What are the best gears for drag racing a 1988 5 speed trans am with a stock 305

 

Depends on what rearend you have too. 10 bolt gears will not fit 9 bolt and vice versa. Carriers will need certain gears too depending on the series. I don't know about 305 TBIs, but I would probably say 3.45 or 3.73s.

 

what do you have now? depending on that, it might be pointless to even change.

 

According to the Tech Data page for Firebird/Trans Am "if" its still stock you have 3.08 ring and pinion.
Here's a link to that page if your interested.= https://www.thirdgen.org/1988-pontiac-firebird

 

Whatever ratio has you at redline in 4th at your trap speed.

 

Yeah on the tech data it says I have 3.08 so what would it be safe switch?

 

You shouldn't just plan gear swaps off Tech sheets. You really need to know what you have in it first. You could try to count the turns and etc to find out the ratio, but the safest way is to manually check IMO. Gears should have a metal stamping on the ring gear. That way you can see what the conditions look like in there. If you crack it open and there is metal debris around well then you know you need to get a bearing kit too.

I just got done swapping out a 9 bolt for a 10 bolt few weeks back. If the next owner just went off tech sheets that they would be getting the totally wrong parts since they wouldn't know the carrier series or etc.

Have you considered normal gear labor installs can cost $250-$750 depending on the shop that does them? Throw in another $200-$250 for parts and seals, etc.

 

Put your car in 4th gear (1:1) and drive at 70 mph. The RPM's will tell you your axle ratio.

3.08 = 3000 RPM
3.45 = 3450 RPM

This is assuming stock tire size.

 

70 mph? Gulp! Sounds past speed limit!! Yeah I checked and I do indeed have 3.08 and yeah man I know how much it ranges for.

 

Naaaah. Texas has 85 mph speed limits.

 

I have heard of some TPI guys going 3.73 or more and losing e.t. and going back to 3.23 i dont know about it in your case...you should think about the future what do you plan on doing. are you trying to get more acceleration out of it? If not then just keep your 3.08's and fuel mileage...

 

I'm trying to get better take offs

 

I thought it was tpi not tbi...i'd run 3.73's if it was purely for drag racing. I drive my car all over the place so I run 3.42's

 

is the 305 tbi 9 bolt or 10 bolt?

 

If your running 3.08 ratio than you also have a 26 spline ,2 series carrier.That means a complete up grade would be in your future if you want to use at least a 3.42 ratio.Thats including 28 spline axles,28 spline 3 series carrier (I went with a Eaton Posi.) with a support cover. Either that or if you have bigger plans for a engine I would say 12 bolt or 9". I went with a complete up grade to my 10 bolt but my cars a DD with street tires.Its not intended for the track.

 

3.08 ratio = "10 Bolt"
as far as I can tell no TBI in "88" came with a 9 bolt.