I just dragged a 1986 F350 diesel out of a field and discovered that it has a Doug Nash 2 speed that must be in low because top speed flat out is only about 65. The switch and wires to the splitter are long gone and I hope one of you remembers which terminal will shift the splitter up and which terminal will shift it down. There are two terminals and I suppose the best way to ident them is to say that one terminal is closer to the transmission and one terminal is closer to the rear end. Any help with identifying these terminals will help greatly when I wire up this thing to try to get it into hi range. Thanks. L -o-

 

lewismohr,
Welcome to FTE and the IDI diesel forum.

If I remember right the Doug Nash unit became the Gear Vendors unit.
Every once in a while someone will post up with questions about them.

Also if I remember correctly Gear Vendors can give you some information about the Doug Nash unit.

Gear Vendors under/overdrive transmissions the most awarded auxiliary transmissions.

 

Dear Dave: Thanks so very much for your reply. We are going thru the truck right now and now that I know that gear vendors is the new go to location for advice on the Doug Nash I will call them. thanks again. L -o-

 

If I remember the story right, when Gear Vendors started up, they bought out Doug Nash Enterprises.

Not sure how much support you can get through them, but it is the best place I can come up with for you to get information about the unit.

 

ok thanks. so far every independent trans shop I have called including the one that installed the unit on this truck from the papers i found in the glove box have all gone out of business and help identifying how to wire this thing and if a plain old 3 pole center off spring loaded toggle switch is all I need to shift it. I will try them in the morning. L -o-

 

I thought it was US Gear that bought out Doug Nash! I found this article on the Nash unit. I know Dave was thinking US Gear and wrote Gear Vendor, long working hours are taking it's toll on Dave's gray matter Ha Ha Ha!

The US Gear Dual Range unit was originally designed and initially built by Doug Nash Transmissions several years ago. Internally it's a very conventional-looking husky two speed gear box that uses an electric servo motor to shift between its two ranges. It stays in the range it's left in, even in reverse or with the engine off. Because of its basic gear box design, it can be configured as a conventional overdrive or as an underdrive. (Older models at least can be reversed back and forth - but two of the gears need to be replaced to do that. There's also the issue of putting new gears in with worn. Also keep in mind that US Gear reportedly doesn't support the Mile Marker and Doug Nash manufactured units - those with serial numbers below 20,000 - if you're thinking about buying a used unit.) Shifting requires selecting the new range via the switch, waiting a second or two for the servo motor to pre-load the shift fork, then backing off the throttle momentarily to allow the unit to actually change gears. So it operates and acts very much like a two speed axle. The driver's experience and technique determine the smoothness of the shift - badly managed shifts tend to be somewhat jerky and noisy (it is not hard to learn to shift the unit smoothly however). There have been reports of the older units running hot under extreme conditions, but I have an article which claims that's almost always the result of overfilling and/or using the wrong oil. Repairs can be made by any mechanic who's competent with manual transmissions.

 

Dear Mistaken ID: Thanks so much for that description. You have answered almost all of the questions we have except for the terminal ID and I can work on that now by trial and error now that you have confirmed that the unit can be shifted on the fly. It will be easy now to determine which terminal is hi and which is low. Do you know if power must remain on the terminal after the shift is complete and could a 3 pole center off spring loaded to center switch be used or is a plain old double pole double throw switch for keeping the 12 v on the terminal full time even after the shift is completed? We have no cab interior switches that we can find that look like a Doug Nash shifter switch so there is no way i can determine the theory of operation and I do not want to damage anything if the unit is salvageable. If I knew if the last thing the dog/gear solenoid slider did at the end of its stroke was remove power from itself, then the plain double pole double throw switch could be used. Any thoughts? Seems like back in the 60's when I was running those old delivery trucks with a 4 speed and a splitter, when I pulled up on the little plunger switch hose clamped to the front of the shift lever, the switch stayed up, but I do not know if that means the power stays on the solenoid, or like I question, is the last thing the slider does at the completion of its stroke, is take the power off the solenoid? any thoughts? Thanks again. L -o-

 

Don't forget, a lot of 'splitters' are vacuum or air, not always electric, kind of a different animal.

 

Check on the floor by the headlight hi/low button. There may be another button there for the overdrive. I've seen floor mats and carpet cover up the button/s and guys ripping apart an overdrive button trying to fix the headlights.

 

The switching is done via a screw drive inside the unit. Once it's in gear, power to the solenoid is turned off. So a 3 position momentary on toggle switch would do the job well. You would have to make sure and hold it on till it engages...
Good luck

 

Thanks for the advice. We have been working on other repairs while trying to determine what was going on inside the unit itself. We did not want to damage anything so we have not even experimented. With what you have identified I know what to do now. Thank you for the advice. L -o-

 

Hello Lewismohr

Contact U.S. Gear and request an information package for their Dual Range unit. It consists of a brochure for the unit and an installation and repair manual that includes pictures and an exploded view. The planet gears need to be timed properly so you will need the manual. I have both the Doug Nash and U.S. Gear manuals and they are identical. Some differences exist between the actual units but the books are the same. A two speed shift motor can be used with these units, some power either terminal and ground the housing while others alternate power and ground between the two terminals. Use a relay (bosch makes one) that provides constant power to the motor in either position, this prevents the motor from reversing over time due to vibration. It has internal contacts to disconect power. Put the relay under the hood and use the standard red **** two speed switch on your gear lever, this keeps the wires that handle a lot of amps off moving parts (the lever) and out of the cab. Go to the "clutch, trans., diff. etc." thread here, then look up "A new brownie thread..." by Acheda, on page two, I posted some more things. Good luck

MetalZ

 

Dear MetalZ: Thanks for the advice about the info pack from U.S. Gear. And I will followup on the brownie thread. L -o-

 

OK. I have a Gear Vendor's Under/Overdrive electric solenoid unit. I will take a look at it when I get home and see how it's wired. It has the plunger style switch as you describe, but the wiring goes through a control box, and is interrupted by a speed sensor on the speedometer cable. This prevents activation of the OD gear below about 25 mph, and resets the gearbox to low gear when the vehicle drops below that speed. I think it is a magnetic revolution sensor similar to the diesel's tachometer. I had trouble with it when the speedometer cable began to freeze up, because it would cause the unit to slam out of OD at highway speeds (OUCH! felt like I was getting rear-ended!). When the speedometer cable completely failed, the OD unit could no longer be activated into OD mode because the control unit "thought" the vehicle was standing still. Not sure if any of this applies to your unit but... I thought I'd mention it in case yours has wiring tied to the speedometer somehow and needs speed information to activate.

 

Dear Ford F834: WOW. So many things about which I did not think. I will check out all that you cited. Thanks so much. L -o-