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  • Transmission / Overdrive: 700R transmission conversion

    I know some of you have converted your stude to newer automatics with overdrive. My friend has a GT hawk that he'd like to convert. (The previous owner's son had already pulled the automatic & replaced it with a manual tranny w/OD, but never finished it.) Chuck has ordered the adapter plate stuff from Fairborn but would like to talk to someone who's actually done it to gain as much knowledge as possible. Would any of you be willing to talk with him? Contact me with your phone number & I'll pass it along.
    thanks,
    Mike Saltsgaver
    SDC life member

  • #2
    Mike

    Something to think about...
    If you/your friend doesn't have a trans. yet, do yourself a favor and look into a T-200-4R rather than a T-700-R4.
    The T-200 is smaller, lighter, the strength or a higher power capability, (depending on the builder), similar in cost to build. But the best thing it has over the T-700, is the gear ratios. The T-200-4R's gear ratios are MUCH better for overall driveability and mileage.

    Just so you know, yes, I have about three years in driving with a T-700-R4 trans.

    All three of my Studebakers have the T-200-4R in or ready to go into one of them.

    Mike

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    • #3
      Is there a list somewhere of what brands, models, and years were fitted with 200-4R transmissions?
      RadioRoy, specializing in AM/FM conversions with auxiliary inputs for iPod/satellite/CD player. In the old car radio business since 1985.

      17A-S2 - 50 Commander convertible
      10G-C1 - 51 Champion starlight coupe
      10G-Q4 - 51 Champion business coupe
      4H-K5 - 53 Commander starliner hardtop
      5H-D5 - 54 Commander Conestoga wagon
      56B-D4 - 56 Commander station wagon
      60V-L6 - 60 Lark convertible

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      • #4
        First, this conversion has been discussed at length a dozen times here already.

        Yes, agree with Mike a 200-4R is the preferable transmission and if one is buying a new rebuilt transmission, there's not a great deal of difference in cost. However, the perfect is the enemy of the good. If an owner is brave enough to slog through the U-Pik yards and install a used transmission or a locally rebuilt one, there are many more 700R4s and 4L60s than 200-4Rs.

        jack vines

        PackardV8

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        • #5
          Agree with Jack and Mike but as Jack said, 2004R's are hard to find in the yards. So unless you want to buy from a rebuilder like Bowtie the 700's are around in higher numbers but my guess is the non-electric shifting 700's are also getting scarce in the yards.

          The 700's are generally used in heavier cars and pickup trucks with low number rear ends so they are usually geared lower.

          If you match your rearend ratio to the tranny a 700 is a darn good choice but they are larger.

          Here's a size chart. https://paceperformance.com/p-28983-...imensions.html

          Bob

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          • #6
            And don’t forget the rear end ration. I switched from a BW to a 700r but did not change the rear end ratio. I have a stock Dana 44 with 3.31. My gas mileage went from 18-20 down to 10. Every thing I read here says 3.73 would be the best overall, so looking to change gears.

            Mark

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            • #7
              Thanks for all the comments. I bought a 200R to convert my Avanti II, but it took me a while to find a core to trade in on a rebuilt unit. None of the local junkyards have them anymore as the drag racers snagged them all. That's why I told him that maybe a 700 would be easier to source.

              I was at his house last night & determined that the car no longer has the original engine. It's got a 259 w/ the manual OD tranny. He has a full flow 289 that he's going to rebuild & attached a modern tranny to, then swap it into the car.

              Mark, I'm a little confused on why your mileage went down. Charlie hasn't checked his rear end yet, but suspect it will be a 3:31 since the car was originally an automatic (but nothings for sure yet).

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              • #8
                Originally posted by Bullet View Post
                And don’t forget the rear end ration. I switched from a BW to a 700r but did not change the rear end ratio. I have a stock Dana 44 with 3.31. My gas mileage went from 18-20 down to 10. Every thing I read here says 3.73 would be the best overall, so looking to change gears.

                Mark
                Mark, I'm a little confused on why your mileage went down. Charlie hasn't checked his rear end yet, but suspect it will be a 3:31 since the car was originally an automatic (but nothings for sure yet).
                There are many factors in the inter-relationship between gear ratio and fuel mileage, but agree if it drops 50%, all of them and more are suspect. In my conversion the 700R4 definitely increased cruise fuel mileage.

                1. Was the throttle linkage and throttle valve cable adjustment done to GM specs? BowTieOverdrives has the kit.

                2. Was the correct stall lockup torque converter chosen and the GM wiring done properly so it locks at cruise and unlocks as speed drops?

                3. Was the shift governor chosen to match the Stude torque curve?

                4. Was the odometer gearing corrected so the calculated fuel mileage is known to be accurate?

                5. Terrain and altitude have everything to do with choice of final drive ratio. The Studebaker V8 is small and relatively low torque. It won't pull a steep hill with the converter locked and a 2.31 (3.31 x .7) final drive ratio. This is no problem if the lockup function of the torque converter is properly set up to unlock at the appropriate throttle opening.

