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Turbo TH350 vs. 4L60E

This is a discussion on Turbo TH350 vs. 4L60E within the Automatic Transmission forums, part of the Drivetrain category; I do not know much about auto transmissions. I am looking at an LT1 with with Turbo TH350 tranny and ...

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    Rice Killa JwMonE99's Avatar
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    Turbo TH350 vs. 4L60E

    I do not know much about auto transmissions.
    I am looking at an LT1 with with Turbo TH350 tranny and a 3800 stall.
    My question is what advantages does the Th350 have over the 4L60E?
    Also does having a big stall like a 3800 affect DD much?

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    Senior Member Bottesini's Avatar
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    I don't know much about autos anymore, but the TH350 is a tried and true strong tranny. There is a major drawback though, no overdrive, and depending on how they are built you might still have to shift through all the gears. Back when gas was cheaper and I was not doing as much highway driving the 350 was fine. For the modern me I know that I could never get away without overdrive. In fact it is one of the reasons I have to have a 6 speed since the second overdrive made the car feasable as a DD.

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    Rice Killa JwMonE99's Avatar
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    So the TH350 only has 3 gears?

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    Moderator Firebirdjones's Avatar
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    Yes the 350 turbo is a 3 speed auto with 1:1 3rd gear. No overdrive.

    It does have a better gear spread than the 4L60.

    With 2.52 first gear, 1.52 second gear, and 1:1 3rd gear.

    With the 3.06 first gear of the 4L60,,,it has a huge rpm drop the engine has to recover when the 1-2 shift accurs, and is not a fan favorite among serious racers.
    If you want a better gear spread between gears and you must have an overdrive to boot, not to mention much stronger,,,,then the 4L80E would be the way to go.

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    Rice Killa JwMonE99's Avatar
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    How bad on gas is is TH350?
    the reason why I am asking all this is because I might buy another camaro with it already in it so I dont have much choice in decision.

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    Slow'er'Ass Mr. Luos's Avatar
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    Quote Originally Posted by JwMonE99 View Post
    How bad on gas is is TH350?
    It wouldn't be pretty.

    It obviously depends on rear gearing...but even average gearing will eat up fuel.

    I know a guy that runs a TH400 with 4.11 rear gears. 55MPH is roughly 4,000RPM on the highway....

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    TH350 with 3.73 gears? also on a 383 stroker

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    Slow'er'Ass Mr. Luos's Avatar
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    Quote Originally Posted by JwMonE99 View Post
    TH350 with 3.73 gears? also on a 383 stroker
    My best guess using www.f-body.org/gears as my guide.

    75MPH with the TH350 would be 3600RPM.

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    Member performabuilt's Avatar
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    th350 verse 4l60e on cost of gas equals "I'm scared" Hell I have and escort I drive and even putting gas in it is scary for me and it gets 39 MPG !

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    TH350 is very similar in design to the 4L60 in a lot of ways. It's a pretty decent transmission that will last (with reasonable modifications) to around 500-550 HP. After that, you are best off with a TH400. Actually, I would take a TH400 anyday even in a 300-400 HP car. It is a better and much stronger transmission.

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by JwMonE99 View Post
    How bad on gas is is TH350?
    the reason why I am asking all this is because I might buy another camaro with it already in it so I dont have much choice in decision.
    Well thats a vague question really as most people have different ideas on what is good mileage.

    I personally run a 400 turbo in my chevelle,,,with a loose Coan converter and 4.10 gears,,,,and I can cruise at 55 mph on the highway at only 2,700-2,800 rpms, with a 28 inch tall tire,,,it's not that bad,,,,,not sure where Mr. Lous got 4,000 rpm from with a 4.10 gear.

    Shucks at 4,000 rpms I'm going well over 70 mph in that car..

    Your cruise rpm with a 350 turbo, 3.73 gears,,,and depending on the tire height in the rear and how loose the converter is,,,should be very reasonable in my opinion. 3.73 gears are nothing to me,,,they were factory and considered middle of the road on alot of 60's muscle cars,,,it's just what I'm used to..

