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Old 01-17-2026, 12:50 AM
Joog Joog is offline
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Default Tips on buying a built trans off Marketplace

I am looking at buying a built th400 this Sunday and was wondering if there are any things to look for. He doesn't have any paperwork for the trans, but he said it was built by TSI trans in Addison Illinois and has Kevlar bands and clutches, and a reverse manual valve body. Capable of 650hp. He seems like a straight shooter kind of guy and he said he has had transmissions built there before for his GTO. His reason for selling it is that it wouldn't fit in the trans tunnel on his other car.

What should I look for so I can make sure I'm not buying a dud?

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Old 01-17-2026, 07:30 AM
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KS circutguy KS circutguy is offline
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https://www.hughesperformance.com/street-strip-trans/
The only way you know for sure with a used unit is to install it .
You don't need 'Kevlar' bands or clutches. IMO
650hp is nothing for a t400 trans. I would recommend Hughes Transmission.
I ran a stock used 350turbo for 4yrs. before it finally failed. With a 350hp 400 Pontiac and a 200 hp hit of nitrous.
Good luck.
Maybe Half-inch stud will chime in on this.

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Last edited by KS circutguy; 01-17-2026 at 07:44 AM.
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Old 01-17-2026, 09:11 AM
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Half-Inch Stud Half-Inch Stud is offline
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Another way is to open the pan to verify VB and soot. Then pull the front pump and run through the 3 friction packs. Seller probably won't allow that huh.

Get the converter anf verify red fluid.

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Old 01-20-2026, 07:32 PM
Joog Joog is offline
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Quote:
Originally Posted by Half-Inch Stud View Post
Another way is to open the pan to verify VB and soot. Then pull the front pump and run through the 3 friction packs. Seller probably won't allow that huh.

Get the converter anf verify red fluid.
I got it last weekend. Guy I got it from was very knowledgeable and gave me his phone number. I did notice it had the vacuum block off plate so I know it was a manual valve body. Did I mention he has a SD Catalina with a cross ram with the correct aluminum hood and some other goodies . He had a 3 star rating on facebook marketplace, which was surprising for his credibility.

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