Transmission thoughts

[scherpich]

So I'm currently running a auto 3spd stock tranny, but i'd like to get something with overdrive to make freeway driving easier, like a 700r4. I know these are common for 67-72 pickups, what mods are required to make this fit? I've heard you have to shorten the driveshaft, and some guys like to use tranny coolers. Also, has anyone bought the $500 deals on CL? I see a lot in my area for this price.

[Longhorn Man]

you will need;
tranny
converter
TV cable
provisions to (properly) hook the TV to carb
converter lockup kit
trans cooling lines
radiator with cooler
new sterter possibly (never personally messed with a 3 speed, may have the same part)
New steering column or floor shifter
small wire job to make back up lights work
some will say a neutral safety switch, I say screw that, just put it in park if it's not moving or running
auto tranny crossmember
tranny mount
A case of ATF
Speedometer gears that match your rear end ratio
possibly new driveshaft yoke
driveshaft mods

[Wrenchbender Ret]

I see you already have an auto in it. The starter, Radiator, & cooler lines should work. The column shifter will work with a little mods at the bellcrank but you might not have a lockout position for first gear, which you never need unless you do some serious mountain driving. You can move the trans. crossmember back & drill new holes. If you have a 200-350 in it now the yoke will fit. If you have a 400 you will need a different yoke. The drive shaft will need to be modified.
This is a great swap. I run one in my 70 & it is a pleasure to drive. 70-80 MPH is cruiseing.

[Longhorn Man]

i missed that... I thought I read 3 speed as in manual.

[scherpich]

I was referring to an auto transmission...and thanks for all the advice, I think it's a TH350, and I wanted to make it a floor shift with the Lokar shift kit anyway as far as that goes.

[dsy1]

Anybody use a 2004R instead of 700R4? The case is a little shorter, so I'm wondering if it still requires a drive shaft modification. A 2004R should be able to be built to handle the same horsepower and torque as the 700R4.

I have a Th350 now and am considering a swap also.

[Hubscrub]

from what i understand a 200 is more the size of a 350 as length goes, i have a 700 in my 71 and like it so far

[6772owner]

If you run a 700R4, I would also recommend an external trans cooler in addition to the radiator cooler. I ran mine w/o one for awhile and feel it would get pretty hot in stop-n-go traffic. I do love my 700R4 though, great first gear and awesome when the convertor locks up... my only complaint is the gap between 1st and 2nd gear, but I believe that the 200R does not have this problem.

[ebfabman]

200-4r is the way to go

[Longhorn Man]

the 200 4R is a tick longer than the short shaft TH350 (what our trucks came with) and the crossmember goes in the TH400 location. So physicly installing it is a nuts and bolt job.
You do still have to set the TV cable, and that can be a nightmare. I recomend spending the cash and going to bowtieoverdrives.com and getting there kit. It's expensive, but so is a replacement tranny if the cable isn't dead nuts right.

[68GMCCustom]

I bought TCI's "geometry corrector" bracket that bolts to the carb linkage and my trans builder provided a nice TV cable...but to keep my set uniform I think I'll be using a Lokar TV cable to go with the Lokar throttle cable and bracketry. I also have 200-4r bracket...but its made for OEM style (like the cable my trans builder gave me) with square type openings for the cables.

Thats what you're getting going with Bowtie Overdrives...uniformity in that everything works together. Had I bought all TCI or all Lokar hardware...maybe I wouldn't be looking at making changes.

[Longhorn Man]

plus they set you up with a pressure guage and detailed instructions on how to use it.

['70_402]

So educate me... What is a tv cable and what does it do??
Posted via Mobile Device

[Wrenchbender Ret]

Originally Posted by '70_402

So educate me... What is a tv cable and what does it do??
Posted via Mobile Device

I think it stands for throttle valve. Someone correct me if i'm wrong. It is a cable that connects the throttle to the trans. to control the pressure. It must have the right geometry & adjustment or the trans will not work right or last long. It is used on the 200-r4 & the 700-r4 trans. The 350 & 400 used vacuum modulators to control it.

[6772owner]

Correct, the TV cable controls the fluid pressure in the tranmission and if Im not mistaken also controls the timing of upshifts and the "kick down" abilities of the trans. I had mine set incorrectly the first time I drove it and the trans would not part throttle upshift until apx 4K RPM, I also HIGHLY recommend you get the Bowtie Overdrives kit and also source your (mechaincal) speedo gear/housing set up from them. Very knowledgeable, courteous and they know what works.... I wish I would have bought my TV set up from them, regrets...