Which Tranny do I have
- Thread starter Mattrob
- Start date
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- Joined
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- Location
- Usually not in Ohio
- First Name
- Andy
- Truck Year
- '77, '78, '79, '84, '88
- Truck Model
- K5 thru K30
- Engine Size
- 350-454
I *believe* that the standard automatic for 3/4 ton was the TH400, starting in '77.
mtnmankev
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- Ash Fork, Arizona
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- Kevin
- Truck Year
- 1984, 1983
- Truck Model
- K10, C20
- Engine Size
- 383 Stroker, 350
Crawl under the truck and look at the transmission oil pan, that will tell you for sure.
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nvrenuf
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- John
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- 1991
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- K5
- Engine Size
- 454
That RPO code with “M40” in it, that’s a th400.
84c10Tony
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- 3.0
Trans, trans, tranny is a whole nuther' thing.
Uh, escuzie!...just had to click lol.
Oh, wait...never mind.
Uh, escuzie!...just had to click lol.
Oh, wait...never mind.
Bextreme04
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- Eric
- Truck Year
- 1980
- Truck Model
- K25
- Engine Size
- 350-4bbl
M40 is usually the code for TH400. MX1 would be the baseline trans, which would be the TH350. As others have said, the only way to know what you actually have is to climb under the truck and check the pan shape. If its a square shape its a TH350, if it looks a bit like Texas, its a TH400. A previous owner could have put anything in there in the last 45 years.
oldretiredafguy
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- First Name
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- Truck Year
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- Truck Model
- GMC V-Jimmy, GMC Suburban 4WD, GMC Suburban 4WD, GMC-2500 CrewCab
- Engine Size
- 350, 350, 350, 350
Who is the "Botox Babe"?
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- Truck Year
- 1984
- Truck Model
- Scottsdale
- Engine Size
- 305
Bruce Jenner lol
oldretiredafguy
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- Truck Model
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- Engine Size
- 350, 350, 350, 350
S__t! GD frapping weirdos.
75gmck25
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- Truck Model
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- 5.7
I don’t know for sure about a ‘77, but on my ‘75 K25 the M40 code is a TH350. Kind of confusing, since on later years ( I think it started in ‘77) the M40 option was a Th400.
Nasty-LSX
TogetherforeverCovid19
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- LSX
LMMFAO!!!!!
oldretiredafguy
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- Mike
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- Truck Model
- GMC V-Jimmy, GMC Suburban 4WD, GMC Suburban 4WD, GMC-2500 CrewCab
- Engine Size
- 350, 350, 350, 350
Keep laughing you sarcastic SOB'S. As soon as I can get a GPS installed on the wheelchair, I'm going to visit each one of you, and have a come to Jesus meeting!