    But don't take it from me,,,,I'm old school and still tool around in muncie 4-speed cars with 4.56 gears,,,,and driven them accross country


    Another example of no overdrive,,,my fathers 69 GTO,,currently runs a 3.73 gear in the car,,,,with a very loose Coan converter and 400 turbo and a 29 inch tire,,,,he can cruise effortlessly on the highway,,,when I'm spinning 2,800 rpms at 55 mph in the chevelle,,,,he's only spinning 2,400 to 2,500 rpms,,,he can cruise at 65 mph and still be a tick under 3,000 rpms. It's nothing really.


    Tire height plays a role in this as well,,,but as far as mileage goes,,,it depends just as much on the motor and the tuneup as well... here are some examples of mine,,,,

    Chevelle with 400 turbo, 4.10 gears, loose converter and 28 inch tire cruises at 2,800 rpms all day with the air on,,,,with a 638 hp 454, big roller cam etc....and it gets a solid 10 mpg..
    My fathers GTO with 3.73 gears, 400 turbo, loose converter, 29 inch tire, runs a 620 hp 455 and he also gets about 10 mpg...
    My 79 monza, 406 ci, muncie 4 speed and 3.23 gears and 26 inch tall tires gets 15 mpg, it cruises at 65 mph at about 2,600 rpms,,,(short tire)
    My 79 1 ton truck with mild 454, 400 turbo and 3.73 gears has tickled 14 mpg highway, cruising at 65 mph and spinning 2,800 rpms with a 30 inch tire.
    My wifes 71 454 vette is a stocker with 3.08 gears, 400 turbo and 27 inch tire, gets a solid 15 mpg cruising at 70 mph, about 2,800 rpms.
    My 70 Formula with 3.31 gears, 400 turbo and 400 engine is a stocker,,gets 16 mpg highway cruising at 70 mph at 2,800 rpms....
    My nomad runs 4.56 gears with a muncie 4 speed, and 28 inch tire,,,cruising at 55 mph is around 3,200-3,300 rpms with a little 327,,,and it gets 12 mpg.
    These are examples of cars I have without overdrive. I would think a newer 4th gen with a modern fuel injected engine could do a little better.

    I think people have gotten soft over the years,,,thinking if they can't chug the motor at 2,000 rpms on the highway then it's horrible and the car just isn't driveable
    Last edited by Firebirdjones; 05-27-2008 at 09:25 AM.

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    Driving my Camaro SS with a 4l60E making 383rwhp to work I'll get 22 MPG Avg. thatís with a 3200 RPM stall. Driving my 79 Corvette thatís making less power and has a T350 with a little stall converter I get 13 MPG.
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    Point I would make if you bought the car then bought a built 4l60e with a stall and drove it for a couple months your savings in gas would more than offset the cost of the swap. Your talking near a 30 percent increase in gas mileage over the 350 with equal on all other points

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    I love the 4l60e. It is perfect for todays economy and also can be made into a high performance piece. I think the lower 3.08 1st gear is better. it will allow great low end torque multiplications. 2nd gear is also lower with a 1.63 ratio, so the gear to gear jump isn't that bad. The 4l60e allows for 30% greater low end acceleration. And with a stall the motor will fall into its power band on very shift.

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    Member silverz28camaro's Avatar
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    Just to put thinks into comparison i raced my buddies 68 camaro that has 4.10 gears 350 tranny and a 3500 stall. My car has 3.73 gears 4l60e and a 2800 stall. his car weights 3390lbs and mine weighted 3480 at the time. we took both cars to the dyno and his car had about 30hp more than mine (again at the time)

    That night we did a little street racing. We left at the same time....even in first, even into second and in third he started pulling away. his hp showed when we were both in 3rd but in 1st and 2nd we were even due to my tranny having the lower gears internally. I think if i had a th350 he would have had me the entire race, or if i had the same stall speed he did i think i would have hole shotted him and stayed in front.

    I had this same discussion with a guy i work with about the lower gear in the 4l60 being better or not.

