Transmission Upgrade
Thread Starter
Registered User
Joined: Feb 2012
Posts: 359
From: Didsbury, Alberta
Transmission Upgrade
I have the original 3spd TH350 transmission in my 72' Cutlass, no overdrive. I would like to get an overdrive transmission for it so the RPM's aren't so high driving down the highway & to save a bit of gas mileage. What would be a good transmission to use? Anything I get I would want to also install a good stall converter & Transgo shift kit in as well for some added street/strip performance. The car still has original gear in the rear end, but would also like to upgrade that in the future.
Registered User
Joined: Nov 2008
Posts: 227
From: Palmyra, NY
200-4R. Slide the crossmember back to the TH400 holes, TH350 driveshaft bolts right in.
http://cpttransmission.com/
My 750HP tranny is sitting in front of my cutlass waiting for the engine to get done.
http://cpttransmission.com/
My 750HP tranny is sitting in front of my cutlass waiting for the engine to get done.
Registered User
Joined: Sep 2012
Posts: 484
From: Gilbert, Arizona
My experiences on swapping......
TH 350 swapped out with a 200-4R, my experiences.....70 Cutlass with a 403.....
Starting off with a new universal dipstick, its tube will probably have to be modified by cutting back the tube height to get it properly calibrated (full mark on stick equal to bottom edge of case).
The new torque converter might need to be shimmed, as was in my case, to get the proper distance in relation to the flex plate (1/4” away maximum). Put a qt of ATF in the converter and take you time indexing it into the trans. It has to engage the front pump properly.
The cross member will be moved back, no big deal, the holes are already there, but I also had to notch it in a couple of places. The very farthest back pan bolt of the 200-4R tranny is very difficult to get a socket on to r&r the pan because the bolt is right under the cross member lip, making a u-shaped notch in the cross member gives easy access. Also, if your exhaust pipes tip in toward the middle to soon, they can hit the crossmember since it's about 6" farther back now , requiring more notch work for clearance or a new exhaust pipe. A muffler shop had made my drivers side pipe, it was to close, so a bit of clearance was needed in the crossmember to prevent possible interference.
A bit of parking brake work is also needed to make up for the extra slack that comes with moving the crossmember back. I drilled a new hole in the cross member so I could move the hook (that holds one side of the intermediate cable) farther to the outside to take up most of the slack, or an intermediate cable from a turbo 400 tranny will work.
The cooling lines seem to line up fairly well, the top outlet is the pressure fitting. No driveshaft work was needed. There is also a floor shifter kit available that allows the manual use of all four gears, it requires the removal of the console assembly to replace the index plate, cable and shift indicator plate. The new plate is marked; P R N (D) D 2 1. The new index plate is needed to properly hold the shifter in the new added positions of the overdrive gear. The kit also comes with a new needed transmission end cable bracket. Don’t forget to re-adjust the backup light/neutral switch while the console is out. Not a huge job, the console work, but time consuming. It all seemed to fit nicely, though the cable seems like it should have been a few inches shorter, but then again the stock cable seemed that way also. It’s important that the click stops in the tranny match the stops of the console shifter index plate, it required a bit of fiddling and adjusting to get the trans click stops, indicator shifter lever positions and lever index plate stops to all match up.
Biggest pain in the neck was the very critical TV (throttle valve ) cable setup, If you use the stock Olds Qjet, here’s the problem, the stock intake has the Qjet carb sitting rather low, thus the bottom part of the throttle arm does not extend down far enough for a proper TV cable hook up with an Olds carb. I tinkered with it the better part of a day before I realized the stock Olds carb linkage wasn’t going to work with the TV adapter and universal cable that was supplied by Bowtie. But because I’m using an Edelbrock Performer RPM manifold , there is lots of room below the carb, so I used a junk Chevy Qjet from the mid 80’s (Ebay) and used its throttle arm by grinding off the swedged on arm, off both the stock carb and Chevy carb and swapping them. Then by using one of the two available custom adaptors from Bowtie Overdrives for the Qjet which includes a carb spacer plate that has the proper cable bracket built into it, and a matching TV cable, I was able to be set up the TV system without any problem. There are 2 styles used, of course they sent the wrong one (cable and plate) the first time. The TV cable has to be setup so there never is any slack in the cable at slow idle and there should be an instant pressure rise with any movement of the cable, also the spool valve the cable controls has to be buried all the way in the valve body at the full throttle position.
The last hurdle was hooking up the torque converter lock up dis-connect switch. A keyed hot terminal wired thru a relay controlled by the brake switch and then run to the transmission. It was not too difficult. I don’t know yet if I’m going to need lockup delay kit or not.
With this tranny, and running 3.42 gears, at 80 mph cruising speed in fourth gear, locked up convertor,I saw a big difference from the 3100 rpm previously down to about 2100 rpm with the engine just loafing along in overdrive. The fourth gear in a 200-4R is a .67 ratio, so RPMs drop by a third, plus first gear is also a bit lower, 2.74 compared to the 350 turbo 2.52 low gear.
Is this a job for a do-it-your-selfer? That depends, If you can’t get your Olds up off the floor about two feet or more, and do not have a tranny jack, then it’s a bear of a job, I could only get my car lifted high enough on car stands, to slide the tranny on the floor to under the car, then I had to get creative to the get tranny up and balanced on a modified car jack, using two other jacks and wood blocks, then install the dipstick tube and bolt it up. It wasn’t the safest or quickest way to go, but doable. I did save about $1500 doing this job my self and only ended up with a few skinned knuckles.
The only thing left now is to get the stock cruise control linkage set up to work with the new Chebby throttle arm, but that project will be for another day…….
Starting off with a new universal dipstick, its tube will probably have to be modified by cutting back the tube height to get it properly calibrated (full mark on stick equal to bottom edge of case).
