direct replacement transmission w/ OD for my '71

[nickp51chevy]

Is there a direct replacement transmission with overdrive for my '71 4x4? I don't like the engine's rpms up so high when I'm at 55mph, and I'd like to get better gas mileage also. If there isn't a direct replacement what are my options? Or what would I have to do to make something work?

Thanks
Nick

I did search but replacement and transmission were to long to search with.

[clinebarger]

check out www.bowtieoverdrives.com read up on TV operation and how important it is to any non-electronic GM overdrive. I sell many TV kits from them a year, ALONG with the transmission that got fried!

[Dingfodgy]

Ahhh Grasshopper- you have many choices before you......the secret is to choose wisely.
If you want to row the gears with a 5 speed manual the T5 out of an S10 w/ 4.3 is a good choice. They aren't meant to be beat up too much, so if you have a heavy right foot and a twitchy left one....you're probably gonna scatter one fairly soon. A step up would be the NV3500 out of a late 80's or 90's 1/2 ton or the very sturdy NV4500 out of the 3/4 and 1-tonners. There's also the Tremec TKO500 and 600, as well as the Richmond 5-speeds. All of which are high quality products. Lastly if you can find a mashed up '97 or later camaro or 'vette- you can kype the T56 6-speed out of that.

If a slush-box is your cup-o-tea then you can run a TH350/400 3 speed and bolt on a Gear Vendors over/under drive unit which is basically a gear splitter-so you essentially end up with a 6 speed auto. IMHO this setup seems a bit cumbersome. For replacement 4-speed OD automatics alot of guys run the 700-R4 which can be built to take some punishment, but are finicky about their TV cable adjustment, which is the #1 cause of failure but they are relatively cheap to get. Another option is the 200-4r out of a mid-late 80's Monte, Fleetwood, Cutlass, Regal, etc. These are a bit tougher to find, but when properly built will take gobs of power. They also have a taller first gear than the 700-R4 which makes the 1-2 shift alot crisper. Later model 4L60E, 4l65E and 4L80E trannies are generally more durable, but require a TCU (transmission control unit) either as a stand-alone module or as part of the PCM module if doing an LS motor swap too.

Being as our trucks never came with a 5-speed manual or 4 speed auto a certain amount of adaptation will be necessary. Luckily- all these trannies will bolt right up to the Small Block in you're '71. However, with the manuals you'll probably need to relocate the x-member, have the driveshaft lenght adjusted and mix-n-match clutch parts depending on whether you want cable or hydraulic clutch.

The auto's will also most likely need the x-member moved and the driveline shortened, but I have heard that the 200-4r is exactly the same size as a TH350, so don't quote me on that. You'll also need to get the TV cable linkage and TC lockup switch ironed out.

Do a search on each of these trannies and you'll find all kinds of info as to what it took to shoe-horn them into our rides.

[Sams68C10]

I put a 700R4 in my 68C10 behind a 76 350 4-bolt. I replaced the brake-light switch on the pedal with a brake cruise switch and wired the T-Convertor to the cruise so when the brake is applied the convertor unlocks. Also, wired in a vaccume switch with the same circuit off the carb vac, so when the gas is applied with a heavy foot the vaccume from the carb unlocks the T-Convertor as well, allowing downshift. Pretty easy, if interested can draw you a diagram. Let me know, Sam.

[nickp51chevy]

Will a 700r4 hook up to a transfer case? Would this swap be more than a weekend project?

[gkesseru]

Sams68c10: I would be interested in your circuit diagram. What kind of vacuum switch? Normally open or normally closed? Same question on the rest of the switches.

[capev86]

there are 4x4 700r4's out there. if you are looking to get better fuel mileage.....that starts with cutting out the fat......the extra drivetrain are great if you spend a lot of time offroad or in the snow, but it adds weight and drag.....you might pick up a mile or 2 just with going to a 2 wheel drive. my dad once got 19mpg on one trip on his 84 burb 2wd 350 w/ q-jet, 700r4 and 3.73 rear gears. regularly it got 17-18 on a tank if doing mostly highway driving. even switching to a 406sbc it got 16-17 and we were doing less highway driving by that point.

[nickp51chevy]

How hard would it be to put a 700r4 with with a transfer case in?
Are we talking lots of fab work or a simple swap?
I'm guessing that I would have to get something done to the drive shafts.
And my truck is already a 4x4 I'm just looking for an overdrive gear.

[nickp51chevy]

Can a Moderator move this to the 4x4 section?

[WIDESIDE72]

Notice the original post states "4x4" which adds some complexity to this swap due to the transfer case. My opinion would be a 700r4 with an adpater to his NP205 t case , or install whatever case came behind a 700r4 (NP203?). whatever the case, not a bolt in affair. Cutting of drive shafts would be required.

Originally Posted by Dingfodgy

Ahhh Grasshopper- you have many choices before you......the secret is to choose wisely.
If you want to row the gears with a 5 speed manual the T5 out of an S10 w/ 4.3 is a good choice. They aren't meant to be beat up too much, so if you have a heavy right foot and a twitchy left one....you're probably gonna scatter one fairly soon. A step up would be the NV3500 out of a late 80's or 90's 1/2 ton or the very sturdy NV4500 out of the 3/4 and 1-tonners. There's also the Tremec TKO500 and 600, as well as the Richmond 5-speeds. All of which are high quality products. Lastly if you can find a mashed up '97 or later camaro or 'vette- you can kype the T56 6-speed out of that.

If a slush-box is your cup-o-tea then you can run a TH350/400 3 speed and bolt on a Gear Vendors over/under drive unit which is basically a gear splitter-so you essentially end up with a 6 speed auto. IMHO this setup seems a bit cumbersome. For replacement 4-speed OD automatics alot of guys run the 700-R4 which can be built to take some punishment, but are finicky about their TV cable adjustment, which is the #1 cause of failure but they are relatively cheap to get. Another option is the 200-4r out of a mid-late 80's Monte, Fleetwood, Cutlass, Regal, etc. These are a bit tougher to find, but when properly built will take gobs of power. They also have a taller first gear than the 700-R4 which makes the 1-2 shift alot crisper. Later model 4L60E, 4l65E and 4L80E trannies are generally more durable, but require a TCU (transmission control unit) either as a stand-alone module or as part of the PCM module if doing an LS motor swap too.

Being as our trucks never came with a 5-speed manual or 4 speed auto a certain amount of adaptation will be necessary. Luckily- all these trannies will bolt right up to the Small Block in you're '71. However, with the manuals you'll probably need to relocate the x-member, have the driveshaft lenght adjusted and mix-n-match clutch parts depending on whether you want cable or hydraulic clutch.

The auto's will also most likely need the x-member moved and the driveline shortened, but I have heard that the 200-4r is exactly the same size as a TH350, so don't quote me on that. You'll also need to get the TV cable linkage and TC lockup switch ironed out.

Do a search on each of these trannies and you'll find all kinds of info as to what it took to shoe-horn them into our rides.

[nickp51chevy]

OK then. I guess this will have to be a summer project, but I would still like to get some more info as to what I would need in order to do this.