TH350 / 200R4 swap summary

Discussion in 'The "Juice Box"' started by techg8, Apr 11, 2009.

  1. techg8

    techg8 The BS GS

    ***WARNING Crazy Long Post***

    This is a summary thread about my 72 Skylark 350 and its TH350/200R4 trans swap. My experiences and learnings for what they are worth. This is not a by the numbers How-To, but a summary of sources and tips I think valuable for those attempting the swap. Enjoy.

    My goal was cruiseable hiway RPMS with my 3.42 posi rear, in a stout transmission that could handle my mildly built Buick 350 and whatever thrashing I might throw at it. I wanted to achieve this in a low-buck manner as well.

    Consult or to determine which 200R4 core is right for you. There are a lot of versions of this trans, each with its own characteristics. Some are better suited to performance than others.

    I started with a 200R4 out of an 86 Olds Cutlass, because it was found local. I paid $150ish. OG valve body (low performance…ugh) for the 307 V8.
    Sources of information and parts: – I bought their rebuild manual, VERY informative and worth every penny. I also used their #24RSRK/A shift recalibration kit with excellent results. An excellent resource for all things 200R4. – I bought speedometer gears here that suited my 3.42 posi rear. Their site makes gear selection a no brainer. – The Turbo Buick guys know all about the 200R4 trannys and there are a lot of deals on parts to be had there. Great resource for information and parts. I scored a Superior Oversize Intermediate Servo there, as well as a D5 torque converter from a Grand National and a Used Hurst QuarterStick shifter. – These guys have about anything for about any auto trans. I bought several odds and ends here, including a Hardened stator support, Trans assembly goo and some pump upgrades.
  2. techg8

    techg8 The BS GS


    Shift Kit
    This was straightforward. The CK Performance shift kit came with EVERYTHING I needed, and the instructions were crystal clear I cannot improve on it. One thing worth mentioning is that in order to install the pressure regulator and boost valve updates, the front pump of the trans needs to be removed. For this reason I added upgrades to the pump as well.

    A hardened Stator support, 7 new pump vanes, and new hardened pump vane rings were installed. The stock rings evidently are susceptible to shattering and destroying the pump, and the stock (non hardened) stator support splines are susceptible to stripping. Now would be the time to consider a 10 or 13 vane pump upgrade if you are so inclined. See transmissionpartsUSA .

    Speedometer gears
    The oil pan must be removed to gain access to the governor cover. Once the cover and the governor are removed, installation of the new gears is self explanatory. See the PATC site for their speedometer gear selection made easy.

    Intermediate Servo
    Unless you have a performance 200R4 core (consult or you will need to upgrade the servo for faster, harder band apply. This is a simple procedure. Servo is located on the Passenger side, the big round thing sticking out. Cant miss it. Remove the internal retaining clip that holds the Servo cover on, and gently pry out the cover. I used channel loks and in the process scarred up my nice aluminum serco cover. I found that a twisting motion helped move the cover out. The rest of the servo is easily removed.

    HINT: I found it easiest to get the band apply pin to properly engage the band on reassembly by installing the new servo with the trans in the horizontal position, sitting on its oil pan. Install the new servo and cover, then put the internal retaining clip back on. If the servo cover doesnt go back in all the way like it should, the servo apply pin isnt engaged properly with the band.

    Attached Files:

  3. techg8

    techg8 The BS GS

    The 200R4 has a dual bolt pattern on the bellhousing, making for an easy install. It is the same length as the TH350, so your driveshaft length will remain the same when doing this swap.

    Trans mount & Crossmember -
    The TH350 trans mount can be used on the 200R4, although the 200R4 will require a spacer between the trans and the mount to correct your driveshaft angle. I just used longer mount bolts with an extra nut or two between the trans and the mount. If you do not get this right, you will have driveline vibrations. My body mounts are sagging/worn so I could fit only .33-.5 of spacer before the forward driveshaft Ujoint would contact the tunnelhump.

    The TH350 trans crossmember will need to be moved toward the rear of the car due to the trans mount location on the 200R4. Luckily the holes are already drilled in the frame. Just slide the crossmember back into position, loosely install the trans mount bolts, and bolt the crossmember into position.

    Torque Converter-
    Install like any other, but I wanted to mention that the flexplate/TC bolts are METRIC. I found mine on Ebay in a set of three. They are the same bolts for the 4L60E or 700 trans. From Blazinhot tramsmissions.

