MN Doug Nash overdrive unit for TH400 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Chris H · 03-05-2011, 02:49 PM

I have had this one sitting on the shelf for a while, bought a Gear Vendors and no need to keep them both...

Doug Nash Engineering Dual Range Auxiliary Transmission, bolts on your TH400 transmission instead of the tailshaft housing. Gives a .75 to 1 overdrive ratio. Electrically shifted like a 2 speed truck rear end, and can stay in either direct or overdrive. Commonly used on RVs, motorhomes, bigger trucks. Probably not well suited for hot-rod gear splitting, but pretty handy for the right applications. USGear bought out Doug Nash, very similar to the Dual Range.
Your 4.10 rear becomes a 3.08 in overdrive, 4.57 to 3.42, or 5.13 to 3.85. Keep your deep gear for off the line grunt, then shift to overdrive at highway speed to lower your RPM, maybe even save some gas in the process? Or leave it in overdrive when unloaded. Or...

All manuals and electric controls are included.
$900 plus shipping (less than $75 in the US48 I would guess).

qksilver · 03-05-2011, 09:42 PM

man.........temptation, very sweet.
A thought, total with shipping to 28387 business address...........pay pal?
pm me, i tend to forget things.

Thanks,
Steve

**special-K** · 03-06-2011, 11:11 AM

I wish it bolted to the tailshaft. Then,it probably would work on my M22. Bump for you^^

Chris H · 03-07-2011, 09:04 AM

Quote:

Originally Posted by special-K

I wish it bolted to the tailshaft. Then,it probably would work on my M22. Bump for you^^

I know there was a version of this overdrive that operated as a stand alone or divorced type box. I think it was just a yoke input/housing for the front side.
Probably more trouble than it is worth, but a good excuse to top this ad!

Here is a picture I borrowed from a completed sale on ebay to give an idea on size:

**va72longhorn** · 03-07-2011, 02:08 PM

Chris, are you suppose to be able to use the original drive shaft since it takes the place of the tail? It looks a little longer. Just what I need on my C30 longhorn, though. I had actually been looking to change the 4:56 gears out, but this may be a little nicer set up. Gotta check the funds though.

Chris H · 03-07-2011, 04:03 PM

Quote:

Originally Posted by va72longhorn

Chris, are you suppose to be able to use the original drive shaft since it takes the place of the tail? It looks a little longer. Just what I need on my C30 longhorn, though. I had actually been looking to change the 4:56 gears out, but this may be a little nicer set up. Gotta check the funds though.

You will need to modify/change the drifeshaft. The book says: "Establish new driveshaft dimensions (GM is 12 5/8" shorter ... FOMCO 1' 1/2") . If the vehicle has extremely short front half, it maybe more appropriate to use a new one piece shaft."

PM me your email if you would like me to send the scanned install manual.
4:56 with an overdrive would work real nice!
I will take paypal, so you could pay with your credit card

Chris

**va72longhorn** · 03-07-2011, 05:13 PM

pm'ed

How does the "switch" usually set up? Manually on the dash? Defenitely interested, especially after you call and talk the other half into it. I'll stand in the corner and listen....

Chris H · 03-07-2011, 05:57 PM

Basically an on/off button that attaches to the gear shift lever.

**va72longhorn** · 03-07-2011, 06:06 PM

I knew a guy who had something similar, years ago, that had it hook up to another dimmer switch on the floor. I thought it was the coolest thing. I'll study the book tonight and see how much more it may cost me past the price of it. I hate to get into cutting and balancing the driveshaft. Im assuming you never had it on your 133" wheelbase (same as mine)? Anyway, put me in line for it, and see what my cost would be getting it to the porch. I can have it shipped to a business in 20166 if its any cheaper. Thanks

junkyardjohn · 03-07-2011, 08:07 PM

THATS ABOUT 1/3 THE PRICE OF A GEAR VENDORS UNIT. AT $4 A GALLON IT WONT TAKE THAT THING LONG TO PAY FOR ITSELF. A NO-DOUBT BARGAIN. JOHN

junkyardjohn · 03-08-2011, 11:03 AM

Ttt for a bargain

john

fattyarbuckle · 03-08-2011, 11:13 AM

sweet!

Wish I could swing it but....

good luck with sale.

Chris H · 03-10-2011, 02:12 PM

Still available until someone posts "SOLD" on this thread...

