If the 8000 series is 500lbs it must be pretty big - anyone have any specs on the size?

 

[cojhl2]

The one thing to remember though is that the 2t trucks of the vintage that used those aux transmissions were flathead ford v8s and chev 6cyls, and maybe a 6cyl Binder.



Also WOT you are gonna potentialy place this box behind the transfer case which will again double the torque that it would have felt behind just one transmission.



I would really be afraid of an installation like you would like to do.

 

[blacksheep4x4]

Do a web search for Klune-V. They make a planetary gear box that goes behind your transfercase and can handle 1500 hp. They make these things for the rock crawler guys. Reduces gear ratios unbelievably low. I picked one up for my '89 w250 works as addvertised. I don't know why they couldn't make one to raise your gear ratio instead of lower it. If they can't you could probably put high gears in you truck for highway use and then when you want to tow just engage the box for a lower gear ratio.