What's the diference between Turbo 400 & 475
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Thread: What's the diference between Turbo 400 & 475

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    Default What's the diference between Turbo 400 & 475

    I have four GM transmissions that came out of 4BT stepvans and they were advertised as Turbo 400s. Two of them have a flexplate dust cover that is built into a deep aluminum oil pan. It's all one piece and I have never seen this before so I was wondering if anyone could tell me how to determine the difference between the Turbo 400 and the Turbo 475 that I have heard about.

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    I have heard that the 475 has a lower first gear and heavier internal stuff. If any body here has used a shift kit or any other performance stuff on there 475 I would like to know and where to buy.
    1967 Mercury 350 7.3 IDI c6 gearvendor OD dana 70 4.10s rolling on 19.5s
    1986 kabota hst7100 3cyl diesel yard worker and my toy, 1968 jd 112 with single cylinder diesel with stack running on veg oil!!

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    Thats what I have found out so far just by searching. I guess there is no real distinguishing features to look at and say it is a 400 or 475. I am not going to tear into them just to find out.

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    I know that on my pan is says 475 hydro-stat.
    1967 Mercury 350 7.3 IDI c6 gearvendor OD dana 70 4.10s rolling on 19.5s
    1986 kabota hst7100 3cyl diesel yard worker and my toy, 1968 jd 112 with single cylinder diesel with stack running on veg oil!!

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    I haven't really looked in detail at the pans so I will check tomorrow. Thanks for info.

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    The 475 has straight cut gears so it runs a little louder.
    1973 Chevy C-20
    4-53N Detriot Diesel
    Clark 285V transmission

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    straight cut gears,perhaps heavier planetaries...definitely heavier pan,heavier case.the 475 in the cube vans has a valve body with fixed line pressure.might only need a few simple parts to fit a regular vacume modulator.
    currently modding an 86' m-1010 cucv ambulance,with factory 14-bolt/detroit in back and an open 60 in front.lifted 6 inches,running 37's on 17 x 8's.now swappimg in a mild 6bt,and an nvg-4500/np205 combo.hope to have it running by fall.
    link to engine build... http://www.4btswaps.com/forum/showth...n-engine-build...

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    The GM400-475 was a good transmission except when it was installed behind a 4BT on a retrofit conversion. The wave ring & flexplate had a tendency to provide excessive lateral movement of the torque converter which generally ended up in front seal failures. I had three of these front seal leakers here out of three total. Two were reman transmissions with less than 100K miles. You could go to a Frito-lay distribution lot and see the puddle stains where the vans were normally parked. Maybe someone had better luck with the ones they bought but this is from what I have seen and experienced.
    BobS

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    90 Dodge W250 6BT Cummins 5 speed Getrag
    91 Dodge W250 6BTA Cummins NV-4500 conversion

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    I pulled the fourth TH400 yesterday and it is the third one in a row that has the full oil pan/flexplate cover. For some reason all three of these type were missing pan bolts and several other pan bolts were loose. I guess whoever at frito lay that is servicing these trannies have the wrong torque info or there needs to be some kind of loc-tight used.

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    The bad seal lets the torque converter drain out and has no effect on the pan being full. Also check the flexplate and the wave ring closely for cracks due to flexing. This leakage usually happens anywhere from two weeks or more of setting and not being run. I had one that set for three months before it decided to let loose.
    BobS

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    Armed people are called citizens. Unarmed people are called subjects.

    90 Dodge W250 6BT Cummins 5 speed Getrag
    91 Dodge W250 6BTA Cummins NV-4500 conversion

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