Question re: Gear Ratio in Transfer Case

[mikekwesell]

Hi Gang, I have a 1973 K5 Blazer that I put a 4" lift on and threw on a set of 16" wheels with 35" tires. Do I need to swap out the transfer case now? Or can I somehow adjust/change the gear ratio in the transfer case that is on the vehicle? Please see pic of tag on transfer case - still not sure what this tag tells me about the current gear ratio. Thank you in advance for your help!!

 

[Bent77]

Well, let’s ask a few more questions

What is your axle ratio, and how are you planning on using it?


That ratio is about 2:1 reduction

 

[mikekwesell]

No idea what my axle ratio is - how do I get that information? Plan for use - mostly roads/highways, not much 4-wheeling. Will tow boats to rez, tow dirt bike trailer to trailhead, tow snowmobiles to mtns, etc, grocery getter, dates with girlfriend, etc...

 

[Fordum]

Well, there are gear ratios and then there are gear ratios..........
You don't normally change the actual drive gear ratio in a transfer case. Some transfer cases have a lower low range than others, but that does not come into play when driving down the road when in high range, its pretty much a 1:1 ratio. If your final drive ratio is wrong for those tire sizes, you will have to change the ratio in the front and rear end.

If you are wanting to correct the speedometer, there is a small gear in the side of the transfer case that you can change that will help

 

[Bent77]

No idea what my axle ratio is - how do I get that information? Plan for use - mostly roads/highways, not much 4-wheeling. Will tow boats to rez, tow dirt bike trailer to trailhead, tow snowmobiles to mtns, etc, grocery getter, dates with girlfriend, etc...

You don’t need a doubler or even a different Tcase really

You may want different gears, or even need, depending on what you have
fool proof method of knowing the axle gear is to take the cover off the diff and read the ring gear,
They are stamped
41-10 would be a 4.10 (41/10)

 

[mikekwesell]

Got it. Will remove the cover this week and see what is stamped on the gears. Will follow up asap. Thank you!!

 

[Bent77]

Rear is the easiest to get to, and Right Stuff sealant works best to put that back on after you get the gasket surface spotless and clean

 

[diesel4me]

If your real lucky and live in a rust free climate,you might find a tag on one of the front differential cover bolts that will have the tooth count stamped in it.(like the 41/10 example)
Here it is rare to find one,they rust away,or someone leaves the tag off first time they take the diff cover off for a fluid change or repairs..
Out of a half dozen GM trucks I've had only 2 still had the tag on them..one was dragged over a rock and illegible by the looks of it..