how do I Know what rear end I have?

[brennecke]

Someone offered me their parts truck for 100 bucks, and it is supposed to have 373 posi rearend. How can I tell if that's true, and what rear end I have?
Sorry for all the newbie questions, but I've got to find out somehow.

[ckhd]

To check posi:

jack up one tire. Make sure tranny is in neutral and parking brake is off (and if you are on any type of slope, chock the wheels that stay on the ground).

Grab wheel that is in the air, attempt to spin.

If it spins, then either a) non-posi, or b)posi is shot. The only way to tell for sure is to take off the rear cover.

If it doesn't spin, it has posi (providing you don't have the parking brake on, or the tranny in gear/park).

------------------
Bowen
'68 K20 fleet
'69 K10 swb fleet
'72 C10 lwb step

[COBALT]

First, what type of truck is it? 1/2 ton? 3/4? What year and what suspension (coil or leaf).

Second, once you know all that the next thing I'd do (since you really can't take his word for it!) is check the shape of the cover. If it does have a posi unit in the carrier then the cover SHOULD NOT look like this:



This is a corp GM HO52(72?) axle under a 3/4 ton truck (notice the coils). The carriers in this axle cannot take a posi unit, BUT it can take a locker (sometimes people confuse the two) therefore, you may have a locker and that's what the guy means.

If he's right about having a posi unit then you should have a wierd shaped cover (NOT perfectly round) that has 6 sides to it, which would make it a dana-something (others here can help you with those). Perform the test the previous member instructed you on, and that should tell you more.

Finally, unless the number codes on the axle tube or housing can tell you what gear set it has (unless they were replaced) you'll have to pull the cover and count teeth on the ring gear (R) and the pinion gear (P), and do some math:

R/P = ratio

Good luck.

------------------
'69 3/4 ton C20 2wd w/ 350ci/400THM and a wood bed!
'69 3/4 ton Custom 20 2wd w/ ORIGINAL 350ci/4sp Manual and a wood bed (parts beast).
Seattle, WA.

*See pics of my trucks and project at www.webshots.com!


[This message has been edited by new69owner (edited March 27, 2002).]

[brennecke]

I have a 1/2 ton, but I'm thinking it may be a heavy half. I have the coil rear and huge drum brakes. The pumkin on my truck is odd shaped not round like the one in the pic.
To tell if it has the heavy rear, what weight would the plate on the door say? It says something like 3500 for the rear including the truck, and 2900 with out.

[Fast68Chevy]

you have a normal 12 bolt axle used from 64-81 1/2, if posi is original ot the truck then it will be listed on the glovebox door

there were no heavy half until 73-up, all they are are extra springs, axles are same, are no difference, there is only one 12 bolt for our trucks, there were 5 different 12 bolt axles, but we have the next to the heaviest one in our trucks, IE the 3500lb one.
G10 Vans used both the 2900lb and the 2400lb axle and G20 used 3600lb(the heaviest) the G20 started using the 10 bolt 8.5" axle by 1977, but the G10 on the other hand still used the 12 bolt in 74 at least, so.. GM was wierd like that,,

-others like P10 use 3500, K10 use 3300,
the only difference in later years on the big 10 and heavy halfs was the larger brakes IE., 11x 2 3/4" instead of the common 11x 2


G10 3.36* ratio or 4.11* ratio:
2400lb

G10 3.73* or 4.11* ratio:
2900lb

K10 truck 3.73 ratio: 3300lb

C/P10 3.07** 3.73* 4.11*^ ratios 3500lb

G20 4.11* 3600lbs

* also available with positractioon
**C10 models only
^ Standard on P10 models, positraction available
new69, false about the eaton round cover axle not having posi, G86 NoSpin was available in those H052 and H072 axles but not in the H110 axles


good luck
------------------
-71/C-10(thx teeitup and crews!)350 4+4/CH465(thx 71Chev, GMCPaul, and CPNE)longfleet bed(thnx meathead95)!still building it-
-'84 Z28(Z28) 1G1AP87GXEL100000 with H.O. 305/4bbl/190net/hp(L69) 3.73 rear(GT4/YC4) 700R4(MD8-MXO) & other goodies
-79 G20 pass van, 350/th350/10bolt,
paint is overrated
Randy- Lincoln, IL

r68c30@hotmail.com
© RSS Enterprises 2000




[This message has been edited by Fast68Chevy (edited March 27, 2002).]

