Over Drive & Options - The 1947 - Present Chevrolet & GMC Truck Message Board Network

vtblazer · 10-02-2005, 07:37 AM

Age old story, low gears and highway driving...

Trying to sort through all the ways that can help out the highway travel situation.
Any input, advise or "done that" would be helpful.

The vehicle in need of this 'upgrade' is a 4wd truck with an 8ft bed and a big block.
Used as a daily driver/work truck/tow vehicle, running a th-350, 4:11's & 33's

The better of the options I'm aware of are:
Change the final drive gears
Change to a 700r or some other overdrive tranny
Install an overdrive unit behind the t-case for 2wd travel

1) Changing the final drive is the way I'm currently leaning.
If I go to 3:08's it gets me about 2100rpm's on the highway @ 65mph
Just trying to decide how the big block would do when towing with those gears.

2) I have a 4wd 700r but I'm sure it needs a rebuild, to me this adds up to big $$
and a timely retrofit.

3) Gear Vendors overdrive unit, totally big bucks but still worth looking into given the relative simplicity of it.

Longhorn Man · 10-02-2005, 07:44 AM

If the gear vendors is doable to you as far as the $$ goes, then it is the only way to go.
I would never want a 700R4 with a big block and towing....that's an expensive combo.
the 3.07 gears would be fine with the big block, however, good luck finding those gears for both diffs....pluss, the cost would add up onless you can do it yourself.

classicchev · 10-02-2005, 01:41 PM

Quote:

Originally Posted by Longhorn Man

If the gear vendors is doable to you as far as the $$ goes, then it is the only way to go.
I would never want a 700R4 with a big block and towing....that's an expensive combo.
the 3.07 gears would be fine with the big block, however, good luck finding those gears for both diffs....pluss, the cost would add up onless you can do it yourself.

This ones going to up for discussion for a while. I have a shop that is rebuilding my 700r4 for my 502 in my Jimmy, He says that the 7oo is the only way to go. He rebuilt a 4oo for a large motorhome with a 454, then installed a gearvendors behind it, that combination did not last long for the customer. They had problems with the tranny overheating, bad fuel economy etc. The shop then built a 700r4 to go behind the 454 with the same rear rear gears, and according to the onboard tripometer , the 7oo was even better in fuel economy. I dont know if it was a issue with a faulty unit, I really doubt it was the install, because one person did the rebuild to install, but something just didnt work.
This tranny shop has been around in Calgary for many years, building many high engine torque trannies and the shop owner even has some ties with GM becuase of his modifacations to the 700, and he FIRMLY told me NOT to use the gear vendors. I was all set on the 400./ gear vendors setup, so at one point I was a beleiver in the gearvendors.

One question I would like to ask if there is anyone out there who has a Gearvendors installed in their truck, and drives the truck daily, what is their opinion??

, Darren

gator2511 · 10-02-2005, 06:36 PM

Like I said above I have a 72 swb 4x4 with a stock chevy 350 crate engine, th400 tranny, gear vendors od and 3.73 gears. Its my only truck and my daily driver. I didn't help my mileage by changing to a th400 but I wanted the strength. I have not checked the highway mileage but after driving to the same hunting grounds with and without the od I can tell you the mileage is a LOT better. Cruising the interstate at 70 mph at 2100 rpm should be right where you want it. You have six gears so if you can't find the right rpm combo you never will. When pulling my 6200 lb. 25 foot trailer the tranny runs below 180 degrees. I have talked to a lot of people at the local car and truck shows and have never heard any complaints about the unit. GV was the way for me but maybe not for everybody.

67-72williso · 10-02-2005, 09:59 PM

If its 8 lug you can use a Dana 61 to get the 3.07 gears in the rear. Very heavy duty rears. I`m using one in my 70 C-20 daily driver.
Later Willis

Chris H · 10-03-2005, 01:00 PM

http://www.rverscorner.com/info/auxtrans.html

Here is a link to some information on the 2 currently marketed auxiliary transmissions. US Gear and Gear Vendors are the 2 main players, and mainly marketed to motorhome/rv folks.

I have 2 Doug Nash overdrives. (US Gear bought out Doug Nash, still lots of parts/support available). I bought one set up as a true auxiliary box, with a driveshaft yoke in and out. It would mount in place of a carrier bearing. My other unit bolts in place of the tailshaft on a TH400. I am planning on using the transmission mounted overdrive on my 72 C30 with a 402/TH400 and 4.10 rear.

