Going from 273s to 373??

[84scottsdale454]

hey guys, I have a stock 10 bolt rearend in my 2wd k5 blazer and it has 273 gears.I also have a th350 trans. I enjoy these gears due to highway driving but i plan on installing a taller tire. I plan on going roughly a 30" tall tire. Could these gears still be used for highway driving or should i not go that low? Also where is the best place in your opinion to get a posti trac setup. I have the gears and rearend already but would like it to be posi.

[ehjorten]

what is the size tire you have on there now?

In my opinion it might be a little low for highway driving.  My '77 has 31" tires and 3.73s and driving on the highway is bearable, but it does fatigue you if you drive say 100+ miles.

[305chevy c-10]

well when i had 3.73 in my 305 it pull off really fast but u lose a lot of top end speed .they were in the truck when i bought it along with a rv cam .i bought a posi from junkyard and it had 2.73 ,pulls off slower but runs faster on top

[bake74]

     I think with only a 30" tall tire, 3:73 gears will be too low for you, I believe you would not be happy with the end results and your top end speed.

[Edahall]

hey guys, I have a stock 10 bolt rearend in my 2wd k5 blazer and it has 273 gears.I also have a th350 trans. I enjoy these gears due to highway driving but i plan on installing a taller tire. I plan on going roughly a 30" tall tire. Could these gears still be used for highway driving or should i not go that low? Also where is the best place in your opinion to get a posti trac setup. I have the gears and rearend already but would like it to be posi.

What's the reason for the switch?  If it's so it'll tow better or lower your 1/4 mile times, then certainly yes.  But if its for going down the highway and get good fuel economy, keep your 2.73's.

I did some looking up for you and based on the 30" tires you're looking into, your rpm's at 65 would be 2041.  That's not bad all.  In fact, you could go with an even taller tire.

Here's the RPM calculator.
http://www.csgnetwork.com/multirpmcalc.html

[SUX2BU99]

My 2wd C10 with 27" tall tires and a 3.40 gear with a non-lockup TH350 revs at 3000 at about 65 mph. It's a little much and I don't drive faster than that.

I don't think those RPM calcualtors take into account non-lockup transmissions.  I could be wrong though. There's a good 3-400 RPM lost there.

[VileZambonie]

Go with a 700R4 and a 3.73 or 3.42 and you'll be happy

I'm partial to the Auburn Gear units http://www.auburngear.com/aftermarket/product_details.aspx?SKU=GM%208.5%20and%208.6&ReturnURL=%2faftermarket%2fproduct_listing.aspx%3fCategory%3df1c3cf23-6c3c-46c1-a5dc-d67fae11ed26%26page%3d1%26pagesize%3d9%26text%3d%26EPCString1%3d%26EPCString2%3d%26EPCString3%3d

Others seem to like Eaton. I've had great luck with Auburn behind big blocks which should say something.