    Neutral Safety switch / reverse lights
    I found that my original NSS for 3spd TH350 broke when I first tried out my 200R4. My theory is that when I shifted into D1 manual low on the 200R4 it involved more sweep on the Column shifter than the original NSS was designed for.

    So I bought a NSS for an 86 Cutlass (200R4 car) and tried it out. Would not mount correctly, and was made all of plastic.
    In the end I took the metal backing of the 3 speed TH350 NSS and glued it to the front side circuitry of the 4spd NSS with JBweld and plastic weld. This way I have the mounting ears correct from the original NSS and the circuitry correct for a 200R4 trans. After trimming a couple plastic tabs, the original fittings hook right up to it.
    Installed it and it works like a charm!

    Emergency Brake Cable
    I needed to change the emergency brake cable routing because of the relocated crossmember. It created too much slack in the cable and it needed to be taken up. The forward end of the intermediate cable was interfering with the forward knuckle of the driveshaft when the original crossmember cable hanger was used. I fixed this by moving the large crossmember brake cable hanger off the crossmember and to the bottom of the floor, passenger side second hole. I then fabricated a hook for the crossmember location nearest the trans on the passenger side. See pics with ruler for size.
    I have also heard that the crossmember is being mounted in the TH400 position on the frame when moved to accommodate the 200R4, and as such you theoretically could use the shorter TH400 intermediate emergency brake cable in conjunction with the TH400 primaty Ebrake cable.

    Attached Files:

  4. techg8

    techg8 The BS GS

    The 200R4 trans reads engine load by Throttle position, not vacuum like a TH350. It does this by using a Throttle Valve that raises line pressure as your throttle opens. The throttle valve is depressed by a lever actuated by a cable connected to the throttle shaft on your carb.
    Do yourself a favor and be SURE to grab the TV cable and the TV cable bracket from your donor car, along with your trans core. Will save you a buck or two.

    TV stud -
    Your Quadrajet will need to be modified to accept the TV cable. This involves an arm with a 5/16” stud (Summit SUM-M08081) that must be added to your current Throttle arm.

    TV arm –
    The arm must position the TV stud 1.1” center to center from the throttle shaft. It must also position the stud approximately in the 4:30 position at idle and the 7:30 position at WOT. I have heard the figure of a 78degree sweep used as well. There are plenty of online TV informations available. Check it out and get it right or cook the trans.
    I cut the arm off a GM style TV compatible throttle shaft and tack welded it into place on my Qjet throttle arm with good results. You could fabricate one too.

    2018 EDIT: Everyday Performance LLC has made a TV arm conversion kit for Buick and Olds Quadrajets...see link:

    Carb spacer –
    The carb must be lifted off a stock intake to clear the low swinging TV cable arm. I found that .750” additional height was required. I used a .5” phenolic spacer (Summit – Moroso MOR-64941) with a thick intake gasket (.200”) to the manifold and a thin gasket to the carb. Works fine.

    TV/Throttle cable bracket –
    I got the stock TV/throttle cable bracket off the donor car when I got the trans core. It is the style that mounts to the two rear carb mounting bolts, and holds the throttle cable above the TV cable. Works great. There are also aftermarket options. Check out TVmadeEasy or any one of a million chrome brackets at Summit or Jegs.

    Choke thermostat and fuel inlet line–
    With the carb a .5” higher, the choke thermostat link had to be straightened out completely, and the thermostat plate clearanced in order to achieve the “sweep” that was required to completely close the choke flap on cold starts. Another option could be to lengthen the link .5” or so.
    The Fuel inlet line to the front of the carb I bent a little to get the additional .5” height required.

    Attached Files:

    Last edited: Apr 2, 2018
  5. techg8

    techg8 The BS GS

    The used D5 (Grand National) converter I scored on stalls around 2200RPM, grabs pretty good and is lockup capable. A new T/C costs, but might provide better performance.
    To use the Lockup, I simply wired 12V on the IGN circuit (keyed) to the solenoid (+) lead and wired the solenoid (-) lead to a ground side switch mounted under the dash just left of the stock radio position. Flip the switch and its locked. I had a 2 wire solenoid, and a 1 wire normally closed 4th gear pressure switch that I did not wire into. A normally open pressure switch would be nice for auto lockup in 4th but I did not want to spend the $.
    I recommend wiring the circuit through a brake switch that will disconnect lockup during braking. There are also kits available on ebay, at Summit, everywhere that achieve varying levels of this mod. Find what will work for you. is also a good source for valvebody switches to achieve automatic lockup in certain gears.
    Last edited: Dec 17, 2009
  6. techg8

    techg8 The BS GS

    I started with a core in good useable condition, so I did not HAVE to do a complete rebuild including new frictions and steels. Longevity? Who knows, we will see. The rebuild kits Ive seen are in the $350-$550 range, and I wanted to avoid that expense. Choose a good core if you’re on a budget like me.

