Looking to learn about rear ends!

[Heavy87Chevy]

Hey guys,

I'm sure like alot of you guys I spend alot of time thinking about my truck, but it was winter when I bought it & up where I am that meant I didn't get much of a chance to thoroughly check it out, & I've learned so much more since I've last laid my eyes on her.. Right now its sitting at a transmission guys place about to be fixed up, theres something wrong inside the transmission & that is beyond my current knowledge so now I wait..

What I'm wanting to learn/discuss is this: how do I figure out what the gears are in my rear end? I've got an '87 Chev V10 LWB 4X4 with a 92 corvette tpi 355. The rear end is 10 bolt I believe (does that mean its posi!??), & when I looked on Chucks Chevy Truck Pages, everything is leading me to believe that I would have 3.08:1 ratio.. I'm running 33" tires & I'm considering going to 35" tires & I'm wondering if my rear end could handle 35s, so I'm also wondering, how do I know what rear end is best for specific tire sizes. I'm willing to swap axles & everything, over time, to get the most out of my baby

Thanks for any help, I'm really just a youngan getting into squares & I have much much more to learn, but heres a pic of mine .. I'll post more pics when I get back from vacation in a week!

[hatzie]

A good place to start is the service parts identification label in the glovebox or sometimes under the hood on the inner fender.
The Limited Slip diff will be RPO code "G80".
The original axle ratio(s) might be listed. 3.08 would be GU4

[James McClure]

Heavy, nice truck, especially for a snow belt truck. OK, now for your question. Yes you can run 35's. How well is another issue. You'll have the power but there may be a durability\reliability issue. Everything you do is a balancing act and if you don't get close to right something is going to suffer someplace along the way. Bigger tires effectivly lowers the rear end ratio (EG, a 3.08 rear end may behave like a 2.73) Great for fuel ecomomy but performance will suffer and rear end gear loading increases. You could go to 3.73's or 4.10 but your fuel ecomomy will suffer. Next is finding the gear ratio. With our trucks you can never be sure exactly what's in them, so here are a few ways to check. Not real accurite but it'll get you close. Jack up the rear end. Leave 1 tire on the ground. (if the shaft won't turn it's posi so you'll have to jack the other tire and let it rotate 1 full turn without dividing by 20 Mark the floor and tire and mark the drive shaft at the rear pinion. SLOWLY rotate the drive shaft and count the turns until the tire has rotated EXACTLY half a turn, OR, if you let the tire go 1 full turn, divide the pinion rotation number by 2. Next is accurite IF no one has changed gears. On top of the right axel tube there are a series of numbers and letters. Record them and do a search to find the ratio. Last check is positive. Pop the rear end cover and rotate the ring gear until you see a series of numbers. Your looking for a set of numbers that look like this "00:00" those aren't the numbers you'll see, just an example of their arrangement. 15:41 = 2.73. Divide the big number (41) by the small number (15). The 41 is the number of teeth on the ring gear. 15 is the number of teeth on the pinion gear. With the rear open you'll be able to see if it's posi by looking at the guts inside the carrier (the caasting the ring gear is bolted to) if all you see is 4 gears and a cross shaft it's non posi (open rear) If there looks to be plates under the side gears or some gearing mounted to the carrier it's posi. Hope this helps, jim

[Tony@AirRideTech]

Heavy... good looking little truck there. To run 35 / 36s the closest gear match to put you back in average hwy operating range would be 4:56. Especially if you are using a 700r. My suburban was factory 3:42. When I put the 35's on I geared it to 4:56 and installed Eaton / Detroit truetrac's in both front and rear diffs. Excellent combo for a driver. I have been most happy with it.

[motornut]

very nice looking truck

[Tony@AirRideTech]

Here is my "big-ole-ugly-blue burb-winter-beater" ha ha ha ha ha ha

[joelsdelone]

heavy, I dont know alot about rear end configuration, but dude your truck is a beaut. I would love to get my hands on a Four By one day.

[russgt]

Good 6 lug upgrades for the rear are the semi floating 14 bolt and the 12 bolt.
for the front, dana 44.

If you dont mind going to 8 lug wheels, there is the full-floating 14 bolt rear and the dana 44 or 60 front axle.

With 35s I would suggest at a minimum 4.10 gears with 4.56s being a more desireable way to go.

[Mr. 250r]

great looking truck, i'd take cover off rear end just to be sure nothing has been changed gear wise, and i run 38.5s with 4.10s don't really have a problem but i don't use use 4th either and its through a stock tbi 350