External Overdrive??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

impalaboy9 · 02-21-2011, 09:31 PM

Ok guys I'm nearing the end of my build I will try to update and post some pics later. When I started I was going to be in town with a few very short trips. Now I may have to make an 850 mile trip on a fairly regular basis. I used the m20 I had laying around and I spent quite a while making the linkage work. I also have a new tremec 5 speed collecting dust. Problem is that the transmission is way nicer than my truck and I'd like to use it on a different project. I have heard about overdrives for the 4speed but I don't know anything about them and the search hasn't yielded much. Can anyone tell me the pros and cons and how they work. Also how do you shift into the overdrive? Currently I'm running a stock 305 but this summer I'm building a 283 with tunnel ram for it. Nothing with ridiculous power the tunnel ram is more for the novelty of it. Thanks guys.

**Corts60** · 02-21-2011, 09:46 PM

Hey, I am not sure about the factory overdrives that were offered or their availability but, I use a gear vendors overdrive in my '78. It is electro-hydraulic and is basically a two-speed transmission that bolts to the back of my turbo 400. I don't know if they are available for the manuals but you may be able to get pointed in the right direction by looking at gear vendors website.

'63GENIII · 02-21-2011, 10:20 PM

I have seen a 3 spd with an external O.D. that was electric. My brother had one in his '56 wagon until he put in the 700r4. Seems I remember he would flip a switch, lift his foot and it would engage. It would also downshift automaticaly too if he would give it enough gas. I think it was out of a mid to late 50's passenger car. All cast iron and way heavy.

impalaboy9 · 02-22-2011, 12:45 AM

Holy buckets those gear vendor units are expensive but they look sweet. Didn't Corvette do something like that for a while?

mikie 1954 · 02-22-2011, 02:37 AM

There is a ranger overdrive also. The way I understand it ,it goes between the bell and trans. It has a lever you use to ingage or disingage to split each gear. ADVANCE ADAPTER in PASO ROBLES , CA. make them.

NCD1966 · 02-22-2011, 10:33 AM

I have a saginaw 3 speed with a factory borg warner T-85N overdrive attached to it.
Its not installed in my truck yet; its still going under restoration.

They are not easy to find. But if you do find one you can attached the T-85N to a saginaw 4 speed.

here is some info on how to wire the T-85N:

http://www.classictruckshop.com/club...over/drive.htm

http://www.hydratech.com/pctc/Public...s/bwwiring.pdf

how to rebuild one:
http://www.classictruckshop.com/club...n/rebuild.htm\

impalaboy9 · 02-22-2011, 12:31 PM

Can the t-85n be attached to a muncie?
Posted via Mobile Device

NCD1966 · 02-22-2011, 01:25 PM

That I really don't know.

**Bugeyev8** · 02-22-2011, 01:33 PM

Quote:

Originally Posted by impalaboy9

Holy buckets those gear vendor units are expensive but they look sweet. Didn't Corvette do something like that for a while?

yes it was a Doug Nash 4+3, which was a super T10 with a Doug Nash overdrive on it, I had a few Corvettes with them and even rebuilt a few myself, they are not the best units and have a short life span when the badly designed bearing wears out and the atf in the od mixes with the 80w 90 in the gear box...its all over, I had $1200 in parts on mine not couning the 20 hrs it took to rebuild it and the special tools I had to machine to assemble the thing

the gear vendor is expensive new but there are used ones out there, I saw 5 of them at the last Turloc swap meet ranging in prices 350-500$

**Bugeyev8** · 02-22-2011, 01:34 PM

why don't you just change the rear end gears ??

jimmydean · 02-22-2011, 01:43 PM

We did a gear vendor split drive on a Dodge 3500 dually with factory 5 speed. It was crazy expensive ($1500 for the gear vendor, $200 for the shortened drive line, $300 for custom coupling for the transfer case) but when it was all doen, it was pretty sweet.

