Up Dated Transmission

I have never seen this done in a 400, but thought I would comment. In general, the 200-4R transmission should be a decent replacement for the TH400 in the 400. The first 2 gear ratios are close with the 200 having a slightly lower (higher numeric) first gear, 3rd is identical (1:1), and the 200 adds a 0.67:1 OD 4th gear. RPM in 4th will be about 33% lower with an OD trans. Overall length is similar (200 is 1" shorter) and the driveshaft will probably have to be altered for length. Unknowns that you would have to solve are:

Bellhousing: Did Ferrari use an adapter plate, how did they get the V12 to match up to the TH400? If they use the Chevy bolt pattern that makes it easy(er).

Tailshaft housing: IIRC Ferrari used their own tailshaft housing on the TH400, presumably so the output shaft would work. Again, this might be solved by altering the driveshaft.

Transmission mount/crossmember: this might have to be fabricated.

TV cable: shift points in the TH400 are controlled by vacuum, but any later OD trans that you would install relies on a cable that basically tells the trans how far the throttle is opened. There are plenty of adapter kits that mount to Holley carbs, you would have to fabricate something that would allow the TV cable to connect to the V12 throttle linkage.

TC lockup: there is some debate about this, but for street cars, most people use an electronically controlled lockup torque converter. Most people have a setup that locks up in 4th, and unlocks at idle or on downshifts, with a manual override. You could skip the override, or find a way to mount a switch somewhere to control it.

 

I am interested in this as well. There tons of options using the same bell housing that fits up to a basic GM block that have overdrive that should bolt to the V12 since it has the spacer for the bolt patern for the GM block. I have seen that there are some street rod proformace companies that are making 6 speed autos to fit on old GM blocks for muscle cars and hot rods.

 

I have done this conversion for a number of street rod owners. The torque converter lockup is essentialy turned on by a vacuum switch and dis engaged by input from the brake pedal switch so that the converter unlocks when the car is stopped in gear. I use a relay to unlock the converter so that you can use the stock brake light switch. I am not sure about the bellhousing bolt patterns but a good number of them had the bellhousing separate so that the transmission could be used in different applications. As far as I recall the 200-4r has an electrical kickdown and vacuum modulator for shifting. If you want more info pm me and I will look a little further into it. My only question is rpm at cruise it might be pretty low and cause the engine to 'lug'. Although as I recall when they first came out it improved fuel economy by about 22%

 

These guys are the kings of tranny swaps - http://www.johnscars.com - though they focus on Jags, they may be able to point you in the right direction.

Regards,

Art S.

 

Danger, Will Robinson. Unless you're planning on doing a full engine swap, you won't get a 6-speed auto in there. The transmissions used in those rods use aftermarket ECU's for engine and transmission controls, they are either using Chevy LS(x) engines or sequential FI on a classic big block. The 400i engine has enough torque that a 6-speed auto is overkill, you mostly want to do this to get the OD for more relaxed cruising. Also, any electronically controlled transmission would not have a gear drive for the speedometer, so you would have one more thing to tear into - your gauge cluster, if you wanted a working speedo.

Doing some rough calculations, assuming a 4.30 rear end ratio (I think this is correct for automatics), it should drop engine RPM at 70 from around 3800 to around 2500 with a 200-4R.

 

I looked into this a while back. It seems like the biggest problem is the tailshaft housing and the torque tube/drive shaft. Some issues that will have to be overcome;

* If I remember correctly the newer transmissions are longer than the TH400.
* The TH400 Ferrari made tailshaft won't bolt up to the newer trans.
* Given that the torque tube to transmission issue is resolved it will likely be necessary to modify the frame crossmember.
* At the front of the TH400 there is a support added to strengthen the connection between engine and trans because the whole driveline is bolted together and suspended by 2 engine mounts and 2 differential mounts.

Just some thoughts.

If somebody gets this worked out be sure to let us know the details.

Al
'84 400iA 50605