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Technical Low gears with Over Drive

Discussion in 'Traditional Hot Rods' started by 31hotrodguy, Jan 7, 2019.

  1. 31hotrodguy
    Joined: Oct 29, 2013
    Posts: 718

    31hotrodguy
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    So once again my brain is working over time and I am thinking about the 55 Gasser again. Question, if you run a really low rear end gear ratio with an over drive on the street are you going to have issues with premature wear with either the trans or rear end?


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  2. squirrel
    Joined: Sep 23, 2004
    Posts: 42,062

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    what gear ratio are you thinking of?

    and what kind of rear end, and what kind of transmission, and what kind of overdrive?
     
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  3. Beanscoot
    Joined: May 14, 2008
    Posts: 883

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    The overdrives based on the Ford Toploader and Chrysler 833 (and probably others) use third gear as an overdrive, so will wear more than a conventional four speed when in top gear.
    In top gear the four speeds have the power going straight through, so no load on the countershaft.
     
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  4. Boneyard51
    Joined: Dec 10, 2017
    Posts: 1,947

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    Most all overdrives “ gear up the final drive”. Never could figure where the smarts was in gearing up and then down on a passenger car!
    Now for a hot rod(or truck) , I can see where they work good, using the direct drive when you put full power to the ground.
    To answer your question, the wear on your rear end or transmission will be at a minimum. What slight premature wear will be way overshadowed by better mileage and reduced engine wear.


    Bones
     
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  5. DDDenny
    Joined: Feb 6, 2015
    Posts: 11,396

    DDDenny
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    from oregon

    Jim
    You should be a seasoned professional in reading minds here by now!
     
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  6. squirrel
    Joined: Sep 23, 2004
    Posts: 42,062

    squirrel
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    like all psychics, I need to get some feedback from the "mark" first :)
     
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  7. 31hotrodguy
    Joined: Oct 29, 2013
    Posts: 718

    31hotrodguy
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    Squirrel, I was hoping you would chime in. The rear end is a Pontiac with either 6.17’s or 5.38’s (I cant remember) The trans is now a M21. I was thinking of a gear vendors OD. I have a friend that had issues with his 57’ jr stocker wearing out the tail shaft bushing. He likened it to having had 5.38’s and the trans spinning too fast for too long. Just a side note, the Gasser is not a street car but it is licensed. Like I mentioned my brain was just thinking in over time and I was wondering what it would be like to drive short trips to the drag strip or down to the car hop while keeping the 5 or 6 something gears.


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  8. Deuced Up!
    Joined: Feb 8, 2008
    Posts: 3,353

    Deuced Up!
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    Man that is a pretty low gear set what are you planning on using to spin those bad boys if you don't mind me asking?

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  9. 31hotrodguy
    Joined: Oct 29, 2013
    Posts: 718

    31hotrodguy
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    64’ 283 bored 4 inch, factory forged 350 crank, small journal 6 inch rods, SRP pistons, comp cams solid roller 254/260 @ .050 .582/.588 lift, porter 461’s with a lot of machine work. I’m not sure on the intake/carb yet. I’d like to run Hilborns but I have a lot of learning to do before we get there. Sadly it’s not running yet but I’m hoping 2019 will be the year.


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  10. Kind of a hard way to end up with a 350, isn't it?;)
     
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  11. DDDenny
    Joined: Feb 6, 2015
    Posts: 11,396

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    from oregon

    Curious if the 283 block was from a Nova or just got lucky on the overbore.
     
  12. 31hotrodguy
    Joined: Oct 29, 2013
    Posts: 718

    31hotrodguy
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    Yes and no. Yes being it would have been easier to build a regular 350. No in that the 283 block=free, buggered up forged crank =free, 6 inch small journal rods= not cheap . My plan is to build an outward period correct care and get it in the high 10’s. Most people wouldn’t care but to me the later “smog” engines with later valve covers don’t look as cool.


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  13. 31hotrodguy
    Joined: Oct 29, 2013
    Posts: 718

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    The 852 block tends to have plenty of “meat.” They can typically go 4 inch plus without any issues. Plus they have rom for the larger counter weights unlike the early blocks. Just to be safe though I had mine sonic tested.


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  14. squirrel
    Joined: Sep 23, 2004
    Posts: 42,062

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    you'll be spinning the driveshaft pretty fast! I doubt you'll have any problems wearing out the trans or rear end, because you won't put a lot of miles on the car.
     
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  15. 31hotrodguy
    Joined: Oct 29, 2013
    Posts: 718

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    So back to the over drive. Does anybody have experience running an over drive in their race car and what gear ratio are you running?


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  16. squirrel
    Joined: Sep 23, 2004
    Posts: 42,062

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    I have a GV in my Chevy II behind a TH400. 3.89 gears out back. Ran a 10.05 last November.
     
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  17. jimmy six
    Joined: Mar 21, 2006
    Posts: 4,133

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    I run a Tex T101 which has 3rd as an overdrive. They've a chart where you pick every thing. They say not to use on the street as it has dog "syncros" and you drive it without using the clutch. It's essentially a 3 speed OD with the 3-4 shifter arm upside down. They were originally built for NASCAR at Pocono.
     