'78RV · 03-14-2011, 12:44 PM

Mark it SOLD......Going in a 1978 P-32 based RV behind a 454/TH400 combo....
The adventure begins.....

junkyardjohn · 03-14-2011, 01:16 PM

Saweeeeet!!!! Bus. John

'78RV · 03-14-2011, 04:24 PM

Thanks....it's my favorite toy. We carry two bikes & two 50cc Suzuki's on a single wheel swivel trailer plus two inflatable kayaks in storage bay...just a rolling collection of R&R toys.....Hoping Chris' OD is going to quiet things down a little at 60mph. At 24', I've got the same drivetrain & gearing as units that go to 36', so I shouldn't be pushing the OD or the TH400 too hard......

http://i283.photobucket.com/albums/kk304/leeschiek/DSC_0810-1.jpg[/IMG]

junkyardjohn · 03-14-2011, 05:12 PM

It ought to be a great match. At almost $4 a dogone gallon, it ought to payoff immedeately. Thats an awful nice looking setup you've got there. I can see why it's your favorite toy. I'd much rather have a classic looking setup like your's than any new one I've seen. Niiiiice. John

MTWayne · 09-18-2012, 11:43 AM

Hi, I have one of these units in my truck, there is no wiring though, is there a way that '78RV or anyone else could send me or e-mail me a scanned copy of the manual so I can figure out how to wire it? Any help is much appreciated!

Thanks,
Wayne

**special-K** · 09-19-2012, 08:10 AM

I never see '78RV on here. I think these are his only 2 posts. Have you tried contacting Doug Nash?

Chris H · 09-19-2012, 09:23 AM

PM me with your email address if you would like a copy of the installation manual and the wiring manual.
I have them as .pdf but too big to attach here.

I did talk to 78RV after installation, and he seemed very pleased with its function.

You can read about his installation here:
http://www.barthmobile.com/eve/forum...267#2543922267

'78RV · 09-19-2012, 09:40 AM

'78RV here.......the overdrive manual is waiting for you in several places out there in cyberspace....here's one of them:

http://www.bangshift.com/forum/showt...ained.../page4

FWIW-some observations after a season's use:

1. Unit has performed great for me...I was sold a solid unit.

2. Weakest link is all the wiring, mainly for the OEM shifter - the electro-mechanical relay was undependable and trouble-prone.

3. My solution was to remove ALL of it....clip the wires of the two gray elipitcal plugs on the case and toss out shifter button, relay and all associated wiring. All it does is send signals to shifter - they do nothing regarding the actual shift change. You only need TWO wires to OD, one on each terminal of slide switch.

4. Replace all that with a truck style floor mounted dimmer switch. Keyed power goes to the center post, one wire from one leg goes to one terminal on slide-switch on passenger side of case, other wire goes from other leg to other terminal on slide switch. Now you just tap dimmer switch and switch motor compresses spring, ready for shifting when you unload the driveline torque.

5. When you figure which one is hot in OD, scab in a peanut LED light and you've got visual status of OD mode.

6. Electrical wear parts are shift motor and slide switch on case. I got new replacement motor over the counter at NAPA and switches are readily available.

7. Remember, shift motor doesn't shift anything...it merely preloads a spring that stays compressed until you unload driveline, then spring slides the gears. Shifting from normal to OD produces a noticeable CLUNK.....shifting from OD to normal produces a light CLINK...just the nature of the beast I guess.

Let me know if you need part #'s & sources for motor & switch. Hope this helps.....

03-05-2011, 02:49 PM	#1
Chris H 72 C30 Trailer Queen Join Date: Dec 1999 Location: SE MN, USA Posts: 794	Doug Nash overdrive unit for TH400 I have had this one sitting on the shelf for a while, bought a Gear Vendors and no need to keep them both... Doug Nash Engineering Dual Range Auxiliary Transmission, bolts on your TH400 transmission instead of the tailshaft housing. Gives a .75 to 1 overdrive ratio. Electrically shifted like a 2 speed truck rear end, and can stay in either direct or overdrive. Commonly used on RVs, motorhomes, bigger trucks. Probably not well suited for hot-rod gear splitting, but pretty handy for the right applications. USGear bought out Doug Nash, very similar to the Dual Range. Your 4.10 rear becomes a 3.08 in overdrive, 4.57 to 3.42, or 5.13 to 3.85. Keep your deep gear for off the line grunt, then shift to overdrive at highway speed to lower your RPM, maybe even save some gas in the process? Or leave it in overdrive when unloaded. Or... All manuals and electric controls are included. $900 plus shipping (less than $75 in the US48 I would guess). Attached Images __________________ Chris H 72 C30 133" 72 C30 157" flat-dump 69 C10 short fleet 71 ElCamino 2000 K2500 crewcab shortbed (sold, sorry old friend) 2005 GMC 2500HD shortcrew Duramax 2006 K1500 RCSB and a couple other projects/parts Last edited by Chris H; 03-05-2011 at 03:13 PM.