I am leaving the Muncie and just swapping the rear gears.

**jocko** · 02-22-2011, 01:46 PM

another option before you drop a few house payments on a gear vendors... especially if you like your Muncie. An M-21Y o/d 4 speed. Probably a fairly wide split between 3rd and 4th, but certainly would make the long trips a little better. I believe the o/d is not as much as your tremec (i.e. it's in the .8-ish range I think), but this is just an option. You could probably buy the trans outright for less than a GV unit - or, better yet, the company may be able to mod your own 4-speed for a much lower price. Anyway, not sure if this might scratch the itch - but here's an option: http://www.m-22.com/m22/

02-21-2011, 09:31 PM	#1
impalaboy9 Registered User Join Date: Dec 2006 Location: lincoln ne Posts: 57	External Overdrive??? Ok guys I'm nearing the end of my build I will try to update and post some pics later. When I started I was going to be in town with a few very short trips. Now I may have to make an 850 mile trip on a fairly regular basis. I used the m20 I had laying around and I spent quite a while making the linkage work. I also have a new tremec 5 speed collecting dust. Problem is that the transmission is way nicer than my truck and I'd like to use it on a different project. I have heard about overdrives for the 4speed but I don't know anything about them and the search hasn't yielded much. Can anyone tell me the pros and cons and how they work. Also how do you shift into the overdrive? Currently I'm running a stock 305 but this summer I'm building a 283 with tunnel ram for it. Nothing with ridiculous power the tunnel ram is more for the novelty of it. Thanks guys.

02-21-2011, 09:46 PM	#2
Corts60 Just here to tinker Join Date: Jun 2008 Location: Holland, MI Posts: 3,697	Re: External Overdrive??? Hey, I am not sure about the factory overdrives that were offered or their availability but, I use a gear vendors overdrive in my '78. It is electro-hydraulic and is basically a two-speed transmission that bolts to the back of my turbo 400. I don't know if they are available for the manuals but you may be able to get pointed in the right direction by looking at gear vendors website. __________________ 78 C10 SWB Diesel #1 (wrecked)http://67-72chevytrucks.com/vboard/s...1978+silverado 78 C10 SWB Diesel #2 (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=650751 60 GMC Suburban (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=445526 60 GMC 1000 (sold)http://67-72chevytrucks.com/vboard/showthread.php?t=298235 67 GMC 1500 (sold) http://67-72chevytrucks.com/vboard/s...d.php?t=803695 73 Chevy C20(Daily)http://67-72chevytrucks.com/vboard/s...d.php?t=852767 86 Suburban(summer unit) http://67-72chevytrucks.com/vboard/s...d.php?t=810697 88 Suburban 4x4(sold) Last edited by Corts60; 02-21-2011 at 09:47 PM.

02-21-2011, 10:20 PM	#3
'63GENIII Registered User Join Date: Sep 2008 Location: San Carlos, Ca. Posts: 3,048	Re: External Overdrive??? I have seen a 3 spd with an external O.D. that was electric. My brother had one in his '56 wagon until he put in the 700r4. Seems I remember he would flip a switch, lift his foot and it would engage. It would also downshift automaticaly too if he would give it enough gas. I think it was out of a mid to late 50's passenger car. All cast iron and way heavy. __________________ Chris '63 k15 long step Vortec 7.4 - L29 Blackbear tune, Five 0 Motorsports injectors, Chris Straub Cam, NV4500, divorced 205 52" front and 63" rear spring swap D44 / 14bff - disc axles Milemarker 9K and 10.5K hydraulic winches 63" & B52 Spring Install http://67-72chevytrucks.com/vboard/s...ng+swap+thread NV4500 Reverse Build Thread http://67-72chevytrucks.com/vboard/s...=reverse+build L29 - 7.4 Vortec Build http://67-72chevytrucks.com/vboard/s...&highlight=L29

02-22-2011, 12:45 AM	#4
impalaboy9 Registered User Join Date: Dec 2006 Location: lincoln ne Posts: 57	Re: External Overdrive??? Holy buckets those gear vendor units are expensive but they look sweet. Didn't Corvette do something like that for a while?

