I went over the same concerns some have expressed in Digest #277 for
about a year before deciding on the 3.70 gear change rather than a final
drive change. Not being a technical person I have to be cautious about what
I say and hope others will correct me if I put wrong information on the net.
The information I had was that the 400 series transmissions (400/425) are
strong enough to take far more torque than the 455 was producing and a 20%
increase in engine speed and the corresponding torque increase was still
well below what was safe for the transmission. I'm sorry I don't have the
figures. Hopefully someone does.
The torque converter and transmission pump are before the gear change so
there no increase in stress on the torque converter and the pump is running
20% faster so there should be no concern about low pressures in the
transmission. The slight drop in transmission temperatures that I have
experienced may be because more fluid is being pumped through the cooler or
there is less heat produced in the torque converter. I take the temperatures
at the converter not at the pan.
Two years ago the cost was over $300US more for a final drive and that
didn't take into account the movement of the final drive and the core to the
supplier and there is no cost correcting the speedometer with a gear change.
Pat,
I think I still have a "happy" transmission.
Al Hamilton
76 Eleganza II
Kingston, Ont
about a year before deciding on the 3.70 gear change rather than a final
drive change. Not being a technical person I have to be cautious about what
I say and hope others will correct me if I put wrong information on the net.
The information I had was that the 400 series transmissions (400/425) are
strong enough to take far more torque than the 455 was producing and a 20%
increase in engine speed and the corresponding torque increase was still
well below what was safe for the transmission. I'm sorry I don't have the
figures. Hopefully someone does.
The torque converter and transmission pump are before the gear change so
there no increase in stress on the torque converter and the pump is running
20% faster so there should be no concern about low pressures in the
transmission. The slight drop in transmission temperatures that I have
experienced may be because more fluid is being pumped through the cooler or
there is less heat produced in the torque converter. I take the temperatures
at the converter not at the pan.
Two years ago the cost was over $300US more for a final drive and that
didn't take into account the movement of the final drive and the core to the
supplier and there is no cost correcting the speedometer with a gear change.
Pat,
I think I still have a "happy" transmission.
Al Hamilton
76 Eleganza II
Kingston, Ont