Also see: http://www.6066gmcguy.org/spicer-5831-b.htm
This is information on an older Spicer auxiliary transmission with manual shifting. I cant see how you would get this one to shift on the fly with an automatic trans, but interesting anyways.

Scrubby · 10-03-2005, 03:28 PM

Quote:

Originally Posted by gator2511

I have not checked the highway mileage but after driving to the same hunting grounds with and without the od I can tell you the mileage is a LOT better.

If we're just talking gas mileage, you can buy a lot of gas for the $2500 price tag of a Gear Vendors overdrive.

I would get new gears if it was really bothering me, but I might just drive it and try not to worry about the high revs.

TP from Cntl PA · 10-03-2005, 05:40 PM

Hey Chris, I wanted to use a Brownie Over/Under in my truck but I couldn't find one

They are cool!

Had anyone ever seen the OD unit Dana made that for stick trucks...............It bolted on the bell housing and had an imput shaft on it, the trans(3/4spd) bolted on the rear of it then. Driveshaft was shortened 6" because of the extra length............It had a stick which was shifted manually, it was fully syncro too. Had an OD in each gear.

I seen one on ebay awhile back and got confused on when it ended and I missed it............Always wanted one of them too!

vtblazer · 10-03-2005, 06:19 PM

Quote:

Originally Posted by Scrubby

If we're just talking gas mileage, you can buy a lot of gas for the $2500 price tag of a Gear Vendors overdrive.

Yep, I agree with ya on that.

My biggest concerns are two fold, one is the constant 2800 plus rpm's of basic 65mph highway driving on a big block.

Two, that's as fast as I'm willing to push it. (the r's)
I typically like to travel around 70/75 and right now, that's currently not an option with these gears/this set up. (can't go fast enough)

Gas mileage is pretty much the last issue, I'm more concerned with preservation of the motor.

As of a couple of years ago, these trucks are all I own, all I drive and all I care to drive so buying gas for 'em, really dosen't matter...I do it and like it.

*FormerMember* · 10-02-2005, 08:46 AM

It's a matter of costs, Kurt. I can do the gears in both diffs.

Gear swap: 500.00 in parts, BBC will be fine towing with 33's.
Trans rebuild and adapter: 1200-1500 plus R+R still a shakey proposition. There's a reason GM got away from the 700 series, and they're still going out (4L60E)
Gear vendors OD: 2700 new (?), best of both worlds IMHO.

4th option: 4L80E

gator2511 · 10-02-2005, 09:06 AM

I was in the same boat. I just didn't want to put a 700r4 in my 4wd truck. I had one in my 82 vette and it was a good tranny. I wanted heavy duty components that would pull my travel trailer and go in the mud holes with no worry. I'm not knocking the 700r4 but the th400 is no doubt tougher and Much easier to set up. At todays gas prices it will pay for itself in about 3 years and the driveline is almost bullet proof. Only drawback is the GV unit shifts hard but driving technique gets around that. AT 70 mph it dropped my rpms by 1000. I think its the best of both worlds, six speeds when you are towing and back to the low gears when you are in the woods. The 27 of this month The trailer (6000 lbs) will be towed to our muzzloader camp and after camp is set up the od unit will be turned off and into the sugar sand and mudholes we go !

GMC71k20 · 10-02-2005, 12:01 PM

would you consider putting on bigger tires?
did you get this truck your talking about...and if so wheres the pics?

cableguy0 · 10-02-2005, 01:31 PM

the gear vendors is great if your only concern is lowering rpms. the problem with the gear vendors is the parasitic drag on the engine eating horsepower and i have seen a lot of times zero mileage improvement. 4wd big block with big tires rarely equals gas mileage in any case. your moving a ton of weight with a bunch of wind resistance. getting down to 2100 rpms could actually have negative affects on mileage depending on the engine combo and the cams cruise rpm

Longhorn Man · 10-02-2005, 01:41 PM

I never heard of the gearvendors being a big load, but in all reality since they are designed for RV's and straight trucks, I can see that.
And good call on the lower RPMs maybe not helping on MPG.

classicchev · 10-02-2005, 01:46 PM

You guys type too fast, totally forgot about the low rpm's. That was another thing that the shop said, you can only go so low on the rpms, before you kill the pump in the tranny. He gave me a perfect example with the S10 with the 200r4/2.8L POS.