03-06-2011, 11:11 AM	#3
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,863	Re: Doug Nash overdrive unit for TH400 I wish it bolted to the tailshaft. Then,it probably would work on my M22. Bump for you^^ __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

03-07-2011, 02:08 PM	#5
va72longhorn Senior Member Join Date: Dec 2009 Location: Culpeper, VA Posts: 431	Re: Doug Nash overdrive unit for TH400 Chris, are you suppose to be able to use the original drive shaft since it takes the place of the tail? It looks a little longer. Just what I need on my C30 longhorn, though. I had actually been looking to change the 4:56 gears out, but this may be a little nicer set up. Gotta check the funds though.

03-07-2011, 05:13 PM	#7
va72longhorn Senior Member Join Date: Dec 2009 Location: Culpeper, VA Posts: 431	Re: Doug Nash overdrive unit for TH400 pm'ed How does the "switch" usually set up? Manually on the dash? Defenitely interested, especially after you call and talk the other half into it. I'll stand in the corner and listen....

03-07-2011, 05:57 PM	#8
Chris H 72 C30 Trailer Queen Join Date: Dec 1999 Location: SE MN, USA Posts: 794	Re: Doug Nash overdrive unit for TH400 Basically an on/off button that attaches to the gear shift lever. Attached Images __________________ Chris H 72 C30 133" 72 C30 157" flat-dump 69 C10 short fleet 71 ElCamino 2000 K2500 crewcab shortbed (sold, sorry old friend) 2005 GMC 2500HD shortcrew Duramax 2006 K1500 RCSB and a couple other projects/parts

03-05-2011, 09:42 PM	#2
qksilver Senior Member Join Date: Dec 2004 Location: Southern Pines NC Posts: 3,853	Re: Doug Nash overdrive unit for TH400 man.........temptation, very sweet. A thought, total with shipping to 28387 business address...........pay pal? pm me, i tend to forget things. Thanks, Steve

03-07-2011, 06:06 PM	#9
va72longhorn Senior Member Join Date: Dec 2009 Location: Culpeper, VA Posts: 431	Re: Doug Nash overdrive unit for TH400 I knew a guy who had something similar, years ago, that had it hook up to another dimmer switch on the floor. I thought it was the coolest thing. I'll study the book tonight and see how much more it may cost me past the price of it. I hate to get into cutting and balancing the driveshaft. Im assuming you never had it on your 133" wheelbase (same as mine)? Anyway, put me in line for it, and see what my cost would be getting it to the porch. I can have it shipped to a business in 20166 if its any cheaper. Thanks

03-07-2011, 08:07 PM	#10
junkyardjohn Registered User Join Date: Aug 2001 Location: SOMERSET KY. Posts: 6,427	Re: Doug Nash overdrive unit for TH400 THATS ABOUT 1/3 THE PRICE OF A GEAR VENDORS UNIT. AT $4 A GALLON IT WONT TAKE THAT THING LONG TO PAY FOR ITSELF. A NO-DOUBT BARGAIN. JOHN __________________ junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. THERES ROOM FOR ALL OF GODS CREATURES RIGHT NEXT TO MY MASHED POTATOES// LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST

03-08-2011, 11:03 AM	#11
junkyardjohn Registered User Join Date: Aug 2001 Location: SOMERSET KY. Posts: 6,427	Re: Doug Nash overdrive unit for TH400 Ttt for a bargain john __________________ junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. THERES ROOM FOR ALL OF GODS CREATURES RIGHT NEXT TO MY MASHED POTATOES// LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST

03-08-2011, 11:13 AM	#12
fattyarbuckle Registered User Join Date: Nov 2010 Location: St. Louis Mo. Posts: 282	Re: Doug Nash overdrive unit for TH400 sweet! Wish I could swing it but.... good luck with sale.

03-10-2011, 02:12 PM	#13
Chris H 72 C30 Trailer Queen Join Date: Dec 1999 Location: SE MN, USA Posts: 794	Re: Doug Nash overdrive unit for TH400 Still available until someone posts "SOLD" on this thread... __________________ Chris H 72 C30 133" 72 C30 157" flat-dump 69 C10 short fleet 71 ElCamino 2000 K2500 crewcab shortbed (sold, sorry old friend) 2005 GMC 2500HD shortcrew Duramax 2006 K1500 RCSB and a couple other projects/parts

03-14-2011, 12:44 PM	#14
'78RV Registered User Join Date: Mar 2011 Location: College Park, MD Posts: 3	Re: Doug Nash overdrive unit for TH400 Mark it SOLD......Going in a 1978 P-32 based RV behind a 454/TH400 combo.... The adventure begins.....