    I have pressure tested the trans and the CK kit does all it is intended to do. Very firm shifts under heavy throttle. Nice firm driveable shifts under lighter throttle. The trans pulls hard, can burn the tires up easily if I want.

    I cruise 3<SUP>rd</SUP> gear around town. This is where my engine likes to be 2000-3000RPM cruising. When getting on the hiway I take 3<SUP>rd</SUP> up to 60 mph (75 if pushing hard) and shift into 4<SUP>th</SUP>.
    In the 4<SUP>th</SUP> OD gear I can cruise easily at 80 MPH 2500RPM. (3.42 rear)

    Lockup in 3<SUP>rd</SUP> and 4<SUP>th</SUP> is nice and saves you the slip associated with a Torque converter. Gets you maybe 200RPM back anytime its on.

    The downfall of the trans core (nonperformance valvebody OG remember) that I chose is the automatic shift points are WAAAAAY off. I can either now do valvebody and governor mods to correct this (lots of work), or manual shift the trans (little work). I have decided to manual shift for now and am investing in a Hurst QuarterStik gate shifter for 4spd auto trans. TurboBuick came through for me again. I posted a wanted ad and immediately scored a nice complete setup for about $100 cheaper than new.

    If you don’t want to manual shift, be careful with your core choice. Read up on the performance cores and their governors – the CK rebuild manual has lots of this info.
    Last edited: Aug 22, 2009
  7. techg8

    techg8 The BS GS

    86 Olds 200R4 core w/ bracket and cable $150
    Speedo Gears, new seals Etc. $80
    CK performance Shift Kit $90
    D5 GN Torque Converter $60
    Converter bolts $10
    Carb spacer and TV stud $30
    Superior intermediate servo used with seals $50
    Stator support, pump parts, misc assembly parts $57
    Hurst QuarterStik 200R4 $160
    86 Olds NSS $16
    TOTAL ~ $713 more or less

    time and aggravation, hair loss $PRICELESS
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    Keep in mind I shopped around, got all the good used parts deals I could to keep my costs low. I am not a $1500 transmission guy.
    Thanks to all the guys and gals that helped me out on this project with information, advise and parts deals!!!!!!!
  8. 71skylark3504v

    71skylark3504v Goin' Fast In Luxury!

    Lots of good info here. Sweet!

    However, I have to disagree with you on the way you handled your lockup wiring. TCI's lockup wiring kit is a VERY wise investment. It includes a vacuum switch and it provides immediate lockup in 4th. You MUST lock-up in 4th because it provides extra lubrication and cuts the heat way down. Also, it includes a lead so you can lockup in 2nd or 3rd if you desire.
  9. mikebart101

    mikebart101 Well-Known Member

    Awesome info. I am in the middle of this swap and every bit of info helps.

    In regards to the spacing needed between the tranny mount and tranny, I could also only fit about 0.5" of space before hitting the floor, and that is with brand new rubber body mounts. I meausured the distance between CL of output to mount surface on the TH350 at about 2.5", the 200-4r is around 2", so 1/2" is close enough for me.
  10. d2_willys

    d2_willys Well-Known Member

    Very good thread, and well worded.

    I do agree with the lockup always active in 4th, but like the 3rd lockup capablility. Seems it could be accomplished easily.:Do No:

    Definitely saving this thread.:kodak:

  11. techg8

    techg8 The BS GS

    I am glad to see the thread being read, and the info found useful! Thanks for your feedback.

    Addressing the 4th lockup: I wired the solenoid to switch on whenever I want. Ususally I lock up in 3 and 4. I am in the process of modifying a T handle for my Hurst shifter to incorporate the toggle switch.

    If I wanted to lock up all the time in 4th I would get a normally open pressure switch for the 4th gear port in the valvebody. So whenever 4th was selected the lockup would automatically happen. PATC sells the switch.

    However, I read a couple articles lately that include the opinion of Art Carr of CPT that Lockup converters are not the way to go with a performance 200R4.

    I believe the reasoning is that
    1)a performance kit installed in a 200R4 will help correct the lubrication issues to which you refer.
    2)the extra rotating WEIGHT associated with lockup capability effectively negates the lockup advantages, especially when you are talking about high quality ($$$), very efficient, performance designed T/C's (like CPT's)

    Just what Ive read FWIW. I will continue to lock up in 3 and 4 via toggle switch, and let you know when it breaks.

