Switched 3.00 to a 3.70 rearend

Discussion in 'Ranchero Tech Help' started by Stuntdummy, Oct 23, 2011.

  1. Stuntdummy

    Stuntdummy In Fourth Gear

    Messages:
    249
    Location:
    Pasadena, CA
    And the results are...!

    --Not a very noticeable difference in ability to accelerate.
    --My driveshaft had to extend a lot further and did not feel very tight on the AOD end.
    --Didn't know my speedometer was connected to my driveshaft. How do I fix/adjust that for my new ratio?

    I think the reasons for not seeing a noticeable difference in power come from the fact that my engine is out of an '85 thunderbird with a 2 barrel carb and an AOD tranny. It's a lot of car to be pulled by a mild 2bbl 5.0 with an automatic. Any thoughts on that? I was thinking of doing the EFI swap, but maybe I should look into getting a different 5.0 engine. I imagine a 5.0 from a mustang GT is a bit different from a thunderbird, no?

    As far as the driveshaft feeling a bit loose on the transmission end, I'd also imagine that isn't normal either? I felt a little bit of vibration while going 70mph, but I think I usually feel that anyway.
     
  2. billg72469

    billg72469 In Fourth Gear

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    Location:
    corona ca
    To adjust the speedo you need to change the gear that is on the trans end of the speedo cable with a different gear, don't know the correct color but that part is easy. Don't understand the drive shaft problem, how doe's changine the gears change the driveshaft. I changed from a c4 to and aod and all I had to do was to have a shorter driveshaft. I fixed that by changing the yoke on the diff to an f100 yoke which is shorter and it all went to gether well.
     
  3. LSChero

    LSChero In Maximum Overdrive PLATINUM MEMBER

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    Made a big performance improvement when i changed 3.00 to 3.50.
    Maybe motor is not performing at peak output?
    AOD spline yoke is about 4" longer than C-4 to make contact with bushing in tail shaft,did you use AOD yoke?
    21 tooth speedo gear worked perfectly,3.50 rear, 255-60-15 rear tires.
    Most 80s 302 had same HP output.Bolt on improvements,heads,intake,exhaust will improve performance.
    Id look for 5.0 from 99-02 explorer,mountineer.Better heads and maybe not flogged as hard.Run carb or better yet,mustang EFI+mass air.
     
  4. ribald1

    ribald1 Banned PLATINUM MEMBER

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    You may not like this, but there is a serious likelihood that you reduced performance, and for sure you reduced gas mileage.
    To get the advantage of that aggressive gear change you will need to alter the engine to perform better at high rpms. (cam, intake, headers etc) Next you will have to make adjustments to the tranny so that it shifts at higher rpms. (vacuum modulator adjustment, possibly governor adjustment)
     
  5. Stuntdummy

    Stuntdummy In Fourth Gear

    Messages:
    249
    Location:
    Pasadena, CA
    My previous performance was this: not having any acceleration ability in overdrive. The slightest slope and I would start decelerating.
    I have headers already.
    I agree, the tranny probably needs adjustment.
    As for fuel economy, I don't think I'll lose much or any: there's a bell curve on efficiency and my previous rear end was definitely not at the top of the bell (like trying to ride a bike with the gear ratio always one notch higher than desired---harder to pedal, more energy required). With my 235R16's on the back I'm probably now on the other equal end of the bell curve, haha.

    I think the whole thing just needs a tune up. :rolleyes:
     
  6. ribald1

    ribald1 Banned PLATINUM MEMBER

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    Location:
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    A 302 is on the low end of being powerful enough for a car that heavy, and the AOD was making the gearing too tall on the freeway.
    A 3.25 rear end would have been a good choice, then making changes to bring your power level up and adjusting the transmission to match the much heavier car it is in.
    Well before you start slowing down on a hill the AOD should shift out of overdrive. A vacuum modulator adjustment would have resolved that problem.
    I understand that 'done is done', and redoing the rear end is probably out of the question for a while.
    Intake and carb changes won't make an appreciable difference without changing the cam.
    Before you make the changes, come up with a plan. Set you goals, design the engine to achieve them, then start getting parts. That will save you a lot of money and you will end up with something that works properly.
     
  7. Stuntdummy

    Stuntdummy In Fourth Gear

    Messages:
    249
    Location:
    Pasadena, CA
    Changing the pumpkin out wasn't too bad. I should see if anyone wants to trade a 3.25 for a 3.00 (or the current 3.70 for that matter).
    Yeah, the 302 isn't much engine for that car. I think doing the EFI is the next project (I already have most of the parts for it).
     
