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Why the g56 and 660 ft lb. rating?

ISB6.7

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Trucks have come along way from shifting old pickups from the 60's with the muncie sm465 (non syncro first gear) , many medium duty farm trucks and semis. Many today assume the dual mass flywheel is the 660 lb ft. rating limit on the new trucks and I'm sure it is at it's limit, but in the medium-heavy duty trucks (class 6-8) the transmission 660 lb. Max. input torque rating has been common from the early 1970's to today, Automatics, 5-6-7 speed manual transmissions are common in todays medium dutys in the 300hp range and 660 torque ratings, trucks have less packaging concerns with the cabs lifted above the frame rails and lots of room compared to the pickups tight fit, with the high performance medium duty ISB and alot more than 660 ft lbs on tap, not to mention bolting it to a transfer case. (and the transfer case rating) gets complex as cost vs. performance/ sales. The next torque rating of many class 6-8 truck transmissions is in the 900 ft lb. rating with everything sized accordingly, the transmission case gets quite large for packaging it in the pickup. And around 4% sales of manual transmissions sales in pickups, ease of assembly with only automatic transmissions on the production lines. Aisins track record of stellar performance, sealed the fate of the manual transmission fans, I ordered a 1997 3500 5-speed, 215 hp, 440 ft lbs. 4.10's new back in the day, and the automatics were the ones derated at 185 hp. if I remember correctly, my the times have changed indeed.
 

Jared B

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They definitely have, and automatics have come a long long way from the power robbing slow shifting automatic transmissions of the past. It's my understanding that the G56 just can't handle any more torque and with a small take rate as you mentioned there isn't much of an incentive for FCA to invest in it. Unfortunate but from a business perspective it makes sense.
 

devildodge

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What is also crazy is my V10(488 cu in 310hp and 450 lb-ft of stump pulling power)used to be more powerful than the Mighty Cummins and the 2 made other engines look silly.

Now the Cummins makes everything look silly, but there are 4cyl motors that have higher outputs than the old guys (although not the duty cycle)

The neat thing about the derated Cummins with the manual, you get more of the power sooner as the torque management doesn't nanny the manual anywhere near as much as the auto.

My V10 will eat my 2013 cummins through 3rd gear til the torque management let's out, then it is see ya later gasser.
 

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