hi,what gears came in that in 86 305 A4 trans am

 

do you still have your RPO sheet? It would tell you on that the gear code.
9-bolt gear ratios are mostly different. Like a 3.27 instead of the common 3.42 in a 10-bolt.

 

86 Sport Coupe
Berlinetta M5,A4 LB8 V6 8.9:1 2.8 (173) 135@5100 160@3900 MFI 3.42 ---- 3.42 ----
86 Sport Coupe
Firebird M5,A4 LG4 V8 9.5:1 5.0 (305) 155@4200 245@2000 4bbl 2.73 ---- 2.73 ----
86 Berlinetta
Firebird S/E A4 LG4 V8 9.5:1 5.0 (305) 155@4200 245@2000 4bbl - 2.73 ----
86 Z28
Trans Am M5,A4 LG4 V8 9.5:1 5.0 (305) 165@4400 250@2000 4bbl 3.23 3.73 2.73 ----
86 Z28
Trans Am M5 *L69 V8 9.5:1 5.0 (305) 190@4800 240@3200 4bbl HO 3.23 3.73 ---- ----
86 Z28
Trans Am A4 LB9 V8 9.5:1 5.0 (305) 190@4000 285@2800 TPI ---- ---- 2.73 3.23
86 IROC-Z
Trans Am M5,A4 LG4 V8 9.5:1 5.0 (305) 165@4400 250@2000 4bbl 3.23 3.73 2.73 ----
86 IROC-Z
Trans Am M5 L69 V8 9.5:1 5.0 (305) 190@4800 240@3200 4bbl HO 3.23 3.73 ---- ----
86 IROC-Z
Trans Am A4 LB9 V8 9.5:1 5.0 (305) 190@4000 285@2800 TPI ---- ---- 2.73 3.42
86 IROC-Z A4 +L98 V8 9.5:1 5.7 (350) 220@4200 320@3200 TPI - --- 3.27* ----

The only correction I see is that the 3.73 is really 3.70
If you don't have the RPO build sheet, there still may be a tag attached to the diff cover with the code on it.

 

X2. Most 9-bolts I ever saw were on 350 cars. Im not saying that having a 305 and 9-bolt wasnt done. Just never seen one.
Like Skinny said, the gear ratios are close but differ. Also there was a small tag on the 9-bolts Ive come across.

 

Interesting.
For the record, the only 3.70 9-bolt I've seen is on a 305 powered 5 speed.
That was on a 86 Firebird.
I have come across several 9 bolts in other applications. My current install is a replacement for the 3.70 gear set that I shredded with what turned out to be a 3.27 ratio from a another wrecked Firebird.

 

..oh i cant read the rpo code b/c im lookin at this rear from a parts car(craigslist)...i need a rear for my 89 formy tpi....so it probly has 3.23s in it?

 

89 RS
Firebird M5,A4 LB8 V6 8.9:1 2.8 (173) 135@4900 160@3900 MFI 3.42 ---- 3.42 ----
89 RS
Firebird M5,A4 LO3 V8 9.3:1 5.0 (305) 170@4400 255@2400 TBI 3.08 ---- 2.73 ----
89 IROC-Z
Formula
Trans Am M5,A4 LO3 V8 9.3:1 5.0 (305) 170@4400 255@2400 TBI 3.08 ---- 2.73 ----
89 IROC-Z
Formula
Trans Am A4 LB9 V8 9.3:1 5.0 (305) 195@4000 295@2800 TPI ---- ---- 2.73 ----
89 IROC-Z
Formula
Trans Am M5 LB9 V8 9.3:1 5.0 (305) 220@4400 290@3200 TPI 3.08 ---- ---- ----
89 IROC-Z
Formula
Trans Am
GTA M5 LB9 V8 9.3:1 5.0 (305) 230@4600 300@3200 TPI ---- 3.45* ---- ----
89 IROC-Z
Formula
Trans Am A4 L98 V8 9.3:1 5.7 (350) 230@4400 330@3200 TPI ---- ---- 2.77* ----
89 IROC-Z
Formula
Trans AM
GTA A4 L98 V8 9.3:1 5.7 (350) 240@4400 345@3200 TPI ---- ---- ---- 3.27*
89 Turbo Trans Am (TTA) A4 LC2 V6 8.0:1 3.8 (231) 250@4400 340@2800 SFI ---- ---- 3.27* ----
*Borg-Warner rear axle

Given the size of the list, it would be difficult to say exactly what you have or need.