TP from Cntl PA · 10-02-2005, 02:31 PM

Haven't ever drove a truck with a GV in it, but I know my homemade OD setup greatly increase mpg with the Cummins. It lets us control what rpms we want to run at so we can utilize the torque curve of the engine to maximize efficiency.

Granted I am talking a manual system, but I imagine just like farm tractors, you loose efficiency with the auto and maybe the GV does make it worse, just like a straight gear drive tractor vs a powershift, or even worse, a Hydro.

**pjmoreland** · 10-02-2005, 02:37 PM

One nice thing about the 700R4 (other than the overdrive) is the torque converter clutch. Eliminating the torque converter slip is significant when it comes to improving efficiency. Switching to a TH350C transmission or a manual transmission are other options for eliminating torque converter losses. I'm going out on a limb saying this, but I wouldn't be surprised if a TH350C combined with 3.07 gears might get better mileage than a 700R4 with 3.73 gears. When a 700R4 is in overdrive, the planetaries are spinning and generating heat. When a TH350C is in 3rd gear, there are no planetaries spinning. Of course you miss out on the nice low first gear of the 700R4.

Ochre · 10-03-2005, 10:16 PM

I remember hearing about how the frito-lay box trucks made in the 80's had a Gear vendors/TH400 combo behind a diesel, I don't know anything else about them but maybe thats a route thats worth considering...

Personally, I hate automatics (especially that rat bastard 700r4) with an intense passion, and would dump either automatic in leiu of an NV4500 mated to an NP208 or NP241. I'm waiting for somebody to make a bellhousing so we can get the NV5600 behind a SBC/BBC...

Longhorn Man · 10-03-2005, 10:20 PM

Frito lay trucks don't have a G/V on them, the older ones are TH400's, then the 6.5 trucks have a 4L80E, and the later ones with the Cummins 4BTA run allison trannys. Our shop rebuilds them.

see ten · 10-03-2005, 10:33 PM

Classic trucks ran an article a month or so back where they installed a Gear Vendors unit in an early 70s truck they are building. I would have to dig the article up for the specs. I do remember them saying it was expensive, but if you ever drove a truck with one you would become a believer. Seems like they had one that shifted or "split" the gears with a floor mounted dimmer switch. I think they said that there was another available that worked automaticaly.

gator2511 · 10-04-2005, 08:56 AM

Mine has a switch panel that lets you shift manually or automatically. It uses the foot switch like our headlight switch. I use the manual feature in slow heavy city traffic and because it shifts hard. With the manual mode you can shift it smoothly. In manual mode you get six forward gears and in automatic you get four. Main thing for me is I can drive fast at low rpm to the woods hauling my trailer and then go to 4wd drive low in the woods. The th400 will take it all without breaking a sweat.

**special-K** · 10-04-2005, 08:16 AM

I think GV is the way to go.I want to retro-fit a 4L80E at some point.Either one will give same results.

**truckster** · 10-04-2005, 10:46 AM

I think if your main issue is to reduce the RPMs at cruise, the final drive is going to be the cheapest way to go. And with a BB you don't really need to worry about getting off the line.

vtblazer · 10-13-2005, 06:46 AM

Ended up getting an older Doug Nash 2spd tranny.

It's 22" from yolk center to yolk center so when mounted behind the transfer case, the drive line should be about the same length as a shortbed's would be stock, maybe even a bit longer.
That being the case, driveline angles should be fine.

The other (IMO) good thing about this one as opposed to the GV's, is that once in either gear, it can be left there.
I'll be able to just drive around unloaded shifted into the overdrive gear.
Yes it will be only for 2wd operation but that's fine.

This overdrive will give me roughly a 3:23 final drive when engaged.
Add this to the 33" tall tires and it gives roughly a 3:08 final at the ground.
Sum it all up and it works out to about 2100/2300rpm's @ 65mph.

Note:
Ratio's and tire sizes posted above are not "exact" but close enough for me.

Thanks for all the input, it was informative and helpful.

farside847 · 10-13-2005, 11:27 AM

Quote:

Originally Posted by vtblazer

Ended up getting an older Doug Nash 2spd tranny.

It's 22" from yolk center to yolk center so when mounted behind the transfer case, the drive line should be about the same length as a shortbed's would be stock, maybe even a bit longer.
That being the case, driveline angles should be fine.

