Originally Posted by Eatmorefish
I made the switch on tires to 285’s then drove it from Boise to Salida and here’s what I found. With the original gearing at 373 the performance is definitely not what it could be. Not that I’m a heavy foot off the line but sometimes, like merging or trying to get ahead of that truck, you need a little pep and going from 265 to 285 definitely made a difference. Hills are also a tougher nut to crack. Mileage didn’t seem to change all that much. I’m leaning towards changing out to 410 and if I can find a rear end possibly switching to full float. Does anyone have a recommendation for a Phoenix area shop that can do the work?
I just finished my 3.73 to 4.10 conversion. 5.4L 285/70-17's. I'm very pleased, much improved. The van still downshifts on steep climbs out of OD but no longer shifts down to 2nd and I can maintain speed up the grades much better. The speedo error is less than 5% compared to 10% with 3.73s (the actual speed is still slightly higher than indicated by speedo). Haven't checked mileage yet but won't be going back to 3.73s anyway.
If you are inclined to do this yourself the ring & pinion sets are between about $180-$300 depending on brand. $300 is for OEM Spicer. ..and if you are in there may as well do bearings and seals.
3.73's are 11 tooth pinion and 41 tooth ring 41/11=3.73 4.10's are 10 tooth pinion and 41 tooth ring 41/10=4.10. The ring and pinions are matched sets.
I bought everything from either East Coast Gear Supply or Denny's driveshafts....both online.
I bought shim kits, bearing puller, setup bearings/races, grease paint and a few other bits and bobs to do this; I'm planning on listed that stuff on CL and Ebay so if anyone here is interested please PM me.
There is tons of info online to do this job, it's not rocket science or voodoo, but it's tedious. There are three places that you shim, and each time you shim one it changes the others. So lots of installing/removing.