Ok so the input side is what mounts to tranny? The output side mounts to driveshaft? Right? So if I marked both input and output sides with a marker and when I turn the input side 1 full rotation and my output side turns 1.25 rotations then I for sure have an OD unit?
US Gear Dual Range / Doug Nash Info
- Thread starter jaluhn83
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jaluhn83
Full Access Member
Correct. The input is the same flange and female shaft as a transfer case and the output has a regular driveline yoke.
jaluhn83
Full Access Member
Though thinking about it now, I don't think there's any technical reason use and underdrive box backward for an overdrive. You'd need to mount it as a divorced case using the output yoke for an input with a short driveshaft to the trans, and then fabricate some sort of adapter to mate the rear driveline up to the old input shaft splines. You'd want to fab a support assembly with another bearing to stabilize the new output shaft adapter, and would need a long frame but I don't see why it wouldn't work.
Typically the limitation with running a gearbox backward is the helical gear thrust, since most boxes are designed for high thrust loading only in one direction corresponding to forward rotation. Reverse rotation reverses the direction of thrust load, and most boxes are not designed to handle this load for any length of time.
On these the thrust bearings are symmetrical, so in theory it should stand up just as well to being run in reverse as it would forward, ie could be driven backward just fine.
Typically the limitation with running a gearbox backward is the helical gear thrust, since most boxes are designed for high thrust loading only in one direction corresponding to forward rotation. Reverse rotation reverses the direction of thrust load, and most boxes are not designed to handle this load for any length of time.
On these the thrust bearings are symmetrical, so in theory it should stand up just as well to being run in reverse as it would forward, ie could be driven backward just fine.
But mine is an OD unit right? I turn input one full rotation and output turns 1.25 rotations. I got confused and thought the higher number meant it was UD. So if mine is OD then I can just mount it normal. And if I open my case and don't find a limit switch, I can purchase the one off rock auto, install inside my case then I can use a push pull switch like a grain truck has to operate hi/low. Right?
Well I am really confused now. At first when I turned my shafts, I thought I had a UD unit. But jaluhn83 you said if my input turns once and my output turns 1.25(which mine does)then that makes it an OD unit. Which now that I think about it makes sense, the transmission side is turning less while the driveshaft side turns more. Right? But according to this this http://web.archive.org/web/20060327003955/http://www.usgear.com/dr_ratio.htm a UD unit has 1.25:1 and a OD unit has 0.80:1 Any thoughts as to if mine is UD or OD?
Yes, 1 rotation on the input and 1.25 on the output would be an overdrive.
If you turned the input 1 rotation and the output turned .75 that would be an underdrive.
Let's think about a 5 speed transmission in the trucks.....
First is 4.14:1 so the input turns 4.14 times the output turns.... this is why you only go 10-15 while on the governor...
Second is 2.37:1...... 2.37 in 1 out
Third is 1.42:1...... 1.42 in 1 out
Fourth is 1:1...... 1 in and 1 out. In this case, if you think in RPM, if the engine is turning 2000 RPM the output of the transmission (driveshaft) is turning 2000 RPM. In all gears lower than this, the engine RPM will be higher than the driveshaft RPM (the same as an underdrive would be)
Fifth is .77:1.... 1 revolution of the input, you would get 1.27ish revolutions out. Now engine RPM is lower than driveshaft RPM. This is what defines overdrive.
So if you don't have an overdrive transmission, like a C-6 it T-19, which the highest gear is 1:1, you can see how an external overdrive factors in.
Now, lets take a look at what happens if you have an E4OD or ZF-5 transmission AND an external overdrive. When the external overdrive is "off" (direct), your ratios work just like listed above.
But, if the overdrive is "on" (overdrive), let's see what happens. Now, in overdrive on the transmission (5th on a ZF-5 or 4th on an E4OD) when the input turns 1 time, the output turns the same 1.27ish as before, but this is now the INPUT to the external overdrive. Now, like you see with your overdrive 1 turn of the input gives you 1.25ish out. However, that 1 input turn on the external overdrive is already an overdrive... so now with both in overdrive for every 1 turn of the transmission input shaft, you are now getting 1.5ish turns of the driveshaft. This is "double overdrive" which is how Gary (icanfixall) got his picture of 85MPH at 1500 RPM.
