I have an 85 trans am 305 TPI stock with a 2.73 posi and I am planning on doing 350 TPI swap soon and I was wondering if that 2.73 is going to hold back the 350 and if so how much.(this is a daily driving car so I am not trying to make an 11 sec car out of it) I just want some more power then what the 305 w/2.73 is giving me.

I also have a 9-bolt B-W 3.27 posi gear but no rear end do you think it would be worth it to find a 9-bolt rear end to put the gears in.

I am also on a very limited budget.

Thanks
Richard

 

wow, i didnt even know you could get a posi with 2.73s...



new gears will make a noticable diff... and if you keep to a reasonable ratio, they will have very little effect on your overall fuel economy.

 

Yeah, My car came stock with a 2.73 posi in 89.

 

Nothing rare about a 2:73 with a Limited Slip. Common on IROC's with a Auto & 305 TPI.

 

Yeah fairly common, I just wish they would have had more 3.73's stock.

 

i just wish i had posi

 

yep, mines posi, BFD, theyre still 2.73's

 

oh yeah I took that 2.73 posi out of an 87 T/A 305 TPI auto b/c I only had a limited slip before but could I still get good performance out of the 2.73 w/300 hp 350

 

stock 350 tpi comes with 3:42's. I think 2:73 will hold you back. You won't see the performance your looking for. Stock 350 gets ok gas mileage and is still pretty peppy.

 

Stock 350 TPIs came with 2.77s and 3.27s, or the equivalvent 10-bolt ratios. I don't think it was even possible to get 3.42s with a 350 in one of these cars.

2.73 was the standard gearing for the 305 LG4, TBI, & TPI auto cars. Lots and lots of these cars have that.

I don't know what you mean by "limited budget"; but about the cheapest thing you could do would be to put your 3.27 9-bolt in your car, and see how you like it. You can do that for very little money. Then figure out if you want ot buy gears and all that for either it, or your 10-bolt.

The only ones of these cars tha tcame with 3.73s were the L69 cars. They were really the only engines that had enough RPM potential to use them.

 

The 3:42 10-bolt only came on 305 TPI cars with the G92 option **.
Only ratios available stock on a 350 TPI were 3:23 10-bolt and 2:77 & 3:27 9-bolt rear axles.

** Also on v-6 cars with a open rear end, if anyone cares.

 

"Limited Budget" means that I am a High schooler and since I am saving up for a 350 I do not have extra money for a good rearend and the motor comes first

I can not put the 3.27 in b/c I only have a good diferential (spelling?) the axle housing is bent just enough so that it is unusable but the gears are good so I would need to find a 9-bolt rear with no gears. And I know that 9-bolt parts are hard to find.

And I also hav'nt decided if I am going TPI or 4bbl but I will at least have 300 HP But do you guy's think I would be happy with a 2.73/350 4bbl 300 HP

 

Wrong, I have a 91 gta. I just took the rearend out. Ihave a 3:42 gear. Sorry Must be a mistake.