The other (IMO) good thing about this one as opposed to the GV's, is that once in either gear, it can be left there.
I'll be able to just drive around unloaded shifted into the overdrive gear.
Yes it will be only for 2wd operation but that's fine.

This overdrive will give me roughly a 3:23 final drive when engaged.
Add this to the 33" tall tires and it gives roughly a 3:08 final at the ground.
Sum it all up and it works out to about 2100/2300rpm's @ 65mph.

Id be VERY interested in hearing more about this install, and pics!

10-02-2005, 07:37 AM	#1
vtblazer Registered User Join Date: Oct 2003 Location: Central Vermont Posts: 8,538	Over Drive & Options Age old story, low gears and highway driving... Trying to sort through all the ways that can help out the highway travel situation. Any input, advise or "done that" would be helpful. The vehicle in need of this 'upgrade' is a 4wd truck with an 8ft bed and a big block. Used as a daily driver/work truck/tow vehicle, running a th-350, 4:11's & 33's The better of the options I'm aware of are: Change the final drive gears Change to a 700r or some other overdrive tranny Install an overdrive unit behind the t-case for 2wd travel 1) Changing the final drive is the way I'm currently leaning. If I go to 3:08's it gets me about 2100rpm's on the highway @ 65mph Just trying to decide how the big block would do when towing with those gears. 2) I have a 4wd 700r but I'm sure it needs a rebuild, to me this adds up to big $$ and a timely retrofit. 3) Gear Vendors overdrive unit, totally big bucks but still worth looking into given the relative simplicity of it.

10-02-2005, 06:36 PM	#4
gator2511 Registered User Join Date: Mar 2005 Location: tampa florida Posts: 776	Like I said above I have a 72 swb 4x4 with a stock chevy 350 crate engine, th400 tranny, gear vendors od and 3.73 gears. Its my only truck and my daily driver. I didn't help my mileage by changing to a th400 but I wanted the strength. I have not checked the highway mileage but after driving to the same hunting grounds with and without the od I can tell you the mileage is a LOT better. Cruising the interstate at 70 mph at 2100 rpm should be right where you want it. You have six gears so if you can't find the right rpm combo you never will. When pulling my 6200 lb. 25 foot trailer the tranny runs below 180 degrees. I have talked to a lot of people at the local car and truck shows and have never heard any complaints about the unit. GV was the way for me but maybe not for everybody. Last edited by gator2511; 10-02-2005 at 06:44 PM.

10-02-2005, 09:59 PM	#5
67-72williso Junk/Daily Driver Club Join Date: Feb 2004 Location: Manheim, PA 17545 Posts: 253	If its 8 lug you can use a Dana 61 to get the 3.07 gears in the rear. Very heavy duty rears. I`m using one in my 70 C-20 daily driver. Later Willis __________________ Daily Driver: 1970 C-20 400 sbc,sm-465,Dana 61 one ton SRW rear, 3.07 gears, locker. There are three kinds of people: those who make things happen, those who watch things happen, and those who have no idea what happened!

10-03-2005, 01:00 PM	#6
Chris H 72 C30 Trailer Queen Join Date: Dec 1999 Location: SE MN, USA Posts: 794	http://www.rverscorner.com/info/auxtrans.html Here is a link to some information on the 2 currently marketed auxiliary transmissions. US Gear and Gear Vendors are the 2 main players, and mainly marketed to motorhome/rv folks. I have 2 Doug Nash overdrives. (US Gear bought out Doug Nash, still lots of parts/support available). I bought one set up as a true auxiliary box, with a driveshaft yoke in and out. It would mount in place of a carrier bearing. My other unit bolts in place of the tailshaft on a TH400. I am planning on using the transmission mounted overdrive on my 72 C30 with a 402/TH400 and 4.10 rear. Also see: http://www.6066gmcguy.org/spicer-5831-b.htm This is information on an older Spicer auxiliary transmission with manual shifting. I cant see how you would get this one to shift on the fly with an automatic trans, but interesting anyways. __________________ 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; 10-03-2005 at 01:07 PM.

