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  • Mitchell Overdrive Info!

    Original Thread


    Go to a national meet, and you'll see that a large percentage of the Model A's that are driven are sporting a Mitchell Overdrive. That extra shifter in the car is the tell tale sign. I just posted a news letter tech article which tells of the advantages when using the gear split in different situations and not just for high gear. The O/D units cost in the area of roughly 2,400.00 but do seem to give you a good bang for the buck. They come complete and ready to drop in with new shafts and torque tubes. These can be installed without the complete overhauling of the differential or transmission.
    Can you give your insights and experiences on installing and cruising with one. Most A's have a 3:78 gear ratio, Is that the most desired set up to use? What are your experiences when using say a 3:27 or a 3:54 ratio? What about a stock head vs a high compression? Let's try and keep this thread on topic for the Mitchell Overdrive. We know that there are many other alternatives such as overdrive trannies and so forth, but you can always start another thread for those. I will attach that newsletter article onto this post.


    1E4CEFFB-98BE-4A9F-85B4-827EE8D372D1.jpeg
    Attached Files
    3 ~ Tudor's
    Henry Ford said
    "It's all nuts and bolts"


    Mitch's Auto Service ctr

  • #2
    Mitch, the only experience I have is I don't want to be behind anyone with a Mitchel. For some reason their driving technique becomes unpredictable. I think the driver becomes lazy and only wants to shift the Mitchel, lugging his engine, then taking off when he does shift. Also I have seen drivers get confused in stressful situations like in the mountains. That may be age related. Maybe it is just me but I get very aggravated because I have to watch the car in front of me at all times and can not look at anything Geri is pointing out. Yes I can leave more space between cars but that space closes fast when the jerk in front wont shift and he is lugging his engine. I know I am going to get a lot of flak over this but that is ok.

    Comment


    • tbirdtbird
      tbirdtbird commented
      Editing a comment
      how can you tell by being behind the guy that he has a Mitchell?

    • carolinamudwalker
      carolinamudwalker commented
      Editing a comment
      Dave, I know the people and their cars on our tours.

    • tbirdtbird
      tbirdtbird commented
      Editing a comment
      sounds like they just do not know how to drive, period.
      I think lots of ppl lug because they are trying to save gas, which is a false economy.
      Anyway, you can't take it with you, so spend a couple extra bucks and get out there and enjoy it.
      I chuckle when somebody complains they only get 18 MPG. So what? If mileage is what your goal is, you never should have bought a vintage car, they all have terrible mileage. It is about having fun.

      And trust me, from this side of the keyboard, I can testify that life is too short, so get out there and soak it up

    • Jwmckenzie
      Jwmckenzie commented
      Editing a comment
      My '67 Jeep has an overdrive behind a three speed. Still learning how to drive it, don't follow me close. I am getting better, but it will take some more time until I get the feel for splitting the gears. Something you have to learn by doing, regardless of brand of overdrive.

  • #3
    Not flak from me because you make a good point however that said having driven a truck in my lifetime I do have a Mitchell and it works quite well you definitely do not want to lug any engine and you want to be in the right gear to utilize the engines power band not doing so is a great way to over heat an engine or break a crank so actually learning how to properly drive your car is what you want to learn this is why I have a tachometer and a temperature gauge and I have seen plenty of people lug their car even without an od. All cars are different from stock to modified or improved pick your poison. Bob you are an exception because of all the miles you have actually driven and because of where you live so I very much understand what you are saying. Hope your world is coming back to normal I know it has been a challenge but I also know you do not give up either.

    Comment


    • carolinamudwalker
      carolinamudwalker commented
      Editing a comment
      Thanks CHIEF, House is finished moving full time to the car. Our modern had 3 feet of water and was trashed with only 20,000 miles. My philosophy has always been : when confronted with a blockade, find a way to go over, under, or around but never give up. Maybe its military!

    • BNCHIEF
      BNCHIEF commented
      Editing a comment
      Never could take no for an answer always had to find a way. Yeah it could have been the military.

    • Mitch
      Mitch commented
      Editing a comment
      That is good news Bob
      I was always thinking about your ordeal

  • #4
    Originally posted by BNCHIEF View Post
    Not flak from me because you make a good point however that said having driven a truck in my lifetime I do have a Mitchell and it works quite well you definitely do not want to lug any engine and you want to be in the right gear to utilize the engines power band not doing so is a great way to over heat an engine or break a crank so actually learning how to properly drive your car is what you want to learn this is why I have a tachometer and a temperature gauge and I have seen plenty of people lug their car even without an od. All cars are different from stock to modified or improved pick your poison. Bob you are an exception because of all the miles you have actually driven and because of where you live so I very much understand what you are saying. Hope your world is coming back to normal I know it has been a challenge but I also know you do not give up either.
    Steve, you have covered the entire topic very well right in that one paragraph!