[brennecke]

So was posi standard? and what kind of ratio would a 71 c-10 have?

[COBALT]

That's pretty light. The pic I showed you is (I think) rated for 5200 lbs. That's strong. The 1 ton axle is rated for 7200! My GVW on my C20 is 7300 (truck + max load). I've got both "G" options for heavy springs and overloading springs.

OK, so you have an odd-shaped one. That tells you some things, but not everything. I'd do some tests, like the previous member instructed. You'll have to pull the cover either way if you want to verify what you've been told. Find a picture of typical posi units (you can try Randy's Ring & Pinion), and compare. You'll have to count teeth as well.

------------------
'69 3/4 ton C20 2wd w/ 350ci/400THM and a wood bed!
'69 3/4 ton Custom 20 2wd w/ ORIGINAL 350ci/4sp Manual and a wood bed (parts beast).
Seattle, WA.

*See pics of my trucks and project at www.webshots.com!

[COBALT]

Well, posi may have been available when the corp. axles were made but not now. I know I tried to get one through Randy's and they told me to forget it...

------------------
'69 3/4 ton C20 2wd w/ 350ci/400THM and a wood bed!
'69 3/4 ton Custom 20 2wd w/ ORIGINAL 350ci/4sp Manual and a wood bed (parts beast).
Seattle, WA.

*See pics of my trucks and project at www.webshots.com!

[Fast68Chevy]

hehe, can find them in parts trucks though ho52 parts are not available anymore, long since been discontinued,.

posi was not standard, posi was very optional and will be listed on glovebox door sticker label if it is original to truck or if truck ever had it, 3.73 was standard in 12 bolt trucks however, the rear cover has 12 bolts, correct ? if has 10 and the wheels are not 8 bolt then its a dana60 and will be 4.56 4.10 or 3.54


click around on here and it iwl show pic of axle cover shape of each listed axle to the right in the black box:
http://www.sixstates.com/products/ax...uide/index.htm

[This message has been edited by Fast68Chevy (edited March 27, 2002).]

[Fast68Chevy]

and it wont show the eaton H052 or 72 or 110 axles like new69 posted above because they dont have parts for them, no one does, actually..

[brennecke]

OK. I got under there and checked it out. Here's the numbers. K300 on the side facing the bumper, GM 56 on the front driver side, and NF3896838. And the glove box just says heavy coil springs. It's a twelve bolt.
So what do we know now? I didn't have time to check posi, but I would guess I don't have it. I shift out of second around 35-40 MPH on a three speed manual.

[Fast68Chevy]

3.07 gears it sounds like, if it were 3,73 then it owuld be in topo gear before you got up to 30 mph, thats how 3.73 is unless you rail the engine pretty good,.

you just have a 12 bolt axle, standard equipment under half ton chevies til 82 1/2 when they quit making them., you probably dont have posi if it doesnt say it on the glovebox door, unless someone installed it on their own later after truck was new.,

------------------
Randy- Lincoln, IL
randy@ccaonline.com
-71/C-10(thx teeitup and crews!)350 4+4/CH465(thx 71Chev, GMCPaul, and CPNE)longfleet bed(thnx meathead95)!still building it-
-'84 Z28 H.O. 305 L69 700R4 GT4 3.73
- 1984 Firebird SE 2.8L T-5 GT4 3.73
-1981 Cutlass Supreme, dunno what im gonna do with it yet...
-79 G20 pass van, 350/th350/10bolt
*Paint is overrated
© RSS Enterprises 2000