hi im new to this whole gear change thing. i have an 89 rs 305 tbi not sure what i have for a rear end. i would like to learn how to LEARN what i have and what i can do cheaply to upgrade. i heard swapping in different gears will make my nearly stocker somewhat faster. what can i do and what can i expect? not looking to do an entire rear end swap just some advice and pointers please

 

If you're lucky, the RPO code list will still be glued to the underside of the center console lid. Check there then do a search of the RPO codes and / or, ref. the rear end tables in a Haynes repair manual. If you're un-lucky and the RPO sticker is gone, you can always find the stamping on the top of the passenger side axle tube just a few inches out from the differential. Want to dig deeper? Pop the cover off the rear. Look for the stamping on the ring gear and go from there...

The fastest / cheap way to a limited slip rear end with better gears is probably a (wrecking yard) rear end swap. Then there's the (many) question's of drum to disk conversion... speedo gears, etc.

Good luck

 

ill prolly check the axle but what am i looking into the ?RPO? code for anyway? what is it? and like i said i dont want to do a complete rear end swap just an idea of what gears i could use for the best street performance out of another stock rearrend. or if i could find another vehicle that will bolt right up to my car with a better rearend than i'll do that too. any suggestions?

 

The 89 RS rear end is open/drums with 2.73 gears with an automatic transmission, and 3.08 open/drums with a manual transmission.

What I did, was bought a posi/disk rear from a junkyard, $100 without the brakes.

To convert to disk brakes, you should replace the proportioning valve, although I have heard some people didn't. But disk brakes require a different volume and pressure of brake fluid than drums.

Read, read, read, it's all on here. That's how I learned, searching is a very valueable tool.

 

search i did but not alot on my gears is specific. thanks though i now know i have 3.08 gears cuz of the manual. so what now? what gears can i change out to get more performance?

 

Click on the link for RPO code info: http://www.sethirdgen.org/reardata.htm

As far as gear choice selection goes, for improved performance select 3.42's or 3.73's (the latter might be a bit much for the 305). You might want to also consider a new 3 series limited slip carrier for the new gear set otherwise you'll need a brand new thick gear set to match your 2 series carrier.

If you're on a tight budget, you could probably find these parts used from a junkyard, eBay or from the classified's on this site. All said and done... IMO, all the work involved still warrants considering swapping the entire rear end.

Good luck

 

great great info for me thank you. i'll be on the phone with local junkyard as soon as i know what the 3.73 gears came on.

 

Best way to tell, go to the yard, take the 10 bolts off the cover, rotate the differencial until you see a bunch of numbers on the ring gear. There will be a 7 or 8 digit number, and then there will be a number that looks like XX:XX. (13:42 for example = 3.23 gears) Just divide the second number :XX by the first number XX:. I hope you understand what I'm tryn to explain.

In the example 13:42, divide 42 by 13 and it equals 3.23. While the cover is off you can def tell if it has posi too.

 

sweet that helps a **** load as well! one more question...do i check any car? or is there specifics involved with finding my correct junkyard gears?!

 

I would start by checking all the F bodies that have disk brakes, then start popping off the covers and check to see if it's a posi, then check to see what ratio it is. I lost a bit of top end on my 305 TBI car when I switched to 3.42s from 2.73s. So now I'm gonna try out 3.23s. But with your manual car you may want leave 3.23s alone and look for 3.42s, possible 3.73s. I dunno about the 3.73s, maybe someone else could chime in.

 

i really wish a few more people would try to help out i know they know about all this stuff but i post alot of questions...and honestly, i learned a ton since i started reading. but ii think they may be getting fed up with me. does it make a difference how many bolts there are? im assuming 9 bolt 10 bolt refer to how many bolts hold the back plate of the "pumpkin" on.

 

You are correct in the # of bolts on the "pumpkin" cover. If you see a 9 bolt, open it, if it's posi grab it. If you don't use it, sell it.

 

thanks alot ill check it out this weekend

 

try the search function, peoples alreay answered your question long before it was ask.