1985 C20 rear end decode help please

[Chevhughes]

I have a 1985 c20 from Calif. it has a 700r4 and stock 350. I am trying to figure out what rear end is in the truck, and having no luck in my search. Thank you in advance for any help. The axel tube is stamped BDB G0921 Thank you again. any oil recomendations for this rear end ?

[zieg85]

Do you have the sticker in the glove box?

[Chevhughes]

Glove box sticker is tough to read unfortunately

[zieg85]

I can not find any info on the numbers you posted

[zieg85]

I re-read your post.  You more than likely have a corporate 14 bolt semi float rear end.  Post a picture with the hubcap off to confirm

[Chevhughes]

it is 14 bolt

[zieg85]

14 bolt semi float or 14 bolt full float are your 2 stock choices.  The first has a 9.5 " ring gear and the brake drum goes over the axle like a car rear end.  The full float axle bolts to the drum.  Pictured is the 10.5" full float

[zieg85]

Semi float

[Chevhughes]

i'm thinking semi thank you very much, any idea on gear ratio ?

[zieg85]

Try and get it from your glovebox sticker.  The only way is to take the cover off and see the stamped numbers on the ring gear.  For example 41 10 would be a 4.10 ratio

[zieg85]

on car rear ends that first letter "B" is supposed to be the gear ratio but I can't find info on the corporate 14 bolts to decode it ratio wise

[Chevhughes]

Thank you for the help zieg. any oil recommendations for this rear end ?

[zieg85]

The manual calls out for 80W-90 GL-5

[Chevhughes]

you guys are the best..

[Chevhughes]

After looking closer at the glovebox door, I think it reads GU5 ?  I think that is 3:23 ? does that sound right with a 350, 700r4 and bone stock from cali ?