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Technical overdrive

Discussion in 'The Hokey Ass Message Board' started by flatheadgary, Oct 20, 2019.

  1. flatheadgary
    Joined: Jul 17, 2007
    Posts: 667

    flatheadgary
    Member
    from boron,ca

    this is for all the guys who have overdrive transmissions in their cars. do you drive as fast as all the new cars on the road? if you don't, why do you have the overdrive trans then? just easier on the motor at the lower rpm? as a matter of fact, does anybody try to keep up with new car traffic? or is that another thread topic?
     
    LOU WELLS likes this.
  2. Blues4U
    Joined: Oct 1, 2015
    Posts: 3,816

    Blues4U
    Member
    from So Cal

    No overdrive, but I don't have a problem keeping up with traffic.
     
    Truckdoctor Andy likes this.
  3. fastcar1953
    Joined: Oct 23, 2009
    Posts: 1,644

    fastcar1953
    Member

    Overdrive for lower rpms. I do drive it like a new car. Keeps up just fine, i do alot of interstate driving.
     
    Peter Nowak likes this.
  4. loafer
    Joined: Sep 2, 2015
    Posts: 2

    loafer

    I drive my flatty O D at hiway speeds. Sure I get passed, but that's the flathead experience!
     
    LOU WELLS likes this.
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  5. squirrel
    Joined: Sep 23, 2004
    Posts: 43,445

    squirrel
    Member

    I usually drive old cars around 60-70 mph, which isn't quite up to traffic in most places. There are several reasons, engine speed is not the greatest concern.
     
    47ragtop, LOU WELLS, Jet96 and 2 others like this.
  6. Had a fresh 292 six in my ol' pickup with a 55 chevy 3 speed, O.D. and 3.73 rear gear. Kept up with interstate traffic just fine.
     
    Jet96 likes this.
  7. Mr48chev
    Joined: Dec 28, 2007
    Posts: 25,544

    Mr48chev
    ALLIANCE MEMBER

    I always thought it was their job to keep up with me.
    For the current build with the 292 6 a a few tricks in the engine and the AX15 trans with the 3.5 rear and 27 (?) inch tall tires it means about a 500 rpm drop at 70. From there long road cruising speed depends on exactly where the best gas mileage with a reasonable speed goes.
    The truck is going to be what it always has been and that is a reacher that I can get in and drive wherever I want to go. First real road trip will be to Texas to visit my wife's family some of our Texas friends and go to Lone Star. From there who knows.

    We have a wide diversity on how we drive our HAMB cars among members. We have the guys who subscribe to the Bob-K train of thought in that "that sounds like fun and it's only a thousand miles from here to there. and we on the other hand have the guys who will never drive their HAMB cars far enough from home to have to add gas to get home after attending an event. Plus everything in between.
    Some guys in large metro areas think an event on the far side of town is too far to go while others drive 300 miles that morning to get to the same event and the only worry is where they plan to stop for breakfast on the way down and where they plan to stop for dinner on the way back.
    Older Texas guy will remember Johnny from Waco in his blue 40 Ford Sedan in the mid 70's He drove from Waco to Tulsa for one day at the street rod nationals in 1973 and drove home that night and made it home to sleep in his own bed. Later a friend from here told me that when he lived in the Rio Grande Valley Johnny had driven to an event there and left and drove home that night. He very honestly drove several hundred miles, registered for the event and got his goodie bag, walked around and took photos and got back in the car and drove home. His wife seldom got out of the car at an event although she rode everywhere with him.
     
    Jet96, 31hotrodguy and Hnstray like this.
  8. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 7,581

    mgtstumpy
    Member

    I keep up with traffic in my 35 Chevy, occasionally overtake and don't care if others pass me. Given what we pay for gas down here, you'd be surprised and understand why ODs are great for economy. Plus I run the OEM gas tank so I get better a longer (Distance) range from a fill.
     
    Jet96 likes this.
  9. Colonial Coupe
    Joined: Dec 22, 2010
    Posts: 62

    Colonial Coupe
    Member

    My chopped and lowered 51 is no match on the interstate for a 5000 pound SUV with a 20something chick driving on the cellphone at 85 mph. We stick to the side roads, but we're lucky to have some nice 2 and 4 lane highways that kinda parallel the interstates that we use. I get great gas mileage with my 302 HO and AOD. 3:43 gears in the rear work out just fine. With the mustang gas tank I'm worn out before it will run out of gas.
     
    Frankie47, Hnstray and mgtstumpy like this.
  10. Boneyard51
    Joined: Dec 10, 2017
    Posts: 2,710

    Boneyard51
    Member

    Just got back from a two day 300 mile trip in my three speed automatic avatar car. Some interstate, some back roads. I was running 60+ on the back roads and 70+ on the interstate. Plenty fast, was actually breaking the law(speed limit) most of the time and people were passing me right and left! But that’s my speed in light traffic. If it was heavy traffic I would have sped up or got off. I have updated disc brakes and the car is in good shape steering wise, so handling and stopping is no problem.
    Now my old ride a 1960 Econoline with a 200 six three speed overdrive 4:11 rearend . I would drive it 80 plus if the traffic warranted it. Most folks didn’t think those things would even go that fast! Lol






    Bones
     
    alanp561 likes this.
  11. Budget36
    Joined: Nov 29, 2014
    Posts: 2,321

    Budget36
    Member

    I don't even keep up with traffic in my daily...eff'em, I drive the speed limit.
     
