Differential Ratio

**CarpenterGuy** · 09-13-2008, 11:05 PM

Is it possible for a Z71 to have a 3.43 gear ratio? I've been looking and I cant find anywhere that shows a Z71 with a 3.43. I'm hoping this is a mistake. I looked in the glove box where those numbers are listed and it showed the 3.43 number. I was under the impression that i had a 3.73. Where could i get a 3.73 G80 for a good price? I need it for trailering and stuff. Oh, and do i need to make any modifications to the front transfer case if i swap ratios?

**MrShorty** · 09-14-2008, 12:29 AM

Originally Posted by CarpenterGuy

Is it possible for a Z71 to have a 3.43 gear ratio? I've been looking and I cant find anywhere that shows a Z71 with a 3.43. I'm hoping this is a mistake. I looked in the glove box where those numbers are listed and it showed the 3.43 number. I was under the impression that i had a 3.73. Where could i get a 3.73 G80 for a good price? I need it for trailering and stuff. Oh, and do i need to make any modifications to the front transfer case if i swap ratios?

If that's what the RPO codes say, then I'd be inclined to believe that was what it left the factory with. Maybe the original purchaser special ordered it with a 3.43, or just the luck of the draw. Only other way to check gear ratio would be to count tire rotations vs. driveshaft rotations or to open the diff count the teeth on the ring and pinion gears.

3.73 G80 seems to be pretty common, especially in Suburbans. If you want to go the route of finding a junkyard axle, you'll just have to shop and compare until you find one you're willing to pay for.

AS for the front diff, you have to do something to it when you change the rear gear ratio. Either permanently disable/remove the front drivetrain and convert to 2wd, or change the front diff ratio to match the rear.

**tbplus10** · 09-14-2008, 12:29 AM

Any gear combinations possible. 3.43 is an optional gear for all Light Duty GM trucks.
If you regear the rear you'll need to regear the front diff, and recalibrate your speedo either by mechanical means or electronic. The transfer case needs no changes.
Look on line for gear sets at parts vendors. Most likely though your best deal will be buying a set of gears from whatever shop you decide to have do the work, most shops tack on an extra 10 to 25% for shop fee's or labor when carrying in parts. Look to spend between $600 and $1000 for a regear.

**Pete95Sierra** · 09-15-2008, 01:28 AM

i believe there should be a little plate on the diff cover being held by two of the bolts that says your gear ratios. and if you change the rear gears you absolutely have to change the front

**4x4_only** · 09-20-2008, 03:43 PM

Yes you can have a Z71 with 3.43 gears....my 07 Z71 came stock with 3.43's. I'm in the process of switching to either 4.11's or 4.56's. There's another good post about gearing going on right now...

And yes, whatever you swap the back out to you MUST do the same to the front.

**CarpenterGuy** · 09-21-2008, 12:57 AM

Originally Posted by 4x4_only

Yes you can have a Z71 with 3.43 gears....my 07 Z71 came stock with 3.43's. I'm in the process of switching to either 4.11's or 4.56's. There's another good post about gearing going on right now...

And yes, whatever you swap the back out to you MUST do the same to the front.

Where the heck do you get 4.56's? Oh, and do you know if it's bad to run 35" tires on 3.43 gears?

**mehoff400** · 09-21-2008, 01:05 AM

there is a chart for the optimonal gear ration http://www.4wheelparts.com/aux_incl/gear_ratio.html

**CarpenterGuy** · 09-21-2008, 01:13 AM

Originally Posted by mehoff400

there is a chart for the optimonal gear ration http://www.4wheelparts.com/aux_incl/gear_ratio.html

What effect would it have on my truck if i ran 35's on my 3.43 gears? Would it kill the tranny or something? i REALLY want to lift the truck, and money wise, i'm over half way there. I'm eventually going to change out the gears too, but that'll probobly be in about 3 years from now or so.