    Initially I had a stock motor with a 3.54. Well, the 3.54 did almost nothing, and was a waste of money.
    Once I retired to Texas, I added bigger intakes, Stipe IB330 cam, etc etc performance wise (trying to get a better power band), and I wanted to be able to do 60-65 without grenading the motor. A lot of club members here have Gary Bernard's 4-speed OD conversion, because he is such a master at making them work.
    I liked the idea of a gear splitter, having driven big trucks with 2-speed rear axles. My car is the 180A, ie the deluxe touring, and it is light compared to other models. I talked with Ken Davis, the local A guru, and he said the cost would be about the same either way, but advised me to yank the 3.54 and swap back in my 3.78. He said even with my performance mods, the motor would not be able to handle the 3.54 in OD. If you had a heavier car, I wouldn't even dream of anything less than a 3.78

    And you know what? He was right. I can run at 65 mph in OD at 2200 rpm, which is my personal redline for an A, all day long, and it is comfortable. Some complain about having the extra lever, but that makes no sense to me, I think it is just an excuse.
    There have been many hill situations where second high has really worked out quite nicely.
    And my brakes are fully and properly restored and stop the car very well

    Some kind of OD is important to many of us here because this is a huge state and we tour every inch of it, including going into nearby OK, LA, AS, and we can easily take a tour that is 1000 miles one way

    Just my experience, your mileage may vary. Enjoy the trip!

    PS an added trick of having the Mitchell, is at a stop light, you can shift the Mitchell to N, and pull the main box stick back into first without grinding, and just sit out the light. When the light changes, you pull the Mitchell stick back into low range, and there is no grinding, because it has synchro! Voila, no more grinding shifts into first.
    Even tho the Mitchell is synchro, I ALWAYS double clutch it, to help the synchros out, they love it

    Comment


    • Mitch
      Mitch commented
      Editing a comment
      So going with a 3:78 is preferred.

    • Dennis
      Dennis commented
      Editing a comment
      If you are considering it for a Tudor, yes 3:78. And I would stay with the 26% OD.

    • BNCHIEF
      BNCHIEF commented
      Editing a comment
      Could not agree more with Dennis.

  • #5
    Exactly T-bird my car has 3.78 gears a lightened flywheel, b cam and police head my car runs out quite nicely performs i would say the dame as yours I never find myself between gears(ratios I mean) so you do not have big gaps in your ratio. I once learned to drive a truck that had three transmissions the combo gave you 60 forward gears. Now days everything is getting automatics. A Mitchell is a tool to improve your driving experience. As an example both of my model T's have Ruckstell 2 speed rear ends and will perform nicely out here on the plains without the Ruckstell but put them in hills and you will go slow in low gear and your leg will get very tired. You will like it then. Not trying to stray from Mitchs point however. Some say they do not like the lever well they do make a cable set-up for it that will mount to your shift lever I have even thought about an elctric servo to shift the Mitchell it is a very short stroke at the box.

    Comment


    • tbirdtbird
      tbirdtbird commented
      Editing a comment
      Steve, there were Ruckstells all over the place for the T, and Colombias all over the place for the early V-8s, and both OD were as sweet as could be. I have always been baffled why back in the day there was never a third party OD offered for the A. God knows they had every other known accessory for the A, just look at the unauthorized accessory book. The had gerbil driven wipers, tire air ups from your cylinders, pontoons for crossing lake Superior, snow tracks for the swamps of Louisiana, dual ignition set ups, hand operated magnetos to get a hotter spark, plugs with 14 electrodes for better combustion, all kinds of useless stuff, but never an OD!

    • BNCHIEF
      BNCHIEF commented
      Editing a comment
      Dave that is a great point especially when you consider that for model T there were warfords and muncie transmissions, you would have thought those manufacturers would have been interested in more sales.

  • #7
    I notice that their table corresponds to my experience at 2200/65 MPH.

    Honestly, for a heavier car, I don't think you are gonna get over 60 MPH at 2200 rpm.
    My 2200 redline is my limit because no matter what you do to the guts of the motor, it is still a long stroke motor, and you will grenade it or any other long stroke, with too much RPM.

    We use highway speeds to get to our location, such as Hot Springs, AS, then once there, we slow down and drive along at 35 MPH so we can enjoy the sights. As far as the hiways, there is not much to be seen, except billboards and large signs for fireworks

    I should add that the quality of the manufacturing of the Mitchell is unsurpassed. No chineseium here

    Comment


    • #8
      No doubt the Mitchell is a fine piece of engineering. But I am just curious, how many of your wives drive hundreds of miles while on tour?

      Comment


      • tbirdtbird
        tbirdtbird commented
        Editing a comment
        Not sure what you are asking, but the wives always join in, they love touring, also.
        We hit every historic place we can. Small town American cannot be beat

    • #10
      Have one 12 years old with the following experiences (and in our hilly terrain):
      1. Install relatively easy except adjusting pinion preload can be a challenge if setup disturbed or special puller unavailable.
      2. Have cable installation but lever shift may be a little more direct feeling.
      3. 26 % (with 3.78 rear) can be tall on hills so need to prevent lugging as stated by others
      4. can use OD in all gears forward especially on extended steep grades
      5. uses common gear lube ; pressure relief (tubing) from side of case needs to be high enough above case to allow a little seepage to drain back
      6. Not sure if OD may block rear end venting if via torque tube but still working on this ( our F150 4speed in another A does block the pressure relief )
      7.Great design and well built ; very infrequent lube seepage from front horiz.shifter rod