                6. Sometimes the carburetor and distributor must be recalibrated to match the new cruise conditions. With a very tall gear ratio, the throttle will be open wider and the manifold vacuum will be lower.

                jack vines
                PackardV8

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                • #9
                  From 1991 to 1996, Impala's were equipt with the 700 (4L60) trans and the read end ratios from 2:56 to 3:42 with the majority being around 3:00. My point is the 700 was geared low initially to get a heavy car moving with a high number rear end.

                  Bob

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                  • #10
                    Originally posted by sweetolbob View Post
                    From 1991 to 1996, Impala's were equipt with the 700 (4L60) trans and the read end ratios from 2:56 to 3:42 with the majority being around 3:00. My point is the 700 was geared low initially to get a heavy car moving with a high number rear end.

                    Bob
                    Bob, we know you know, but point of clarification, "The TH700R4 has a lower than usual first gear (3.06) to get heavy cars and trucks moving with higher than usual (but low number) rear axle ratio."

                    It should be mentioned that old carburetor/distributor engines do not like to pull as hard at very low RPM as will EFI computer controlled engines. FWIW, the SBC never had main bearing problems until the lockup converter and low numerical axle ratios enabled heavy loading at low RPM.

                    jack vines
                    PackardV8

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                    • #11
                      I put a 4L60 in my GT behind the Stude 289. Beyond the fact that I made my own adapter, it's a piece of cake. I have a 3.54/1 axle.

                      However, I will say as I have many times before; I would not do it without installing a rear engine mount! To fit the GM trans you have to remove the crossmember that supports the rear of the very heavy Stude engine. The GM alluminum 1/2 bellhousing was never ment to carry the entire weight of a 700lb engine . The engines it was designed for have mounts mid way on their sides that carry the engine weight, the trans tail mount only balances it and, the small block Chevy is about 200lbs lighter. Without a rear engine mount , using just the Stude front mounts and the GM tailshaft mount the entire weight of both the trans and the engine is being carried on that thin aluminum 1/2 belhousing. Imagine hitting the right bump and having that belhousing break, dropping the engine and trans to the ground at highway speed.

                      Keep in mind, along with an adapter you'll also need a new drive shaft and yoke, a starter, a flexplate, a trans dipstick and tube, a TV cable, converter and lockup wiring, a carb that will accept the TV cable or a proper adapter, a trans cooler or radiator with one (the latter is usually required if the trans has a warrenty), cooler lines, a case of fluid, and a speedo drive, gears and cable. If your trans is a late one you may need to remove a reluctor and install a speedo gear under the tailshaft housing.

                      Also, these transmissions are metric so any bolt that goes into them is too. The bolts for the tailshaft mount are 10mm, NOT 3/8". 3/8" will tighten up if you don't get carried away but WILL NOT stay tight. ( I just built new engine mounts and trans mount for a custom car that the builder used 3/8" bolts instead of 10mm. They came out and ,due to the design of the trans mount, dropped the trans, breaking the engine mount positions off the frame and messing up a lot of stuff. ) Trust me, the stock GM bolts cost $15 for the pair; that's WAY cheaper than a repair.

                      This is my adapter with engine mounts. The mounts bolt the frame where the stock crossmember is removed. There is also a crossmember that bolts between these frame mounts, that clears the GM trans. Notice: The small cutout in the adapter plate below and to the left of the starter hole, is needed to clear the Bendix power steering control valve when turning fully to the left.
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                      Last edited by bensherb; 08-01-2021, 04:56 PM.

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                      • #12
                        Really nice piece of work!

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                        • #13
                          Excellent work on your adapter Rick (bensherb)! You make an excellent point as to supporting the weight with center mounts at the bell housing.
                          Paul
                          Winston-Salem, NC
                          Visit The Studebaker Skytop Registry website at: www.studebakerskytop.com

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                          • #14
                            Bensherb I like your setup, but did you lose much ground clearance with the center of the support? Looks like it dips pretty low. Thanks

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                            • #15
                              Originally posted by JoeHall View Post
                              Bensherb I like your setup, but did you lose much ground clearance with the center of the support? Looks like it dips pretty low. Thanks
                              The cross member is a bit lower than the original, so technically yes I lost a bit of ground clearance. I made the crossmember before installing the torque plate and converter, so it's location was a "questimation". It's lower than it needs to be, I could move it up at least an inch. It hasn't been an issue at all, and does add a bit of protection for the trans pan, as it will hit ground first. The AOD actually hangs lower than the original 3 speed OD. Every time I leave my neighborhood I have to go over three "speed humps" (they're speed bumps about 4 feet wide) If I hit them too fast the crossmember will bottom on them as the front wheels drop off and I straddle them; but it saves the trans pan and exhaust. If I go over them as one should it's no problem though. The low point of the exhaust where it goes around the trans and under the "wing" is at the same point as the bottom of the crossmember. It is 2 1/4" pipe though not the tiny stock pipe.
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