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350 turbo to 400 turbo


madmonte

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swapping a 350 small block,350 turbo,to a ,468 big block,400 turbo. would like info on what the nessesary changes are required in the transmission part of this swap.one thing i noticed,the shift mount on the shaft on the trans. was different. (this is a coloumn shift car)any info appreciated, thanks

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A shorter drive shaft with a TH400 yoke on it.

Possibly the shaft that your shifter linkage attaches to, the one that pivots in a bracket on the frame rail. If I remember correctly the TH350 one will work but the PRND2L in the dash will not line up quite right (visually).

The trans crossmember is the same, just mounts in a different position.

 

I can not think of anything different.

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  • 3 weeks later...

Don't forget the TH400 electric kickdown switch and bracket for the gas pedal, not that you need it with a 468 BB.... laugh

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you say the shift mount on the shaft is differnet.

 

The one from the Turbo350 should fit the 400.just take the nut off of the shift shaft. the piece should swap . as for the PRNDL1L2 not lining up that should be adjustable at the Crosshaft attach point.and you can also adjust the indicator needle position . on the right hand side of the steering column under the dash....( possibly need to remove the panel directly under the column)you should see the cable which operates the shift indicator . it clips to the end of the shift bowl.some have a screw to hold them.this little clip can be moved to adjust the indicator needle.

 

mike

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May I ask why you are changing to the TH400? I have known TH350's to last 200k miles behind very high torque engines. While the engine puts out a lot of power, the car is relatively light compared to what a 468 would normally be powering (i.e. something the size of a Suburban). The TH400, while very stout, is geared more for trucks than for cars (slightly), but tends to slow you down a little at the dragstrip compared to a TH350 which has less internal friction.

 

It's just a thought, but if your old transmission is in good shape and you maintain it properly you may be surprised how much it can put up with.

 

Just my 2 cents.

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gm used the 400 turbo in all its big block cars,so i figured i'd do the same .nothing wrong with a good 350 turbo,just i already had a 400 and the 350 turbo out of my monte is going in my sons 72 chevelle.(SS ,smallblock car)thanks for all the info guys. ed

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Hi:

You also must change the emergency brake cables, the one that attaches to the floor and the e brake pedal and also the middle cable that connects the two rear cables. If you don't the cable will rub right on the driveshaft u joint, not very safe.

Hope this helps

Ed

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