      Comment


      • #11
        With out a doubt one of the best things to happened to a Model A.. I had one in my Fordor 160c and drove over 25K with it and on tour to Niagara Falls and everywhere in between. I also drove at at comfortable 65 all day long with no issues at all. If you lean to use it as a gear splitter as it is intended you will love it..it totally changed my driving for the better, I am hoping to be able to have one now for the 155a town sedan...Wise good investment

        Comment


        • #12
          I am two years into the hobby. When searching for my "A" I intended to convert the standard three speed to a Mitchell or a T5. I bought a 1930 Cabriolet which had a T5 with a 3.78 rear; it performs beautifully, New York's Hudson Valley hills are no problem, and you simply only have to deal with one shifter( gas mileage is 20+ MPG). However, anyone that I have spoken with using a Mitchell loves them as they are well engineered and also perform beautifully; you can't go wrong with either one!

          Comment


          • #13
            Is there anybody else out there that makes an OD kit for a Model A using a stock Model A transmission? The only instance I have heard that is a negative is a possible clearance problem in a Victoria and possibly a SW Fordor. There are a lot of Model A owners out here with BW and units from Volvos. I've heard a lot of stories about driveshafts breaking welded together crooked, failed solenoids etc etc. They are less expensive but who are you going to get parts from? The Mitchell in not just for OD on an open highway. They work great in the mountains on slow winding and steep grades. I too come from the past truck driver crowd, so it's more fun for me to have the shift lever. In city traffic as Tbird mentioned, the Mitchell is great for stop and go. Come to a stop and slip it in neutral.

            Comment


            • Dennis
              Dennis commented
              Editing a comment
              Another note, if you are considering installing one yourself, find a club member that has the Mitchell pinion tool so you don't have to buy one. They might even offer to help. I helped a club member with mine when he asked to borrow it.

            • Mitch
              Mitch commented
              Editing a comment
              They have different units available.
              Victoria and A400
              &
              S/W with the floor tool box

              Maybe this addresses the clearance issues

            • tbirdtbird
              tbirdtbird commented
              Editing a comment
              It does, my deluxe touring also has the dropped floorpan and needs the same low clearance as the vicky.

              Tom Endy addresses the outdatedness of the Borg Warner units in one of his articles, and parts for them at this point are virtually non-existent. They also tilt back at a dangerous angle and the gear oil flows to the diff, overfilling it, and leaving the BW dry. The two most important areas of the BW are the planets and the sprag clutch, and without being marinated in gear lube, those parts burn right up

            • Dennis
              Dennis commented
              Editing a comment
              And you don't go in reverse with a BW. All of them I have seen are leakers.

            • tbirdtbird
              tbirdtbird commented
              Editing a comment
              yep, if you don't lock out the BW OD before shifting into R, you are gonna lock up the sprag clutch so bad the entire thing will have to come apart to be fixed

          • #14
            Getting back to the clearance issues on certain body styles. Do the other two specific units / part numbers that are available for those body styles address that issue? This is taken off the Bratton's site
            See attachment

            You do not have permission to view this gallery.
            This gallery has 1 photos.
            3 ~ Tudor's
            Henry Ford said
            "It's all nuts and bolts"


            Mitch's Auto Service ctr

            Comment


            • tbirdtbird
              tbirdtbird commented
              Editing a comment
              yep

            • Mitch
              Mitch commented
              Editing a comment
              Thanks Dave
              Do you know what the differences are on those two units, vs the standard O/D that fits all the other body styles?

            • tbirdtbird
              tbirdtbird commented
              Editing a comment
              for the low clearance units, the gearbox is shifted rearward. For the other units it is more midline in the torque tube

          • #15
            So getting back to rear end ratios. For a heavy car, like my Station Wagon, should I consider a 4.11 ring gear and pinion. The purpose for the OD would be a gear splitter rather than a faster top end.....
            Jon.

            Comment


            • tbirdtbird
              tbirdtbird commented
              Editing a comment
              If the motor is stock, then definately

          • #16
            D7A376ED-8148-4477-8D43-3F10065666B7.jpeg
            3 ~ Tudor's
            Henry Ford said
            "It's all nuts and bolts"


            Mitch's Auto Service ctr

            Comment


            • #17
              Another Mitchell Overdrive Thread

              https://www.vintagefordforum.com/for...nd-experiences

              https://www.vintagefordforum.com/forum/model-a/242591-mitchell-overdrive-differences
              3 ~ Tudor's
              Henry Ford said
              "It's all nuts and bolts"


              Mitch's Auto Service ctr

              Comment


              • #18
                I found this article in a newsletter, and figured that this would be an appropriate place to put it.

                9A068893-678A-401C-B658-5C6A5ABC0461.jpegAAF1AB2C-C1AC-4192-AB19-8266137D7B06.jpeg7F34F163-EBEB-4669-B9ED-B75CDEE7929C.jpeg
                3 ~ Tudor's
                Henry Ford said
                "It's all nuts and bolts"


                Mitch's Auto Service ctr

                Comment

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