TH400 shift linkage

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FluoFerret

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Apr 2, 2018
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Who has swapped a TH400, or has a TH400 factory delivered in his G-body? I ask for a specific reason: the backup- and neutral switch are usually on the steering column, linked to the transmission even if you have a floor shifter. I need to find the correct parts to get my TH400 working as a replacement for the old TH200C. The shift linkage from the latter one do not fit anymore as its geometry is different. Any help here is welcome! Even second hand parts for sale are welcome!
 

pagrunt

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Sep 14, 2014
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From my understanding the linkage should work between all 3 speed Hydramatics so the switches on the column won't be an issue. Floor shifters need a specific TH400 cable bracket to mount on the trans case, not 100% on the cable. The electric kick down will have to have a switch mounted on the carb throttle lever or on the gas pedal (like most TH400 original cars.) The TH200 4R aftermarket crossmembers will work. A shorter driveshaft & TH400 yoke wil be needed. Over all it's an easy swap. My uncle did a TH400 swap in my cousins '82 Monte they had back in '91/'92 & this is the details I can remember.
 

lilbowtie

Comic Book Super Hero
Jan 7, 2006
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Canton Mi
Don't believe a g body ever came w/ a 400 as they were being phased out of passenger cars by 1980. As pagrunt said there should be a problem w/ the linkage and they have kits for floor shifters
 

FluoFerret

Greasemonkey
Apr 2, 2018
184
243
43
Luxembourg
From my understanding the linkage should work between all 3 speed Hydramatics so the switches on the column won't be an issue. Floor shifters need a specific TH400 cable bracket to mount on the trans case, not 100% on the cable. The electric kick down will have to have a switch mounted on the carb throttle lever or on the gas pedal (like most TH400 original cars.) The TH200 4R aftermarket crossmembers will work. A shorter driveshaft & TH400 yoke wil be needed. Over all it's an easy swap. My uncle did a TH400 swap in my cousins '82 Monte they had back in '91/'92 & this is the details I can remember.

I am still wondering what place would be best for the electric kickdown. right now i hooked it up to the carb, but i try to find one for the accelerator pedal, as i prefer clean looks under the hood. any ideas here on what might be best for the car?
 

Local Hero

G-Body Guru
Nov 24, 2016
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Northcoast, Cleveland, Ohio
Mine is connected to the carb using a lightly modified linkage bracket from a car that originally had a TV cable. But I have it on a car that I really don't car what it looks like under hood. Works great though.

Oh and I'll confess the previous owner already ditched the column linkage and put a cheap-@ss floor shifter in it. I've since upgraded the shifter to one with a neutral safety switch. It uses a cable to a bracket bolted the to pan.
 
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Blake442

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Apr 24, 2007
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I went from a 200-4R to a TH-400 and was able to adjust the stock linkage to work correctly with no issues.
There is a lot of adjustment available, maybe a slight tweek or bend to the long rod to the column, but you shouldn't have to do anything major at all...
 
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pagrunt

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Sep 14, 2014
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A square body C/K might be a good source to find a gas pedal mount. Shop the resto companies to see what they have. Most likely you'll have to make it fit on your gas pedal. I couldn't find any '77 up B body info on having a TH400 ('76 last year?). But there might be some aftermarket kits that could be done up to keep it clean.
 
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500/600

Royal Smart Person
Nov 17, 2018
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For a short period of time I swapped a TH400 behind my 3.8 in place of the TH200C.
The column shift linkage bolted directly from one to the other without modification. I did crack the pinch bolt loose and let the linkage 'relax', then retightened.
 
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