03-14-2011, 01:16 PM	#15
junkyardjohn Registered User Join Date: Aug 2001 Location: SOMERSET KY. Posts: 6,427	Re: Doug Nash overdrive unit for TH400 Saweeeeet!!!! Bus. John __________________ junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. THERES ROOM FOR ALL OF GODS CREATURES RIGHT NEXT TO MY MASHED POTATOES// LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST

03-14-2011, 04:24 PM	#16
'78RV Registered User Join Date: Mar 2011 Location: College Park, MD Posts: 3	Re: Doug Nash overdrive unit for TH400 Thanks....it's my favorite toy. We carry two bikes & two 50cc Suzuki's on a single wheel swivel trailer plus two inflatable kayaks in storage bay...just a rolling collection of R&R toys.....Hoping Chris' OD is going to quiet things down a little at 60mph. At 24', I've got the same drivetrain & gearing as units that go to 36', so I shouldn't be pushing the OD or the TH400 too hard...... http://i283.photobucket.com/albums/kk304/leeschiek/DSC_0810-1.jpg[/IMG]

03-14-2011, 05:12 PM	#17
junkyardjohn Registered User Join Date: Aug 2001 Location: SOMERSET KY. Posts: 6,427	Re: Doug Nash overdrive unit for TH400 It ought to be a great match. At almost $4 a dogone gallon, it ought to payoff immedeately. Thats an awful nice looking setup you've got there. I can see why it's your favorite toy. I'd much rather have a classic looking setup like your's than any new one I've seen. Niiiiice. John __________________ junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. THERES ROOM FOR ALL OF GODS CREATURES RIGHT NEXT TO MY MASHED POTATOES// LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST Last edited by junkyardjohn; 03-14-2011 at 05:13 PM.



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09-18-2012, 11:43 AM	#18
MTWayne Registered User Join Date: Apr 2009 Location: Sailda, CA Posts: 2	Re: Doug Nash overdrive unit for TH400 Hi, I have one of these units in my truck, there is no wiring though, is there a way that '78RV or anyone else could send me or e-mail me a scanned copy of the manual so I can figure out how to wire it? Any help is much appreciated! Thanks, Wayne

09-19-2012, 08:10 AM	#19
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,863	Re: Doug Nash overdrive unit for TH400 I never see '78RV on here. I think these are his only 2 posts. Have you tried contacting Doug Nash? __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

09-19-2012, 09:23 AM	#20
Chris H 72 C30 Trailer Queen Join Date: Dec 1999 Location: SE MN, USA Posts: 794	Re: Doug Nash overdrive unit for TH400 PM me with your email address if you would like a copy of the installation manual and the wiring manual. I have them as .pdf but too big to attach here. I did talk to 78RV after installation, and he seemed very pleased with its function. You can read about his installation here: http://www.barthmobile.com/eve/forum...267#2543922267 __________________ Chris H 72 C30 133" 72 C30 157" flat-dump 69 C10 short fleet 71 ElCamino 2000 K2500 crewcab shortbed (sold, sorry old friend) 2005 GMC 2500HD shortcrew Duramax 2006 K1500 RCSB and a couple other projects/parts

09-19-2012, 09:40 AM	#21
'78RV Registered User Join Date: Mar 2011 Location: College Park, MD Posts: 3	Re: Doug Nash overdrive unit for TH400 '78RV here.......the overdrive manual is waiting for you in several places out there in cyberspace....here's one of them: http://www.bangshift.com/forum/showt...ained.../page4 FWIW-some observations after a season's use: 1. Unit has performed great for me...I was sold a solid unit. 2. Weakest link is all the wiring, mainly for the OEM shifter - the electro-mechanical relay was undependable and trouble-prone. 3. My solution was to remove ALL of it....clip the wires of the two gray elipitcal plugs on the case and toss out shifter button, relay and all associated wiring. All it does is send signals to shifter - they do nothing regarding the actual shift change. You only need TWO wires to OD, one on each terminal of slide switch. 4. Replace all that with a truck style floor mounted dimmer switch. Keyed power goes to the center post, one wire from one leg goes to one terminal on slide-switch on passenger side of case, other wire goes from other leg to other terminal on slide switch. Now you just tap dimmer switch and switch motor compresses spring, ready for shifting when you unload the driveline torque. 5. When you figure which one is hot in OD, scab in a peanut LED light and you've got visual status of OD mode. 6. Electrical wear parts are shift motor and slide switch on case. I got new replacement motor over the counter at NAPA and switches are readily available. 7. Remember, shift motor doesn't shift anything...it merely preloads a spring that stays compressed until you unload driveline, then spring slides the gears. Shifting from normal to OD produces a noticeable CLUNK.....shifting from OD to normal produces a light CLINK...just the nature of the beast I guess. Let me know if you need part #'s & sources for motor & switch. Hope this helps.....

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