02-22-2011, 02:37 AM	#5
mikie 1954 Registered User Join Date: May 2009 Location: caliente ca. Posts: 297	Re: External Overdrive??? There is a ranger overdrive also. The way I understand it ,it goes between the bell and trans. It has a lever you use to ingage or disingage to split each gear. ADVANCE ADAPTER in PASO ROBLES , CA. make them.

02-22-2011, 10:33 AM	#6
NCD1966 Registered User Join Date: Jun 2010 Location: Lafayette , La Posts: 404	Re: External Overdrive??? I have a saginaw 3 speed with a factory borg warner T-85N overdrive attached to it. Its not installed in my truck yet; its still going under restoration. They are not easy to find. But if you do find one you can attached the T-85N to a saginaw 4 speed. here is some info on how to wire the T-85N: http://www.classictruckshop.com/club...over/drive.htm http://www.hydratech.com/pctc/Public...s/bwwiring.pdf how to rebuild one: http://www.classictruckshop.com/club...n/rebuild.htm\ __________________ 1966 Chevy C10 Stepside 355ci sbc with 3speed OD 2021 GMC Sierra 1500 AT4 6.2 1980 Chevy Camaro z28 383ci 1990 Chevy Suburban 350 tbi 2x4 (sold) 1984 Chevy C10 sliverado short fleet 1997 Chevy C1500 short fleet Last edited by NCD1966; 02-22-2011 at 10:34 AM.

02-22-2011, 12:31 PM	#7
impalaboy9 Registered User Join Date: Dec 2006 Location: lincoln ne Posts: 57	Re: External Overdrive??? Can the t-85n be attached to a muncie? Posted via Mobile Device

02-22-2011, 01:25 PM	#8
NCD1966 Registered User Join Date: Jun 2010 Location: Lafayette , La Posts: 404	Re: External Overdrive??? That I really don't know. __________________ 1966 Chevy C10 Stepside 355ci sbc with 3speed OD 2021 GMC Sierra 1500 AT4 6.2 1980 Chevy Camaro z28 383ci 1990 Chevy Suburban 350 tbi 2x4 (sold) 1984 Chevy C10 sliverado short fleet 1997 Chevy C1500 short fleet

02-22-2011, 01:34 PM	#10
Bugeyev8 Senior Member Join Date: Aug 2009 Location: San Leandro, Ca 94577 Posts: 854	Re: External Overdrive??? why don't you just change the rear end gears ??

02-22-2011, 01:43 PM	#11
jimmydean Registered User Join Date: May 2005 Location: Beaverton, OR Posts: 3,728	Re: External Overdrive??? We did a gear vendor split drive on a Dodge 3500 dually with factory 5 speed. It was crazy expensive ($1500 for the gear vendor, $200 for the shortened drive line, $300 for custom coupling for the transfer case) but when it was all doen, it was pretty sweet. I am leaving the Muncie and just swapping the rear gears. __________________ New Project: 1966 LWB C20 Plans: 1/2 ton conversion Dropmember front Dropmember rear Corvette discs Restored raised bed http://67-72chevytrucks.com/vboard/s....php?p=4295210

02-22-2011, 01:46 PM	#12
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,975	Re: External Overdrive??? another option before you drop a few house payments on a gear vendors... especially if you like your Muncie. An M-21Y o/d 4 speed. Probably a fairly wide split between 3rd and 4th, but certainly would make the long trips a little better. I believe the o/d is not as much as your tremec (i.e. it's in the .8-ish range I think), but this is just an option. You could probably buy the trans outright for less than a GV unit - or, better yet, the company may be able to mod your own 4-speed for a much lower price. Anyway, not sure if this might scratch the itch - but here's an option: http://www.m-22.com/m22/



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