Rear diffs 3.73 vs 4.30

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  1. #1
    CelicaSupra.com Member
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    Rear diffs 3.73 vs 4.30

    I have a 4.30 in my 85 now but a spare 3.73 from a 82 I am parting out, What is better and what are the pros and cons to each? Sorry im a newbie to these things... Also how much do each diffs go for? my buddy said the 3.73 is hard to find but didn't really know why its better lol

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  3. #2
    CelicaSupra.com Member tdream's Avatar
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    I have an 85 that had a 4.3. It whines at highway speeds, the car was running at 4K on highway. Had it rebuilt. Less noise but still there. I was going to go 4.1 but found a brand new never used 3.73 in box online. Installed and love the way it drives. I have a habit of second gear starts, with 4.3 it did this without problems. Even the 4.1 (had an 83) was able to do this. Now itís just stutters a little. That is the only issue I have. But one I can correct by using first gear to start. One other benefit your now switching into second before your rear wheels go into intersection.


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  4. #3
    CelicaSupra.com Member
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    Quote Originally Posted by tdream View Post
    I have an 85 that had a 4.3. It whines at highway speeds, the car was running at 4K on highway. Had it rebuilt. Less noise but still there. I was going to go 4.1 but found a brand new never used 3.73 in box online. Installed and love the way it drives. I have a habit of second gear starts, with 4.3 it did this without problems. Even the 4.1 (had an 83) was able to do this. Now it’s just stutters a little. That is the only issue I have. But one I can correct by using first gear to start. One other benefit your now switching into second before your rear wheels go into intersection.


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    so its less noise on the highway and better off to start in first then 2nd, anything like a difference in fuel economy or speed off the line ect…?

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  6. #4
    CelicaSupra.com Member tdream's Avatar
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    Fuel economy will be better. Less revs. The 5m is not a powerful engine and if you donít do burn outs go with the 3.73.


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  7. #5
    CelicaSupra.com Member
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    Quote Originally Posted by tdream View Post
    Fuel economy will be better. Less revs. The 5m is not a powerful engine and if you don’t do burn outs go with the 3.73.


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    ok I understand, I plan to do a 7mgte swap will either of these give me a issue?

  8. #6
    CelicaSupra.com Member tdream's Avatar
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    No you will like it better with the turbo. So you can enjoy the higher revs to get boost.


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  9. #7
    CelicaSupra.com Member
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    awesome! I don't know why but im seriously addicted to this car... I keep seeing in my head what I want it to look like when its done and I just keep finding out more that I keep liking

  10. #8
    Boosting Mod SilverMk2's Avatar
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    You'll drop your revs at every speed about 15% with the 3.73s at the expense of acceleration. If you have more power you can offset that loss of acceleration. Personally I love the 3.42s in my car. I'm about 2600 RPM at 80 MPH

  11. #9
    CelicaSupra.com Member drjim's Avatar
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    I have the 4.30 in my '85, and it's a bit "busy" on the highway, but sure scoots around town.

    Since I don't do any cross-country cruising, the 4.30's are fine for me. If you regularly drive the car at 65~75MPH, you might be happier with the 3.73's, but you'll lose some "snap" around town.
    1985 5-speed "Ms. Swan"

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  12. #10
    With 3.73 your car will be slower in acceleration 0-60 as your gears are longer, and with 4.30 it will feel quicker around the town/low speed driving. Look at it this way- longer gears (3.73) is for fuel economy or cars with a lot of HP. Shorter (4.30) for sporty/spirited driving with cars that have small amount of HP. With that said if you interested in selling your 3.73 please let me know. My 2JZ sucks with 4.30 gears.

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