Loading ...
Sorry, an error occurred while loading the content.
 

TH-325 TRANSMISSION TRACTION QUESTION

Expand Messages
  • theoldsarge2002
    Hi. Just found this site. Searched the archives, and didn t find anything that would help me, so have to ask. First some background. For those who don t know,
    Message 1 of 7 , Aug 30 4:33 PM
      Hi.
      Just found this site. Searched the archives, and didn't find anything
      that would help me, so have to ask.

      First some background. For those who don't know, the TH-325 is a front-wheel drive transmission, three-speed, automatic, used in 1979-1981 Olds Toronados, Buick Rivieras, and some Cadillacs models. No, not a
      transaxle, it is a transmission, the engine runs front to rear, and it has a
      separate differential. Mine is a 1980 model, with a OEM 350 Olds V8.

      OK, this engine and transmission will go in the back of a project car, making it mid-engined, rear drive. Some engine mods will be made, and the total weight should be about 2500 LBS, maybe less, so I anticipate traction problems. Oh, yes, I anticipate running 205 wide tires, maybe 195.

      I have been told that traction devices, such as positraction, locker, etc., will not fit in this differential. Of course, the people who told me this also have never tried or checked it, or even know what a TH-325 is.

      This will be street driven, close to a deily driver. Any strip time will be with street tires, full fluids, spare tire, etc., I want to know what it will actually do, not what it is capable of. So no "Lincoln locker".

      So, can anyone tell me how to get traction with a TH-325 transmission?

      Thanks
      Theo
    • tremorj10
      Theo, I posted your question on the MTS Message Board. We use this Yahoo site mostly for archiving posts on that board and to post pictures. Go to Links and
      Message 2 of 7 , Aug 31 1:57 AM
        Theo,
        I posted your question on the MTS Message Board. We use this Yahoo
        site mostly for archiving posts on that board and to post pictures.

        Go to "Links" and click on the MTS link.
      • William Lucke
        Fiero? Don t worry too much about it. The rear weight bias will give you a whole lot of traction. With 16x8 Turbo Grand Prix wheels and 5x115 hub carriers from
        Message 3 of 7 , Aug 31 8:20 AM
          Fiero? Don't worry too much about it. The rear weight bias will give you a
          whole lot of traction. With 16x8 Turbo Grand Prix wheels and 5x115 hub
          carriers from a Pontiac 6000, you can run 255/50-16's in the rear.

          Admittedly, the longitudinal setup won't be as good in that regard as the
          transverse setup, but it should still be quite good. Why not a V8 Archie kit?


          Will



          > From: "theoldsarge2002" <jakofalltrades@...>
          >Subject: TH-325 TRANSMISSION TRACTION QUESTION
          >
          >Hi.
          >Just found this site. Searched the archives, and didn't find anything
          >that would help me, so have to ask.
          >
          >First some background. For those who don't know, the TH-325 is a
          >front-wheel drive transmission, three-speed, automatic, used in 1979-1981
          >Olds Toronados, Buick Rivieras, and some Cadillacs models. No, not a
          >transaxle, it is a transmission, the engine runs front to rear, and it has a
          >separate differential. Mine is a 1980 model, with a OEM 350 Olds V8.
          >
          >OK, this engine and transmission will go in the back of a project car,
          >making it mid-engined, rear drive. Some engine mods will be made, and the
          >total weight should be about 2500 LBS, maybe less, so I anticipate
          >traction problems. Oh, yes, I anticipate running 205 wide tires, maybe 195.
          >
          >I have been told that traction devices, such as positraction, locker,
          >etc., will not fit in this differential. Of course, the people who told me
          >this also have never tried or checked it, or even know what a TH-325 is.
          >
          >This will be street driven, close to a deily driver. Any strip time will
          >be with street tires, full fluids, spare tire, etc., I want to know what
          >it will actually do, not what it is capable of. So no "Lincoln locker".
          >
          >So, can anyone tell me how to get traction with a TH-325 transmission?
          >
          >Thanks
          >Theo
        • theoldsarge2002
          ... OK, Thanks. Theo
          Message 4 of 7 , Aug 31 10:56 AM
            --- In Cadillac_Performance_Association@y..., "tremorj10" <JOEOILER@A...> wrote:
            > Theo,
            > I posted your question on the MTS Message Board. We use this Yahoo
            > site mostly for archiving posts on that board and to post pictures.
            >
            > Go to "Links" and click on the MTS link.

