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Discussion Starter · #1 ·
what is the different between the (400 3peed )&(700 4speed) g.m auto trans .which one better?
I want to change my trans to the 700 on my 4x4 subrban what should I change beside the trans any
adapter or something?
or should I forget it.I need an advice guys
thanks.

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The TH400 is a bulletproof 3 speed auto without overdrive. Usually used in heavy duty applications by GM.

The 700R-4 is a 4 speed auto with an overdrive and locking convertor. It has a prety crappy rep for reliability...mostly deserved. Towing, heavy vehicle or high torque applications will kill one of these quickly unless it been built by a real pro. About the only 700R-4's that will stand up to abuse would be the 'Raptor', Art Carr built, or other quality builder. The largest tranny cooler available will also help.

If you have a TH400 and you want to swap to the 700R-4 (bad plan IMHO) you'll need to address the spline issue. A new input on your T-case would prolly be easiest. The TH400 has a 32 spline output and the 700R-4 has a 27 spline output. The adaptor may work or not...it depends on the vintage of T-case you want to bolt the 700R-4 up to. If your T-case was ever mated to a 700R-4 from the factory (NP 208, NP241) you should be OK.

Rene

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God hates a coward!
 
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