I am contemplating "upgrading" my transmission from the (stock) dynaflow to a T400 and wanted to "do my homework" before investing significant $$$ and/or time. Answers to any of the following questions would be greatly appreciated: (1) Putting aside all considerations of $$$, time, and effort (for the moment), is this a "good idea"? I am under the impression that such a swap will at least: (a) increase MPG; and (b) make the car more "powerful" from a start. (2) What exactly do I need to acquire in order to be able to do this? Obviously I need the T400, and I am under the impression I'd also need a corresponding flexplate (which would need to be machined for my car). Is there anything else? I've been told there is some wiring involved (possibly a microswitch to control the downshift and some other wiring for the switch-pitch). Would I have any of this wiring on my car as it currently is (i.e. stock). (3) What years (and on what cars) was the T400 available/provided? It would help to know when searching for cars that are being "parted out". (4) How can I tell whether a particular flexplate is the right one? I've seen several pictures of flexplates for sale, and although they look very similar, I've noticed some subtle differences (i.e. holes around the outside diameter) that may, or may not, make a difference as to applicability for my purposes. Can I get a T400 from one car (and one year) and a flexplate from another car (and possibly a different year)? (5) Once all of the appropriate parts have been acquired, what "modifications" would still need to be done to my current car? For example, one mechanic I spoke to thought the driveshaft would need to be shortened. Is this correct? Any other such modifications? (6) What is a reasonable range of prices for a T400 (and if it needs it, for rebuilding it)? How about the flexplate? How about the installation job? (7) Other than EBay (on which I will certainly be looking), anyone have any suggestions on where I might find a T400 and corresponding flexplate at a reasonable price? Again, any any all information would be incredibly appreciated. Thanks. Adam T. Bernstein
Adam, I think you will get a much better response over at the Nailhead Forum. The Nailhead had a unique bell housing bolt pattern. The common BOP bolt pattern for most ST, and THM 400's will not bolt up. Now if you were planning on going to a 455, that would make things easier and possibly cheaper. Good Luck. BTW, the switch pitch is easy to wire up. There's one wire going to the trans. Apply 12 volts, you get high stall, take it away, you get low stall. A simple 2 way switch is all that's needed. The stock set up used throttle position to initiate the stall change. You'll have a hard time finding the necessary hardware to set it up as stock. I use a timer box for mine. There's a number of ways you can go at this.
Dynaflow to 400 Adam, The th400 is a better trans than the dynaflow for a number of reasons. But, you some situations to deal with. The biggest is that the back hub of the crank in your car will not match up to the 400 flexplate you need. Some machining to the crank is necessary to accomplish this. You'll need to find the 400 from a 65 or 66 to match the bell housing. Your shifter quadrant is going to be wrong. The dynaflow is PNDLR, the 400 is PRND2L. Or,you could also find an adapter plate to mate the nailhead to a late model BOP trans. I'm going to put a 200r4 4speed automatic w/ OD in my 63 Riviera. The first gear is low - quick off the line; the OD puts the engine rpms down and the converter locks up for cruising - better mpg. It's quite a bit more driveable and it's much more efficient because of modern technology. Here's a web site for some quality transmission adapters you might be interested in. http://www.transmissionadapters.com/53-66_nailhead.htm Keep me posted Ed
