what gears to get and where?

Discussion in '40- & 55-Series Tech' started by milesstarkey, Jun 27, 2005.

  1. milesstarkey

    milesstarkey

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    my 71 fj40 is my daily driver and i want to go on the highway without it over heating. what gear ratio should i buy for front and rear and where should i buy them from?
    it has a 350 with a th350 tranny and stock transfer case with 31" tires now but i'll be switching to 35"s hopefully next spring. thanks for your help.
     
  2. PabloCruise

    PabloCruise SILVER Star

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    Does it still have the 4.11's in it?

    Those would be fine for highway and 35's...

    You won't have much crawl, but fine for highway.

    Overheating could be due to other issues that need your attention, like the v8 conversion, improper radiator, etc...
     
  3. Mace

    Mace rock scientist.. Staff Member s-Moderator

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    Overheating is not really a gear thing..


    fix the motor overheating issues. 4.11's and 35's are a fine combo for a good running 350.
     
  4. milesstarkey

    milesstarkey

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    on the highway i'm running 3000 rpm's around 55 mph. i don't know what gears are back there but 3000 rpm's at 55 doesn't allow me to drive very far or go any faster. and i shouldn't have said 'overheating' but it gets hotter than i like it. 230 F. off the highway it stays around 190 or less.
     
  5. Cat Scan

    Cat Scan

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    Please check out the other two threads running currently on this site regarding heating problems and the 350 conversion. Doubt very much that the gearing is the cause of your problems. I run at 3000 rpm at freeway speeds and no longer have any heating issues. And I also have the 4.11 gears. The 230 F is too high. There is something else working against you here.

    Good Luck!
     
  6. milesstarkey

    milesstarkey

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    ok, forget about the temperature, i'll work on that. but please, someone answer the gearing question. let me restate the problem i'm having and some one please tell me if they are running a different gear ratio. when i go about 55mph i'm at 3000 rpm. I WANT TO GO FASTER. i do not want to go over 3000 rpm's. therefore, don't i need different gearing?
     
  7. JJB77FJ40

    JJB77FJ40

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    If you haven't corrected your speedometer for the tires you are running and I believe stock is 29.0" then your 55MPH@3000is actually 58.8 MPH and when you go to 35", without correcting speedo for tire change you will be travelling 66.4MPH @3000. However, your speedo will still be reading 55 MPH and your tach will still be accurate @ 3000 RPM without changing any gears.

    Tires are like big driven gears.

    Hope this helps.

    John
     
  8. woody

    woody unhelpful spotter Staff Member Admin

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    the 35's are a big overdrive versus the 31's...55 will actually be 62... effectively an 11% overdrive, so your rpm's will drop from 3000 to 2670. IMO, spend the $$$ you would on gears for tires instead, and do gears later if you really think it's still necessary (gears = $150 per end, plus $100 per end installs, plus $100+ for setup...$700 is a set of 35's, last I checked....)

    your stock gears are 4.1x's, the only other option is 3.7x's....your cheapest/best option would be a used set, since VERY few people bother keeping those (I know folks who have tossed many sets out...) install and setup kits still apply, and regardless of what you do, you'll need fine spline flanges for your pinions, $30 ea.
     
  9. milesstarkey

    milesstarkey

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    thanks guys. where can i get the install kit and flanges? the way i want it setup i'll probably do the gears and the tires. should i post a wanted ad for the gears?
     
  10. dgangle

    dgangle total rice

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    you can find complete used working third members w/ 3.70 ratios for $100 or less. Buy one and try it out.
     
  11. Cat Scan

    Cat Scan

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    Ok, despite the several provided hints that you are going in the opposite direction of most folks, consider this. If you are going to get higher gears (3.7) and 35's, and are running everything else stock, you are not going to like doing any serious rock climbing or rough trails.

    Have you considered getting a NV tranny five speed? The overdrive and the 35's will take care of your freeway rpms and you will not defeat the purpose on the low end. Heck, even the 35's will take care of most of it as stated by others here.

    Once you go down the gear route, and then go larger tires, you will be seeking ways to crawl at slower speeds provided you use your rig off road. If you don't wheel with it, then don't worry about this post.
     
  12. honk

    honk

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    You've got the wrong car, Miles.
     
  13. Cat Scan

    Cat Scan

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    Correction, adding the 35's will take some of your crawling speed away, but with the 3.7 gear set, you are really going to be luging that engine on the trail. Again, who cares about all this info if you don't use the cruiser for crawling?
     
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