Need Gear help...Not a "Gear Head"

[brent c]

Hey guys,

Finishing up on a '70 K5 and want to add new gears to help move the 35" Nitto Mud Grapplers on Weld Racing 18" bad to the bone wheels! My calculations say 4.88's should do the trick; any advice one way or the other? 4.56 vs. 4.88 with a fresh 350?

Also, if I order gears, what do I have to do to make the rear end "Posi-Trak".

Dumb, I know, but not a gear head...sad.

Any help appreciated,
Brent at South Padre Island, TEXAS

Hook 'em 'Horns!!!

 

[1979jimmy350]

what tranny are you running?

 

[OffRoad]

with a fresh 350, i think you'd be fine 4.56s if you do trails and mud. if you do rockcrawling, go with 4.88s.

 

[mr_blasto]

4.88's or 4.56's will work fine. If you have an OD transmission go with 4.88's, if not you may want to consider 4.56's. Here is a nice calculator to play around with gear ratios:

http://www.dfw-tx4wd.org/Tech-Dept/Tech-Dept/gears.html

As for a posi... are you looking for a locker or a limited slip differential. Figure out what your looking for, then buy one, and install it or have someone install it.

If you happen to have a d44 front and 12 bolt rear axle, I have some 4.88's with master install kits new in the box that I am no longer going to be using (I am going to 1-ton axles). Let me know if you are interested.

 

[trailblazr81]

I have run 4.56's with 35" tires with a TH350 and 700R4. I wouldnt do the 4.88's unless I had the OD. And then I dunno cuz the 700R4 has the deaper 1st gear to get you out of the hole so its not needed. For "posi" look at an Auburn or Eaton limited slip. What you ar doing is replacing the carrier (its what the ring gear bolts to.) Posi is Chevy's name for limited slip which uses clutches to limit wheel spin. Some use hellical gears. They do about a 70/30 split and can wear out or be overpowered. They need some resistence to work. Myself and many others will sugest you get a detroit locker tho. It uses gears to lock the wheels and give a 50/50 split whenever power is applied.