Also, looking at this, you can see how you can "split" gears with the external overdrive. For example "3rd over" (transmission in 3rd, external overdrive "on") would be a higher ratio than 3rd, but not as high as 4th..... sometimes this is just the sweet spot you need.
All this is just driveshaft RPM, has nothing to do with the ratio in the differential(s)...... The combination of the two determined wheel speed.
Sorry for the long winded post, but when I first started looking into stuff like this it took a while for me to wrap my head around it. So hopefully my one time struggle will help someone else understand a bit easier.
If you turned the input 1 rotation and the output turned .75 that would be an underdrive.
Let's think about a 5 speed transmission in the trucks.....
First is 4.14:1 so the input turns 4.14 times the output turns.... this is why you only go 10-15 while on the governor...
Second is 2.37:1...... 2.37 in 1 out
Third is 1.42:1...... 1.42 in 1 out
Fourth is 1:1...... 1 in and 1 out. In this case, if you think in RPM, if the engine is turning 2000 RPM the output of the transmission (driveshaft) is turning 2000 RPM. In all gears lower than this, the engine RPM will be higher than the driveshaft RPM (the same as an underdrive would be)
Fifth is .77:1.... 1 revolution of the input, you would get 1.27ish revolutions out. Now engine RPM is lower than driveshaft RPM. This is what defines overdrive.
So if you don't have an overdrive transmission, like a C-6 it T-19, which the highest gear is 1:1, you can see how an external overdrive factors in.
Now, lets take a look at what happens if you have an E4OD or ZF-5 transmission AND an external overdrive. When the external overdrive is "off" (direct), your ratios work just like listed above.
But, if the overdrive is "on" (overdrive), let's see what happens. Now, in overdrive on the transmission (5th on a ZF-5 or 4th on an E4OD) when the input turns 1 time, the output turns the same 1.27ish as before, but this is now the INPUT to the external overdrive. Now, like you see with your overdrive 1 turn of the input gives you 1.25ish out. However, that 1 input turn on the external overdrive is already an overdrive... so now with both in overdrive for every 1 turn of the transmission input shaft, you are now getting 1.5ish turns of the driveshaft. This is "double overdrive" which is how Gary (icanfixall) got his picture of 85MPH at 1500 RPM.
Also, looking at this, you can see how you can "split" gears with the external overdrive. For example "3rd over" (transmission in 3rd, external overdrive "on") would be a higher ratio than 3rd, but not as high as 4th..... sometimes this is just the sweet spot you need.
All this is just driveshaft RPM, has nothing to do with the ratio in the differential(s)...... The combination of the two determined wheel speed.
Sorry for the long winded post, but when I first started looking into stuff like this it took a while for me to wrap my head around it. So hopefully my one time struggle will help someone else understand a bit easier.
Man I thought I had a good understanding of overdrive units but the way you explained it was perfect.
mnnathan
Registered User
So only sort of related to this thread. I have a US Gear box in my truck. I do not believe that my shift motor grounds thru the case. I think it is a normal, 2 wire DC motor. I am not sure though.
I do have a couple questions though. First, Are the DNE2 front cases able to bolt to a US Gear rear cases? What parts will and will not swap from the US Gear to the DNE2? Can I put an entire US Gear gearset into a DNE2?
Second, I posted in the WTB section but maybe i'll have better luck here. My front D/S let go and punched a hole in the case of my US Gear overdrive. So now I am looking for another one to put in. The one I had was a C6 4x4 but I think my rear half is still OK. Basically, I am looking for the front case as I have all other parts but I am expecting to buy a whole unit. Let me know if you have an extra, even if it is a "Parts Case."
I do have a couple questions though. First, Are the DNE2 front cases able to bolt to a US Gear rear cases? What parts will and will not swap from the US Gear to the DNE2? Can I put an entire US Gear gearset into a DNE2?