    Thanks again guys for your interest in the thread!:beer

    ***I am adding a 2020 EDIT here because I am working on yet another 2004r, and this time I am adding a third friction to the 4th clutch pack because the trans will be behind a 455. This is accomplished by cutting .080" off the 4th apply piston and inserting the extra friction between the paired 4th steels. more friction, less slippage less heat. I scored the piston with a Vernier caliper to mark the .080", used carbide bits in a die grinder to take most of the material off, then sanded flat with a belt sander.***
    Last edited: May 30, 2020
  12. techg8

    techg8 The BS GS

    Hi Guys.

    An update:

    I have completed modifying the stock HEAVY weighted Governor from my 200R4 and test drove it today.

    I had found a picture in a car mag of a set of heavyweight gov weights and a set of light gov weights side-by-side. The light ones were supposed to WOT shift at 5000rpm or thereabouts.

    SO I used my digital calipers to compare the dimensions of the two sets and get a percentage difference in dimensions.

    Then I applied that percentage difference in size to my own heavy weights, scribing lines where material would be removed.

    I used a dremel with a thin cutting wheel to remove the excess material, trying to cut on the conservative side.

    I reassembled the gov with my new "lighter" weights, and like I said, I test drove today.

    Results were very nice.
    1) Part throttle shifts are quite nice. into 2 and three just a little early. I can now comfortably drive the car in "AUTO"!!!!!!!!:laugh:
    2) WOT shifts at 4500rpm...a little low, but again I tried to be conservative with my cuts. I will mod again, removing a little more material and try for 5000rpm shifts, maybe 5500.
    3) Downshifts are firm and occur when I expect them to. No complaints.

    I do have my notes for the mods I have made. If I can figure how to scan them I will post here. I will also try to get more specific data on shift points when I have completed modding for WOT shifts.

    The other option was to buy a Monte SS or GN gov from CK performance or on ebay. But Id just rather do it myself.

    Last edited: Dec 17, 2009
  13. sailbrd

    sailbrd Well-Known Member

    There is now a good valve body replacement if you do not have one of the performance 200R4's. It may seem like a lot but price out a good BRF or CZ code transmision.

    Have not talked to anyone using this yet but this company has a good rep with the GN crowd. I am thinking about trying it and selling my CZ code valve body next year.
  14. Snowbound

    Snowbound Well-Known Member

    My BRF code shifts right at 5500 rpm behind my stock 340. Not sure about the Monte SS units.

  15. techg8

    techg8 The BS GS

    So I finally did some more mods to the governor and I wanted to give a final report.

    I have achieved 5000 RPM WOT shifts by cutting down the heavy governor weights into a shape that resembles the "light" weights in a BRF or CZ code trans.

    I scanned the results I have achieved so maybe you can try it out if you dare.

    Low throttle shift points occur where they "should". Driveability is just fantastic.

    Shift points are very responsive to TV cable. I couldnt be happier with the driveability.

    And the 5000 rpm WOT shifts make my GS118 cammed 350 sing......

    Do I dare go for more? 5500 anyone?

    Attached Files:

  16. DaWildcat

    DaWildcat Platinum Level Contributor

    Very good info!

    FYI, it's 200-4R, not 200R4.

  17. gm4life

    gm4life if you let up you loose

    Very good post 10 years ago when i installed my 200 out of a 86 gn we pulled the car in the shop at 7 pm at 8.30 we were driving around setting tv cable i opted to just run the tv cable into the fire wall and connect right to the gas pedal just like the 350 trans ...I did not touch the shifter i cannot use manual low once i install bucket seats i can fix that made the car a dream to drive esp on the hwy with a b&m lockup kit locks in third and 4th 3 gear lock up i great for cruising the city :beers2:
  18. nekkidhillbilly

    nekkidhillbilly post whore

  19. Phoenix350

    Phoenix350 Well-Known Member

    Definitely Sticky this:Smarty:

    I plan on doing the 200-4R swap before i even touch my motor, it is almost stupid not to in my situation as this car will be a daily driver for me. Not that it really matters when one talks about 3800lb+ muscle cars but any idea on what your mpg is at around 60?
  20. techg8

    techg8 The BS GS

    mpg? it isnt good I can tell you that. I can about watch the guage move.

    but its as good as it'll get with my 3.73s, cam and modded Qjet

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