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dodge flathead t5 conversion mpg?

Discussion in 'The Hokey Ass Message Board' started by 1950coronet600hp, May 22, 2012.

  1. probably going to catch flak for this, to the folks with flathead mopars and the converted t-5, what are ya gettin for mpg? thinking about selling my non hamb friendly daily driver and buying a nice stock 4 door desoto. so has anyone checked their mpg increase after converting to a 5 speed?
     
  2. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,355

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Gotta be better than the typical semi-automatic that is in most of the old Dodge/DeSoto/Chryslers. However, be aware that these cars all have a very long bellhousing due to the space needed for the fluid coupling and manual clutch assembly. As a consequence, a fully manual clutch/transmission input shaft has to be very long to reach the flywheel. Mopar did that with the full manual versions in '53/'54 models, but a T5 input shaft isn't going to make it.

    You can use most any Plymouth bellhousing, or Dodge/DeSoto 6 bell from '55/'59 to get a short bell. But that requires relocating the rear crossmember forward (or fabricating a new one) as it also serves as the rear engine mount.

    All doable, just added effort and parts needed. There are, I think, some adapters available to go directly from the Mopar block to a Chevy/GM bellhousing/transmission (Wilcap and Bendtsens). I think that might be preferable since the T5 isn't a direct bolt up to the Mopar bellhousing anyway.

    Ray
     
  3. great project/idea...keep us posted.
     
  4. Just as a heads up, my '51 Plymouth got 26-28 mpg on a regular basis with a '54 Plymouth OD.

    How about an 833?




    BloodyKnuckles
     

  5. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,355

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    The factory O/D trans is the easiest solution, I have one in my '49 Plymouth Club Coupe, but they weren't that easy to find 15 years ago and haven't gotten easier since.

    I put a Mopar O/D in a '51 Dodge before that and that trans, because of the input shaft length referred to in my previous post, is found only in '53/'54 Dodge and DeSoto models, and was/is even rarer, I traveled about 600 miles round trip to get that one.

    There is a thread on the Mopar Forum ...P15-D24... about using a an early Ranger/Mazda 5 speed that is fairly easy to adapt to the Plymouth bellhousing.

    I do not know what would be involved in the A883 or A833....whatever it is called.

    Ray
     
  6. 73RR
    Joined: Jan 29, 2007
    Posts: 7,175

    73RR
    Member

    The swap portion of this discussion has been covered many times, including the A-833 OD and the 'mysterious' late 50's bell that is damn close to working as is, as well as other 5-speed swaps.
    Check www.p15-d24.com for a rundown on the Ford Ranger 5-speed with a near stock bell (as opposed to the required adapter parts for the t5).
    Search for 'Ranger'.

    .
     
  7. Shitboxdodge
    Joined: Sep 29, 2008
    Posts: 68

    Shitboxdodge
    Member

    Well all I can give is a "wild ass guess"...my fuel gauge and odometer don't work! But on the trip to the LSRU this year I knew about how far I had gone and how much fuel I was adding...it was easily 20+ mpg...

    My conversion was a little tricky too because I was going from a powerflite to the t5...needed bell housing and new flywheel. Because my car has the 230 in it (more bolts on the crank) the only flywheel I found was for a power wagon...which caused me to have it redrilled for the pressure plate / clutch I was using. That said, if my dumb ass could get it done, anyone can!

    I also went with a wc t5 out of a fox body for the gear ratios...the tranny mount angle on that thing was a bitch and the shifter location made it pretty tight with my seat.
     
  8. P51captain
    Joined: May 21, 2012
    Posts: 13

    P51captain
    Member

    I just got a 55 Plymouth and want to do this conversion. Out with the 3-speed in with a 5 speed.
     
  9. hkestes
    Joined: May 19, 2007
    Posts: 585

    hkestes
    Member

    The final drive ratio of the T5 and the Mopar R10 3 Speed OD are nearly identical 0.72 to 0.70. In my 48 Plymouth coupe with 57 model 230 with dual Carter Webber 2bbl carbs and cast iron headers I get right at 21 mpg with the OD trans and stock 4.10 rear gears.
     
  10. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,355

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL



    Sorry to be a nitpicker.....but T5 OD ratios are all over the place, from .86 to .63, depending on application, with high .70's to high .80's being the most common. Most of them have pretty deep 1st gear though, so a bit taller (lower numeric) rear axle ratio can work okay with the higher numeric OD.

    Just complicates the matter a a little if you just want to change the trans and call it a day, whereas the BW R10 units are all .70, so far as I know.

    As many of you already know, the website www.britishV8.org/Articles/Borg-Warner-T5-ID-Tags has a great apllication list that makes it easy to figure out what will work best for your needs.

    Ray
     
  11. P51captain
    Joined: May 21, 2012
    Posts: 13

    P51captain
    Member

    I do have a line on a Dodge 3-speed OD trans (direct fit) to replace the std 3-speed. That seems to be the quickest and easiest swap. I need to refresh the 'chattering' clutch anyway. Might go that route and amass the parts to do the 5-speed swap later.
     

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