    Colonial Coupe likes this.
  12. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 300

    ekimneirbo
    Member
    from Brooks Ky

    It all boils down to whether you want to be able to drive on the expressway or not. With todays smooth running and powerful vehicles, its hard not to drive 80+ mph once you get on the xway. I have caught myself running 85-90 and had to convince myself to slow down. If you get in the slow lane, you most likely will need to be doing 70 or more or people will be tailgating you.

    Whether you enjoy the noise of your engine or not, running those speeds with a non-overdrive transmission is an exercise in hearing loss.......
     
  13. Hyvolt
    Joined: Jun 12, 2016
    Posts: 225

    Hyvolt
    Member

    I run my 221 flathead at 70 mph, or I'll get trampled. The bw r10 helps out tremendously. Now if I could keep oil in the engine, I'd be set. My small town has nowhere to go, so if I want to drive much at all I gotta run interstate.

    Sent from my LM-V405 using The H.A.M.B. mobile app
     
  14. Blues4U
    Joined: Oct 1, 2015
    Posts: 3,816

    Blues4U
    Member
    from So Cal

    Do overdrives really help with gas mileage? OD will certainly lower RPM's, but I'm not sure that always equates to reduced fuel consumption. Unless paired well with rear end gears an OD can put an engine out of it's best efficiency range. And that is going to vary with each engine/power train. I'm not going to argue that OD never equates to improved fuel mileage, but I don't think you can say it always does. I think the best advantage about OD's is they allow higher rear gear ratios, which allow for quicker acceleration, as well as relaxed engine speeds on the highway. If you also get reduced fuel consumption, well IMO that is icing on the cake. But don't be surprised if you don't get that.
     
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  15. Gman0046
    Joined: Jul 24, 2005
    Posts: 5,607

    Gman0046
    Member

    Blues4U, how is it possible not to get better fuel consumption with lower RPM's? My 60 Pontiac Bubbletop has a cammed up 400 C.I. engine and a 2004R overdrive transmission. Turns 1900 rpm's at 75 MPH when in overdrive. On Interstate highways can run 80 MPH plus all day long without breaking a sweat with great fuel economy. Its also no slouch when driven like a conventional 3 speed automatic.
     
    Last edited: Oct 21, 2019
    firstinsteele likes this.
  16. error404
    Joined: Dec 11, 2012
    Posts: 132

    error404
    Member
    from CA

    I have a hard time imagining that running OD will do anything other than give better mileage. Your gearing, tire size, and how fast you want to go will make a difference for sure though.

    In my 46 Willys, when I had the original motor, trans and axles, I had to put an OD unit on the transfer case just to keep up with traffic. It would run out of gearing before it hit 45. It had 5.38 gears though, haha!

    I don't have OD in my 33, I still drive 80 on the freeway. My rear tires are 31" tall now, so that helps. Even with the older 28" tall tires I would still do 80, but definitely ate more fuel.

    As much as I'd like to have overdrive, I'm going to leave the transmission in my truck for a while until I put in a manual, at which point I'll have overdrive. :)
     
  17. Boneyard51
    Joined: Dec 10, 2017
    Posts: 2,710

    Boneyard51
    Member

    Overdrives vs standard three speeds, when used right will give better fuel mileage. But not double, just a small increase, usually. Like Blues said, it depends on a lot of factors.

    I had two OT Ford pickups that both had the 300 six. One auto ,one four speedOD. The mileage difference was staggering, 11 vs 18/19 on the highway. Same engine.








    Bones
     
  18. squirrel
    Joined: Sep 23, 2004
    Posts: 43,445

    squirrel
    Member

    the OD in the Hudson didn't seem to do much for mileage, but when you have 4.56 rear gears in a big car with a flathead engine, I guess you're gonna get lousy mileage. 12 was about all it would do.

    Didn't do much for mileage in the Edsel, either....about 14 either way, and it had 3.55 gears.

    But when I put OD in that 39 Chevy I had years ago, with a stockish 350 engine, it went from 15 to 20 on the highway.

    YMMV
     
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  19. Back in the 70s, I was driving my 55 on the street with 4.57 gears. I installed a Hone-O-Drive overdrive, and on the highway, it made the truck much quieter and more economical at freeway speeds.
    I am now running a 3.73 gear set with the overdrive, and never took the time to figure the mileage. I just like it.
    Bob
     
  20. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,134

    oldsman41
    Member

    Well kinda depends my 41 I’m in lead foot mode most of the time. The 51 merc flatty I back road a lot cause I just like it for crusin.
     