10-03-2005, 05:40 PM	#8
TP from Cntl PA Registered User Join Date: Apr 2003 Location: Central PA....In the Berg of Nisbet Posts: 790	Hey Chris, I wanted to use a Brownie Over/Under in my truck but I couldn't find one They are cool! Had anyone ever seen the OD unit Dana made that for stick trucks...............It bolted on the bell housing and had an imput shaft on it, the trans(3/4spd) bolted on the rear of it then. Driveshaft was shortened 6" because of the extra length............It had a stick which was shifted manually, it was fully syncro too. Had an OD in each gear. I seen one on ebay awhile back and got confused on when it ended and I missed it............Always wanted one of them too! __________________ '72 K-20 EFI'ed 250 Inline/4spd stake body, Farm Truck '71 C-20 Cummins Diesel Powered, In storage thanks to $5.00 diesel! '69 3500 GMC 305V-6/4spd, Still under reconstruction.......... Inlines Rule! 6 soldiers standing is better than 8 laying down!!!!!!!!

10-02-2005, 07:44 AM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	If the gear vendors is doable to you as far as the $$ goes, then it is the only way to go. I would never want a 700R4 with a big block and towing....that's an expensive combo. the 3.07 gears would be fine with the big block, however, good luck finding those gears for both diffs....pluss, the cost would add up onless you can do it yourself.

10-02-2005, 08:46 AM	#10
FormerMember Account Suspended Join Date: Feb 2004 Posts: 3,051	It's a matter of costs, Kurt. I can do the gears in both diffs. Gear swap: 500.00 in parts, BBC will be fine towing with 33's. Trans rebuild and adapter: 1200-1500 plus R+R still a shakey proposition. There's a reason GM got away from the 700 series, and they're still going out (4L60E) Gear vendors OD: 2700 new (?), best of both worlds IMHO. 4th option: 4L80E Last edited by FormerMember; 10-02-2005 at 09:52 AM.

10-02-2005, 09:06 AM	#11
gator2511 Registered User Join Date: Mar 2005 Location: tampa florida Posts: 776	I was in the same boat. I just didn't want to put a 700r4 in my 4wd truck. I had one in my 82 vette and it was a good tranny. I wanted heavy duty components that would pull my travel trailer and go in the mud holes with no worry. I'm not knocking the 700r4 but the th400 is no doubt tougher and Much easier to set up. At todays gas prices it will pay for itself in about 3 years and the driveline is almost bullet proof. Only drawback is the GV unit shifts hard but driving technique gets around that. AT 70 mph it dropped my rpms by 1000. I think its the best of both worlds, six speeds when you are towing and back to the low gears when you are in the woods. The 27 of this month The trailer (6000 lbs) will be towed to our muzzloader camp and after camp is set up the od unit will be turned off and into the sugar sand and mudholes we go !

10-02-2005, 12:01 PM	#12
GMC71k20 Registered User Join Date: Aug 2002 Location: mass Posts: 1,277	would you consider putting on bigger tires? did you get this truck your talking about...and if so wheres the pics?

10-02-2005, 01:31 PM	#13
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	the gear vendors is great if your only concern is lowering rpms. the problem with the gear vendors is the parasitic drag on the engine eating horsepower and i have seen a lot of times zero mileage improvement. 4wd big block with big tires rarely equals gas mileage in any case. your moving a ton of weight with a bunch of wind resistance. getting down to 2100 rpms could actually have negative affects on mileage depending on the engine combo and the cams cruise rpm __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

10-02-2005, 01:41 PM	#14
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	I never heard of the gearvendors being a big load, but in all reality since they are designed for RV's and straight trucks, I can see that. And good call on the lower RPMs maybe not helping on MPG.

10-02-2005, 01:46 PM	#15
classicchev Senior Member Join Date: Nov 2003 Location: Calgary Alberta Posts: 1,936	You guys type too fast, totally forgot about the low rpm's. That was another thing that the shop said, you can only go so low on the rpms, before you kill the pump in the tranny. He gave me a perfect example with the S10 with the 200r4/2.8L POS. __________________ 67- 72 Parts collecter

10-02-2005, 02:31 PM	#16
TP from Cntl PA Registered User Join Date: Apr 2003 Location: Central PA....In the Berg of Nisbet Posts: 790	Haven't ever drove a truck with a GV in it, but I know my homemade OD setup greatly increase mpg with the Cummins. It lets us control what rpms we want to run at so we can utilize the torque curve of the engine to maximize efficiency. Granted I am talking a manual system, but I imagine just like farm tractors, you loose efficiency with the auto and maybe the GV does make it worse, just like a straight gear drive tractor vs a powershift, or even worse, a Hydro. __________________ '72 K-20 EFI'ed 250 Inline/4spd stake body, Farm Truck '71 C-20 Cummins Diesel Powered, In storage thanks to $5.00 diesel! '69 3500 GMC 305V-6/4spd, Still under reconstruction.......... Inlines Rule! 6 soldiers standing is better than 8 laying down!!!!!!!!