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    Moderator Firebirdjones's Avatar
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    Well the lower gear is okay for about the first 30 feet.
    It's fine on the street but you'll find that most serious racers, especially those in stock eliminator NHRA sanction racing,,,,will ditch the 4L60E simply because the gear spread stinks for all out ET's...

    As you mentioned, with the 3.06 first gear and 1.63 second,,,thats a drop of 1.43,,,which is huge. Takes too long for the engine to recover and it hurts the ET.

    Most will switch to the 350 turbo,,,,with a 2.52 first gear,,,second is 1.52,,,,so the drop on the 1-2 shift is only 1.00,,,,the engine recovers faster hence the reason they generally produce slightly quicker ET's

    The higher 2.52 first gear is simply compensated for with more rearend gearing. More rearend gearing will also put the engine closer to it's optimum RPM range at the end of the traps in 3rd gear as well. If you try that with the 4L60E,,,,then first gear would be so short it renders it useless and much more difficult to 60 foot the car as a result. Ever drive a 4L60 with 4.56 gears???? It's a joke in first gear. But thats an example of the kind of rear gear it would take to get a high strung engine in it's power band at the end of the traps in high gear.

    It's just not the best racing transmission,,,the gears are not friendly.
    But I agree that if you want a cruiser, that only sees the strip for fun once in a while,,,the 4L60 works nice.
    Last edited by Firebirdjones; 05-28-2008 at 07:58 AM.

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    Quote Originally Posted by shiftless View Post
    TH350 is very similar in design to the 4L60 in a lot of ways. It's a pretty decent transmission that will last (with reasonable modifications) to around 500-550 HP. After that, you are best off with a TH400. Actually, I would take a TH400 anyday even in a 300-400 HP car. It is a better and much stronger transmission.
    I'm going to have to politely disagree. With the right internals, (like a hardened sprag, 8 clutch pack, etc), a 350 will be just as strong as a 400. I wouldn't ever use a 400, simply because it takes more horsepower to turn. Just by switching from a 400 to a 350, you'll gain a little over 20 horsepower to the rear wheels. Not only that, but a 350 is a very strong and reliable tranny. I know for a fact it's safe up to 600 horsepower, with the right internals. I raced a '73 Camaro that had a 383 pushing 630, and made literally hundreds of passes without a problem. The only thing I wouldn't do to a 350 is tranny brake it. They just aren't made for that. I don't even consider the 400 to be an option when racing. It's either a 350 or powerglide, depending on the power of the engine.

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    With the right internals, (like a hardened sprag, 8 clutch pack, etc), a 350 will be just as strong as a 400.
    Not true. The 400 is much stronger in stock or modified form than the 350 because it has a center support.

    I wouldn't ever use a 400, simply because it takes more horsepower to turn. Just by switching from a 400 to a 350, you'll gain a little over 20 horsepower to the rear wheels.
    This is true. I think you'll find though that when rubber meets drag strip, the 400 really isn't any slower than the 350. Maybe a tenth or two at most. In my opinion (and yours may differ), the extra reliability and peace of mind is WELL worth the small horsepower loss.

    Not only that, but a 350 is a very strong and reliable tranny. I know for a fact it's safe up to 600 horsepower, with the right internals. I raced a '73 Camaro that had a 383 pushing 630, and made literally hundreds of passes without a problem.
    600 HP on a small block, sure. It will probably handle it with the right mods. 600 HP behind a big block? No way. A big block will eat a 350 for lunch, whereas the 400 will last just about forever.

    I don't even consider the 400 to be an option when racing. It's either a 350 or powerglide, depending on the power of the engine.
    I think if you built a big block race car, or a really powerful (700-800+ horsepower) street car, you might feel differently!

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    Member knappbunch's Avatar
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    I have heard that the 4l60e is basically a turbo 350 with overdrive and the 4l80e is the turbo400 with overdrive is this true???

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    In a rough manner of speaking, yes, sorta. The 4L60E is an electronic version of the 700R4, which is very similar in a lot of ways to the TH350. The 4L80E is a lot like the TH400 and many parts even interchange.

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