            OK, Thanks.
            Theo
          • theoldsarge2002
            ... Well, mainly because this will be in a VW Beetle. 205 is probably the widest tire I can use, and no taller than 25.4 . Wheels with be 14 , if I can use
            Message 5 of 7 , Aug 31 11:01 AM
              --- In Cadillac_Performance_Association@y..., William Lucke <wlucke@s...> wrote:
              > Fiero? Don't worry too much about it. The rear weight bias will give you a
              > whole lot of traction. With 16x8 Turbo Grand Prix wheels and 5x115 hub
              > carriers from a Pontiac 6000, you can run 255/50-16's in the rear.
              >
              > Admittedly, the longitudinal setup won't be as good in that regard as the
              > transverse setup, but it should still be quite good. Why not a V8 Archie kit?

              Well, mainly because this will be in a VW Beetle. 205 is probably the widest tire I can use, and no taller than 25.4". Wheels with be 14", if I can use them, otherwise 15".

              Theo
            • cody_g_carson
              Keep in mind the TH325-4L made from 82 through 85 is also an option. The same 1st -3rd gears and ratios are used, and are just as strong. The 4l gives you
              Message 6 of 7 , Aug 31 11:15 AM
                Keep in mind the TH325-4L made from '82 through '85 is also an
                option. The same 1st -3rd gears and ratios are used, and are just as
                strong. The 4l gives you the option of a lockup converter, and a 4th
                gear. Aftermarket kits are available through Summit, Jegs and others
                that can allow the useage of these options without a computer.
                For your front diff, in the Eldorado, '79 and '80 models used 2.19:1
                ratios, in '82-'85 a 3.15:1 ratio was used in gas models and a 2.93:1
                ratio was used in Diesels. All are interchaingable. Traction will not
                be a problem in the light car since the engine & trans (together
                about 900 pounds) sit directly over the wheels. The 3.15 gear will
                not break free as easy as the 2.19 will. A TH325 running a 2.19 will
                have 3rd gear RPMs in the same range as a TH325-4L 4th gear RPMs
                runing 3.15 gears. This is due to non-lockup slip in the 325 and the
                overdrive in the 325-4L. I ran some numbers using a tire height of
                25.6" (275/40ZR 17) (235/55R 16) (205/70R 15) and came up with these
                figures: The first listing will be third gear on the 325, and the
                second listing will be 4th gear on the 325-4L: 1500RPM=50MPH,
                1500RPM=54MPH, 3000RPM=100MPH, 3000RPM=108MPH, 4500RPM=150MPH,
                4500RPM=162MPH
                As you can see, both variations would have the same RPMs. A Big
                Block Caddy would easily break traction in most any car even with
                slicks, and would not need the lower gears of the TH325-4L set up to
                get moving in a light car, but the issue there would be transmission
                survivability. An Olds 350, 4.9 Caddy, or Northstar V8 could make use
                of the lower 1st through third ratio to get the car out of the hole
                without breaking the tires free, and would bennifit by being able to
                run higher RPMs for making use of their power band. And the 4th gear
                final would be good MPGs and a 200MPH possible top end on a high rev
                HP motor that develops its horses at or above 5000 since in both
                cases, 5500RPMs is where the 200MPH mark would occur. It depends on
                how much engine you have, how safe the car is, and what you are
                trying to do with it. 500 horsepower is the minimum to get a
                mid '80's Vette body to that speed. I do not know how your car will
                compare in areodynamics or weight. 160 MPH is a much more attainable
                top end goal and could be reached at 4500RPM eaily in the Caddy Big
                block without over reving it.
                Of course, you can use the 2.93s and the 3.15s in the 325 without the
                overdrive if top end is not the goal. Other ratios are available in
                the Olds and Buick versions of the trans, but I cannot find my
                information on those. If Cory is reading this, he may have the info
                available----Cory, calling Cory-----he he, would you please post the
                diff gears on the olds and Buick? Perhaps a post with all including
                the Eldo/Seville so that it can all be in one message. Also please
                include the TH440 FWD trans ratios if you have them, thanks.
                I will post a link to the tire size calculator and the auto math
                calculator web sites in a future posting, and you can play with gear
                ratios, transmissions, and tire sizes until you find what is best for
                the powerband and weight of your car.
                PS. I calculated the 325's RPMs based on a 4% trans slip rate. It is
                possible for the 325s and the 200 metrics to slip at 8% under WOT
                with a strong motor and/or a heavier car. I would like to get a
                better idea of what you are building, and would like a pic of it in
                the phot section.(page two of the photo albums has an album for
                unfinished projects if you have one or two pics, or you can make your
                own album if you have a lot of pics)
                Thanks
                Cody



