I have a 91 L03 Firebird with the 10 bolt non-POSI rearend. It's starting to get snowy and icey out, so I want to replace it with a POSI.

Someone told me that you can pull the carrier and pinion/ring out of my diff and replace them with a POSI carrier and gears... Any truth to that?

I'm not sure if it's easier to replace the diff or the inards... Let me know what you guys have done to your cars... It woudl be nice to get rid of the highway gears (i think i have 2.73s) and pop in something like 3.73s 3.90s or 4.10s to improve acceleration.

Any advice is appreciated!

 

if you have a t-5 you have 3.08s. no it won't be just a plug and chug. you will need some experience to work on your rear end, theres all kinds of backspacings, and shims, and depts, ect....

 

snow + ice + posi = accident waiting to happen. Camaro's weren't meant to be driven in snow or ice. I lived in Washington State for 10 years and had a few slip and slide with even with open rear RS. You can try adding some weight to your trunk to help with traction.

 

You don't want a posi for winter. rain driving can be tricky enough with one. you really have to change driving styles with a posi.

run lower psi in your tires and toss weight in the back and keep the tank full.

I drive mine year round and don't have to much trouble. Having a stick and good tires help.

 

all you'd need to do is swap your ring gear over to the new posi carrier, set back lash and check contact pattern and you'd be all set.

 

So, if I found a POSI out of an S10 or something, they're interchangable with my differential? What are some common gear ratios I might be able to find at the wrecker that could improve acceleration? And what vehicles woudl be my best choice to start the hunt?

As for winter driving.. I might just go buy a beater Blazer for the winter. I realised last night that Firebirds are great in the snow if you want to do donoughts, but thats about it.

 

Hotrod did a test a while back and said 3:55s were the best over all for street strip. 3:73s are nice though. having the stick 4;11 wouldn't be to awful for a daily driver.

Need to see what you can get first, make sure you have the right axel splin number when you search.

 

First you can't just swap the ring gear to a different ratio, the ring and pinion gears are a set. You have to stay with the same ratio or swap the whole thing. Second you have to use the same series carrier when swapping in a posi. Since you have an L03 you have a 2-series carrier, so you need a 2-series posi. This is the only way you can do it.

I'd just find a 2-series carrier and swap you ring gear on.

If you want different gears, buy a used rear with different gears. I say this because it will cost the same or more to get new gears installed.

 

Heh, sounds like a job and a half. Is it any easier to just replace the stock ring/pinion with a different set of gears to improve acceleration? Say, 3.73?

 

yah but if you gonna put in 3.73s....you'll never get traction with that one legger...posi is a definate with whatever ratio you go with, no one likes that embarassing single burnout mark

 

IMO the 4.11 is too steep, GM put 3.73's in the 5speed cars and they nailed it. Here's a quick vid, if you pay attention to it, I have to make an upshift and a downshift in a very short timeframe to run this course. I have a set of 3.73's in a box, and they're going back in when I get time. This car is also a posi car, and again IMO if traction is an issue which in snow, I assume it is, then I would go with the posi unit. (but what do I know? I live in florida, we just do hurricanes).
http://www.fl-thirdgen.org/blacksheep-1/camaro.mov

 

Nice vid.

So, what year and type of GM vehicles came with 3.73 POSI rear-ends? At our autowrecker, we just go in with a wrench and pay by the pound pretty much.

 

in an open diff. the power will go to the wheel with the least traction, a clutch style posi unit will spread power equally, which can mean both your tires will spin like crazy. While a Torsional posi will send the power to where there is the most traction. If you don't feel comfortable doing the swap, don't. Setting things like pinion bearing pre-load is hard and you'll definetly need a micrometer and a good array of tools.

 

I don't have any intentions on doing the job myself. I'll gop find myself some cheap parts from the wrecker or somewhere and then get a transmission shop to put it together.

 

well no you cant swap in a carrier out of an S-10 . They run a 28 spline setup. I just went through all this . You need a new carrier for a gear swap ( 2.73-3.08 series 2 ...3.73 series 3 carrier) You can get a shime so you can run series 3 gears on a series 2 carrier .....but it just seems like you are makeing a weak setup ...weaker ...so I wouldn't go that route. I just bought a rebuilt series 3 carrier ( eaton gov loc ...crap) for 200 bucks . But I knew it was mint. I bought a used one ( looked as good) for another project ....and it was onlt 50 bucks .


hope somethnig here helps you a bit

 

More information than you ever wanted to know about diffs.
These are aslo good people to work with.
http://www.reiderracing.com/rtech_diffs.htm

 

not to steal the post but why is posi worse in the winter and hard rain? i mean cause there is power to both rear wheels wouldnt you have more traction? since one doesnt just spin?

 

I would disagree with that statement about posi's being worse, but.. in some cases I can see a posi unit causing the car to "push" in the corners, and that could be a problem. Other than that, I really don't know.