i have an 88 firebird originally with a 305 tbi. everything i have read says that limited slip wasnt available in the base bird. but mine has it and i was curious if anyone had an idea what the gear ratio may be? the rpo codes are no longer in the car so thats no help either. could u order the limited slip as an option on the base firebird? i bought the car from its original owner and he says nothing has been changed and it looks that way

 

Please on TGO...The process for checking has been answered MANY times.

 

305 TBI automatics came with open 2.73 rear ends. We have no idea what rear end you have now.

 

Welcome to TGO. Drop the cover and look (actually the diff cover should have a metal limited slip tag, but those are often lost over the years). Here's what the limited slip should look like:

https://www.thirdgen.org/forums/atta...s-dsc00148.jpg

Here's how to determine what ratio the rear is (numbers are stamped on the ring and pinion):

41 : 15 = 2.73
41 : 14 = 2.93
40 : 13 = 3.08
42 : 13 = 3.23
41 : 12 = 3.42
41 : 11 = 3.73

JamesC

 

That link shows the Auburn. It could also have the Governor Lock. Any Camaro or Firebird could be ordered with the limited slip differential.

 

Was the gov lock still around in 88 in thirdgen cars? My 85, as shown in the link, has the Auburn.

JamesC

 

ill pull the cover this weekend and check it out. thanks
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appox. how much power can these diffs handle?

 

I don't know when the Gov Lock was used, but I know many of the 3rd gen cars had them. I have never heard of a 4th gen with one.

 

I just assumed that they were gone by 85.

JamesC

 

Could be, but someone could have put one in.

 

I pulled a 3.73 Gov-Loc out of an 85 Iroc with the L69 HO and T5, but I have to say that probably 85 or 86 would've been about the time they were phased out, at least in f-bodies. I've never seen an 87 or newer with anything other than an Auburn unless some poor, uninformed guy was suckered into buying a Gov-Loc off ebay and putting it in there himself. I think they used them for quite a few years longer in the S-10's and what not, but not the f-body. 4th gens definitely all got Auburns until the Torsen came along in 98. I also agree that any f-body could've been ordered with the posi option. I've come across a number of RS cars with G80 on the service sticker, so it's no real surprise that a "base" bird might have one.

 

The Gov Lock is still being used in GM trucks. It was designed for trucks in the 60s, but a few cars got them too along the way. Some of the Monte Carlo SS got them through the 80s.

 

assuming its the auburn will this diff handle 400 horse? any way to get rpo codes if the tags are gone?

 

I don't know if the 7.5 rear end will handle 400 HP with any differential. This rear end is just not very strong.

 

what would u suggest thats fairly cost effective?

 

i guess im looking for something that will handle more torque than the high rpms. ive got a 406 im puttin in and im not planning on racing just a toy pretty much but i wanna know i got a diff that will handle the power when i need it to

 

The 9 bolt is a little stronger. As long as you have street tires and keep wheel hop under controll it might hold up fine for a while. If it gets good traction then you might loose it. A Moser 12 bolt would be MUCH better, but over $2000.