Guest khjertquist Posted November 18, 2008 Share Posted November 18, 2008 I've been reading several topics on how to convert your th350 trans to an overdrive 700R4 trans. I have a small block 350 that I'm going to be putting into my monte from a mid 70's chevy truck. (Somone told me a truck motor is ideal because its stronger then a car block.) And I also have a 700R4 that came out of a mid-80's chevy full-size van, and has been rebuilt to stock specifications. My confusion is what needs to be done exactly to put this in my monte. I've read that some people didn't have to modify the frame or cross-member at all, and others who said they had to drill new holes for the adjustment. Some people are complaining about the TV cable adjustment and resulting fried transmissions. I guess my question is; what is the difference from the lockup torque wiring from summit racing, versus www.bowtieoverdrives.com. Then I read some people use this kit taht detects speed and vacuum to lock up the torque converter. Then...some people use a constant valve pressure plate to eliminate the TV cable altogether? I know the drive shaft will most likely need shortened. I'm planning on getting in touch denny's drive shaft company to have a new one made. (trying to keep all the monte's original parts unmodified) I"m just confused on the three different types of torque lockup. Some use TV cable, others use constant valve pressure plate, and some use a vacuum system that controls the electric lockup. Does anyone have a recommmendation on which one is the best solution. The car originally had a small block 350 with a TH 350 trans, 10-bolt rear end. Thanks, Kenny Quote Link to comment Share on other sites More sharing options...
monte70car Posted November 18, 2008 Share Posted November 18, 2008 kenny the vacuum system i believe is used on a computer control car i believe. the constant valve pressure plate i believe is fairly new. if the tv cable is set right you will have nothing to worry about. i would measure the 350 trans and the 700r4 and get an ideal on how much longer or shorter on is. its a easy swap going from a 350 to a 700r4 bowtie overdrives tells you to use a 350 yoke as its stronger then a 700r4 yoke. i have the bowtie overdrive trans in my monte and i did not shorten the drive shaft or have to drill new holes. i think what the trans comes out of plays a big deal on what gets done to the drive shaft and cross member. depending on the carb you run you will need the right brackets for the tv cable. Quote Link to comment Share on other sites More sharing options...
monte70car Posted November 19, 2008 Share Posted November 19, 2008 like allan said i do have a toggle switch but its put of the bowtie overdrive kit. they toggle switch is used for towing. i put the trans in od when we go out to shows or just a drive. when i hit the brakes the trans unlocks and then locks back up when i let off the brake. my toggle switch stays in the off postion as the car will not be used for towing. http://www.700r4.com/tech/tcc/brake_install/diagram.shtml shows how to wire it up. this is close to the kit they sent us http://bowtieoverdrives.com/catalog/catalog_inc/viewitem.php?ITEMID=332 Quote Link to comment Share on other sites More sharing options...
kc8oye Posted November 20, 2008 Share Posted November 20, 2008 personally, I don't like automatic lockup control becuase it never does what I want it to, when i want it to do it!! i drive my 700r4 around town all the time and never use the lockup. I only hit hte switch when i know I'm going to be running a steady speed for some distance. (mainly the freeway) to that end, I installed an extra, and large trans cooler in front of the rad to make sure the trans temps don't get excessive. you will need to get a different switch your brake pedal. anything GM from the 80's should have to two sets of contacts in it. one set closes when you hit the brakes (that's the brake lights) the other set opens when you hit the brakes (this is for the torque converter) this isn't NEEDED.. but it's nice to have so if you have to hit hte brakes in a hurry, you don't have to worry about hitting the switch right away. one thing I'm working on tho, is adding a manifold vaccum function to it. by doing a little bit of research with a data logger and a MAP sensor (you could use a vac gauge and your eyeballs) I've determined that I'd like the torque converter to automatic unlock around 10" of vaccum to stop the engine from 'chugging' up steep hills on the freeway (there are only a couple around here) this also suggests a need to prevent re-locking until a set vaccum is reached to stop it cycling on and off as i go up the hill. one other problem you will run into. there are about 12 different ways a 700r4 can be wired internally. Ask your trans builder what layout the trans uses. at the very least, get a picture of the trans all assembled before the pan is put on, I can tell you which one it is by looking at it. Some 700's only lock up in 4th, some in 3rd and 4th, some in 2nd, 3rd and 4th (mine does this) some have internal switches for the computer to know what gear the trans is in. if he can tell you what 'broadcast code' the trans is that helps too. it will be a 3 leter code like "MX4" usually printed on a tag attached to the trans, but it was rebuilt in the past, that info may not be there. keep us updated Quote Link to comment Share on other sites More sharing options...
