Hi,

I have a 96 Chevy Silverado 4x4 with an upgraded 3/4 ton posi rear end sittin' on 37in superswampers.  I jacked up the rear end with the truck in neutral and one revolution of the tires turned the driveshaft just over 4.5 turns.  Thus, I'm thinking it has a 4.56 set of gears.  Anyway, the fella who owned the truck before me must have never factored the rear ratio with the stock 3.42 listed in the glove box because after replacing the front 8.25 IFS differential seals, I realized the center shaft was sheared in two.  I now know why he said he didn't know if the 4x4 ever worked as I noticed the front driveshaft in the bed of the truck.  

My dillema is this.  I need to obviously match up the front ratio with the rear, but don't know what I should use.  The glove box code says it came stock with a 3.42 ratio/limited slip.  I don't know if this means that the ring/pinion ratio for the front and rear were both 3.42.  I say this because I don't know if the front ring/pinion ratio could be different due to any transfer case input at the shaft.  Not sure if that effects anything or not.

So, I just need to know if there should have been a matching 3.42 ratio at the front gears and the rear to keep things from going bad .  If that's the case, I guess I'll be ordering a 4.56 set of  gears for the stock front differential.

Thanks in advance,

Newbie  

they need to match, though if you have a 1500 w/4l60 or a 2500 w/4l80 auto, running the 37's a 4.88 at least or 5.13 (the best) gears will be a better option.

but definately at the very least put the 4.56 in the front to match what you already have...  

I think a 5.13 would be a better match too. Even with 4.56's, OD is gonna be kinda useless most of the time with 37's.  

Thanks to both of you.  That explains a lot of how the truck acted when I had it on the highway.  In OD it seemed like it would hesitate/slip up the hills.  It's a first truck or vehicle for that matter for my son anyway, so I guess I'll just put the 4.56 up front and call it good.  Anything else for the upgrade that would cost a bunch more is up to him.  I'll have to make the 5.13 proposal to him before putting the 4.56 up front and wasting my money.  I think me paying for the front gears and him paying for the rear to upgrade to the 5.13 is fair .

Later,

Brian  

yeah the 5.13 will help eliminate the trannie getting done again, which will cost more than the gear swap..

@65 the 5.13's will be turning about 2100 rpm with the 37" tires, thats what those big tires need..the 4.56 is below the stock rpms...1880rpm, be sure to get it out of OD when it starts searching for gears.  

You guys are great. I'll definately go with the 5.13 gears then and avoid the expensive tranny failure on the road.  The searching for gears is exactly what it felt like and fortunately I did pull it out of OD when it acted up.

Thanks again,

Brian