Second, I posted in the WTB section but maybe i'll have better luck here. My front D/S let go and punched a hole in the case of my US Gear overdrive. So now I am looking for another one to put in. The one I had was a C6 4x4 but I think my rear half is still OK. Basically, I am looking for the front case as I have all other parts but I am expecting to buy a whole unit. Let me know if you have an extra, even if it is a "Parts Case."
jaluhn83
Full Access Member
The motor does ground through the case. It does have 2 leads, but internally it's wired with 2 coils both with a common ground. Those are the hot legs of the 2 different windings. Instead of reversing by flipping lead polarity like a common motor these use 2 separate windings for fwd/rev.
I am not sure about using a USG case. The flange bolt pattern and dimensions are the same as far as I know, but the USG uses needle thrust bearings for the countershaft instead of brass washers on the DNE. I can't remember if there a difference in the case design. The bearings ride on hardened steel washers that I think sit in the same pockets and the shafts are slightly shorter to account for the added thickness of the thrust bearing assembly. I'm not sure however.
I personally would not mix cases unless you had too, and I'd want to take a endplay measurement on the main and countershafts with the unit assembled. Not sure how you would be able to do this though with the way the case is designed. Maybe measure race depth from the parting flange on both cases?
I don't have any spare parts, sorry. Best bet is probably ebay or similiar.
Have you looked at welding up the case? Might be worth pursuing if it's not major damage.
I am not sure about using a USG case. The flange bolt pattern and dimensions are the same as far as I know, but the USG uses needle thrust bearings for the countershaft instead of brass washers on the DNE. I can't remember if there a difference in the case design. The bearings ride on hardened steel washers that I think sit in the same pockets and the shafts are slightly shorter to account for the added thickness of the thrust bearing assembly. I'm not sure however.
I personally would not mix cases unless you had too, and I'd want to take a endplay measurement on the main and countershafts with the unit assembled. Not sure how you would be able to do this though with the way the case is designed. Maybe measure race depth from the parting flange on both cases?
I don't have any spare parts, sorry. Best bet is probably ebay or similiar.
Have you looked at welding up the case? Might be worth pursuing if it's not major damage.
mnnathan
Registered User
3 inch hole. I am worried about the structural integrity of the case...even with welding it. I would rather not mix cases of course but so far I have found one 2wd case for more than I want to pay. On the othet hand, if I can get a dne2 cheap enough I will probably try to see if it will work. I am hoping they are close enough so I can use all the later bearings from my USG case be we shall see.
Thanks for the info on the shape though.
Thanks for the info on the shape though.
UMR_Engnr
Full Access Member
The motors with the external two pin connector (not with the bolts going through the side plate) seem to not be grounded through the case. I had to put 12V on one pin and ground on the other for the motor to do anything.
mnnathan
Registered User
That is the situation I had too.
jaluhn83
Full Access Member
Yep, forgot about the newer ones, sorry.
So if it has internal wires from the motor to screw terminals on the side case cover it's a 3 wire grounded case motor, if it's got external terminals on the back of the motor case it's a non grounded motor.
So if it has internal wires from the motor to screw terminals on the side case cover it's a 3 wire grounded case motor, if it's got external terminals on the back of the motor case it's a non grounded motor.
mnnathan
Registered User
Hey, just an FYI...
I have a US Gear Case and a Doug Nash case.
Having them both apart I have yet to see a difference in the two except for the following:
1) There is a difference in controls BUT it appears that you can use either control in either case.
2) in the OD USG case the pitch of the gear is MUCH smaller than on the UD DNE2 case.
3) the connection from the lead screw to the case is different but either screw works with either motor.
If anyone has an interchange question about the different cases now would be the time to ask.
I have a US Gear Case and a Doug Nash case.
Having them both apart I have yet to see a difference in the two except for the following:
1) There is a difference in controls BUT it appears that you can use either control in either case.
2) in the OD USG case the pitch of the gear is MUCH smaller than on the UD DNE2 case.
3) the connection from the lead screw to the case is different but either screw works with either motor.
If anyone has an interchange question about the different cases now would be the time to ask.
jaluhn83
Full Access Member
Was this a 2 terminal motor, ie later USG?
I have also done this with my USG (3 wire motor) and DNE2 and the gear pitch was the same.
I have also done this with my USG (3 wire motor) and DNE2 and the gear pitch was the same.
