My tranny has no forward gears in my 79 C-10, was wandring if a 400TH would fit in there, where my the 350TH was.
Usually the 400 is longer, & uses a different spline on the front yoke. That means shortening the driveshaft & changing the yoke [or picking up a different driveshaft]. The 400 torque converter may be different, as well. The frame should have the right holes to move the crossmember back. The 350 uses a cable from the carb to the trans to regulate trans pressure. The 400 uses an electrical switch on the throttle linkage [probably under the dashboard] to control kickdown. The changeover isn't tough; just takes some different parts. The best way to do it is to grab all the pieces parts from a truck with a 400. Maybe you can find someone parting out a truck where the 400 is gone, but all the goodies remain.
Thats what I needed to know . The guy is selling me the tranny the fly wheel,the torque, and the complete driveshaft for 200.00. What about the modulator valve? Someone told me the 400TH doesnt use an external modulator valve, Will this be a problem or an easy fix with a passing gear cable? I appreciate the help. Thanks a million Russ
Both transmissions use modulators. The 400 does not use a throttle cable & there's no way to connect one. All you have is the modulator & electrical kickdown. Use the correct steel line that goes from the vacuum source to the modulator. The hump at the intake manifold end is there to keep fuel vapor from collecting at the modulator. Because of the presence of fuel vapor, use a short piece of rubber vacuum line at each end. That way the hose can't collapse if it is softened by vapors.
After all that info I got, I ended up putting in another long tail shaft 350TH, on my way to buy the 400TH, He got a 350TH in so I got it instead. However I printed the info for a 400TH, in case the 350 doesn't work. Thanks Again for the info :7 -Russ-
