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Author Topic: NP203 Question  (Read 2593 times)

Offline Jon87V20

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NP203 Question
« on: May 20, 2010, 03:26:16 pm »
Sorry if this is a re-post. I did some searching and looking around on here but didn't really come up with much. I have a '79 K15 with a NP203, 350 and a TH350. A while back, a friend of mine was telling me that you can't swap the TH350 out for a TH400 with the NP203. I was wondering if this was true and why? Thanks!
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1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline Irish_Alley

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Re: NP203 Question
« Reply #1 on: May 21, 2010, 02:53:31 pm »
The th350 has a 27 spline output shaft the 400 has 32. You can make it work just need adapter
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If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

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Offline Jon87V20

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Re: NP203 Question
« Reply #2 on: May 23, 2010, 07:50:05 pm »
Thanks, Irish. It's good to finally know the truth.
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1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline gmcsierragrande

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Re: NP203 Question
« Reply #3 on: June 05, 2010, 07:37:21 pm »
Just Chevy Trucks in Maine has used adaptor plates for the TH350/NP203 as well as for the TH400/NP203. Check his site on Ebay. I'm from eastern Canada and went to his shop a few times for hard to get good condition used chevy truck parts.

This guy really knows Chevy GMC trucks! 
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Offline malibu795

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Re: NP203 Question
« Reply #4 on: June 06, 2010, 07:29:09 am »
1st you need the mounting adapter

2nd you need one of 2 things either a 27spline output shaft for the tranny or a 32spline input bearing for the 2 case
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75 K25 383/400
79 malibu 454/T56 305rwhp/432rwtq 15.6@92.8mph
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