Grease Posted November 20, 2008 Share Posted November 20, 2008 I am quite happy with the PainlessWiring lock up switch kit . It has the brake light switch , vacuum break switch and a new pressure switch to install in the trans along with the single wire and plug to the trans. I have added to this a toggle switch so I can block (turn off ) the lock up system. Quote Link to comment Share on other sites More sharing options...
kc8oye Posted November 20, 2008 Share Posted November 20, 2008 i've never looked at painless.. tho their kits tend to be expensive.... Quote Link to comment Share on other sites More sharing options...
footballubet Posted November 27, 2008 Share Posted November 27, 2008 The guy that builds the ones for our shop used a kit for mine that uses different springs to lock up the converter at a MPH setting. Mine is set to lock up at 52 MPH. It's all internal to the valve body with no wiring or switches. It works great for me. Quote Link to comment Share on other sites More sharing options...
kc8oye Posted November 27, 2008 Share Posted November 27, 2008 see, I use mine at all speeds... in fact, the slower I'm going, the more I use it.. if I'm under 2500 rpm, i sort of 'need' to use it other wise the car feels REALLY mushy from the stall converter.. Quote Link to comment Share on other sites More sharing options...
Shadow Gray SS Posted November 27, 2008 Share Posted November 27, 2008 What stall are you running Tim? Quote Link to comment Share on other sites More sharing options...
kc8oye Posted November 27, 2008 Share Posted November 27, 2008 2500 jake. @ 70mph in o.d I run 2250 locked up.. almost 2500 unlocked. @ 55mph I'm doing barely more then an idle when locked up. and close to 2000 rpm unlocked. Quote Link to comment Share on other sites More sharing options...
footballubet Posted November 27, 2008 Share Posted November 27, 2008 What gears you running Tim? Quote Link to comment Share on other sites More sharing options...
kc8oye Posted November 27, 2008 Share Posted November 27, 2008 3.55:1 with 255/60-15 tires (27.04" tall) Quote Link to comment Share on other sites More sharing options...
kc8oye Posted November 27, 2008 Share Posted November 27, 2008 i ran the #'s thru a gear calc this is really meant for a manual trans, so these apply only if the torque converter is locked up (zero slip) 45mph 3rd gear: 2000 4th gear: 1400 55mph 3rd gear: 2450 4th gear: 1700 70mph 3rd gear: 3100 4th gear: 2250 my trans has issues, it used to let me into O.D around 25-30 mph which made for some interesting RPM situations.. w/o that stall converter it would have been a pain. i don't typically allow o.d under 45mph, there is just no reason to be trying to roll along under 1500 rpm, I just don't make that much torque down there. i know that unlocked in 4th gear @ 70, I do about 2500 so I save about 250 rpm. unlocked in 3rd @ 70, there's not a whole lot of difference.. maybe 100 rpm at most. I know about 3rd @ 70 because my TV Valve in my valve body is stuck.. I have no o.d at all right now. occasionly I can get the trans into o.d by downshifting into L3, and back up into O.D SOMETIMES P.S here is the Gearing Calculator I used. 700-R4 gear ratios: 3.06 1.63 1.00 0.70 Quote Link to comment Share on other sites More sharing options...
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