The new torque converter might need to be shimmed, as was in my case, to get the proper distance in relation to the flex plate (1/4” away maximum). Put a qt of ATF in the converter and take you time indexing it into the trans. It has to engage the front pump properly.
The cross member will be moved back, no big deal, the holes are already there, but I also had to notch it in a couple of places. The very farthest back pan bolt of the 200-4R tranny is very difficult to get a socket on to r&r the pan because the bolt is right under the cross member lip, making a u-shaped notch in the cross member gives easy access. Also, if your exhaust pipes tip in toward the middle to soon, they can hit the crossmember since it's about 6" farther back now , requiring more notch work for clearance or a new exhaust pipe. A muffler shop had made my drivers side pipe, it was to close, so a bit of clearance was needed in the crossmember to prevent possible interference.
A bit of parking brake work is also needed to make up for the extra slack that comes with moving the crossmember back. I drilled a new hole in the cross member so I could move the hook (that holds one side of the intermediate cable) farther to the outside to take up most of the slack, or an intermediate cable from a turbo 400 tranny will work.
The cooling lines seem to line up fairly well, the top outlet is the pressure fitting. No driveshaft work was needed. There is also a floor shifter kit available that allows the manual use of all four gears, it requires the removal of the console assembly to replace the index plate, cable and shift indicator plate. The new plate is marked; P R N (D) D 2 1. The new index plate is needed to properly hold the shifter in the new added positions of the overdrive gear. The kit also comes with a new needed transmission end cable bracket. Don’t forget to re-adjust the backup light/neutral switch while the console is out. Not a huge job, the console work, but time consuming. It all seemed to fit nicely, though the cable seems like it should have been a few inches shorter, but then again the stock cable seemed that way also. It’s important that the click stops in the tranny match the stops of the console shifter index plate, it required a bit of fiddling and adjusting to get the trans click stops, indicator shifter lever positions and lever index plate stops to all match up.
Biggest pain in the neck was the very critical TV (throttle valve ) cable setup, If you use the stock Olds Qjet, here’s the problem, the stock intake has the Qjet carb sitting rather low, thus the bottom part of the throttle arm does not extend down far enough for a proper TV cable hook up with an Olds carb. I tinkered with it the better part of a day before I realized the stock Olds carb linkage wasn’t going to work with the TV adapter and universal cable that was supplied by Bowtie. But because I’m using an Edelbrock Performer RPM manifold , there is lots of room below the carb, so I used a junk Chevy Qjet from the mid 80’s (Ebay) and used its throttle arm by grinding off the swedged on arm, off both the stock carb and Chevy carb and swapping them. Then by using one of the two available custom adaptors from Bowtie Overdrives for the Qjet which includes a carb spacer plate that has the proper cable bracket built into it, and a matching TV cable, I was able to be set up the TV system without any problem. There are 2 styles used, of course they sent the wrong one (cable and plate) the first time. The TV cable has to be setup so there never is any slack in the cable at slow idle and there should be an instant pressure rise with any movement of the cable, also the spool valve the cable controls has to be buried all the way in the valve body at the full throttle position.
The last hurdle was hooking up the torque converter lock up dis-connect switch. A keyed hot terminal wired thru a relay controlled by the brake switch and then run to the transmission. It was not too difficult. I don’t know yet if I’m going to need lockup delay kit or not.
With this tranny, and running 3.42 gears, at 80 mph cruising speed in fourth gear, locked up convertor,I saw a big difference from the 3100 rpm previously down to about 2100 rpm with the engine just loafing along in overdrive. The fourth gear in a 200-4R is a .67 ratio, so RPMs drop by a third, plus first gear is also a bit lower, 2.74 compared to the 350 turbo 2.52 low gear.
Is this a job for a do-it-your-selfer? That depends, If you can’t get your Olds up off the floor about two feet or more, and do not have a tranny jack, then it’s a bear of a job, I could only get my car lifted high enough on car stands, to slide the tranny on the floor to under the car, then I had to get creative to the get tranny up and balanced on a modified car jack, using two other jacks and wood blocks, then install the dipstick tube and bolt it up. It wasn’t the safest or quickest way to go, but doable. I did save about $1500 doing this job my self and only ended up with a few skinned knuckles.
The only thing left now is to get the stock cruise control linkage set up to work with the new Chebby throttle arm, but that project will be for another day…….
Last edited by 1970-W30; Jul 18, 2013 at 07:32 PM. Reason: spelling
Old(s) Fart
Joined: Mar 2007
Posts: 50,539
From: Northern VA
A stock 200-4R will not be adequate, you need an aftermarket one built for your car. The best 200-4Rs are well documented and well known, meaning that you won't find one in a wrecking yard. Search "200-4R" on this site, you'll find many, many threads discussing this swap and what changes are required to accommodate this trans in a Cutlass.
Registered User
Joined: Sep 2009
Posts: 2,444
From: mn
The other option and you dont have to deal with the Tv cable to the carb is a Gear vendor They take the tail peice of the tran's you have, there are some shimms to get it set up bolts on. You will need to have the drive shaft cut and re welded and you can put a manual switch to pick what gear you want it in 1st , 1st over ,2nd , 2nd over. You can find them on ebay and on line Have heard they are a good set up two . Easy to keep if you sell the car for another one with same th 350 .
Registered User
Joined: Jun 2009
Posts: 836
From: Windsor, Ontario, Canada
I just recently did a 200R4 conversion. It's one of the better modifications or improvements I have done. It has a nice shift kit and a 2800 stall. With 3.08 gears I can cruise all day at 70+ mph at around 1800-2000 rpm. Just make sure if you have someone do it they know how to build them so they can take the power and torque.
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