Cascade Crew

Xophertony · Posted: Thu Nov 24, 2005 12:33 am Post subject: 9bolt / 10 bolt

when was the change? whats the difference? how hard is it to convert?

i know one has a 26 spline input shaft; and one has a 28 spline..

iansane · Posted: Thu Nov 24, 2005 1:48 am Post subject:

The earlier ten bolt came with 26 spline axle shafts, then later ones (89 and alter I think?) came with 28.

The 9bolt ended in 89 and started who knows when. My buddies 85 had one as well as my old 87. Both posi, disc 3.27 rears.

Supposedly the 9bolt is somewhat stronger but also harder to find parts for. You're best off finding an 89 or later 10 bolt with the pbr calipers. The 9 bolt came with the PBRs in 89 only I think...

Xophertony · Posted: Thu Nov 24, 2005 1:57 am Post subject:

so if i get an 89+ unit with 28 spline axles, is it a direct swap onto my car that came with a 26 spline? will i have to change out my driveshaft?

Sellmanb · Member Joined: 30 Nov 2004 Posts: 727 Location: Tigard, OR

The spline count is in reference to the axle splines. A driveshaft is a driveshaft, GM didnt make specific "9 bolt" driveshafts Wink

.

I can prove that it should swap right over, because the guy who had it before you took a 9 bolt, and swapped to a 10 bolt, right?

Wink

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

I think the 9 bolt is quite a bit stronger than the 10 bolts.

Schultzy's rear has withstood many beatings at the track and on the street. Yup yup

Schultzy89GTA · Posted: Thu Nov 24, 2005 9:44 am Post subject:

Ya I sure have had my rear beat at the track all right Wink

(shut up Paul Razz

)

-Schultzy

Twilightoptics · Posted: Thu Nov 24, 2005 11:11 am Post subject:

chevymad · Posted: Thu Nov 24, 2005 12:11 pm Post subject:

I'd say what you do depends on what your plans are. You're probably eyeing that 9bolt of sellmans. It's plenty strong enough for a fairly hot 350, especially if you arent going to put slicks on. Whereas the 10 bolt is pretty weak without buying all the extras. The stock posi's in the 10 bolts suck too but the 9 bolts have good ones. I'd be gettin the 9 bolt myself.. then if you ever want slicks or something look at the 12 bolt. I'd almost bet your car came with a 9bolt originally.

Xophertony · Posted: Thu Nov 24, 2005 12:38 pm Post subject:

as far as plans.... mild buildup. mostly restoration.

headers/ypipe upgrade somtime in the next year or so.
T56 swap... if my tranny ever blows up. if not stay with 700r4
mostly suspension rebuild.

but i also want to get closer to correct factory gearing. without the RPO there is no real way to know if it had 3.23s or 3.42s

Schultzy89GTA · Posted: Thu Nov 24, 2005 2:01 pm Post subject:

Are you trying to restore the car to exact factory spec or are you just curious about which gears it originally came with? '88 right?

Odds are if it was an auto car and 9 bolt you had 3.27. If it was a manual car and 9 bolt most likely 3.45.

-Schultzy

Xophertony · Posted: Thu Nov 24, 2005 10:41 pm Post subject:

you are correct schultzy. mine is an auto 88. the 5.7s were not offered with a manual. the tourque was "too much" for them acording to the general. 3.27 and 3.45 were the ONLY available rear end ratios for GTAs in 1988. acording to the GTA source page only 809 came with 3.45s. i am pretty sure mine was 3.27s. i am not trying to get it back to factory specifically, but closer would be good. it has 2.73s now Rolling Eyes

.