I have a 1972 GS numbers matching 350/350 car, turning into 455/400. I have a 1972 BS coded tranny (has been rebuilt), what will i need to swap out the TH350?
Off the top of my head, repositioned trans crossover (holes should already be in the frame) shortened driveshaft (can't remember how much shorter) electric detent switch for downshift There's probably more but brain is tired. Devon
Yoke. Vacuum modulator line lengthened. (if you can get or have the one with the BS) Speedo drive gear may need to be changed (to correct the input)
I vote to keep the Th-350 unless it has an issue. Makes the swap much easier. I have a built Th-350 that’s handled 600 Hp for 20 years.
I have done that swap a few times. Using a short tail TH400 and the shortest yoke, I have never had to shorten the drive shaft. good luck, Bruce Roe
Gas pedal with turbo 400 kickdown switch. Any 68 2 speed A body has the right gas pedal and switch as well as any turbo 400 A bodies. The wiring and plug is taped up in the stock wiring harness - look for a yellow and black wire to a double plug. This connects to the kickdown switch. The gs 350 engine wiring harness doesn’t have the wire that runs to the transmission, so run a wire from the switched side of the kickdown switch to the kickdown on the turbo 400. There will be 2 prongs on the 72 turbo 400, search the site for the prong that needs the signal when the gas pedal is floored contacting the switch and sending the signal to the tranni to gear down. Source a turbo 400 kickdown wire harness, or get it from a donor car - it will have the connector and rubber boot. If your handy, I’m sure you can find the right place in the gs350 engine wiring harness where it plugs into the fire wall to add the kickdown signal that connects to the tranni. The frame has the holes in it to move your turbo 350 crossmember back. You will need a turbo 400 tranni mount, the turbo 400 cars also use a different primary and secondary emergency brake cable and hook on the cross member. The slip yoke on a turbo 400 is 32 spline versus the smaller turbo 350 26 spline, so drive shaft mods required. The cooler lines line up, work no issue. I think that’s it……I did the same swap in my 72gs350 as well. When I swapped in the 455, I purchased a 455 engine wiring harness from Todd (on the site) and that came with the proper wire and connector to the tranni. I was able to use the steel modulator line from the turbo 350 after a few bends etc.
