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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: hogwild on October 09, 2008, 09:48:50 pm

Title: 350-400 tranny swap
Post by: hogwild on October 09, 2008, 09:48:50 pm

what are the diffs between 350 and 400 tranny, 86 swb has 350 and i can get 400 cheap . what needs changed? converter the same?

Title: Re: 350-400 tranny swap
Post by: TexasRed on October 09, 2008, 10:15:16 pm

Different converter, different yoke, probably change the transmission mount and possibly change the driveshaft length.

Oh yeah: the 400 is a tougher transmission but it takes more HP to spin up so a th350 can be better for some stuff.

Title: Re: 350-400 tranny swap
Post by: VileZambonie on October 10, 2008, 06:43:48 am

You'll need to hook up the detent solenoid too.

A 12v switch on the gas pedal is necessary for forced downshifts.

Title: Re: 350-400 tranny swap
Post by: HAULIN IT on October 10, 2008, 08:10:38 am

If this is for your 4x4, the transfer case needs added to the list.

Title: Re: 350-400 tranny swap
Post by: lowbucktruck on October 10, 2008, 10:51:17 am

If it's an early model 1970's truck, I think you can swap a TH350 for a TH400 without having to shorten the driveshaft, as long as they are both short tailshaft trannys.  GM's idea.  Early model TH400 truck trannys are short tailshaft.