10-02-2005, 02:37 PM	#17
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,644	One nice thing about the 700R4 (other than the overdrive) is the torque converter clutch. Eliminating the torque converter slip is significant when it comes to improving efficiency. Switching to a TH350C transmission or a manual transmission are other options for eliminating torque converter losses. I'm going out on a limb saying this, but I wouldn't be surprised if a TH350C combined with 3.07 gears might get better mileage than a 700R4 with 3.73 gears. When a 700R4 is in overdrive, the planetaries are spinning and generating heat. When a TH350C is in 3rd gear, there are no planetaries spinning. Of course you miss out on the nice low first gear of the 700R4.

10-03-2005, 10:16 PM	#18
Ochre Registered User Join Date: Mar 2005 Location: minnesota Posts: 78	I remember hearing about how the frito-lay box trucks made in the 80's had a Gear vendors/TH400 combo behind a diesel, I don't know anything else about them but maybe thats a route thats worth considering... Personally, I hate automatics (especially that rat bastard 700r4) with an intense passion, and would dump either automatic in leiu of an NV4500 mated to an NP208 or NP241. I'm waiting for somebody to make a bellhousing so we can get the NV5600 behind a SBC/BBC...



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10-03-2005, 10:20 PM	#19
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Frito lay trucks don't have a G/V on them, the older ones are TH400's, then the 6.5 trucks have a 4L80E, and the later ones with the Cummins 4BTA run allison trannys. Our shop rebuilds them.

10-03-2005, 10:33 PM	#20
see ten WTB this ad Join Date: Sep 2004 Location: Lafayette Georgia Posts: 5,074	Classic trucks ran an article a month or so back where they installed a Gear Vendors unit in an early 70s truck they are building. I would have to dig the article up for the specs. I do remember them saying it was expensive, but if you ever drove a truck with one you would become a believer. Seems like they had one that shifted or "split" the gears with a floor mounted dimmer switch. I think they said that there was another available that worked automaticaly.

10-04-2005, 08:56 AM	#21
gator2511 Registered User Join Date: Mar 2005 Location: tampa florida Posts: 776	Mine has a switch panel that lets you shift manually or automatically. It uses the foot switch like our headlight switch. I use the manual feature in slow heavy city traffic and because it shifts hard. With the manual mode you can shift it smoothly. In manual mode you get six forward gears and in automatic you get four. Main thing for me is I can drive fast at low rpm to the woods hauling my trailer and then go to 4wd drive low in the woods. The th400 will take it all without breaking a sweat.

10-04-2005, 08:16 AM	#22
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,858	I think GV is the way to go.I want to retro-fit a 4L80E at some point.Either one will give same results. __________________ "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 ~

10-04-2005, 10:46 AM	#23
truckster Senior Member Join Date: Jan 2001 Location: Orem, Utah Posts: 7,941	I think if your main issue is to reduce the RPMs at cruise, the final drive is going to be the cheapest way to go. And with a BB you don't really need to worry about getting off the line. __________________ I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson

10-13-2005, 06:46 AM	#24
vtblazer Registered User Join Date: Oct 2003 Location: Central Vermont Posts: 8,538	Ended up getting an older Doug Nash 2spd tranny. It's 22" from yolk center to yolk center so when mounted behind the transfer case, the drive line should be about the same length as a shortbed's would be stock, maybe even a bit longer. That being the case, driveline angles should be fine. The other (IMO) good thing about this one as opposed to the GV's, is that once in either gear, it can be left there. I'll be able to just drive around unloaded shifted into the overdrive gear. Yes it will be only for 2wd operation but that's fine. This overdrive will give me roughly a 3:23 final drive when engaged. Add this to the 33" tall tires and it gives roughly a 3:08 final at the ground. Sum it all up and it works out to about 2100/2300rpm's @ 65mph. Note: Ratio's and tire sizes posted above are not "exact" but close enough for me. Thanks for all the input, it was informative and helpful.

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