    Boneyard51 likes this.
  21. flamedabone
    Joined: Aug 3, 2001
    Posts: 4,503

    flamedabone
    ALLIANCE MEMBER

    389 Pontiac with a TKO-600. Does 80 mph all day long at 2100 rpm. Got between 18-20 mpg on the HAMB Drags trip. Overdrives are fun.

    [​IMG]

    -Abone
     
  22. Beanscoot
    Joined: May 14, 2008
    Posts: 1,064

    Beanscoot
    Member

    It is possible for an overdrive to lower mileage, if the engine ends up lugging because the gear is just too high.
    Then the power valve will remain open, enriching the mixture, plus the engine will be well out of its best torque range.

    Most good things can be taken to an extent where they no longer are good.
     
  23. Atwater Mike
    Joined: May 31, 2002
    Posts: 9,776

    Atwater Mike
    ALLIANCE MEMBER

    My '55 F100 w/350/350, 3.0 nine inch rear, tires are 2.55 X 15. All day long freeway driving @65-70 MPH, true 16 miles to the gallon. (engine is 'loaded to the teeth')

    Very satisfied for a truck as streamlined as a barn door...Better styling, but a 'barn door nevertheless'!
     
    Boneyard51 likes this.
  24. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,677

    s55mercury66
    Member
    from SW Wyoming

    Aerodynamics and the engine's efficiency range will definitely have an effect on mileage. 1900 rpm at 70 mph with some engines will find you with your foot on the floor most of the time. I don't see how that can be very good at all.
     
    seb fontana likes this.
  25. jimmy six
    Joined: Mar 21, 2006
    Posts: 4,653

    jimmy six
    ALLIANCE MEMBER

    First I think OD’s will get better gas mileage but close if your trans without it works out the final rear ratio near the same. I feel if your final ratio is close to 2.75 your first 3 gears are goin to be fun to drive.
    I chose a 2.75 rear ratio and a true upgraded 3 speed from an old Ford-O-Matic, taking out a 3.31, and could not be happier. The speed limit was 55 when the car was new and now cruising 70 is a breeze and not the engine noise of the past. Gained mpg a little on the road but about the same in town.
    I feel the best would be adding efi at the same time. Fuel mileage would definitely improve.
     
  26. tubman
    Joined: May 16, 2007
    Posts: 4,373

    tubman
    ALLIANCE MEMBER

    When I drive my '51 Ford with a warmed-over Merc flathead, it just seems like it should have one more gear left to go when it exceeds 50 mph. Some times I forget myself and actually try to grab that next gear, only to realize that I'm already in high. I have a complete OD assembly that I am planning on installing next spring. My high school car in the late '50's was also a '51 Ford, but that one had a working OD and I remembering being a lot easier to live with than the present car. I am going to leave the present 3.55 rear end gears in it initially as I think the engine has enough power to pull them. It'll be an interesting exercise. I am looking for easier cruising and haven't given much thought to fuel economy. After this thread, I'll probably watch it and see if the OD helps. By all accounts it should.
     
    Boneyard51 likes this.
  27. 55styleliner
    Joined: May 11, 2015
    Posts: 492

    55styleliner
    Member

    I cruise in my Flathead powered A at 75-80mph at 2400rpm on the Texas toll roads. This is thanks to an RTS (T-170) overdrive trans.

    F9A7B742-A062-4C28-A47D-4EED047E5AA1.jpeg
     
  28. fastcar1953
    Joined: Oct 23, 2009
    Posts: 1,644

    fastcar1953
    Member

    Overdrive only gets me about 3 more miles to a gallon. Of course i drive 80 to 85 most times on the interstate. 350 4 speed auto o.d. with 3.42 gears and 27 inch tall tire.
     
  29. lumpy 63
    Joined: Aug 2, 2010
    Posts: 949

    lumpy 63
    ALLIANCE MEMBER

    I have TKO 600s in two of my cars , One is my daily driver 56 pu with a 406 sbc and 3.42 gears . It will pull down 21 mpg at 70 mph...loafing along at 2200 rpm on flat ground. It will also pull the grapevine going home from CHRR in 5th but not getting 21 mpg. My 37 has a 377 tunnel rammed sbc with 3.73 gears , Runs like a scalded ass ape in the first 4 cruises like a Caddy in 5th. The 390 Cad I'm building or my 56 big window pu will have a TKO 600 also.:cool:
     
  30. lumpy 63
    Joined: Aug 2, 2010
    Posts: 949

    lumpy 63
    ALLIANCE MEMBER

    Obviously its all about the combo..I dated a gal a few years back who had bought a 56 chevy pu with a 330 hp 350 crate motor + a 700r4 and a 10 bolt with 2.56 gearso_O It would go in and out of 4th at freeway speeds and was a pretty much a pig with crappy gas milage. I installed a 3.73 posi diff and the truck was fun to drive and got better milage . She still owns it 15 years later and has been on a couple of TV shows with it.:cool:
     

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