straight cut gears th400
straight cut gears th400 I've got a friend who has been working at a local tranny shop for about 12 years he knows his **** when it comes to th350s' and 400s'. So I am having him build me a 400. He says he can put straight cut gears in it apparently they came in hd 4x4s and dumptrucks.He says they are the same dimensions as the regular gears and weight just a different cut he's never used them in a build but wants to try them.They whine a little bit but that doesn't bother me my main concern is are they worth it? Are they stronger?And do they eat up more hp from frictional losses?.....Should I try it and see what happens or can anyone talk me out of it?Let me know what you think.
The straight-cut gears are stronger. GM still uses them in the HD version of the 4L80-E found in medium-duty truck chassis. Those little Isuzu Diesels you see all over the place with small boxes or stake beds have them.
Straight-cut gears handle greater loads because contact is made evenly across the entire width of the gear as it meshes with the other one. With helical gears forces move back and forth across the width of the gears and they rotate. Also, less thrust load is placed on the thrust washers throughout the geartrain, especially with the planet gears.
You will find the straight-cut gearsets to be louder and have a little more play in them, but they are stronger and place less strain on surrounding parts.
I don't know the efficiency numbers. I would have to guess they are MORE efficient since thrust loading is significantly reduced.
Straight-cut gears handle greater loads because contact is made evenly across the entire width of the gear as it meshes with the other one. With helical gears forces move back and forth across the width of the gears and they rotate. Also, less thrust load is placed on the thrust washers throughout the geartrain, especially with the planet gears.
You will find the straight-cut gearsets to be louder and have a little more play in them, but they are stronger and place less strain on surrounding parts.
I don't know the efficiency numbers. I would have to guess they are MORE efficient since thrust loading is significantly reduced.
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Straight cut gears are not necessarily stronger, as I have not seen either set shear themslves, but they just take the load off of the thrust washers. They do run slightly hotter, and eat a little more horsepower.
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From: AUSTIN TX
I supposedly have straight cut gears in my TH400, but they are also supposed to be a lower gear ratio (2.73 or something like that compared to 2.20 or so for the stock ratio). They supposedly came out of like a Frito Lay/beer truck type truck (10 wheel type tractor trailer set up with an auto). This tranny has never been run yet, but we will see how it works eventually. All I know is, if everything is true, second gear should come pretty quick (TH400 with a low 1st gear set, trans brake, 5500 stall, and 4.56 gears).
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From: burbank ca
ratios
Originally Posted by BOWTIE
I supposedly have straight cut gears in my TH400, but they are also supposed to be a lower gear ratio (2.73 or something like that compared to 2.20 or so for the stock ratio). They supposedly came out of like a Frito Lay/beer truck type truck (10 wheel type tractor trailer set up with an auto). This tranny has never been run yet, but we will see how it works eventually. All I know is, if everything is true, second gear should come pretty quick (TH400 with a low 1st gear set, trans brake, 5500 stall, and 4.56 gears).
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From: AUSTIN TX
Originally Posted by john kilgore
gm made only one ratio, spur or helical, 2.48-1.48. l made many ratios for the general and hoped they would go into production, but thet never did. spur gears are very noisy good luck
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From: AUSTIN TX
Originally Posted by Badzracing
The "t-400" with straight cut gears was called the turbo-475.
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From: burbank ca
375-475
Originally Posted by BOWTIE
So was it still the exact sane tranny except for the gear set? Or did it use a different case and stuff as well? Do you know what the gear ratio of that low gear was? Perhaps that is where my gear set came from??? Honestly, this is a new one for me, I had never heard of a TH475. I used to have a TH375, which from my understanding was basically a TH350 with a lock up T/C.
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From: Downers Grove,IL
Thanks, it's just a Hobby for me.
I recently built my own th400 and when I was researching various th400 modifications I came across your site. You have developed quite the specialized th400 transmission!! I am sure we can all learn a lot from you.
Steve
I recently built my own th400 and when I was researching various th400 modifications I came across your site. You have developed quite the specialized th400 transmission!! I am sure we can all learn a lot from you.
Steve
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From: Clearwater, FL
Straight cut gears, specifically in the planeteries, are in fact stronger and they are more efficient in the transfer of power. There are less frictional losses associated with a straight cut gear as oppposed to a helically cut gear.
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From: burbank ca
right
Originally Posted by fastta
Straight cut gears, specifically in the planeteries, are in fact stronger and they are more efficient in the transfer of power. There are less frictional losses associated with a straight cut gear as oppposed to a helically cut gear.
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John Kilgore,
I am aware that you can use the TH475 planets in a TH400. My friend Tim Beebe turned me onto that years ago. However, he also used a sprag, some roller thrusts and clutches from a Allison (AT540???) if I recall and that was his recipe for a stout TH400.
I always use a 4-Speed, but have been wanting to gather parts & info along these lines for a TH400 I am building for customer in the near future.
Could you set me up with a list of the parts that will interchange???
Thanks for your time...Robert 10851man@gmail.com
I am aware that you can use the TH475 planets in a TH400. My friend Tim Beebe turned me onto that years ago. However, he also used a sprag, some roller thrusts and clutches from a Allison (AT540???) if I recall and that was his recipe for a stout TH400.
I always use a 4-Speed, but have been wanting to gather parts & info along these lines for a TH400 I am building for customer in the near future.
Could you set me up with a list of the parts that will interchange???
Thanks for your time...Robert 10851man@gmail.com
