| [GMCnet] GMC POWER DRIVE [message #86973] |
Wed, 02 June 2010 13:40  |
Charles Aulgur
Messages: 78
Registered: March 2006
Karma:
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Member |
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There seems to be some confusion as to what affect the Power Drive
has on the A/T. When Stoddard, or someone, came up with the idea of
changing the gear ratios of a GMC by changing the chain drive pulley
diameters, it was widely excepted because of the high 3:07 final
drive was a little high for the GMC. I assume it was cost effective
for GM because of it having been used on the Tornado cars where the
power train came from. The Power Drive reduced the engine speed
relative to the A/T input speed and seemed to be a simple and useful
change. However, increasing the engine speed increased the engine
horsepower capability and could result in the A/T having to handle
higher loads. Some people had concerns about whether the higher
loads would damage the transmission but that didn't seem to happen
over the long run. People started installing the 3:21 final drive
along with Power Drive, increasing the overall ratio to approximately
3:50 which was a big improvement for people driving in mountainous
country or towing a vehicle. When the 3:42 came out I immediately
bought one any have very happy with it. It wasn't long before people
started offering higher ratio gearing for the final drive and now I
believe Jim K. has 3:55, 3:70 and 4:10 final drives available and I
think Cinnabar still sells the 3:42, so people now have a wide
variety to choose from depending on their needs. I have even heard of
people installing the 4:10, along with the Power Drive still
available from Manny. With the limited slip final drive now
available from Jim K, people will be converting their GMCs to off
road machines.
Chuck Aulgur
La Mesa, CA
76 Royale with fully operating brakes on all six wheels
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