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  18. classiccarjack
    Joined: Jun 30, 2009
    Posts: 1,364

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    The Chrysler A833 OD is .72 to one on the OD ratio. 3rd gear is your overdrive, 4th is one to one ratio. The 3-4 lever is flipped 180° to keep the conventional "H" shift pattern. I may have misread what was posted, but I just wanted to make sure that the way the OD was designed was interpreted...

    1975, first year OD's were the only OD's with a cast iron case... 1976 and up are all Alumninum. Both utilize the large input bearing retainer.

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  19. classiccarjack
    Joined: Jun 30, 2009
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  20. tomic
    Joined: Jan 8, 2008
    Posts: 113

    tomic
    Member

    one of the best tools for messing around with gearing (engine, transmission, axle, tires and wheels) is a spreadsheet. it lets you do 'what if' poking around with gears, tires, transmissions etc and tweak things to match. here's a copy of the one i use: http://sr-ix.com/temp/TransAxleTire.xls.

    i can't imagine picking gearing without the spreadsheet, too much guesswork.

    plug your data into the GREEN values, leave the others alone, they're calculated.

    you can get Open Office or LibreOffice for free (no cost, no ads) if you don't have Microsoft Office...
     
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  21. 31hotrodguy
    Joined: Oct 29, 2013
    Posts: 718

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    Hey Squirrel, 3.89’s wasn’t quite what I had in mind.


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  22. squirrel
    Joined: Sep 23, 2004
    Posts: 42,062

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    well...with a larger engine with a blower, and running the quarter mile, it ends up around 6k or so rpm through the lights. Plenty for me.
     
  23. classiccarjack
    Joined: Jun 30, 2009
    Posts: 1,364

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    That's nice, thanks for sharing that.

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  24. 31hotrodguy
    Joined: Oct 29, 2013
    Posts: 718

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    Thanks classic car jack. Novak adapters is another site that has a hearing calculator. I spend a lot of time there when I can’t sleep.


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  25. wicarnut
    Joined: Oct 29, 2009
    Posts: 2,800

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    Where do race race that 6:17 ? or 5:38 1/8 mile gear is required. most overdrives are between .7 to .8 Back in the day 60's ran 4:56, 4:88, 4:71 detroit locker on driver/street race cars, did not have to go highways to work, gas was 20/25 cents. If you want to drive your Gasser to the ice cream cruise, hope it's a short drive. You mentioned Hilborn Injection, race deal designed for WOT, very tough to run on street. I've called BS on guys that said it will work on street, I've had/built several race systems, with multiple nozzles, bypass's, dailajet, it will almost work, but not really, spent a whole summer with good friend that also understands this injection setup and we finally gave up. If you take it out of trailer and 1/2 mile up road to a cruise anything works then. Have Fun, always like the hard hitting cars coming in. Good Luck !
     
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  26. 31hotrodguy
    Joined: Oct 29, 2013
    Posts: 718

    31hotrodguy
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    The 55 has never raced with that actual rear end (I’m not sure what rear end has when it raced) but the Pontiac rear end with those gears came out of my buddy’s 57’ 150 Gasser. (It raced at a quarter mile track. Let me clarify what I mean by “drive it on the street.” I’m not intending on driving it on the street on a regular basis and especially not if I am able to get the Hilborns going. Also to put things in to perspective I can drive the back roads from house to the Famoso and only have to stop at 3 stop signs and one stop light to get there. Or like you mentioned where I might trailer to the Friday night car just for fun. So it is more of an fun factor to say I did it.


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  27. porknbeaner
    Joined: Sep 12, 2003
    Posts: 40,918

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    I am not totally understanding your logic. Outward appearance you cannot tell the difference between a '64 283 block and any 350 block. From '58 through the LS there is no real difference in appearance of SBC blocks.

    But if punching a 283 to 4" and using an oddball crank makes you happy it tickles me plumb to death. I may have gone a different direction but that is just me.

    All that aside, most factory ODs use a deeper gear than a non OD car. Well at least until they went to computer controlled motors that would run a low RPM and still pull. If you are using a lot of cam you are not going to want to keep your revs down. Lugging a motor is damned hard on it.
     
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  28. squirrel
    Joined: Sep 23, 2004
    Posts: 42,062

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    pretty easy to tell the difference between a 283 and most 1980 or newer 350s, at a glance...the damn oil dipstick is on the wrong side! and there are other more subtle differences on the earlier 350s.
     
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  29. Roothawg
    Joined: Mar 14, 2001
    Posts: 18,511

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    Man, this thread makes my head hurt.
     
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  30. porknbeaner
    Joined: Sep 12, 2003
    Posts: 40,918

    porknbeaner
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    My 80 block has the dipstick on the same side as a 283. No pass side provision.

    Yes very subtle and only people like you and me would notice and wouldn't care. LOL
     

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