Th400

akchevrolet

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I have a 1987 r10 5.0 and i think my th400 is trying to die. Im looking for one that isnt gonna be super expensive or needs to be rebuild so i can rebuild it and learn while this one is still running.
 

Bextreme04

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I have a 1987 r10 5.0 and i think my th400 is trying to die. Im looking for one that isnt gonna be super expensive or needs to be rebuild so i can rebuild it and learn while this one is still running.
Are you sure its a TH400? In an 87 R10 with a 305, I didn't think it could have come with anything but a 700R4 or a TH350. What does the oil pan look like? Is it square or does it look a bit like texas?
 

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It has the vaccuum modular on the side. Idk what the pan looks like its dark now.
 

bucket

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@Bextreme04 I’m not sure what year is started but at some point the th350 was discontinued and the th400 became the “base model” 3 spd trans.

That would explain why so many V6 trucks had the th400.
 

Ellie Niner

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Ahh... that's why that 1987 shortbox 4x4 I looked at before I bought my '86 had a TH400 in it. It was a TBI 350, and otherwise equipped like most higher optioned mid-1980's Squares... was thinking the trans was a heavy duty option at the time.

Looked at a couple of sites with transmission info, and it appears that the TH350 went out of production after the 1984 model year?
 

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The th400 in my old K10 was from an Astro van. It had a short tailshaft with a slip yoke that fit my early figure 8 adapter 205 perfectly.
 

akchevrolet

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Might just have to find some money and go to wrench apart
 

JoeR Jr

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I believe it has a TH375 in it. Looks like the TH400 but has the TH350 output shaft.
If that's the case, you'll need a new yoke on the driveshaft to make the TH400 work.
Joe
 

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I believe it has a TH375 in it. Looks like the TH400 but has the TH350 output shaft.
If that's the case, you'll need a new yoke on the driveshaft to make the TH400 work.
Joe
good point, is that change the driveshaft connection to a smaller kind Like a half ton driveshaft but allows them to use the same length as a same year 700r4 or just the old-gone th350 so they didnt need to change those, just small adjustment to production of the drivetrain
 

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Yes, it's the same yoke as the TH350 and the TH700. And I imagine you're right. GM did it to save money.
Joe
 

akchevrolet

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Isnt the th400 the one with the modular on the side
 

AuroraGirl

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Isnt the th400 the one with the modular on the side
a th350 has a modulator on the side

i believe a th400 also uses a modulator

but it isnt the same exact spot/size/function because there is a difference with the governor or soemthing.
 

bucket

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a th350 has a modulator on the side

i believe a th400 also uses a modulator

but it isnt the same exact spot/size/function because there is a difference with the governor or soemthing.

Both have a modulator. Th350 has a kickdown or 'detent' cable and the Th400 has an electric kickdown switch.
 

AyWoSch Motors

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I know a guy with a TH400 for sale, $200.
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