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  • muskoday
    replied
    Was wondering how you made out with your shifting issue. I'm currently thinking about a 200r4 from a powerglide, and upgrading the doggy 3.08 gears to 373's. I've only got a small block hitting about 300hp.

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  • Paté
    replied
    Sorry.....I don't know how I missed your reply. I'm going to fire it up and do some tests and see if changes shift timing like you suggest.

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  • Barfly
    replied
    Here's what I think is happening.

    It sounds as though the trans is not modulating properly. Shift quality, (firmness), and shift timing, (mph) are tied to each other and controlled by throttle pressure, (throttle cable in your case), and the governor assembly which registers vehicle speed. The two play off each other and determine shift quality and timing. Sounds like the quality, (firmness), is not changing regardless of throttle pressure or vehicle speed, it's always very harsh. When you're accelerating hard there's enough power to the wheels to break them loose and it behaves the way it should but under light throttle and lower speeds it's still shifting hard which it shouldn't do and because of lower speed and torque it just jars the fuck out of the driveline.

    Does this sound right? That sounds like something in the valve body, stuck valve or improperly, or wrong level shit kit installed.

    Also, the shift timing should change considerably from light throttle to heavy. IOW, when you're just tooling down the block easy like the 1-2 shift should occur somewhere around 15-18 mph. when you put your foot into it the 1-2 should be held off much later, 25-30 or higher. If it doesn't it's just another indication of a problem.

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  • Paté
    replied
    I guess I should clarify. If I drive it normally, the shift is early and appears nasty. If you mash the throttle, the big old 454 will wind up and will not only chirp second, but spin the tires again. After thinking about what you said I think it doesn't feel as harsh because the hard shift at WOT is just spinning the tires. I knew I would regret not changing it to a manual when I did this.

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  • Barfly
    replied
    3.42 is a great gear for a torque-y engine with an automatic, you could even ditch the 700R4 and go to a TH400 and it'll be fine. Something screwy is going on with your trans. The shift should occur later and become more firm the more throttle you give it, inversely, light throttle should be earlier and softer. Yours has an early and harsh shift, they ain't supposed to work that way. Sounds like yours has a stuck valve or something is wrong with the install of a shift kit. The GTO in my avatar has a TH400 with 3.42 gears and it moves along nicely. Granted, we don't cruise at 70 with it but that's not what the car is about. 60 mph is no problem, we tach around 2800 or so but remember tire size factors in also.

    I'd reach out to the fella who built it and ask him to see if adjusting the throttle cable helps at all, it's worth a shot I guess. If not and you run out of options lmk and maybe you can run it by the shop one day.

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  • Paté
    replied
    Originally posted by Barfly View Post
    Is it just shift quality alone that is an issue or is shift timing off also, ie, late shift? Sounds like it's moe than a throttle cable adjustment from what you're describing, guy probably went full retard with a shift kit.

    If he put in a Corvette servo that can be replaced with a stock one but it sounds like a shift kit to me.
    It does shift early but I'm assuming that may be a combo of steep gearing and the low 1st gear on the 700R4. I plan to ditch the 4 series carrier and get maybe like a 3.42. My drag racing days are over.

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  • Shamuscull
    replied
    I thought was your screen name but did not want to be incorrect.

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  • Barfly
    replied
    Originally posted by Shamuscull View Post
    Stall speed is measured at wide open throttle. Anything less than WOT will have a lower stall speed. Our 700R4 torque converters lock-up in overdrive automatically. For street use in a 2WD (under 450 horse power) you would need somewhere between 1800 to 2300 stall depending on what feel you like. A 4WD for street use usually uses 1600 to 2000 RPM. Higher stalls than these are usually used on higher horse power motors and for drag racing. The ratings you see on torque converters are for small block motors. The same converter behind a big block will stall as much as 700 RPM higher. A 2800 or higher stall speed on the street would have a jack rabbit take off at full throttle, but have a mushy feeling at less than full throttle. The higher the stall speed the softer the shift feel.

    Maybe? Did you guys invite the transmission guy from the other site????????
    Here I is...

    Leave a comment:


  • Barfly
    replied
    Is it just shift quality alone that is an issue or is shift timing off also, ie, late shift? Sounds like it's moe than a throttle cable adjustment from what you're describing, guy probably went full retard with a shift kit.

    If he put in a Corvette servo that can be replaced with a stock one but it sounds like a shift kit to me.

    Leave a comment:


  • Shamuscull
    replied
    Stall speed is measured at wide open throttle. Anything less than WOT will have a lower stall speed. Our 700R4 torque converters lock-up in overdrive automatically. For street use in a 2WD (under 450 horse power) you would need somewhere between 1800 to 2300 stall depending on what feel you like. A 4WD for street use usually uses 1600 to 2000 RPM. Higher stalls than these are usually used on higher horse power motors and for drag racing. The ratings you see on torque converters are for small block motors. The same converter behind a big block will stall as much as 700 RPM higher. A 2800 or higher stall speed on the street would have a jack rabbit take off at full throttle, but have a mushy feeling at less than full throttle. The higher the stall speed the softer the shift feel.

    Maybe? Did you guys invite the transmission guy from the other site????????

    Leave a comment:


  • mickeyblueyes
    replied
    Should have bought a Glock.

    Leave a comment:


  • Paté
    started a topic Transmission issue

    Transmission issue

    I changed my Chevelle tranny over from the T-350 to a tough ass 700R4 and am loving the overdrive. I broke the input shaft on the T-350 a few times over the years and the 4.11 gears made cruising tough. The issue I have is the guy who built the tranny made the 1st to 2nd gear shift unbearable. It's so nasty that I need to feather the throttle on a normal takeoff to keep from getting whiplash. The shift is also tearing the shit out of the rear. Advice?
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