Doug Nash OD

[1984dually]

Have a couple but need another for parts.what’s out there?

 

[AyWoSch Motors]

Have a couple but need another for parts.what’s out there?

???

 

[Snoots]

^^^ Really!

 

[1984dually]

Not sure what the responses are for but I am assuming they don’t have a clue what a Doug Nash OD is.

 

[TotalyHucked]

Haha it doesn't sound like it. Those are rare as hens teeth, I've only ever run across a couple. I have no idea where you'd find parts for them, they're long out of business. This is about the best info I've found on these units:

GV and Doug Nash/US Gear are 2 very different units. GV is still in production, DNE2/USG isn't. Used units are roughly similar in price from what I've seen - $1k+/-

Very different design. GV is a hydraulically shifted planetary unit similar to an automatic trans in operation and design. It is overdrive & direct only and uses a cone clutch that is spring loaded to the direct drive position. For OD the unit uses hydraulic pressure from an output shaft driven pump to overpower spring pressure and hold the clutch in the OD position. There is also a one way sprag type clutch which prevents the input from rotating slower than the output in forward - this prevents slip while shifting under load and will take load if the clutch slips some under heavy load. Notably, this only happens in forward - in reverse or engine braking all torque is taken through the clutch.

The GV unit is essentially a Laycock overdrive box which goes back to 60's sports car. It is intended to provide a top end overdrive gear - high speed and light load. Yes, you can split shifts, and can tow with it, but the fundamental design isn't really meant for that. The minimum speed is because of the hydraulic pump being output driven - lower speed means lower volume and at some point loss of pressure which means more slippage.

GV is a good unit for it's designed use - high speed highway gears. Same idea as a selectable OD on a E4OD or similar - not really good to tow or run heavy.

USG/DNE2 is a 4 countershaft spur gear (helical) box with a positive mechanical shift system. It can be in either gear at any speed any load forward or reverse. Shifting is a bit harder, but IMHO it's a much stronger heavier duty box. Yes they are long out of production, but they're simple and easy to fix as long as the hard parts aren't trashed. Primary wear points seem to be the shift motor and bearings which are both easy and cheap. DNE2 designs use brass countershaft thrust washers that may be harder to get; USG designs use off the shelf needle bearings. I have also seen wear on the shift collar and fork; I strongly suspect this is an off the shelf GM transmission part but have not determined exactly what it's from yet. The big GV wear part in contrast is the cone clutch which I think costs several hundred dollars if you an even get one and is only available from GV.

Electronics and controls are easy for the DNE/USG. Not sure on the GV, I think you can just run a simple switch and wires as long as you make sure to manually downshift before slowing down too much.

To me the GV is an overpriced box that adds a pushbutton 5th gear and is marginally reliable. USG/DNE2 gives you a heavy duty fail safe splitter box that is much more useful for towing.

 

[Blue Ox]

'84-'88 Corvettes had a Doug Nash 4+3 manual gearbox which was a 4 speed with an overdrive that would work in 2,3 and 4. Don't know if it's the same Nash OD you're talking about or not, but you might try looking at a Corvette forum.

The Chevrolet Corvette C4's 'Doug Nash 4+3' Manual Transmission Is Mechanical Wizardry

The 1980s weren’t a great time for sports cars, with engines choked with smog equipment, tall final drive ratios killing acceleration, and other questionable fuel-saving equipment making cars suck more than they needed to. The “Doug Nash 4+3,” a four-speed manual on the Chevrolet Corvette with...

jalopnik.com

 

[1984dually]

Haha it doesn't sound like it. Those are rare as hens teeth, I've only ever run across a couple. I have no idea where you'd find parts for them, they're long out of business. This is about the best info I've found on these units:

GV and Doug Nash/US Gear are 2 very different units. GV is still in production, DNE2/USG isn't. Used units are roughly similar in price from what I've seen - $1k+/-

Very different design. GV is a hydraulically shifted planetary unit similar to an automatic trans in operation and design. It is overdrive & direct only and uses a cone clutch that is spring loaded to the direct drive position. For OD the unit uses hydraulic pressure from an output shaft driven pump to overpower spring pressure and hold the clutch in the OD position. There is also a one way sprag type clutch which prevents the input from rotating slower than the output in forward - this prevents slip while shifting under load and will take load if the clutch slips some under heavy load. Notably, this only happens in forward - in reverse or engine braking all torque is taken through the clutch.

The GV unit is essentially a Laycock overdrive box which goes back to 60's sports car. It is intended to provide a top end overdrive gear - high speed and light load. Yes, you can split shifts, and can tow with it, but the fundamental design isn't really meant for that. The minimum speed is because of the hydraulic pump being output driven - lower speed means lower volume and at some point loss of pressure which means more slippage.

GV is a good unit for it's designed use - high speed highway gears. Same idea as a selectable OD on a E4OD or similar - not really good to tow or run heavy.

USG/DNE2 is a 4 countershaft spur gear (helical) box with a positive mechanical shift system. It can be in either gear at any speed any load forward or reverse. Shifting is a bit harder, but IMHO it's a much stronger heavier duty box. Yes they are long out of production, but they're simple and easy to fix as long as the hard parts aren't trashed. Primary wear points seem to be the shift motor and bearings which are both easy and cheap. DNE2 designs use brass countershaft thrust washers that may be harder to get; USG designs use off the shelf needle bearings. I have also seen wear on the shift collar and fork; I strongly suspect this is an off the shelf GM transmission part but have not determined exactly what it's from yet. The big GV wear part in contrast is the cone clutch which I think costs several hundred dollars if you an even get one and is only available from GV.

Electronics and controls are easy for the DNE/USG. Not sure on the GV, I think you can just run a simple switch and wires as long as you make sure to manually downshift before slowing down too much.

To me the GV is an overpriced box that adds a pushbutton 5th gear and is marginally reliable. USG/DNE2 gives you a heavy duty fail safe splitter box that is much more useful for towing.

 

[1984dually]

Good info, most seem to not be aware of them or confuse them with the vette transmission(have one of them too). Rated gvw of 35,000;lbs it is far better than gearvenders. Most have decent luck with the gv unit but for pulling a load I wouldn’t have one. Currently have a Nash unit bolted to the back of a NV4500 trans. Allow me to have a od while towing without using 5th in the trans. Double od when not. Unfortunately the one I got has a chipped tooth. Small and may never cause a problem. But will replace it if I find another one. Other one I have is a underdrive box. Going to take it apart and look at the countershafts. If I’m lucky they are the same just turned around. Most likely wishful thinking but you never know.

 

[AyWoSch Motors]

Ah, it's an overdrive unit. Now I get it,x didn't have a clue what you meant. Nope haven't seen anything like that. Only one I've seen was an old style Warn overdrive unit on a Willys jeep at a car show.

 

[TotalyHucked]

Good info, most seem to not be aware of them or confuse them with the vette transmission(have one of them too). Rated gvw of 35,000;lbs it is far better than gearvenders. Most have decent luck with the gv unit but for pulling a load I wouldn’t have one. Currently have a Nash unit bolted to the back of a NV4500 trans. Allow me to have a od while towing without using 5th in the trans. Double od when not. Unfortunately the one I got has a chipped tooth. Small and may never cause a problem. But will replace it if I find another one. Other one I have is a underdrive box. Going to take it apart and look at the countershafts. If I’m lucky they are the same just turned around. Most likely wishful thinking but you never know.

You might be able to contact someone like Tremec or someone that makes gears and see if they have one that's identical or would be willing to make one. It's a long shot but can't hurt to ask. Or maybe even GV would