A little bit of Fud being thrown around here
Alot of trucks from both manufacturers are still on the road towing and dragging crap up and down the road and their frames are still intact with those motors under the hoods. and the FHTSB has forced them to do a recal due to all those broken frames causing accidents and such.
Yes the frames were not what they are today but claiming that it was a rampid problem is a massive exageration. in 1981/82/83 ford experimented with swiss cheese frames in their light duty F250 models (the ones with the dana 44 TTB front end. the speedy holes were between the cab and bed and those frames and the F100 frames of the same era were subject frame cracks. between in 1984-1997 the F250/F350 and the std F150 frames were significantly improved and had minimal issues. Dodge also in 1983-87 was experimenting with weight savings and removing crossmembers in the frames and drilling holes when they added the cummins there were several reports fromt eh test rigs in 1988 that some frame twist was experienced but from 1989/90-1993 the FHTSB had very few reports on frames breaking from fatigue. And I know in our fleet we had a few break at the shock cut out but out of 70 trucks overloading was our culprit not engines. But i could be wrong just Internet searches and fhtsb searches haven't yielded much
Now granted i did that search witht eh FHTSB a few years ago due to a garage beer bet because someone claimed the same things and my response was if this really was a rampid problem you can bet there would be a recall due to the safety issues and concerns ....... i found a few consumer complaints about frame issues more for the 80-83 fords than i ever was able to find for the dodges. Since many of these rigs are / were used by commercial companies and had to cross scales if there had been a rampid issue you can bet DOT would have been sidelining ALOT of hotshot rigs in a hurry for a full scale inspection.
I stuffed a twin turbo'd 5.9L cummins into a 1996 F250, 4x4'd it during hunting season, beat the googly moogly out of it and towed over 400k miles with a 20k lbs GN behind it and when i sold it there wasnt a crack anywhere on that frame..... busted leaf springs yes, wore out R&P bearings yes. cracked broke or twisted frame not like everyone is suggesting here.
further more i know of a 89 dodge that has 680k miles on it now and the first 430k miles on it towing a tire trailer for les schwab from idaho to missoula for over 15+ years at 30k gross weight that to this day is a clean truck. tired and wore out but no broken frame..... it now is used by a underground construction company in town hauling parts for the dozers and such.
As to balance straight-6 engine or also called the inline-6 is virtually a perfect configuration. vertical / transverse forces, like 3-cylinder engine, the vertical and transverse forces generated by individual cylinders, no matter first order or second order, are completely balanced by one another. The resultant vibration is nearly zero. a V12 is also a highly efficient and naturally balanced engine V8's harmonically will never have perfect symetry like a 6cyl or V12. A 6 cyl 5.9L cummins with a balanced rotating assembly will rev smoother than a balanced 7.3L power stroke just by the nature of crankshaft and engine harmonics and detonation timing (verticle and transverse forces)
I think internet rumors have a way or perpetuating themselves kind of like Ford owns cummins and is pulling the contract on Dodge