So I got this hodge podge truck and has 4.30 rear 10.5 and 3.73 front d50... and I have a bunch of OBS trucks in the yard and get this wild hair of just regearing front and rear to 3.55... Diesels have enough torque to pull, so why not regear for MPG. So I took a gear set from a 96 f250 with dana 50 front and 10.25 rear... and take the inner pinion cup and keep the larger inner support bearing from the 10.25... now for the front... I believe the ring and pinion is the same...what do I have in instore for this swap? I am thinking remove the pinion bearing shims and swap bearing and shims and swap carriers. Does this sound right?

 

i am not too sure whats involved for the front change but you better think this one thru before you go to 3.55. With 3.55 at 60mph in overdrive you will not even be doing 1600rpm. This is with a 33" tire. Something to think about.

 

kinda what I am looking for... lower rpms. wasn't liking 2k @ 60.

 

 

If you're not towing/hauling and not running big tires 3.55 should make a fine highway cruiser. Start increasing the load and you might get into trouble.

As far as the technical questions, don't know. I've done very little gear work. Despite all the fairly straight forward looking stuff I've read, it seems to be voodoo magic that even the 'pros' screw up on.