                Cadillac_Performance_Association@y..., William Lucke <wlucke@s...>
                wrote:
                > Fiero? Don't worry too much about it. The rear weight bias will
                give you a
                > whole lot of traction. With 16x8 Turbo Grand Prix wheels and 5x115
                hub
                > carriers from a Pontiac 6000, you can run 255/50-16's in the rear.
                >
                > Admittedly, the longitudinal setup won't be as good in that regard
                as the
                > transverse setup, but it should still be quite good. Why not a V8
                Archie kit?
                >
                >
                > Will
                >
                >
                >
                > > From: "theoldsarge2002" <jakofalltrades@w...>
                > >Subject: TH-325 TRANSMISSION TRACTION QUESTION
                > >
                > >Hi.
                > >Just found this site. Searched the archives, and didn't find
                anything
                > >that would help me, so have to ask.
                > >
                > >First some background. For those who don't know, the TH-325 is a
                > >front-wheel drive transmission, three-speed, automatic, used in
                1979-1981
                > >Olds Toronados, Buick Rivieras, and some Cadillacs models. No, not
                a
                > >transaxle, it is a transmission, the engine runs front to rear,
                and it has a
                > >separate differential. Mine is a 1980 model, with a OEM 350 Olds
                V8.
                > >
                > >OK, this engine and transmission will go in the back of a project
                car,
                > >making it mid-engined, rear drive. Some engine mods will be made,
                and the
                > >total weight should be about 2500 LBS, maybe less, so I anticipate
                > >traction problems. Oh, yes, I anticipate running 205 wide tires,
                maybe 195.
                > >
                > >I have been told that traction devices, such as positraction,
                locker,
                > >etc., will not fit in this differential. Of course, the people who
                told me
                > >this also have never tried or checked it, or even know what a TH-
                325 is.
                > >
                > >This will be street driven, close to a deily driver. Any strip
                time will
                > >be with street tires, full fluids, spare tire, etc., I want to
                know what
                > >it will actually do, not what it is capable of. So no "Lincoln
                locker".
                > >
                > >So, can anyone tell me how to get traction with a TH-325
                transmission?
                > >
                > >Thanks
                > >Theo
              • theoldsarge2002
                ... I wouild agree, however. There is always a however. LOL My donor vehicle has the 3-speed. Brake lines rusted thru (MI car), runs great, $100. ...
                Message 7 of 7 , Sep 1, 2002
                  --- In Cadillac_Performance_Association@y..., "cody_g_carson" <uplink2jesus@h...> wrote:
                  > Keep in mind the TH325-4L made from '82 through '85 is also an
                  > option. <snip>
                  <><><> I wouild agree, however. There is always a however. LOL My donor vehicle has the 3-speed. Brake lines rusted thru (MI car), runs great, $100.


                  > For your front diff, in the Eldorado, '79 and '80 models used 2.19:1
                  > ratios, in '82-'85 a 3.15:1 ratio was used in gas models and a 2.93:1
                  > ratio was used in Diesels. All are interchaingable.
                  <><><> As you say interchangable, and I am informed my has 2.41:1. I thinking a 2.93:1 or 3.15:1 after I get it on the road and sorted out.

                  Traction will not be a problem in the light car since the engine & trans (together about 900 pounds) sit directly over the wheels. <snip>
                  <><><> Supposedly the Olds weight 560, with accessories. But the best weight I have gotten on a TH-325 is "about" 300 lbs, or, two-thirds the weight of a TH-425, which is supposed to weigh 400 lbs.

                  I ran some numbers using a tire height of 25.6" (275/40ZR 17) (235/55R 16) (205/70R 15) and came up with these
                  > figures: The first listing will be third gear on the 325, and the
                  > second listing will be 4th gear on the 325-4L: <snip> 4500RPM=150MPH,
                  > 4500RPM=162MPH <snip>
                  <><><> I had already ran figures based on 2.41:1 and 27.1" and 25.4" tires. I will not take the Olds engine over 5,000 RPM. With the 27.1" tires at 4500 and 5000 RPM, I got 150.60 and 167.33 MPH. With the 25.4" tires I got 141.15 and 156.84. All of these speeds are MUCH higher than I care to go on a highway. With 25.4" and 2.93:1 I got 115.64 and 128.49 MPH. With 3.15:1 it comes out 107.99 and 119.99 MPH. I think either of these ratios would give me more satisfaction on the street. Especially when one of those irritating Hondas, with the coffee can exhaust, and LOUDd stereo, pull up beside me. LOL


                  > PS. I calculated the 325's RPMs based on a 4% trans slip rate. <snip>
                  <><><> It has been so long ago I calculated those RPMs (different calculator than you gave, but probably same results), I forget the slip rate, but believe it was 5%.


                  I would like to get a better idea of what you are building, and would like a pic of it in the phot section.(page two of the photo albums has an album for
                  > unfinished projects if you have one or two pics, or you can make your
                  > own album if you have a lot of pics)
                  <><><> The plans is, this to go into the back of a '70 VW Beelte. Don't have photos yet, but plan on pics all thru the project. Just have the VW and donor. Gathering info and a few parts just now. Plan on a start as soon as I can shake $100 or so loose.

                  Theo
                Your message has been successfully submitted and would be delivered to recipients shortly.