  8. ribald1

    ribald1 Banned PLATINUM MEMBER

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    Don't expect a power improvement from the EFI. Better starting, gas mileage, throttle response, yes, but it also creates added complexity when you alter the engine. Don't get me wrong, I like fuel injection, I have it on my Ranchero. Just passing along information.
    In my opinion, if performance is your goal going to a big block is the only way to go if you are switching engines. (there is no replacement for displacement) The upward potential is almost limitless and you don't have to spend big bucks to get decent performance.
     
  9. airford1

    airford1 In Maximum Overdrive

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    1,396
    Going from 300 to 370 should yield a BIG improvement.

    The drive shaft problem is the shorter yoke on the 3rd member.

    Make sure you have the right u joint going into the 3rd member. 1310/1330/1350 , 3 u joints it could have. Check the cap size to the yoke.
     
  10. DonC

    DonC In Maximum Overdrive SILVER MEMBER

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    3.7 gears ought to be about right for the AOD, not sure why your motor is such a dog. How many miles on the motor? The explorers and alot of the passenger cars had the 3.5 to even 4.11 gears and would run great with a 5.0. I really think you have another problem besides gears.
     
  11. LSChero

    LSChero In Maximum Overdrive PLATINUM MEMBER

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    We need pics stuntdummy..85 bird should of had TB injection with/TV linkage..Maybe too late and tranny is toast.Ribbed boot is TV linkage.
    [​IMG]
    Adjustment of TV cable is important to life of tranny and engine performance..
     
  12. scrnic1

    scrnic1 In Fourth Gear

    Messages:
    274
    I have a 3.00 third member ive been wondering what to do with. If you want it, pay for shipping. Its not a posi, but it didnt make any noise when i removed it this summer, and it was nice and tight(not to tight though ;) If you want it we can work something out.
     
  13. Stuntdummy

    Stuntdummy In Fourth Gear

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    249
    Location:
    Pasadena, CA
    (read thread title) ;)
     
  14. Stuntdummy

    Stuntdummy In Fourth Gear

    Messages:
    249
    Location:
    Pasadena, CA
    It has that linkage, but maybe it needs adjustment.
     
  15. Stuntdummy

    Stuntdummy In Fourth Gear

    Messages:
    249
    Location:
    Pasadena, CA
    The U-joint is fine (I ordered a 1330 to 1310 combo). I think best idea for figuring out problems is to go meet up with another '72 Ranchero owner who's more experienced and so happens to live in a city nearby to Pasadena. Maybe he'll even take me for a ride in his '72! *cough cough*
     
  16. DonC

    DonC In Maximum Overdrive SILVER MEMBER

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  17. Torkair

    Torkair In Maximum Overdrive

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    I'm 99% certain that your 302 is just dead dog worn out, rebuild it or replace it time is just around the corner. A 351w might get you the punch you're looking for (or if you wanna get a more manly motor grab a 351 Cleveland). While the Cleveland has way more cool points going for it the 351w can use pretty much all the same parts as your 302.
     
  18. scrnic1

    scrnic1 In Fourth Gear

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    274
    LOL, i just misread the above post...Or i assumed you junked your 3.00 and wanted another one..IDK, ignore me lol.

    On that note, i agree with Torkair. You should have noticed a pretty substantial difference in feel. I went from 3.00 to 4.11 Now, I must say it wasnt the HOLY SHIT factor i was expecting right off the bat. But as i drove it more and payed attention to how the truck was behaving, there was an obvious huge diffenence. I also went from OPEN rear end to POSI. I figgured with as much power as i make, and the gear change, id be smoking tires at freeway speeds no problem. While its not doing that, it does break loose when i drop from 3rd to second, and throttle response is improved all over. Not to hijack here, sry. I agree with Torkair, and Ribald and whoever else said MOAR POWAAAAAAAAAA
     
  19. ribald1

    ribald1 Banned PLATINUM MEMBER

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    Low gearing is great if you like buying tires, but smoking them up gets old after a while. Especially when you end up eating dust while your tires smoke.
    A decent running 302 will smoke the tires with 3.00 gearing with a moderate stab of the go pedal. My ford van does, and gives a solid chirp coming into second stone stock. Granted it only weighs 3000 pounds, but a stock 3600 pound Mustang with the same set up acts the same.

    Yes, all the guys with high power engines and loose converters run lower gears. But the gearing is just a part of the whole setup, and not even close to being the most important part.
     
  20. Stuntdummy

    Stuntdummy In Fourth Gear

    Messages:
    249
    Location:
    Pasadena, CA
    All biases aside, what are the differences between the 351C and the 351W spec for spec? My uncle, who owns two '68 California Specials, says the Cleveland is an overrated POS and that the Winsor is way more dependable. I've heard others say otherwise.
     

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